Great start I spelt build wrong
Well another nut joins the fray. Today I bought the steel I need to start my machine and starting this week I will start assembly. I figured I had better start a log now so that I can get the community to make sure I finish it! I am pretty good at the first 90% but always slack off near the end.
Anyway here goes.
The machine has the following specs / design features:
Gantry 3 axis plus rotary chuck on table
Configurable to become a 4 axis hot wire
3 table heights
Max working envelope 1.4m x 2.6m x 0.5m
Z drive - rotating ball nut 1:1 belt drive 16mm lead 450 oz/in stepper
X drive (across gantry) - direct driven 16mm lead ball screw 450 oz/in stepper
Y drives (2 independent) - 8:1 belt drive to stationary T5 belt each side in Omega drive config 450 oz/in steppers each side
Frame bolted steel 75mm sq tube and 150 x 75 I beam
Gantry 80mm sq 8020 aluminium extrusion (Item)
Bed / vacuum plenum - 8020 frame with 19mm forming plywood skins each side
Pneumatic counter balance on Z axis
Pneumatic raising and lowering of working bed (pinned in working config)
Epoxy grout used to level I beams prior to Y axis rails installed
Vibration mount feet on bed an fran used to rough level machine
Possibly fill frame legs with sand to increase dampening.
Current chop micro stepping drives
The design is intended to be open enough to allow the machine to be reconfigured to do jobs of varying needs ie.
in the high bed setup it is ideal for sheet work up to 150mm
Mid brings the bed mounted rotary chuck into line with the gantry for small detailed 4 axis work or thicker sheet work
Low position gives maximum working envelope and ability to spin columns up to 500mm in diameter
By being able to decouple the independent Y drives from the gantry this allows two new Z axis to be added to each Y and form a 4 axis hot wire machine with the maximum working envelope.
The design was also limited or built around existing parts that I was able to get for free from some decomissioned printing gear hear at work. the sad thing was I did not get everything and it all went to Simms metals and a crusher THK bearings, linear and rotary stages etc etc. The good news is I save enough to build one machine
So if you are looking at the design and woundering why I used big bits of billet aluminium here or that ball screw there the answer is that I had it.
So far it only really exists in CAD but hopefully I'll be able to post some real pics real soon. All comments suggestions or problems anyone sees please feel free to chime in.
Here's one idea that maybe someone can comment on:
As stated the frame is a bolted affair as I need to be able to dismantle the beast if I want to move it out of the garage and to a proper workshop if I get any work for it. Given my total lack of machining tools I intend to forgo all the nice pin arangements like on MadVac's machine and instead decided that the only critical part is the last surface the rails sit on. So heres the idea. Build the frame and level as best as possible with the vibration feet then form up the top of each of the I beams and have a connecting channel between them. Pour some very low viscosity epoxy grout into the formed area and let gravity and time to the rest. This hopefully will give me a perfectly level and coincident plane on each I beam onto which the 8020 extrusion and THK rails can sit.
BTW not all details are shown yet on the CAD drawings
Here goes nothing.... other than any spare time or cash I had :P
BTW I live on the Central Coast of NSW any one else local?
Great start I spelt build wrong
Looks like you are off to a great start... I am in to see how it all goes
Firstly its great to see another Aussie. But i dont think this is just 'another build' this machine sounds like a dream to most of us. Huge and well thought out. I really look forward to following your build? how long you estimating the build to take? Really good idea to do a timeline just to push you that little furthur with staying on task. lol.
P.S Im on the South Coast, would have been great to be close and watch your build and the finished machine in action.
Looks like it is going to be pretty good I will wait until you start sticking metal together before commenting further.
I havent put a timeline as such on it other than this year as I have been wrong too many times so far and I have a couple of jobs waiting on it so I don't want them to get over confident on a delivery date. Under promise and over deliver was always my motto as a field tech. If you promise to do nothing then everything you do is a great achievement
I checked out your profile Daniel. We head down to Jervis every year at Xmas for some camping and sailing... you live in a great spot.
Hopefully the "dream machine" doesn't turn into a nightmare. My biggest concerns at this point is whether the steppers I have will be grunty enough (not a huge drama as the drives I have can accomodate up to 8 Amps) and how well the belt drive will work. The cost for dual rack and pinions or dual ball screws at this scale made me discount them for now.
I'll see if I can't take some happy snaps of the pile of bits this week and hopefully a start at the frame.
I'm still looking for my camera but progress is being made. All the steel for the base is cut and my son is half way thru what needs welding (handy having a apprentice boiler maker in the family )
Must say the resource boom is evident when you look at the price of steel !
The "Z" on its side of the legs will be welded together to make 4 sub assemblies these are then bolted to the I beam (studs welded to the inside of the legs)
So here's a few more CAD drawings with a bit more detail showing the omega y belt drive with trhe reduction and idlers (without the belts shown).
The extended leg of the side plate on the gantry pic is what attatches it to the Y drives.
Also a closeup of the Z axis driven ball nut.
Need to find the camera so I can post real as opposed to virtual progress
Couple of pics to prove that this thing is starting to take shape outside of CAD.
First off the obligatory messy garage shot. Hopefully over the comming weeks this pile of stuff will start to resemble the drawings.The 8020 framework for the movable bed is standing up on the right.
Pic of the legs with the studs welded to the top.
The last pic shows how the Y rails are a composite construction of an 150 x 75 mm I beams for support with a 80 x 40 Al extrusion (8020 / Item ) and finally the THK bearing rail on top. They are held together by T nuts so they is some slack in mounting to allow for alignment. As stated earlier I intend to create a shim layer between the I beam and the 8020 by pouring a layer of slow setting epoxy and letting it set off hopefully to a level smooth and coplaner surface on each I beam.
like the 3 stage table height, I too was toy with the idea to, like to see more details how you plan to lift it, and your railing system for it to side up and down on. what did you to cad it up in solid edge?
I have a camera
and I couldn't resist....
Now where did I put all them bolts
BTW the real Z axis is not that long.
The design philosophy I'm working under is that it needs to be tolerance tolerant. What I mean is that as all the errors of machining in a assembly (which are quite large tolerances given my lack of machine tools / mill etc) are accumulative and either you try and reduce these to a very small amount or, (as I'm doing), accept them and allow for adjustment in the design to correct them in the critical parts. The critical parts in a 3 axis router IMO are the rails and the axial runout of the spindle.... nothing else. These need to be securely held (to maintaine tolerance) in relation to each other. Thats the theory... now lets see if it works in practice.
I'm using Solidworks.
The table will be lifted by two large air rams I'll post a more detailed pic when I get home. Basically the table has 4 Thomson ball slides mounted to it near the 4 inner legs of the frame. The rails mount on these legs and on the other side of two of them (diagonally opposed) are the air rams. This is the setup that was used in the vacuum frame in the original plate making exposer that they were "saved" from. The idea is that I will lift the table then pin stops below it then allow the table to come down to rest on these stops.
The rails are mounted on angle extrusion with adjustment slots to allow for setting them up parallel etc and will be bolted to the sides of the legs which have tapped holes in them.
I plane on using the same style of air ram as a counter balance for the Z axis.
I hope to be able to level the table out easily at each set height.
Hopefully I'll have some real pics by next week that show this stuff in better detail and "in the flesh".
I would love to get input on my Y axis drive idea as these bits cost money and want to be confident of success.
The AT5 x 25 belt will be held stationary and under tension. It also will lay in a grooved support for its entire length. The belt is lifted outr of this groove around a large smooth idler pulley on the Y drive carriage, around 180 degrees a 15 tooth pulley the laid back down on the support by a second idler. The 15 tooth pulley is driven through a 3:1 belt drive by the stepper motor.
This arrangement should mean that 1 rev of the motor will result in 25mm travel ( 1 rev of 15 tooth AT5 pulley = 75mm, 3:1 = 1 rev of motor = 25mm) devide this by 200 and I have a resolution of 0.125mm per step or 0.0625mm per half step.
I will be using micro stepping however I only consider half step as being considered as a reliable resolution figure.
Accuracy however is going to depend on a lot of factors and at this stage I think only building it will show how good or bad that will end up.
The grooved belt support has two purposes:
stop the belt getting any bounce
help with tracking
I'm hoping that this will form a rack and pinion style drive with better tooth engagement as the belt (flexible rack) wraps the toothed pulley (pinion).
Here are a couple more pics to show that progress is being made. I was able to use the mill at work to make my Z-axis plate.... AKA swiss cheese. With 4 bearings for the Z and 4 on the back for the X plus all the mounting holes for the Z axis motor and X axis ball nut it took me quite a while to get them all done. The large hole you can see is something that was pre existing in chunk of ally I'm scrounged
I am planning a fairly ambitious dust guard for the X axis ball screw which consists of a flexible sheet that is fixed to the gantry and is diverted around the ball nut by 4 rollers similar to what is used in air cylinders that have side access to the piston. The back of the flexible sheet has two rows of foam tape that are forced into the grooves of the 8020 extrusion and form a seal. Bit hard to make out in the pics but it works in CAD so how hard will it to make in real
I also did all the mounting holes for the bearing rails in the U channel Z axis.
Prep'd and undercoated the steel base and will have the last bits welded by my son this weekend so should have nice pic of it built and in its final yellow paint job soon.