CNC router build to machine wood and aluminium (1mX1mX0.4m)

[Tony_Stark]

I got it now when you referred to car wheelbase and track example.

I need to have more cars on each rail. Your point about cars being square makes it clear. That would be one big advantage if I switch to moving bed router/mill design. But unfortunately, Based on the current design I purchased the ball screws and drives already. They are on the way. So moving to 'moving bed' design will render them unused. Moreover I don't have that much space here where I live.

I can place order for 6 more cars and modify the design. As I have no easy access to cutting a shape in aluminium plates, so I decided to use a rectangular plate and chop of the end to use as angled vertical column. Now if I incorporate one more rail, the base of the column will get bigger. I need to find a way to cut aluminium plate to to design.

But this is very helpful. Making modification in CAD is easy rather then doing a mistake that costs more in real.

BTW, out of curiosity your location "dum dum" is of Kolkatta?

[peteeng]

Hi Rupesh - No I'm not in India I live in Dum Dum NSW Australia. I have tried to change that entry but the records in this site don't update for some reason. A jig saw and a file is good to start with on the aluminium cutting front. Also angle grinders are good these days with an aluminium specific blade. Use a "fence" for straight lines. As the outline is not a critical surface in your design. One fellow here "Gully" makes plywood parts for trial before making the metal parts, perhaps you can do that.

A very very strong recommendation is to not buy anything until you have sorted it in CAD maybe next machine... Peter

[Tony_Stark]

Not going to buy anything until my design solidifies. I will buy Angle grinder thou. It is cheaper then jig saw.

I have modified the design. Added cars and changed the vertical column to increase height and house 2 cars. But if you see the Z axis design here. Having 4 cars (2 on each rails) will require very long Z axis to get good travel. Isn't it? or am I missing anything here?

[peteeng]

Hi Rupesh - Yes it means the rail will be long but well supported. Your requirement to cut aluminium is the tough bit. Look at other machines and you will see their Z is quite a bit chunkier then yours. You are making some decisions based on cost vs performance. The Z axis is what most people under size. This is because you start at the bench and work towards the Z. You run out of room. So you should design your Z first to do the intended job then work outward. This results in a bigger machine then you expect but that's how you get the best result. Peter

also use a fine pitch screw on Z so it has lots of plunging force. Plunging into aluminum needs it. If you have a drill press use a kitchen scale to measure its force to give you an idea. Don't drill through the scales

[peteeng]

Keep your column cuts straighter, easier to do and will be stiffer. Peter

https://maxmali.com/ripper-the-different-cnc/ some side webs on the column will help, look at this blog for idaes...

[peteeng]

Hi Rupesh - Just a thought. Since $$$ and access to machinery is short consider a plywood machine. Easy to make and modify in a garage. Here's a link to one that even cuts steel. Worth a read. A timber machine has so many benefits. Extremely damp dynamics, in your size machine very easy to make parts for it and it would be able to make your next machine.... https://www.cnczone.com/forums/cnc-w...h-frame-4.html I keep coming back to a plywood (or MDF) augmented with sheet aluminium. Ticks all the boxes. Peter

[Tony_Stark]

Going through the thread.

I thought plywood/MDF won't give that much rigidity to mill aluminium. But this is a good point, make a router this way and mill your component for the next solid build. I have wood/ply shop just 300 meter from where I live and a aluminium shop 8 km.

so I have easy access to lots of wood to carve from. He he.

I have access to drill press, lathe and dremel to count in my home workshop plus some experience of metals.

A metal one will do the job I intend to (benefit of rigidity).

peter can you look at the first page of this thread. I need a second thought on the power supply calculations I made.

[peteeng]

Hi Rupesh - Here's a short note I wrote about materials a while ago. For PS use highest volts you can. You don't need to go with the total amps, from memory your motors are 4A. So 4x4=16A max. Some say 0.6x max some say more. But if you are undercurrented (if that's a word) its OK. All motors clearly do not operate at full current at the same time. Also some power is gained from back EMF in the system as one motor slows down to feed the one powering up. I have run 12V, 24V and 48V systems. The 48V is the best and I would go higher next time. The 24V works well for lightly loaded machines and 12V don't even think about it. I built a mobile system on 12V using a car battery and it failed to pull the skin off a custard.

Voltage gives you speed, current gives you torque. The quality of your drivers gets you through the mid band resonance and the best drivers can run steppers very fast (but no torque) Your Y axis will have two motors so they will run under cooked, so say 4A for both so a 12A total I think you mentioned a 10A PS this will be fine....Peter

Re plywood - I think its a great material. Seal it well with epoxy or paint and it will do everything metals can do even better as its a very damp material. You can shape it how you want vs being forced into std sizes. make solid sections not hollow so shear stiffness is max and dampness is max.....Plywood is an ex aerospace material. It was developed to make planes in WW2 and timber is a composite itself. Just need to understand and exploit its properties just like any other material.

[Tony_Stark]

That PDF was a nice read sandwiching the plywood in between aluminium metal sheet. Leave cost apart, if you make a router out of ply and then laminate it by carbon fiber. You have a good rigid structure. Don't know how much carbon fiber would flex under load but a ply glued under composite may be very strong. Just thinking out loud.

BTW I will stick with 48Volt 10 amp PSU.

I have made many changes to the design, recalculated the gantry length and position of router and have accordingly modified the column. It is much simpler now to cut using angle grinder. Also I have replaced the Y axis base plate with aluminium solid plates/rectangle. earlier it was profile but I am getting it very costly and availability is limited too. One thing comes in mind is about its flatness. The profile extrusion can be considered very flat as compared to the aluminium plates. I have a small piece of 150 by 150 aluminium plate and it looks very flat to me.

The changes are made keeping the cost in mind and ease of access to material. Extrusion/profile are limited to cross member and bed only now. Will add pic to the post.

footprint
Y 1180
X 720
Z 1000

work area
Y 880
X 480
Z 185

[mactec54]

That PDF was a nice read sandwiching the plywood in between aluminium metal sheet. Leave cost apart, if you make a router out of ply and then laminate it by carbon fiber. You have a good rigid structure. Don't know how much carbon fiber would flex under load but a ply glued under composite may be very strong. Just thinking out loud.

BTW I will stick with 48Volt 10 amp PSU.

I have made many changes to the design, recalculated the gantry length and position of router and have accordingly modified the column. It is much simpler now to cut using angle grinder. Also I have replaced the Y axis base plate with aluminium solid plates/rectangle. earlier it was profile but I am getting it very costly and availability is limited too. One thing comes in mind is about its flatness. The profile extrusion can be considered very flat as compared to the aluminium plates. I have a small piece of 150 by 150 aluminium plate and it looks very flat to me.

The changes are made keeping the cost in mind and ease of access to material. Extrusion/profile are limited to cross member and bed only now. Will add pic to the post.

footprint
Y 1180
X 720
Z 1000

work area
Y 880
X 480
Z 185

Starting to look like a good simple design, the Z axis will need some side plates to stiffen it up, it' would be ok to try it like it is but the Z axis plate will flex depending on how heavy your cuts get, and how thick that plate is

[peteeng]

Hi Rupesh - Design is resolving nicely. The Z axis is the heart of the machine. All my machines I have had to upgrade the Z axis in terms of stiffness. Analysis and optimism is great but reality bits.

Mactec mentions webs and these are needed for the Z and for the columns. Carbon fibre is a difficult material to get stiffness out of unless you really know what you are doing. The fibre itself is same stiffness as steel but you can only get 50-55% by volume into a laminate so you are already down to 100GPa in a UD ply, then you need off axis for internal stability and cross ply strength/stiffness so a quadaxial laminate is at 50GPa. An optimized gantry could be at 80GPa but will have poor shear stiffness (torsional stiffness) compared to Al. Then there is cost at over $100 per kg for std modulus CF you then have to use expensive epoxy to convert to laminate. You buy aluminium sheet for $8AUD/kg and get 70GPa and a very high shear stiffness from the shop. Al is the choice I believe for flat parts.

Your Z axis will need a little more Z (start by making the columns a little higher) and you need to move your router down in the clamp so it sticks out further. Z gets consumed by the waste board, tools and fixtures such as vices. Review what "air heights" and cutting heights you really need. Z disappears real fast when setting up some jobs as there is no knee to move or mill column to adjust. Even though you may have 185mm of Z I find it is in the wrong spot. So check waste boards etc and figure out tooling lengths and check the action is where it should be. Keep at it. Peter

your columns would be a good candidate for al/ply/al laminate. How thick are they now? I also see your gantry is a Channel section. This has poor torsional stiffness and you are going to need lots of this for the job, plus how do you connect the channel to the columns?

[Tony_Stark]

Starting to look like a good simple design, the Z axis will need some side plates to stiffen it up, it' would be ok to try it like it is but the Z axis plate will flex depending on how heavy your cuts get, and how thick that plate is

By side plates do you mean plates on the sides of the base plate of router mount? I can add that. Also the drive for X axis will be housed behind in C section. So some plate from bottom of Z axis will go behind and connect with ball screw nut. That will add to stiffness.

[Tony_Stark]

Your Z axis will need a little more Z (start by making the columns a little higher) and you need to move your router down in the clamp so it sticks out further. Z gets consumed by the waste board, tools and fixtures such as vices. Review what "air heights" and cutting heights you really need. Z disappears real fast when setting up some jobs as there is no knee to move or mill column to adjust. Even though you may have 185mm of Z I find it is in the wrong spot. So check waste boards etc and figure out tooling lengths and check the action is where it should be. Keep at it. Peter

your columns would be a good candidate for al/ply/al laminate. How thick are they now? I also see your gantry is a Channel section. This has poor torsional stiffness and you are going to need lots of this for the job, plus how do you connect the channel to the columns?

Yes, you pointed it right I need to increase the column length and bring Z axis down. I will do that. The 185mm travel is max I can get. It is a compromise at the cost level. I don't need X to be long so I can purchase a 1 meter ball screw and rails for X and cut and use some length of it to make Z axis. So essentially if I increase Z level, the X axis will shrink further.

For milling Al I wont be using waste board above the bed profile. The vice I have is 90mm long so if I mount it on bed profile I will have some 40-50 mm travel left (considering 40-50 mm tool bit in router. This should do the job I intend to do.

At current configuration, the router without the tool bit touches the AL bed. I can increase the height of column by say 40-50 mm(taking tool bit into account) and also further 50 mm to bring the Z axis mount plate down.

I have one more vice which is 140 mm long and heavy. Increasing column height looks right then.

The C channel is just 640mm long and will be bolted heavily with the column throughout the C. The C section would house the ball screw drive connected to Z axis underneath.Earlier I thought of 45X120 profile but that ups the cost and availability is an issue too. Plus aluminium is around $6AUD/Kg in India. So buying plates works.

[peteeng]

Hi Rupesh - You shouldn't rely on using the drive to gain stiffness. The drive should be nearly independent of primary load paths (except its pushing and pulling) if the screw is pushed sideways you will wear the nut prematurely. By webs we mean the Z axis (tool plate) should be a "C" or channel section. A tool plate that is flat has to be very thick and heavy to be stiff in bending. Its stiff sideways but not in the Y direction... Re height- its wasted height if the router collet can touch the bed. This is only done if the machine has an apron or "wells" in the bed. fixtures and tools puts the spindle well above the bed so your bottom 75-100mm may never be used (50mm for a tool and 25+mm for material or waste board) What you can do in your case with the columns is provide extra length and holes for going up or down. As you use it you can then figure out the min height after a bit of experience. cheers Peter

[mactec54]

By side plates do you mean plates on the sides of the base plate of router mount? I can add that. Also the drive for X axis will be housed behind in C section. So some plate from bottom of Z axis will go behind and connect with ball screw nut. That will add to stiffness.

Yes the router mounting plate, that is where the flex will be with this design

[Tony_Stark]

Thanks Mactec. Understood. Will go for C section/channel.

Peter thanks for the heads-up. I now understand, I will lift the height further and having multiple holes can give me flexibility later. Now as I am getting near to design completion I am now thinking of other small parts. What type of coupling should I use to couple the motor to the ball screw. I can see there are 2 types available in the market.

i forgot to answer the column thickness, its 15mm.

One which has single aluminium cylinder with slots/splines cut across and the other one looks like a two part coupling. Both are called flexible coupling. The single body aluminium one is cheaper than the 2-part types.

Also, what about limit switches. Is the switch shown here is ok to use. 2 on X and Y and 1 on Z? I read people using hall effect limit switch. I could not find any online. Some use proximity sensor, costly option.

Today I received ball screws, nuts, rails and guides plus end supports. The ball screw is unmachined one. I need to machine the ends carefully. I checked the data sheet but I didn't find the nut dimensions of the BK15 coupling end support. I need to make a thread on the ball screw at coupling end and I was wondering what thread and pitch it would be. I will be making it through thread die as I am not good with lathe thread cutting.

I checked the guides on the rails. They are smooth,no play. Little draggy so I guess I need to grease them well. I haven't bought screw nut mount(housing), I will be making those. That should not be big deal. Ready made ones are pushing the cost higher.

[mactec54]

Thanks Mactec. Understood. Will go for C section/channel.

Peter thanks for the heads-up. I now understand, I will lift the height further and having multiple holes can give me flexibility later. Now as I am getting near to design completion I am now thinking of other small parts. What type of coupling should I use to couple the motor to the ball screw. I can see there are 2 types available in the market.

i forgot to answer the column thickness, its 15mm.

One which has single aluminium cylinder with slots/splines cut across and the other one looks like a two part coupling. Both are called flexible coupling. The single body aluminium one is cheaper than the 2-part types.

Also, what about limit switches. Is the switch shown here is ok to use. 2 on X and Y and 1 on Z? I read people using hall effect limit switch. I could not find any online. Some use proximity sensor, costly option.

Today I received ball screws, nuts, rails and guides plus end supports. The ball screw is unmachined one. I need to machine the ends carefully. I checked the data sheet but I didn't find the nut dimensions of the BK15 coupling end support. I need to make a thread on the ball screw at coupling end and I was wondering what thread and pitch it would be. I will be making it through thread die as I am not good with lathe thread cutting.

I checked the guides on the rails. They are smooth,no play. Little draggy so I guess I need to grease them well. I haven't bought screw nut mount(housing), I will be making those. That should not be big deal. Ready made ones are pushing the cost higher.

Use Proximity switches less problems than switches, the all aluminum couplings are no good there are some in stainless that are better, diaphragm couplings are the best

[Tony_Stark]

I can get that green box distance sensor here. Should I get a NPN or PNP? and normally open or NC?

That diaphragm coupling I could not find.

[peteeng]

Hi Rupesh - Your design is solidifying but not yet close. In my profession we say the design is in stages of rough, detailed, polished, pre-production, production. Maybe your still in rough in many areas How will the gantry channel "bolt" to the columns? Peter

[mactec54]

I can get that green box distance sensor here. Should I get a NPN or PNP? and normally open or NC?

That diaphragm coupling I could not find.

NPN

Try here for couplings they are every where all different types https://www.alibaba.com/diaphragm-co...suppliers.html