Mid range design cnc machine router discussion

Thanks for starting this thread Paul...

As you guys can see, we are serious about developing a decent open source design.

This is the thread for the mid range design. Benchtop size.

So what do you guys think lends itself better to a midsize design...

Igus W bearings?

Split bushings on supported rails?

Your thoughts?

Mike...

P.S. Here's an Igus design concept...

Does the 80/20 bearings suggest a mid level design, or because of the precision, should that be considered an entry level design?

(See attached)

Mike...

mikesch....the 80/20 linear bearing would be an entry level.

I would personally recommend drawer slides for a machine before I would use the 80/20 bearings - for an entry level machine, that is.

Scott

ok , think this is a more suitable thread for this ,
this is the design of a machine im working on , sorry that the fonts are out in the dfx files , it seems to make them bigger than the original , trying to sort that , but not had time yet
most of it is mdf with some steel parts
i do not have many tools available , so limited to having a hand drill and hand tools.
as to steppers and controls i purchased a www.stepperworld.com fet 3 economy system , i could of used other steppers and built my own controller but in the end decided to go for that package as it seems a good deal , and just left me with the machanical bits to make

theres 5 dfx files that should be attached the drawings are not complete i still have a couple of parts to draw, and assembly views of the machine , i am photographing it in verious construction stages but not uploaded any as yet

its my first cnc machine so any comments would be helpfull

for the cutting tool i am planning on using a bosch pof500a router
the steppers are 60g ones and hope they will have enough power
but the fet 3 controller would easy drive bigger ones if needed

is it just the machanical bits or are you looking at the controller also
i have been conidering developing my own stepper driver board but have not had reason to do so as yet but may have to yet
i have been considering a usb based one (that would offer com port emulation in software so programs like kcam may be used with it
i seem to have a problem with kcam and my laptop's printer port so may need a different controller if i do not manage to solve it

not shure how accurate this machine is going to be but anything has got to be better than my work , that beeing the other problem i have tryed to solve in making it , in that critical cuts to the mdf can be made at the cutting shop , and not left to me and a saw (well 10degrees out for me is about right on a bad day :) as is drilling with a -+ 5mm accuracy )

hence the need for a cnc that can work better than that

Dave

A while back I gathered several parts necessary to build my CNC machine. I acquired Thompson linear rails for X, Y, and Z axis. 48" X 24" table. I have 3 Servo motors and quite a bit of plate aluminum. All this has been sitting for about a year as other things came up. Would this be considered the makings of an intermediate or mid-range design? I'm really out of the loop and would like to get this up and running. I need controller boards and screws, and software. I have the router and a computer.

Let me know if this is the right place for me to watch or if I should be in the beginner area or whatever.

Thanks.

Darren

With Thompson rails, I would consider what you have as the beginnings of a high end machine, especially with that pile of aluminum you've got.

You could watch all the open source threads, they will all give you design inspiration.

I would like to see a high end thread someday, but somebody needs to come to the plate with the knowledge, and the parts to build it. Maybe that somebody is you?

Mike...

I don't think I'm the guy :) I am very handy and am quite capable of building this machine but I know little to nothing about CNC. I just know what I've read on the forums on this site and have forgotten most of it over the last year. I'm trying to ease back into it though so I can get this investment up and running. I hate seeing it sitting there in a pile. Last I remember is I was trying to find a deal on Gecko boards... a bit of an investment. I'll keep an eye on this forum though as it should be interesting.

still not shure if my post is in the right thread , think by the way things are going here 2 threads may be a good idea , for a midlevel design , one for simple construction and one that requires machining of parts ,

my design is almost in the hardware store catogory but seems its to big for there

its a 900mm *500mm *100mm cutting aria design that could be made with minimal tools
and i am working to a budget of £400 (including controls and steppers)
and thats all parts new ,
it would just fit on a table top as the dimentions of the base are 1136mm * 930mm
hmm 47" * 38" approx if my conversion is right

its mainly for working with wood and ply , but trying to build it with enough strenth to mill alluminium also so i have basicaly uprated the Igus design a bit , and some minor changes to make it look a bit better and put the cutting tool more centered on the x axis
as to accuracy well if i can get +-0.5mm from it it would suit my needs but hopefully it will be a lot better than that
with m10 bar i get should get 0.005mm per step with stepers at 1.8deg per step


to darren , sounds like thats going to be one nice machine your making , but from the tools i have to build one from i would need a cnc to make the parts

as to rails i decided to use a steel tube with bearings as runners as this seems to offer good strenth , and easy enough to make ,
i ended up using 20mm staneless bar as it was available from a local suplier , but could use up to 30mm dia bar or tube , depending on the use

sorry about dimentions all being metric for a rough conversion theres 24 mm to 1"

I'm not seeing the enthusiasm for a mid level machine like I am for the hardware store design.

I thought a mid level machine would be built from igus rails and bearings, or supported precision ground shafting and split bearings... but the interest doesn't appear to be there.

Is it the cost, or is the the precision required? A mid level machine is probably a skill level "mill 1", i.e. requires you to already have a mill to machine parts with.

What do you think?

Mike...

I'm not seeing the enthusiasm for a mid level machine like I am for the hardware store design.

I thought a mid level machine would be built from igus rails and bearings, or supported precision ground shafting and split bearings... but the interest doesn't appear to be there.

Is it the cost, or is the the precision required? A mid level machine is probably a skill level "mill 1", i.e. requires you to already have a mill to machine parts with.

What do you think?

Mike...

well after all the chatter there about what bits are available from local hardware stores , and then listing tools required to complete the design :)

ok heres my 2 halfpence worth
i need a cnc , so set about building one , i looked at some of the construction methods used on a number of machines , and took into consideration the tools and equipment needed to build it , then i spent some time sourcing parts ,
it needs mdf for the main structure ( available form local hardware store or wood shop) i have to add here that a lot of hardware /wood shops offer a wood cutting service as long as the cuts are at 90 deg so square /oblong pieces end up accurate , although on this design i have still a lot of cutting out to do to shape some of the pieces but you get what you put in
some effort with a hand saw makes it worth it in the end

i decided to use steel angle iron for suports and bearing holders , these reqire drilling and fileing , no milling
the pricision rails well i originaly designed the machine to use 30mm dia 1.5mm thick tubeing , so something like curtain rods may be used although by using this method anything from 20mm to 30mm bar or tube could be used if it has a good surface , i opted to take an expencive route of using 20mm stainless steel bar for these , as i want to be able to machine aluminium
the size is scailable , and there is a +200mm axis requirement for the lenth of the carrage

i do not have a mill , and only hand tools to make the machine from the only singal part that is going to be a problem to make is the coupler to mount the threaded bar to the stepper motor , this is going to need a pillar drill i think
it could be built using a hardware store only , the steel parts could be made from aluminium angle if , but not shure if it would offer the strenth so opted to use steel

from the sounds of it hardware stores in the uk do not offer the same as in the us , but there is a good base of steel stock ,bearing suppliers here in the uk that makes all the parts available reasonably localy or online so do not see the problem there

but there draw slide version seems a good idea, but would say that the big diy/hardware stores in the uk do not seem to offer that style of slides :)

anyway i managed to fix the problem with my dxf export for the files
and uploaded them to my website http://www.whipy.demon.co.uk

cost well you get what you pay for , if i used 9mm mdf instead of 18mm and used tube instead of bar for the rails and aluminium angle instead of steel then it could be built cheaper , but would be more suitable to a dremill than a 500w router for the cutter , and would limit the materials that could be cut , then almost all the parts would be available from the local B&Q or Homebase here in the uk , the exception being the threaded bar but CEF a trade supplier also throughout the uk stocks this and offer cash over counter for it , and bearings well google for a local supplier theres quite a few

anyway i'm going ahead with this design so feel free to comment on it ,
or come up with something copleatly diferent ,i guess once i get it built there will be problems that need iroing out , i just descovered that the router mounitng will also accept my drill so gives me more tooling options :)

Dave

ok so im not perfect

my design needs a lot of reworking to get it something like
i have finished the metal parts required , and have decided to redesign the MDF parts
i still plan on using the metal parts but want to try to get rid of some problems i can see with the current design

like adding some form of supports along the leanth of the rail to stop flex
one of the things i originaly wanted to do , but in the end i decided not to but am going to have another go at is

the big diy stores offer a wood cutting service , as long as the cuts are at 90deg ( so thay wont cut angles cutouts etc , i want to be albe to go to the store and with std size sheet ask for it to be cut down , then hopefully i should only have holes to drill
thay use a machine that is reasonably acurate and you end up with 90 degree cuts :)
at the moment the design uses 3 sheets of mdf and there is quite a bit of srap , and alot of extra cutting to do once i get the bits home

i seem to be the only one posting in here could do with some input

anyway after some tests of the stepper world fet 3 economy system looks like some bigger and better steppers are going to be needed , have not decided if to build another driver board , but it looks like i may need to

dave

Hey Dragon,

Do you have some photos of what you are doing?

If we can see what you are up to, we'll likely have ideas for you... or at the very least, some ribbing! :D

So what do you say? Share a photo or two!!!

Mike...

anyway after some tests of the stepper world fet 3 economy system looks like some bigger and better steppers are going to be needed , have not decided if to build another driver board , but it looks like i may need to

dave

Unfortunately, you may find that the FET might need to be replaced. I think I've only heard one person say they were happy with the performance they got from it. A HobbyCNC or Xylotex driver will ususally give you at least twice the speed. You may need bigger motors as well, not sure what you have now?

ok
:)
first pic , a pile of bits ,
well the metal work , router , vac (for dust extraction) , some wire, 2 relays and a contactor (for power control of the vac and router) , and a stepper world steppers ,controller and psu

dosent get much better

second pic some idea of what sort of of tools are avalable , here showing the vice in the process of making the bearing holders with two compleated ones painted

third picture , well now got all 6 compleated bearing holders ( waiting for bearings and 4 still to paint along with the stainless runners

the bolts will need shortening but will do that when i have the bearings

the long support rails for the base bed are now finished and painted also

the reworking of the MDF parts is comming on well so far also ,
im looking to be ordering the bearings soon and the mdf in a week or so
leaving only a slightly out of the way trip to pick up some m10 threaded bar
so should have the thing assembled in 3 to 4 weeks hopefully

then it will be down to the steppers and driver , i dont think they will be up to the task , so will be looking to source some that are ,

btw the only power tool used so far is an electric hand drill , as you can see with a wibbly wobbly vice , and basic tools its getting there

the stepper world driver should be able to drive bigger steppers , as to speed it will drive them faster than the steppers will turn so think with better steppers this may be ok , but i may need to change the driver fets to better ones , i have been playing around with them on the bench , it seems that the steppers are the limiting factor with it

i set the software to give me 200ipm (@5080steps inch)and the driver was clocking the steppers fine , just way too fast for it to turn them so theres hope for the driver yet
will need to get the machine set up then i will try it with the steppers and try some different ones on it
maybe there stepper package would suit a minature cnc with a dremill as the cutting tool better :) a future project maybe

Dave

Whats the spec for this machine? I.E. What cutting volume size, precision , accuracy, speed, size of cutter, size of spindle, materials to be cut?

Whats the spec for this machine? I.E. What cutting volume size, precision , accuracy, speed, size of cutter, size of spindle, materials to be cut?

well the cutting aria is 900mm *500mm *100mm (approx 35"*19"*4")
it should be scaleable with not much effort , and only minor changes (to bed thickness and bed suport rails hopefully it should be able to do 8'*4'

the cutter is a bosch pof500 router a 500w router , but also found i should be able to use a bosch csb500w hand drill in the same mounting (but lose some cutting aria hight , but have a chuck for tooling ) but should be easy enough to modify for other power tools / cutting tools

speed well will find out , looks like the steppers i have are going to be very slow so it will need better ones ,

materials , MDF,ply ,soft woods, aluminium and plastics are the goal for it , anything else will be a bonus

trying to get the design so it will scale up or down but i am limited to the size of my workbench (concrete coal bunker see pic in previous post )

the stepping should give 0.005mm accuracy but would say 0.01mm (about 0.00039") should be posable unless theres a flex problem but i got to build it first an see

im in the process of doing a lot of changes to the design at the moment

i am trying to make it easier to make and do more to eliminate any possible flex

anyway no garanttees until its finished

dave

Dave,

Sorry, I was trying to ask what the target specs where for this thread and the Mid range design #1

Andrew

Dave,

Sorry, I was trying to ask what the target specs where for this thread and the Mid range design #1

Andrew

not shure , i moved over to this thread from the hardware store cnc during initial disusions there that pointed to this machine being too big for that ,
and pointed to some bits not beeing avalable from the local hardware store
(there using the same bits there now anyway :) )

anyway
there seems little interest in this thread and the discussions in the hardware store seem to be following the same route im still not shure if i should be posting the design here or there :)

it did look like someone ( sorry can not get name up while in the reply box)
was going to do a design for one with comertial sliders and machined aluminium parts , (big task ) but should be a hi quality machine
but they seem to have backed out
shame , would like to have seen that

Dave

Specs? We ain't got no specs! :p LOL.

Actually since there was more interest in the hardware store design, I figured I'd focus my energies there first.

I see the mid level machine requiring already owning a mill, perhaps even the hardware store design, in order to cut parts for it.

But I didn't have a feel for how much money we should allow for a mid level design. Linear motion components are expensive.

Should we be coming up with a K2 aluminum machine?

Mike...

P.S. Dave, Please expand on your comment. Too big? What bits?
, i moved over to this thread from the hardware store cnc during initial disusions there that pointed to this machine being too big for that ,
and pointed to some bits not beeing avalable from the local hardware store
(there using the same bits there now anyway :) )

Specs? We ain't got no specs! :p LOL.

Actually since there was more interest in the hardware store design, I figured I'd focus my energies there first.

I see the mid level machine requiring already owning a mill, perhaps even the hardware store design, in order to cut parts for it.

But I didn't have a feel for how much money we should allow for a mid level design. Linear motion components are expensive.

Should we be coming up with a K2 aluminum machine?

Mike...

P.S. Dave, Please expand on your comment. Too big? What bits?


well early on they where started working on a draw slide design in that thread and tried calling anything bigger a mid range design , so ended up here then ,, but they seem to be doing a design with tube and bearings so
much the same as this and the draw slide one is now in another thread
btw i have sort of moved back to that hardware store design thread also :)
as theres nothing much going on here

Hey you guys, I was posting on the hardware store design thread and my ideas started to head in the midrange direction... So seeing that I've gone the hardware design route once already, I guess it's time to step it up a notch and hang out w/ you guys. :) Anyways here is my bearing design. I orginally designed it to use 2.5" angle iron for the truck, and 1.5" angle for the rail. But I ended up having to redesign using 2" angle for the truck and 1.5" for the rail in the pictures of the prototype... reason being was that was all that my local hardware store offered. (like I said... I was rotating around a hardware store design originally) Anyways, here's a bunch of ideas, I'm working on building a machine based on this rail concept, I am sort of heading in a "shopbot" style direction... Enjoy! -Carl

Hey Everyone,

I would like to thank those that have helped shape the hardware thread. Now we need some people to do the same with the mid range thread.

Some have asked what the parameters are for the mid range machine. I will tell you what I think they are.

1. Very sturdy and precice. Able to two pass cut aluminum 1/4"

2. Larger than 3'x4' working area.

3. Ability to be rebuilt after years of use

I believe this is the thread for the bought linear items, unless you can come up with a very good homebuilt design. There are no limitations as to the source for the parts as long as they are generally available. No one-off "a friend of a friend who works for Kodak got me this", We are shooting for being able to offer these as plans to the CNC community. So keep all parts easy to get.

I posted on the hardware thread earlier today and asked Carl (Izzlestar),I hope thats right!, to try to start a design around his angle iron idea. I really hope he comes and starts the ball rolling.

Alot of people have been bragging about how the hardware thread is going. The reason is that there are a few of us who are actively working the thread keeping the fresh ideas going in the right direction. We need some volunteers to come and do the same with this one. But you must be open minded. If you have a set plan of attack then start a build log in the general area. If not then come help. You never know you could be designing your dream machine. ;)

I will help all I can.
Jimmy Southern

Ok has anyone settled on construction materials for a mid range design? I my mind, a mid range machine is a step up from wood components, to say aluminum but stays away from the linear slides, ballscrew and servo motor/drive requirements of a high end machine which contribute the the higher cost. Maybe it is a design that could be upgraded to those components or used to build the metal widgets needed for a high end design.

I still think the ball bearing guides and threaded rod with steppers make perfect sense, with an increase in rigidity. One might also expect to have more available equipment to make the construction a bit more professional. Something like a mini lathe and mini mill or a welder.

Hey Everyone,

Dieguy, I agree with you on the linear motion stuff. Ebay is pretty much dried up as far as the great deals on these. Thats why I like carls idea so much. It is about as precise as it gets on the mid range budget. I also agree on the servos they are still pretty high end at the moment so steppers would be the way to go.

Carl, just a bit of advice, I do a great deal of welding in my business, go with the biggest angle iron you can. 4" angle is far better quality material because it is not easy to bend in transit from the mill to your door. Alot of people handle this material before you get it. Also the more distance you put between your bearings the more stable each truck becomes.

I believe steel is the most redily available material to build this from, aluminum running a close second. Maybe build the structurals from steel, then do the sheet goods out of aluminum to keep the weight down.

Just throwing out some ideas. Lets get this one rolling like the hardware one.

Jimmy

Guys -

I would like to become involved with one of these designs - maybe this one or the high end machine design. I can help.

I previously designed composite processing machinery and equipment for processing structural composite bodies for Ford and helicopter transmission cases for Sikorski and Bell helicopter among many other things. I currently design coil processing and coating machinery for Mitsubishi. I think I could be helpful.

The issue I have is reliability. I will help when my time allows but I can't guarantee my availability - hence - I may not appear to be reliable from time to time.

Do you have a use for potentially unreliable me?

The first thing I would suggest is that we identify some solid boundries for each design - or has this been done already?

Scott

ok
:)

well i have not posted here for some time , i seem to have been following the hardware store design , and have taken a different route with my design
see http://www.whipy.demon.co.uk
i have done some changes that i have not posted a picture of yet , mainly changing the x axis to use draw slides , and having a fixed gantry
this cured the x axis rotation that i was having

i have found that the unistrut can provide a stable frame , its easy to get hold of and because it just bolts together is easy to re design and change things with
guess that other materials like angle and box section could be used in place of it
but my machine is a "small" one ,

maybe using unistrut for the frame is a good idea , used right it will prove stable enough for a larger machine

i tend to agree that we should be looking at a 3' * 4' machine and allowing it to be scaled up to a 6' * 8' (so would need to allow for this in the calculations)

i understand that the design i am building would not scale up to that in its current form but it has 2 advantages from the point of view of a home constructor
first is assembly ( cut and bolt together ) ok spend some time aligning it
it should also be posible to weld some of the parts together (if you have welding facilaties)

the other thing is that unistut also has verious "standard fixings" to allow it to be joined in a number of ways

in a simalar way to the extruded aluminium frameing systems commanly used

at £12 for a 3 meter lenth (sorry for metric units ) 9'10" its not overly expencive
data from http://www.unistrut.com/

do we go for a fixed gantry moving bed (so we dont get x twist ) or a moving gantry design ?
Dave

Guys -

I would like to become involved with one of these designs - maybe this one or the high end machine design. I can help.

I previously designed composite processing machinery and equipment for processing structural composite bodies for Ford and helicopter transmission cases for Sikorski and Bell helicopter among many other things. I currently design coil processing and coating machinery for Mitsubishi. I think I could be helpful.

The issue I have is reliability. I will help when my time allows but I can't guarantee my availability - hence - I may not appear to be reliable from time to time.

Do you have a use for potentially unreliable me?

The first thing I would suggest is that we identify some solid boundries for each design - or has this been done already?

Scott


yes any help here is welcome , and no i dont think any boundries have been set for this machine yet , other than it should cut aluminium , mdf and ply
although i do think that if its going to be used for aluminium that and upto 8'*6' that we sould not expect to be cutting a 1"wide 1" deep grove in one pass , 1/4" by 1/16" maybe

dave

sorry for 3 posts in a row

Carl
i like the idea for the slides

im just wondering if they would be upto a machine cutting aluminium ,its the single bearing on the outer edge of the truck , guess if there was 2 i may feel different but i guess that would make it harder to align and require more accurate drilling

anyway glad theres some activaty here again
new machine spec well yes , going to say i dont think i will be building it ,dont have the room for another , but will watch with interest and help where i can

My thoughts of a Midrange design...

It does not need to exactly be large.
It does not need to be expensive.
It does not only require basic tools to build.
It does not require everything to be available locally.

It does need to be exceptionally rigid.
It does need to be made almost entirely of metal (Steel, Aluminum, brass)
It does need to be quick... Rack and Pinion, belt or ballscrew. (I vote for Rack and Pinion for reasons I'll get into in a moment)
It does require a full size router for a spindle at minimum in order to take advantage of the fast motion.
It is able to be used with servo or stepper motors.

I'd suggest a design with good use of an 80/20 based framework, perhaps we can take advantage of our 80/20 advertiser here and get the framework supplied in a kit of scratch and dent surplus since they "do" have surplus and most home users cannot afford first quality 80/20.

I'd like to see the ways utilize steel angle and V-groove bearings in a shopbot fashion. Perhaps with a solid design we can get a ready supply of V-groove bearings from VXB at areasonable cost. Unless of course an affordable alternative for THK or Igus W rails shows up.

I'd like the cutting area to remain around 24"x36".

I'd like to keep the drive system for the X axis away from the underside of the table so that vaccum and other table clamping systems can be adapted easily.

Ideally the mechanicals should cost the builder $800 or less. (minus controller, drive moters and spindle.)

I think that Shopbot's mechanicals (not their control system) and some of the lower end K2CNC machines are good examples of Midrange machines.

Hey Guys,

I was just reading over the posts and noticed we have two completely seperate views on the mission. We need to clear up a few points here.

1st we are doing plan design. If what we design cannot reasonably be built by the advanced novice with available materials, then we can't expect much success from the plans. This machine is not meant to be a starter machine. It is the next step up for most builders.

2nd we do not need to spend alot of money to get a very good machine but I think we would be wasting our time to do a "bolt it together from junk design" also. Lets break new ground! Come up with some new ideas! That is why I mentioned to Carl coming here to kick start the mid range design. His idea may not be absolutely new but it is a solid way to build a very accurate and strong linear motion set up. We can tweak it for strength.

3rd I would like to stay away from needing a lathe or mill to build it. Most don't have these and this would severly limit our list of contributors and future builders.

Now a few personal views. The size of the machine should be bigger than the hardware design. Currently it is shooting for 2'x3' work area. Most 2nd time builders upgrade to a bigger more robust machine, so 3'x4' or even 4'x4' would not be unreasonable. Depending on design the foot print for the 3'x4' machine should not exceed 4'x6'. This would take up about as much room as a garden tractor mower, in the garage. This is definately not for apartment dwellers but they could easily scale it down. It is difficult to make somthing bigger but it is easy to make it smaller!

This is just my opinion though.
Jimmy Southern

ok
clear up 2 points , i use unistrut because its reasonalby cheep and easy to work with , its strong about the same as 1 1/2" box section
its not junk , its modular frameing used for pipe and cable rails in the building trade its also galvanized so the only real rust problem is the ends where its cut
and for most is as easy to get hold of as angle iron and as strong in most cases theres also a range of fixings that make it easy to assemble
(i admit on my prototype i have not taken advantage of using those)

but given that it is steel theres nothing stopping you from welding it together
unless you don't have a welder then your stuck with bolting whatever you do together anyway

thanks for the thoughts on my design anyway , its still a prototype
and having it bolt together at the moment makes it easy to change
once i got the thing compleated i will tidy it up and weld up some of the parts so there is no slip
there are things i want to change on it , and no there is no plans as yet
mostly its cutting and drilling sizes , but i want to finish it and see how well it works , i need a bigger cutting aria than it will have in the long term 2'*3' but once i get it running i can start on the improvements to it

so i guess 80/60 extruded aluminium is also out ( you bolt it together)

sorry but i got thrown into this thread some time ago , i did my best but am a novice at cnc design still working on my first machine
i know that the spesification is open and 3'*4' seems a good size to go with

anyway you guys come up with a new design , i'm going to continue with mine , but not here

btw there are a couple of things i would like to see on the new design

1/. the tool mounting center to be between the rails (not offset) think there will be better stabilaty that way
on the z and y axis as well as the x

2/. the runners should be stainless steel ( given time steel will rust and they will become uneven and aluminium will wear too much if heavy use )
but feel that it should be worth the extra expense in the long term

dave

One more suggestion. It should not only be all the things you mentioned, ANOEL, but it should also be easily built using the low end machine in the other thread.

Don't *require* the parts to be CNC machined...but if this is a "next step" from the low end machine, then let the upgrade path reflect that. GCode could easily be made available for some of the harder to fabricate parts.

Seems like the small X-Y vise is a popular approach, at the moment, which means an envelope of 4x6" or thereabouts.

-- Chuck Knight

Hey Guys,

Dave, I was hoping that no one would take that line to heart, even though I was serious. Your machine was not what I was refering to. So many of the builds on the zone are cobbled together from old scanners, printers, this piece here, this peice there, etc. I want to avoid the scrouging approach. We are designing plans not a guide to where to scrounge good parts. So I hope no one is offended I am just trying to point the general direction as was laid out by CNCadmin, when he started this. This machine must be an upgrade from the hardware machine. In my opinion we have our work cut out for us, because the hardware machine is turning out to be a very robust design on it's own. I hope this clears this up.

Also I don't think we should design this neccesarily as a 2nd machine, requiring having a 1st machine to cut parts. I just believe the beginner will have a hard time with a mid range machine without more advanced cnc knowledge. Not a requirment but a plus if you have it.

This my opinion though
Jimmy

Precisely -- but we can purposely design the precision parts needed, so that they fit within the envelope of the "standard" entry level machine.

Don't require it...but if they got it, let them use it! Gcode is easy to include in a plan set.

-- Chuck Knight

My initial thoughts when I came up with this mid range machine thread, was to have a machine that was similar to the K2 CNC machine. In particular I liked that fact that it was all metal. I figured once I built that it would be the machine I would keep. I also figured I would use the homebuilt machine to cut the parts for the K2 clone. The 3925 machine is $3250, so that would be the price to beat!

However, having said that, I realize that any design that is all metal, whether steel or aluminum, is going to be worth keeping.

Izzle is doing a wonderful job with the angle iron design so far. I'm looking forward to seeing more.

Mike...

i realy like the k2 machine
has it has been mentioned that the hardware store design cnc should machine aluminium i think that this should be included in the choice of available machining options

guess the hard part would be the machining on the non alloy parts used for the runners
although i think that if the machining on non alloy parts is drilling (and maybe tapping ) then it could be posible to supply gcode that could mark out thease parts

may be worth looking at a place like http://www.metalsontheweb.co.uk/ for the metal , ok so thats a uk site but i suspect there will be simalar sites in the us and elseware

problem in cutting aluminium on a MDF design is coolant
well not so much of a problem but it would creep into the mdf making it soggy

unfortuanatly i can see there beeing 2 designs here , one machined from aluminium like the k2 and another from angle iron

personaly i would be doing more aluminium work on it than MDF etc so it makes sence to have metal framed design than a MDF one as i dont want to find i got a pile of mushy mdf once the coolant has been soaked up by it

Dave

Any more progress on your design Carl?

Mike...

I still contend that a Midrange design should have the following requirements...

Rigidity
Durability
Speed
Work envelope.

In that order of priority.

MDF ain't going to cut it for rigidity... so it's got to be a metal frame.
Unsupported rails is not going to work for rigidity, gotta be supported rails with real bearings of some type. Delrin or UHMW bearings won't work unless it's an IGUS solution, where the composite is encased in a metal housing to retard deformation and where the "Stick - Slip" factor is minimal.

Durability... Again MDF ain't going to cut it again, gotta be metal to handle messy material and coolant.

Speed, I'd think that 80 - 150 ipm is a good target for rapids.

Work envelope is subjective... I think a 2'x3'x5" is a great all around size for most applications and is bigger than the average knee mill. And will keep the cost to a minimum for the metal framing. I have a one car garage as my shop and much bigger and it gets very big very quick. Perhaps a modified version or two can be done to accomodate different envelope needs.

Mike, I've been grinding away on the design, I'll post some pics in a day or so when I'm ready for criticism. -Carl

Anoel,

I agree with most of your requirements but I do think a few may not work. 1st we are, at the moment, planning on skate bearings or another ebay bearing, maybe bigger. The speed you mention 80-150 ipm, I am no expert on steppers but I really don't know if these numbers can be reached with any torque left in the motor to do the cutting. Servos would have no problem with the numbers but the cost would put us into the high end design. Now to the size. As the old saying goes "It's easy to take some off but it's hard to put it back on." This definately applies to CNC as well. If we design this machine to be a 3'x4' work area it is simple to downsize to any size you want, with no loss in rigidity. Now concerning rigidity I fully agree no MDF here. We can go steel, aluminum, 80/20 or whatever the group decides. At the moment I am liking Carls rail design. It should be a vast improvment over other, more expensive, designs I have seen on so called mid range machines.

So I hope no one is offended but no MDF in this thread please. Lets also try to come up with some new and inovative ideas that can cut cost and improve quality!

Thanks Jimmy

The speed you mention 80-150 ipm, I am no expert on steppers but I really don't know if these numbers can be reached with any torque left in the motor to do the cutting.

Use 2-4 turns per inch screws (multiple start acme) and you should have no problem. Taus uses Nema23 steppers on his K2 and gets ~120 ipm. See post #84. http://www.cnczone.com/forums/showthread.php?t=10157&page=3&pp=40

3'x4' is managable... as well. I just want to make a point that "midrange" doesn't mean a "bigger" hardware store machine.

Speed... I get reliable rapids of 60ipm on my current MDF machine with unsupported drill rod rails and a 1/2"-10 2 start lead screw... Acetal anti-backlash nuts and 120oz steppers... I'm sure that with 200oz steppers I could squeeze that up to 80ipm or more wth no trouble. My axis are not frictionless by any means either, they are much tighter than they should be but it works and I'm not screwing with it. I did a test axis that moved very freely and with the same steppers and lead screws I could get around 100ipm. So I don't think that the speed numers I posted are out of line at all. 80ipm for steppers and 150ipm for Servos... (I should have mentioned that though)

I guess that my vision of "high" end machine is like that of a Techno-Isel or other manufactured machine with highspeed spindles and run 600ipm rapids and automatic tool changers.

Hey Guys,

I could not remember seeing a stepper design exceed 80 ipm, so thanks for the clear up. I just want to avoid having too high of expectations and people loosing interest. I am really looking forward to seeing the design come together!

Keep the Ideas coming!
Jimmy

I've heard of 300+ ipm rapids with 150oz motors and rack and pinion drive.

another long rant but,

i tend to agree with most points
speed of the machine though well ok 150 ipm well thats going to be determined by the steppers / servos used and the lead screws used
think this is best left to builders choice , its posable to upgraded to bigger steppers and different lead screws but as the builder may not have funds i think the best option is to provide a standard stepper mounting ,
theres nothing stopping it having a stepper mounting drilled to accept a couple of sizes of steppers , and well the lead screw , well again that should be builders chioce, the mountings for it tend to be the same for 2mm per turn as for 10mm per turn (for metric ones )

and yes no MDF , if the main use is going to be woodworking then the bed from ply or mdf maybe (it should be made easy to replace )

i also like the idea of carl's rails , but i can see a problem that may be troublesome
that tends to put me off
if the rails are made from aluminium they are going to wear fast , also aluminium in that configuration is going to deform quickly where most working pressure is applied causing kinks in the rails
making them from steel well the running surface is going to be prone to rust that will make the surface uneven after a year or so
and unfortunatly stainless steel is not readily avalable in angle section
i don't fancy having to strip down the machine and sand down the rails every 12 months or keep having to replace them because they wear, should do the job right and with the right materials so this machine should last a long time

maybe using flat 1/2" by 1 1/2" section stainless steel or whatever size is best suited bolted to the frame for the x&y axis and another method for the z , bar or square section may be better in the long term for wear and environmental reasons
grease is only going to get squashed out of the way by the bearings , and add to the friction

skate bearings well ok there readily available and cheep ( but dose not mean there any good )
we could look for a bearing that is as widely available and used in a comman everyday item like a bike or car (of the right size that is :) ) if skate bearings don't look like there going to do the job

Dave

another long rant but,

i also like the idea of carl's rails , but i can see a problem that may be troublesome
that tends to put me off
if the rails are made from aluminium they are going to wear fast , also aluminium in that configuration is going to deform quickly where most working pressure is applied causing kinks in the rails
making them from steel well the running surface is going to be prone to rust that will make the surface uneven after a year or so
and unfortunatly stainless steel is not readily avalable in angle section
i don't fancy having to strip down the machine and sand down the rails every 12 months or keep having to replace them because they wear, should do the job right and with the right materials so this machine should last a long time

maybe using flat 1/2" by 1 1/2" section stainless steel or whatever size is best suited bolted to the frame for the x&y axis and another method for the z , bar or square section may be better in the long term for wear and environmental reasons
grease is only going to get squashed out of the way by the bearings , and add to the friction

skate bearings well ok there readily available and cheep ( but dose not mean there any good )
we could look for a bearing that is as widely available and used in a comman everyday item like a bike or car (of the right size that is :) ) if skate bearings don't look like there going to do the job

Dave
Using aluminum for the rails would be unacceptable, for the exact reasons that you say. In fact that thought never occured to me, I have been planning on using angle iron. As for the rust, It might be a problem, but it should be negligible, perhaps by keeping the tracks oiled? I'll post some pics tonight. -Carl

ok turns out that it may not be a problem about the rust

looks like http://www.arenastock.co.uk/ do stainless steel in angle section
think there international so there may be a US site for them also
interestingly they only list it with metric mesurements though

Dave

McMaster-Carr has galvanized angle. Much cheaper than SS.

:) supose but galv tends to chip and feel shure that if running bearings on it will cause it to flake off in the long run ( looking at old galv it seems to do this ) a heavy presure rolling on it would cause it to flake after some use , maybe 2 to 3 years , less if under constant use , i dont know if theres any info or figures for that avalable though

and ok so SS is expencive but should be low mantanance and should not need to be replaced normaly in the machines life (unless you waire it out)

Dave

Nah, just regular old angle iron should be adequate...The bearing running across the way will keep the rust down, just paint the angle and it'll be OK. Stainless would be nice if it were hardended, but at that cost point might as well hit up ebay for some used thk style rails.

I still like the way that ShopBot and EZ-Router are using V-groove bearings on the angle iron.

The tables of most of my woodworking machines are unfinished steel. I wax them every now and then. I don't see much rust.

I get a conservative 120ipm on my machine with 1/2" 8 2 start and 200oz steppers. I have run it at 150ipm, but it is so light that the whole machine shakes. I have it just sitting on a table with large casters. Probably not a good idea.

Steve

Steve, What drives are you using? HobbyCNC? What voltage?

Izzlestar

I saw your post regarding your angle iron carriage.

Wow what a nice design... will be interested in your progress.

My design was going to be a copy of the Shopbot design ( using dual-vee bearings ). I dont see why your design may not be even better.

Thank you for sharing your design and especially the pics ( worth a thousand words)

regards
Domenic
(Sydney, Australia)

Jerry,
I am using a PWM HobbyCnc controller and their 200 oz steppers set to 8 microsteps. I am supplying 3 amps per coil from my 39 volt DC supply. Is this what you are asking? I do not like the way it performs on my Z with a heavy router. I can stall the motor by grabbing the shaft collars with my fingers when it is lifting (not when lowering). I can not stall the other motors with my fingers. I plan to switch to a higher tpi for the Z. (?)

Izzlestar, I like it.

Steve

Yeah, that's it. Thanks. Are you using the 1/2-8 2 start on the Z?

Yup, 1/2-8 2 start all around.

I've got 1/2-10 for my Z, and a 250oz stepper. I'm hoping that's enough. I've read about a lot of people on the Mach2/3 group losing steps on the Z axis. Apparently people think the Z needs the least torque, but in reality it needs the most.

I've got 1/2-10 for my Z, and a 250oz stepper. I'm hoping that's enough. I've read about a lot of people on the Mach2/3 group losing steps on the Z axis. Apparently people think the Z needs the least torque, but in reality it needs the most.

How about running a cable counter weight and pulley setup on the Z to lighen the load.

Ok guys, here's where I am at right now. There are lots of loose ends, and things missing in the drawings I attached. Nuts, bolts, certian parts... motors, etc... I'm not done yet by any strech of the imagination. I just wanted to throw this out there, and let you guys tear it apart! :) Well, I decided on a whim that it would be really nice to try and design this machine around the new "HT" extrusion being offered by 80/20, even though I have never inspected it in person... and I have no idea the cost. I was thinking along the lines of this machine being something of an erector set, that you could buy alot of the parts precut, make a few parts, drill some holes and start bolting things together. Not likely, but I'm trying. So someone said something about a rack and pinion drive system, the green bars in the drawing indicate the gear racks, they are the type that have the pre-drilled holes in them from McMaster (.5 x .5) The trucks that the motors would mount to (two on X and one on Y) are actually designed from 4"x4" aluminum tube that you can find at onlinemetals.com, and the trucks without motor mounts are designed from 4" aluminum angle. I'm not sure what I'm doing with the z-axis yet, that why there are parts missing... Oh and the rails are 2" angle iron... and the red pieces in the drawings are .25" aluminum plate, which as we all know is expensive, so I tried my best to keep it to a minimum. And Yes, I do know that the bolts are pushing into the extrusion on the x axis bearings- I haven't fixed that yet! :rolleyes: Thats it for now folks! -Carl

wow that looks good , i like it

can see that you got problems with some of the bearings thay sort of run into the frame

maybe putting the bolt the other way around would give you a little more room
ie putting the bearing on the bolt first so you have the threaded end at the other side of the carrage

like the positioning of the rails ,only point that would concern me looking at it is the stability of the Z axis

Dave

ok never posted on here before. wanted to throw out 2 ideas i have been toying with.

1 drive system. Has anyone ever experimented with a friction drive system. I was somewhat thinking od a rubberized small wheel pulling on smooth steel or aluminum. Just a thought.

2. I have been working with a similar design to the angle iron also trying to copy shop bot. Using Angle iron on edge to create an upside down V with the truck being on top made out of the oposite angle (right side up V) >< Using small wheels or bearings for it to ride on. this would require gravity to hold the truck on the angle however a rack and pinion drive could be used to hold the system down.

Perhaps someone can draw what I am thinking.

Couple of obersvations...

The uprights on the frame should be changed to something that does not need to be cut to length vertically. Getting those pieces to be "Exactly" the same length will be difficult to do at home. (Take a look at ShopBot and EZ Router and their use of the big Channel to support the angle iron.) Using a presized item there would be the way to go. You'd be able to loose the top framing rail also. Looks like a really big footprint for the cutting area as well. Some travel optimization would be good. I'm not convinced that the X axis needs to be driven by two motors and two Racks either. If the thing is as rigid as should be then there should be very little chance of racking and causing binding. There are some really big routers out there that are being driven from one side very effectively.

Couple of obersvations...

The uprights on the frame should be changed to something that does not need to be cut to length vertically. Getting those pieces to be "Exactly" the same length will be difficult to do at home. (Take a look at ShopBot and EZ Router and their use of the big Channel to support the angle iron.) Using a presized item there would be the way to go. You'd be able to loose the top framing rail also. Looks like a really big footprint for the cutting area as well. Some travel optimization would be good. I'm not convinced that the X axis needs to be driven by two motors and two Racks either. If the thing is as rigid as should be then there should be very little chance of racking and causing binding. There are some really big routers out there that are being driven from one side very effectively.

the uprights i dont see as a problem as it can be corrected in the fixings used , more flex of the x sides i can see as a problem , as drawn i guess i would build it from steel box section welded together rather than extruded aluminium section , could even use unistrut , cutting the bits for a welded version would need to be more accurate as you wont get the adjustabilaty

as to dual racks , guess the pinion drive could use a simalar method to the usual dual lead screws , ie a sprocket and chain or belt to a single stepper /servo

the rack idea looks good but i think finding suatable racks may be harder than leadscrews , the other problem is gearing and stepping accuracy
a leadscrew driven with a 200 steps/rev stepper and a 4 revs per inch lead is going to give you 800 steps inch or 0.00125" per step
but with a rack and pinion your going to have a verry fast machine but only someting like 0.015" steps (about .25mm) per step ( about 3" per rev of the stepper)
thats going to be asking a lot to machine out using a router in 1 step from aluminium and if it doesn't miss the step then it may stall the router or worse bend the machine .... but ok for balsa wood i guess
but 3" per rev at a slow 300rpm = 900 ipm what do you want from it ???
so some gearing would be needed i guess

( based on the fact that with a stepper having a 3/16" shaft(opps 3/8") ,and having a 1" dia pinion would give 3.1415" per rev so also giving odd math or a 0.954929658" dia pinion would be needed to correct it )

Dave

Microstepping.... and as small of a pinion gear as possible. And gearing if needed.

Carl

keep up the good work....

Hello Everybody

This is my first post, coming from Western Australia
Here are some pics of a CNC router that I designed and built.
I think it fits the description of the kind of things you guys are talking about here.
I learned heaps from building it, and look forward to building my next.
Since these pics were taken it now has a beautiful porter-cable spindle (you people in America have it lucky with fixed base routers to use on CNC machines - there are none here)

Its 2' x 4' (cutting).
All made from steel and ali tube and angle.
Does 5mm passes in jarrah (very hard west aussie native timber) at 1200mm / min with no problems, although i hope that increases when I upgrade the steppers (much needed).
Skate bearings throughout. ACME lead screw. No expensive precision parts

I am in the tweeking and testing phase at the moment, and trying to find the time to actually build some cool things with it.

Cheers!

Hi Tim

great work...... thanks for the pics

Microstepping.... and as small of a pinion gear as possible. And gearing if needed.

Use microstepping for smoother running motors, but don't count on it increasing resolution. http://www.machinedesign.com/ASP/viewSelectedArticle.asp?strArticleId=56361&strSite=MDSite

Timothytitus88,

Great looking machine. Send us pictures when you cut some projects. Do not forget to start a thread in the project log when you begin building your next machine.

Jason

Carl,

First: I like the layout of the machine, axis etc..

I saw your bearing arrangement already a while ago and find it a good concept, the bearings are used at their normal load unlike the 90° mount, heavily loaded and riding on a pipe or round bar.

But one thing immediatly popped up:
How are you drilling the 6 holes in one single piece of angle so that everything lines up, no play and correct preload of the six bearings?
Every attempt I made was just not good enough.
Or are you using excentric stuff, oversized holes... ?

Luc.

Lucus- Lesson learned for drilling holes that need to line up properly- use a jig. I use a simple jig made of plywood that I clamp to my drill press.
Also, as for the dual motors on the x-axis, I was thinking along the lines of the shopbot design. It looks like they just drive the machine directly off the motor, with no gearing. (Other than the rack and pinion) Is that possible? Or would I have to go with some sort of gearbox? I was thinking that the two motor design would eliminate any axis twisting, and really take alot of stress off off the motors? Wouldn't the torque of the motors on the x-axis be improved if two motors were used? Just throwing things out there! -Carl

Sorry, but I still don't see how you can drill with a 0.1mm precision even with a jig, because approx. 0.1mm is what I think is needed to end up with a rigid bearing arrangment.
It's probably just me who doesn't understand, too little mechanical knowledge.

I don't know the details of the shopbot design but have seen several designs using 2 motors, main advantage is no twist and easier to implement than a 2 point drive using one motor and a belt.
But if one motor looses steps, driver failure, something blocks one side of the chassis etc... this could result in a wrecked chassis.

Direct drive will work but you have to consider precision, a pinion with 10mm OD will result in a travel of 31.4 mm/turn, at 200 steps/turn = 0.157mm/step. An OD of 15 mm results in 0.2355mm.
Halfstep would cut this in half, microstepping would theoretically further improve precision but it looks like that is not the case in practice.
Speed is another issue, driving the steppers at +-250RPM results in 7-8000 mm/min (+300IPM)
So it will depend on your requirements and pinion size if gearing is required.

well quiet here for a while ,

seem to be stuck waiting for bits to turn up here , but getting close to compleation of my cnc , did a compleate redesign of it , its got phisicaly bigger , had to build a sand for it as its to heavy to lift now ,
i added a lot of adjustment points so it can be aligned easy without having to grind off and reweld bits
anyway pic attached
the cutting aria is 650mm * 350mm * 150mm ( 25.5" * 13.5" * 6" approx) so a bit smaller than what you guys are planning

Dave

well finished the main work on it , now trying to debug a stepper driver problem
(works fine driving 1 axis at once but fails to drive 2 at the same time ) think is a power supply problem
then need to strip it down finish of the edges and paint it then rebuild it

but has to be better than my first attempts :)

whats left to do on it , well the bed wants sorting , need a coolant tray and to sort out the coolant pump etc so i can do aluminium , and some welding of brackets for things to mount on the stand , alignment is easy takes a few hrs to adjust and level the whole machine

next thing will be to upgrade the m10 threaded bar that i used for the leadscrews with some proper leadscrews

anyway
hows the other design comming along there seems to be no updates recently , has it stopped dew to drilling accuracy problems or is work still being done on it ??

Dave

Sure has gotten quiet here. What happened?

Mike...

I have tried a similar right angle design a while ago and it never worked. I found out after spending money on Aluminum angles and cam followers that the angle in fact is not at 90 deg and the thickness of the angle is not the same over the length. Leasson leaned.
Any luck with this approach using better angle?

Whilst I agree most fervently about the need for larger motors, I'm not sure I agree with your comments about the driver; I'm not familiar with the stepperworld offerings but their website's photos of the motors shows a current requirement of only 1.8 Amps. Now a more powerful motor in the same frame-size is simply longer and does not necessarily draw more current. Beware that the low-current, high-torque jobbies are NOT what you need - they are intended for low-speed only.
Since the discussion seems to be mainly aimed at routers, I will repeat my remarks in another thread: with a router turning at 25-30,000 RPM, you really need to scurry along so the cutter is cutting and not merely rubbing on the work. To some degree, the wood chips will carry away heat from the cutter. The cutter's life will reduce dramatically if it rubs and heats-up. I know 'cos I am there! My max speed is only 300 mm per min (due to crap motors) and the cuts show signs of rubbing/burning.
Geoff

Hello All,

I just recently got into CNC routing and have little knowlage about it. However I am currently designing and gathering materials to build my own machine. I thought I would post my two cents since it seems you have slowed down. My design may not be large enough to fit into the midrange but I dont since it isnt hardware store I dont know. Being an engineering student it hurts my pride to build one from parts at a hardware store when McMaster sells everything you need almost. I am planning to use 80/20 1" by 1" to build my frame and use acme lead screws and 1/2 inch steel rod as guides. I will later be able to upgrade to precision lead screws or even ball screws someday. Hopefully I will be able to cut things out for people I know and they will throw a few dollars my way to pay for improvements. Steppers motors and a Black and Decker 1 Horsepower, 5amp, 30,000rpm router. Hopefully I am stealing the router from my father, and if im lucky I will get the 80/20 free since im part of a student organization. I will post some design blueprints later this week, and would love for you all to critique it. I am curious if a 1hp router will be able to cut aluminum or not? Anyone know. Also what size torque for the steppes would be good so I can start watching e-bay? 150 ounce inches?

Joshua Updyke

Hello All,

Iand a Black and Decker 1 Horsepower, 5amp, 30,000rpm router. Hopefully I am stealing the router from my father, and if im lucky I will get the 80/20 free since im part of a student organization. I will post some design blueprints later this week, and would love for you all to critique it. I am curious if a 1hp router will be able to cut aluminum or not? Anyone know. Also what size torque for the steppes would be good so I can start watching e-bay? 150 ounce inches?

Joshua Updyke

Hello Joshua,
You should start a new thread for your build.
Yes you can cut aluminium with a router.
I hope you are talking about cutting with your cnc machine. Wouldn't cut aluminium with hand held router.
You will have problems. They mainly relate to the aluminium melting as you cut. Most of the problems are due to not being able to clear the chips fast enough. Spiral router bits help. Low feed rate (about 4-6 inches/minute). I only cut 0.5mm per pass. Some say crc helps but I find continious stream of compressed air better.
Lol
Paul

Hello all, I'm de-lurking after reading both this thread and the hardware store cnc thread start to finish in the last 2 days. Let me start by saying THANK YOU to everyone who has posted here. It was exciting to read what you have done so far, and your hopes for where you were headed.

I was REALLY hoping that either of these 2 projects would have resulted in a "standard" design, based on best practices. I'm finally ready to start my own project, and was hoping for some distilled down, tested designs. That way I could get busy making chips fly, instead of re-inventing the wheel. I decided to post in this thread because this is more the type of machine I'd like to build. It's ok to limit oneself to hardware store items, but it seems kind of artificial, especially when so many better items are available from other stores and the web. (The disagreement about whether to allow square steel tube was the killer for me, it's readily available at most home centers, and every city in the US has somewhere you can buy steel. Worst case it's available mail order.)

There are so many great projects in the worklogs, and so many great ideas in this and the hardware cnc thread, but sometimes the choices are overwhelming. And some of the gaps are just mind-blowing. Like WHY to choose steppers over servos, WHAT actually goes between the CAD drawing, (the G-code) and the drivers, to actually make the machine DO things. Not to mention why choose different methods to drive the axis' like direct coupling, reducing gear boxes, threaded rods, rack and pinion, belts and pulleys...

I'm not suggesting this is the right place for a primer on how and why, but I would think it's the right place for some discussion about approach and choices when designing a "reference" system.

I have fairly sophisticated building ability, and access to a well equiped workshop, although no real machine tools like mills or lathes. I feel confident that I could execute any design presented here. And I can read the worklogs and borrow this good idea from here and that one from there, but the whole point of these threads seems to be to learn from others experiences and distill that knowledge down into what business calls "best practices." To that end, we would need to avoid what I think happened in the hardware cnc thread, people got bogged down in detail, and lost sight of the whole. Would it not be better (and reinvigorating to the thread) to identify the "big chunks" and work in parallel on them instead of working in tiny detail, each item in series?

For example, every machine needs these "chunks" or modules:

supporting structure/ frame
work-holding table (x axis?)
spindle/ router holding structure (y and z axis?)

Then look at choices- moving table or moving gantry? what support for the moving parts, shopbot style? rails? tubing? (square? round?) angle? Purchase or make?
What drive mechanics? threads, pulleys, rack? Linear induction motors?
What drive electronics? What are good choices for the guy who doesn't want to learn electronics and build his own possibly dangerous power supplies/ controllers.
What type of material to cut and what does that require in terms of hold downs, table structure, chip removal, cooling lube? How does that determine the structure of the other parts?

then look at the pieces:

support frame, made of what? how ridgid? how big?

work holding, made of what? move table or gantry?

etc.

Then apply the whole groups ingenuity to solve the problems out of commonly available materials, using simple techniques, with the goal being not the worlds sweetest homebuilt CNC router, able to hold .00001 of an inch over 10 ft of travel, perfect and innovative in every way, and oh yeah only costs beer money, but to provide a CNC that can hold real world tolerances, be built by a reasonably handy person, without esoteric materials, tools, or skills, with the goal of actually finishing the machine and cutting stuff!

So, is there any interest in covering some of this ground again, and trying to restart this project? It's possible there isn't really a need for this sort of "reference design." Maybe the people who are drawn to build their own machine tools are also the kind who need to do everything "their own way." But even then, I think there would be great value in having a starting point for basing your own design and custom details on. A design that is "good enough" for 90% of people, that uses proven techniques and materials.

I'd like to hear your thoughts on that possibility too.

With respect,

zuk

izzlestar- I really like your guide trucks and the use of angle iron. I know though, that all the steel angle I get has mill scale on it, and so isn't particularly smooth. How well do your bearings run on the surface? Do you get much or any tool chatter as the gantry moves up and down slightly when the wheels roll over the imperfections?

The other choice would be aluminum angle which in a normal "mill" finish is very smooth. I saw some discussion that aluminum would quickly wear. Does anyone have any direct experience with this? Do we know what real pressures an average gantry would exert? Would bigger or more bearings solve the wear problem?


achiestdragon - - I love your use of Unistrut. I have used it to build many structures to mount high end projectors and optics. It is versatile, cheap, and available at most home centers in the US. Further it is stiff and has many different bolt together options. It is a great alternative to welding. Most importantly for this forum though is its stiffness. It is much stiffer than 8020 aluminum extrusion. This means less deflection, and a more rigid machine. Granted that the dimensional tolerances are not as tight as 8020, but the low cost, easy availability and stiffness far out weigh any downside. AND your technique for mounting your guide rails is brilliant in its simplicity. I can't believe that no-one commented on it either here or on the Hardware CNC thread. (Others, if you haven't already, take a real close look at this. Even if you don't like unistrut the same principal would work with aluminum U channel, or even 2 angle irons back to back and slightly apart.) I think this is a real, viable way to use CR rod, or drill rod, or ground rod, or even pipe as the guide track, without machining complex mounting hardware.

Anyway, food for though, and I need to get to sleep. Hope to see soem comments soon,

best,

zuk

not been in a position to do mutch with the machine at present
i split with my ex and have moved since then , still have to get the machine over here
and hope it fits in its new home
going to be spring/summer this comming year before i get around to really have a chance to use it and finish it off , i really need it to machine out aluminium sheet thats the main reason for requireing the extra strenth , so going to need a coolant system and tray for it
unistrut is a good material to work with , its makes for a strong frame and allows for easy assembly , the final design i did is welded together but and posed a number of other problems in allowing for it to be aligned

its one thing to undertake welding if you have suitable jigs to allign the parts but if out then it can make the machine unusable , i opted to make all the axis adjustable that
allthough it may take longer to initialy allign the machine it can be done without rebuilding
using unistrut in the right way and allowing for adjustments to each axis should be possible making a machine that would handle quite high loads like ply or some hard woods , and not suffer from the seasonal veriations in the size of the wood used on the designs being discused at the time
guess that idea would need a set of plans to make one easy to reproduce using unistrut
the other thing i managed was all i had to build my machine was hand tools and hand drill and a mig welder , i did not have access to a full workshop to acuratly mesure and cut out ply like the other design was going
i think this is because most are experianced in wood work and shy away from using other materials , but for me i would need a cnc to mange to cutout the wood acuratly enough in the first place

although the machines is heavy about 85kg thats why i had to build a stand with casters for it

http://www.whipy.demon.co.uk//cnck6b.jpg

bad point ,well looking for a 4mm milling cutter with a 1/4" shank to fit the router is a pita here in the uk , think i may get a couple of collets made for it
at least the router mounting lets me replace the bosh router with a bosh drill

i did make this using it
http://www.whipy.demon.co.uk/robot4.jpg
although i hate working with mdf but it proved that the machine works

dave

Impressive. You left the machine with the ex !!! Very trusting I must say. :)

Jason

So are the tracks for the router?:rolleyes:

OK a bit small for that. Maybe you could mount a flame thrower on it and chase RC cars. That could be fun. (flame2)

But seriously what are they for?

Paul

Hello everyone:
I have been reading and following the CNC zone for almost a year now, and I am ready to get started with a mid range build. I want to try to document the build and I am looking for ANY constructive imput along the way. I started another thread here www.cnczone.com/forums/showthread.php?t=27181.

I would like to move either to this thread or start one of my own if that would be more appropreit.
Let me know what you think of the preliminary drawings, and you are welcome to chime in as I go along.

Regards,
Bob C.

I spotted this which led me to research which led me here. Any how check this out: http://www.grabercars.com/content/view/67/2/
It's a 3mx3mx2m router table, or at least the beginning of one. He's got solidworks files there too. Would this be considered mid range?

Hi friends,
I am intrested to buy or build a cnc router for engraving light metals like aluminium and its alloys.
if any one can guide me? my mail id a_gsan@yahoo.co.in

If I missed this in another post, I am sorry. If not, wow is this an OLD idea.

Back in the 1940s and 1950s J V Romig (I think) put together a bunch of plans for Popular Mechanics which used concrete for working parts of metalworking machines. More recently, people who are building milling machines out of cheap drill presses have been filling the columns with sand/cement mixes for two reasons: 1) sand/cement is massive, it limits resonance and 2) sand/cement is rigid, it limits deflection.

If the rails were thinish steel conduit filled with sand/cement mix, might this be a reasonable way to to make rigid, non-resonant structures without great cost?

Has anyone considered making the frame from tubing/pipe/dom amd Keeklamp pieces or equivalent? (see http://www.keeklamp.com/us/)

Advantage: No welding, no drilling, just a pipe cutter and a hex key, may be cheaper than the tooling.

Disadvantage: limited to 90 degrees for rigid connections, expensive.

Thought (mentioned elsewhere), fill the pipe with sand/cement mix for rigidity and dampening.

Has anyone considered making the frame from tubing/pipe/dom amd Keeklamp pieces or equivalent? (see http://www.keeklamp.com/us/)

Advantage: No welding, no drilling, just a pipe cutter and a hex key, may be cheaper than the tooling.

Disadvantage: limited to 90 degrees for rigid connections, expensive.

Thought (mentioned elsewhere), fill the pipe with sand/cement mix for rigidity and dampening.

Wouldn't that be more towards the entry level size?
For intermediate I was thinking something along the lines of salvaged shop track. the smaller, factory railroad rail looking stuff that used to be used for overhead track.


I have a couple of pieces salvaged from a previous job, factory still running since the 30's

Sir David144:
It seems you have not considered the deflection of the rails either initially, or when a load {the '\"Z" ,"Y" axis'} moving along the "X" axis.
ALL pipe will deflect a given amount based on length and wall thickness when suspended between two points. It is a law of gravity.
And trying to use your idea would severly limit the lengths of any of the axis'.

Read through some of the DIY builds here will give you many ideas, as well as forwarn you of potential pitfalls.

Regards,
Bob C.

Sir David144:
It seems you have not considered the deflection of the rails either initially, or when a load {the '\"Z" ,"Y" axis'} moving along the "X" axis.
ALL pipe will deflect a given amount based on length and wall thickness when suspended between two points. It is a law of gravity.
And trying to use your idea would severly limit the lengths of any of the axis'.

Read through some of the DIY builds here will give you many ideas, as well as forwarn you of potential pitfalls.

Regards,
Bob C.

Thanks for the thoughts, Bob. My issue was not deflection, but vibration. Yes, all pipe deflects (it's a law!), but that can be compensated for with predeflected pipe <grin>.

Steel pipe and rod tends to "ring" when excited by an impules. The ringing tends to cause wiggles in lines at certain speeds. The damping effect will reduce the ringing, positional errors can be compensated for in software if they are repeatable.

Just as a thought, would a hunk of threaded rod to a plate and a support in tension (during fill) and between two plates (during curing and operation) so the rod is in tension and the pipe is in compression improve the structural properties? Also concrete/cement-sand mixes tend to be VERY stiff in compression which would (I believe) reduce deflection.

Dave 8{)</grin>

Pre-stressing is usually to allow a beam to lay straight when suspended between end points. With a gantry the load is shifting along the beam so pre stressing will not have much benifit. You need to reduce the flexing of the beam as much as possible by increasing the strenght in the direction of the gravitational force. This can be improved by width of beam but this has weight problems. To reduce the weight you can use tortion box design or composite make up. Concrete in tubing is a composite which uses the strength of concrete together with the light weight (when compared with steel) bound by the steel tubing which will prevent the concrete cracking due to point loading.
Hope this helps. There are some engineers here that could proberbly explain it better.
Paul

I have been following this thread for a while now. Most of the talk has been about steel aluminum or mdf. How about good quality baltic birch plywood? or a machine made with mulitiple materials? For the Axis ways what about ground steel shafting? I know you can buy lengths at metal supermarket. These materials while not cheap or hardware store stuff are not crazy expensive either. Both materials can be worked with hand and basic power tools. Baltic birch plywood could also be machined on the hardware store CNC machine. I have seen very good stationary wood working tools made from birch plywood. Plywood will damp some of the noise caused by the router and the steel shafting is less likely to deflect under load also it provides a very good surface for the bearings to travel on.

Gentlemen,

I’m new to CNCzone. I’ve read through both this thread and the Hardware Design thread. Very interesting. First a bit about my background so everybody understands that I’m not just talking off the top of my head. Machine shop was my major back in high school. After high school I went to work for a machine tool company that produced gear cutting machines. There I was a two year apprentice and got to work on every kind of machine in the machine shop. Then actually worked on the machines themselves to produce master parts, plus customer training. Then I worked a very long stint on the assembly floor bringing the machines to life. Ran machines from full manual operation to 6 axis CNC machines. So after 30 years I’m retired and now have time to spend on my hobbies.

So with that said I’d like to offer my 2cents. I don’t believe you can design a machine without first knowing what it’s supposed to machine. I see no mention of what this router is supposed to cut. Is it, wood, Styrofoam, machineable wax, aluminum, brass, steel, etc. Once that’s decided then you can figure out what materials and electronic equipment you need to fulfill the job.

Obviously the harder the material machined and the faster you want the machine to cut the more you will need a rigid machine. If your just going to make Styrofoam parts rigidity and accuracy, plus a faster feed rate, does not need to be that great. If you want to make parts out of aluminum or brass for say a model airplane, model train or steam engine then you need more precision and to get that precision you will need rigidity. So it depends on what you want to do with your cnc router that will determine the materials used.

Some were in the near future I hope to build a router to make parts for my model railroad, live steam, and RC airboat hobbies.

Regards,
Bernd

Guys and Gals, what happened all activity on this thread has stopped, did I miss the final design direction?

Paul

some ideas:
1.
forego traditional bearings - use polished steel on steel or steel-teflon-steel sandwich. All the serious xy tables I've seen seem to have large steel on steel areas.

2.
use carbon fiber over stout wood , instead of metal, for structural parts. cost comes out comparable and strength if done right may be better

any old timers have some feedback?