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Any ideas on DIY CNC machine ?

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bianchi77

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Friends,

Do you have experience on developing a CNC machine ? Small DIY project ?
Any informations or knowledge will be very usefull and appreciated,

Cheers.
 

Do a google for mach 3 or mach 4, its a software and control system for cnc machines, from ultra simple to very complex.
It does assume you have a little knowledge.
 

dr pepper said:
Do a google for mach 3 or mach 4, its a software and control system for cnc machines, from ultra simple to very complex.
It does assume you have a little knowledge.
Click to expand...

do you have info for hardware developing ( motor, model, etc ) ?
 

I'm developing one right now. Work area roughly 35x40x15cm, made of thick plywood. Utilizing fully supported 16mm rods, linear bearing slides and 16x4 trapezoidal thread drive screws.

I'd say that for a person with electronic engineering background (as opposed to mechanical engineering) this goes pretty hard. I've designed a step motor power driver board utilizing TB6560 IC (the same one as in sh!tty chinese cnc drivers that you can buy on ebay for $40, but properly applied without unnecessary cost cutting).

I'm also developing my own power driver incorporating a BJT H-bridge and chopper current regulation.


Your options generally depend on where do you live. If you earn in either Euro or USD your in good situation. Otherwise (like me: mid-eastern Europe) in most situation shipping costs and prices of new parts are kind of prohibitive.
So the options for drive are following:
-chinese board (qualityn not controlled, f*ckups often reported) - based on TB6560
-your own TB6560AHQ board (tricky, because the ic has extremly stupid pin arrangement which makes proper routing power traces hard even on 2 layer board)
-Allegro Microsystems chip (like A3977)
-Trinamic chips (interesting set of features, but kinda hard to get and expensive)
-discrete solution utilizing discrete power stage (n-n mosfet, n-p mosfet, n-p bipolar) and some microcontroller + some 7400/4000 logic stuffs

Stepper motors generally come in 2 varieties unipolar and bipolar. While unipolar ones are easier to drive can be accomplished with low-side switched only, which is much easier than h-bridge they have typically around 40% less torque than bipolar ones. Bipolar motors need a dual H-bridge (so 8 power devices total) but have better performance. Nice thing to know is that ANY unipolar stepper can be driven by bipolar driver, but not the other way around.

For a domestic/hobby cnc machine motors with roughly 1 newton*meter of rated holdinh torque should be fine. You can get those out ouf various industrial automation machinery. People often sell those in online aution sites (at least in Poland)

If you have any questions I'dbe happy to answer
 

Wow! Will you please upload some photos when it's done? I'm really interested and would like to see how the final poducts looks.
Thanks a lot!
___________________
Adam Worth
 
Last edited by a moderator:

poorchava said:
I'm developing one right now. Work area roughly 35x40x15cm, made of thick plywood. Utilizing fully supported 16mm rods, linear bearing slides and 16x4 trapezoidal thread drive screws.

I'd say that for a person with electronic engineering background (as opposed to mechanical engineering) this goes pretty hard. I've designed a step motor power driver board utilizing TB6560 IC (the same one as in sh!tty chinese cnc drivers that you can buy on ebay for $40, but properly applied without unnecessary cost cutting).

I'm also developing my own power driver incorporating a BJT H-bridge and chopper current regulation.


Your options generally depend on where do you live. If you earn in either Euro or USD your in good situation. Otherwise (like me: mid-eastern Europe) in most situation shipping costs and prices of new parts are kind of prohibitive.
So the options for drive are following:
-chinese board (qualityn not controlled, f*ckups often reported) - based on TB6560
-your own TB6560AHQ board (tricky, because the ic has extremly stupid pin arrangement which makes proper routing power traces hard even on 2 layer board)
-Allegro Microsystems chip (like A3977)
-Trinamic chips (interesting set of features, but kinda hard to get and expensive)
-discrete solution utilizing discrete power stage (n-n mosfet, n-p mosfet, n-p bipolar) and some microcontroller + some 7400/4000 logic stuffs

Stepper motors generally come in 2 varieties unipolar and bipolar. While unipolar ones are easier to drive can be accomplished with low-side switched only, which is much easier than h-bridge they have typically around 40% less torque than bipolar ones. Bipolar motors need a dual H-bridge (so 8 power devices total) but have better performance. Nice thing to know is that ANY unipolar stepper can be driven by bipolar driver, but not the other way around.

For a domestic/hobby cnc machine motors with roughly 1 newton*meter of rated holdinh torque should be fine. You can get those out ouf various industrial automation machinery. People often sell those in online aution sites (at least in Poland)

If you have any questions I'dbe happy to answer
Click to expand...

I'm developing one already, what do you use for lead nut ?
currently with plywood...
now designing the lead screw and nut...
thanks
 

I'm developing one already, what do you use for lead nut ?
Click to expand...
I've purchased 2 brass lead nuts (38mm outer diameter, IIRC 35mm length), costed about $15 a piece. I've also ordered 3 or 4 (can't remember right now) lead nuts of the same dimensions made of tough plastic. IIRC i've paid about $20 for all pieces+shipping. The idea is to use plastic parts for alignment, for eventual screwups to happen on plastic parts, instead of more expensive brass parts.

Problem with leaqdscrews is machining. In Poland you can buy 1m of 16x4 trapezoidal threaded rod for around $6, but machining of rod ends costs upward of $30 per screw. I ended up grinding them by myself using improvised lathe-like construction (electric drill+bed made out of mdf+some needle bearings+elastic coupling made of rubber garden-type hose and a used sparkplug from my car + some hose clamps :cool: ) using angle grinder with very thick disc. I'm not happy with the results, but I think they're enough.
 

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K.
 

poorchava said:
I've purchased 2 brass lead nuts (38mm outer diameter, IIRC 35mm length), costed about $15 a piece. I've also ordered 3 or 4 (can't remember right now) lead nuts of the same dimensions made of tough plastic. IIRC i've paid about $20 for all pieces+shipping. The idea is to use plastic parts for alignment, for eventual screwups to happen on plastic parts, instead of more expensive brass parts.

Problem with leaqdscrews is machining. In Poland you can buy 1m of 16x4 trapezoidal threaded rod for around $6, but machining of rod ends costs upward of $30 per screw. I ended up grinding them by myself using improvised lathe-like construction (electric drill+bed made out of mdf+some needle bearings+elastic coupling made of rubber garden-type hose and a used sparkplug from my car + some hose clamps :cool: ) using angle grinder with very thick disc. I'm not happy with the results, but I think they're enough.
Click to expand...

do you have photo of it ?
thanks
 

Take cover! Image attack!
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Nice photos, any ideas on how to calibrate axis and home in EMC ?
 

I'm using mach 3 currently, because I've got no space for additional Linux machine and display (my workshop is in my room when i normally live and it's about 8.5 sq.meters so space is quite precious :) ). When the mill will be moved to the basement I might switch to EMC (actually got some old pc in the attic with qGHz athlon and 256meg ddr - should be enough).

As for homing I'm not using it. Im generally positioning tool with hand/eye/calipers/precise right angle etc. The mill is still under construction so mainly I'm cutting parts from 18mm waterproof plywood stock, so the homing and zero positioning of tool is not that critical. Of course this has a side effect that i have to pay extra attention when creating toolpaths not to run some axis into construction.

Also, the couplings between motors and threaded rods are made with garden hose+hose clamps. They are tight enough not to slip during operation, but will slip when you crash your axis against something/ That has happened few times before and i didn't notice any damage.
 

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