Homebrew PCB CNC machine 4 less then £100 is this possible??

[jomac]

For more in depth info on this controller, manuals, schematics setting up etc. I did a CNC conversion to an old dot matrix printer and converted it into a vinyl cutter/plotter but used the PC and electronics from my CNC milling machine to test out the mechanicals of the old printer...

http://jomac.asia/index.php/topic,140.0.html

[Techquest]

A few questions
Axis drive ?? which is best leadscrew chain or belt
X axis gantry fixed or moving along the Y

gone over the £100 target ended up buying these on ebay.co.uk Item No170572932367 instead of messing around matching up motors etc.
I can concentrate on the mechanics more

[jomac]

Youve gone for NEMA 23 motors which are quite big, i used 23's on my small milling machine and they pack quite a lot of torque, more then is needed for the average milling machine. If you had gone for the smaller size motors, NEMA 17 and got the controller card separate, this would have cost around the £60, so you will have plenty of torque in reserve

What you need to end up with, is a platform that moves forwards and backwards on a slide driven by 1 motor, this is the 'Y' axis. Then you have the actual drill moving from left to right, this is the X axis, and finally you move the drill up and down, this is the Z axis.

The picture below was taken of a very early machine i made (yes i know the screw is bent, slight miscalculation of measurements)

[jomac]

When you come to actually driving each axis, how you do it isnt important. You can use belts and pulley's and the advantage here is very little backlash in the transmission, but the cost is higher. Most people choose to go for threaded rod as its cheap and simple. If you choose to use belts, you must gear the ratio down, if you drive any of the axis on a 1 to 1 ratio, your accuracy or 'resolution' will be very low compared to threaded rod.

Dont worry about backlash in the system either, if you use the MACH 3 software, you can allow for backlash or 'slack' within the software.

On the photo above, i eventually found a much easier way to drive the Z axis using parts from the local model shop, i used square section brass tube in 2 sizes, one fitting inside the other. The main frame was made fro double sided printed circuit board from Maplins and the joints were soldered. The drill motor itself is a Proxxon 'Dremel' style with the speed control end taken off.

[Techquest]

Yes i know the NEMA 23s are a bit big for what i want to build right now will have a small footprint due to limited space but my intention is to go bigger later.

[jomac]

I fitted NEMA 23's to my Proxxon milling machine, there was enough torque to literally snap a 4mm milling tool.

The controller should come with the MACH 3 software, mine did and it was the 'full' version if you know what i mean?..

If you get stuck on anything, my direct email is [email protected]

John

[kr0ne]

Jomac, how do you calibrate the motors / movement?

I presume there is a procedure in mach3 or something but I didn't spot it when I had a quick skim over the docs and I'm having trouble getting my head around it...

[jomac]

Hi Krone,
First of all you have to enable the backlash calibration in settings for it to actually appear, here is a Youtube video on how its done. Youtube has other very good tutorials and shortcuts if you search for Mach 3 CNC.

Its also worthwhile joining the Mach 3 forum as well. When i first started out i got tremendous help from the guys there.

http://youtu.be/A27nOkTFYDY

Just shout if you are stuck..

[George EI7KO]

Come on ray....get 'er done

[kr0ne]

Ah! Perfect! Thanks...

I got one of the cheap Chinese 5-axis controllers a while back but haven't put anything together yet. No doubt I'll be back with more questions before long though.

Thanks for starting to post about this topic btw. I was aware of the DIY CNC scene previously but it was a lot harder to get started back when I last looked. The scene seems to be getting pretty massive now and very well supported but I'd kind of written it off in my head. Have been pleasantly surprised at what I have found since taking another look...

[jomac]

Fire away with the questions, i know i had plenty when i first started

What most folks learn, is actually how easy it is to make a CNC and you dont even need a fully equipped workshop to make one. I did find a lot of inspiration and idea's from many sites on the web, and what started it for me was looking at a CNC called the Mantis 9. Up to this point, i'd always thought that any CNC had to me made to precision tolerances, and i was wrong, the Mantis 9 was made from wood...

http://makeyourbot.wikidot.com/mantis9-1

The Mantis 9 is part of a bigger project run by the MIT Uni in the States, more machines and idea's can be seen here.....

http://mtm.cba.mit.edu/

And the original 'Make a CNC for less then $100' is here...

http://hackaday.com/2010/06/21/100-cnc-mill/