Re: [Nottinghack] YooCNC experience and advice

[David Hayward]

We have a 6040 on loan from a member. We found that the electronics weren't great as shipped, and David Clarke did a lot of work tracking down and eliminating problems with electrical noise. Some parts weren't even grounded properly, so I'd advise opening up the controller and checking everything. The noise caused it to lose or gain steps on all three axes, so by the time it finished a 20 minute job, X0Y0Z0 would be a few millimetres different to when it started and the milled parts accordingly messed up.

One of the other things we've done is mill a large, perfectly flat bed from a piece of wood clamped to the machine. It stays on the machine, and materials are screwed down to it for milling. Before that, I found it much harder to make sure the surface of a material was completely flat; now it's fairly easy. I've found the quality of the results depends mostly on careful setup, and the wooden bed also shows the safe area (this machine has no limit switches). It's easy to screw up by rushing.

We haven't used it to mill any PCBs, but I have seen it being used to drill one. Matt Little may be able to tell you a bit more about that.

In terms of software, the machine connected to it is running Linux CNC, and a few of us use DraftSight (free but not open source) to do CAD drawings. Conversion to G-code is the tricky part. I'm currently using CamBam (not free), and there's this python script:

http://code.google.com/p/dxf2gcode/

But it's a real pain to work with. Useful at first if you want to learn more about G code, but it takes a lot longer to prepare a job with it compared to proper CAM software.

We've not milled metal on the machine yet. Apparently it will do it, just very slowly and with shallow passes. For materials like wood and polycarbonate, I've found it fine to drop by about 1 millimetre per pass, as long as the feed rate isn't set too high.

David

On 9 August 2012 07:41, Marcus Wolschon <marcus....@gmail.com> wrote:

Hello everyone,

I'm Marcus from Chaos Computer Club Freiburg/Germany.
From your wiki I got the impression, that you got a YooCNC 6040 in your hackerspace.

My background:
I've been 3d printing on a Repman 3.0 with lots of 3.1, 3.2 and custom parts and
a Thing-o-Matic for ages. Doing CAD in Alibre 12 and not Alibre 2012 for just as long.
So I'm pretty used to the pains of working with design-flawed machines. ;)

Now I ordered myself the 6040Z-S80 with the 4th axis.
The primary purpose shall be milling wax and soft wood. Maybe the occational PCB.
Very seldomly (and slowly) small metal parts.
http://marcuswolschon.blogspot.de/2012/08/cnc-mill.html

What advise do you have on this machine? What to check for? What to replace early?
What spare parts to stock?
It looks like I should check all the cables first. Maybe replac pcb-clad, stiff ones that
move a lot with more flexible stranded wire, rubber insulated ones.
Also check all nuts, bolts and bearings to be tight and well aligned.
Check or install end-stops using the existing contacts on the controller board.
Install a good emergency-off.
Start slow. Verify everything works. (of cause)

As for software my current plan is to employ Alibre Design to export STL, then
Skeinforge to create the g-code. For PCBs the vIsolate tool that I became maintainer
of some years ago. No preference for machine control software yet.



Regards,
Marcus

[Marcus Wolschon]

On Thu, Aug 9, 2012 at 12:05 PM, David Hayward <nach...@gmail.com> wrote:

We have a 6040 on loan from a member. We found that the electronics weren't great as shipped, and David Clarke did a lot of work tracking down and eliminating problems with electrical noise. Some parts weren't even grounded properly, so I'd advise opening up the controller and checking everything. The noise caused it to lose or gain steps on all three axes, so by the time it finished a 20 minute job, X0Y0Z0 would be a few millimetres different to when it started and the milled parts accordingly messed up.

Will do that.
What should I check here besides common grounding?
Does the electronics have headers to attach limit switches?
I guess I could easily 3d print some custom mountings to attach some.
(And publish the designs on Thingiverse of cause.)
 

One of the other things we've done is mill a large, perfectly flat bed from a piece of wood clamped to the machine.

Good idea. I'll note that down for my TODO list.

 if you want to learn more about G code,

No need to. My 3d printers work via G-Code and I've hand-edited G-Code long enough. Remember, I became the maintainer of vIsolate. ;)
 

We've not milled metal on the machine yet. Apparently it will do it, just very slowly and with shallow passes. For materials like wood and polycarbonate, I've found it fine to drop by about 1 millimetre per pass, as long as the feed rate isn't set too high.

Thanks for the that info.

What feed rates did you find to work here?


Regards,
Marcus

[David Hayward]

Ah, ok. Didn't realise :)

Feed rates: I tend to work almost exclusively with polycarbonate. Unfortunately, the controller for ours has no readout for spindle speed, so there's a lot of guesswork. With a 3mm cutting bit, z-increments of 1.1mm, and the speed just over 1/3 from the bottom of the travel on the potentiometer, a feed rate of 200mm per minute gives okay results. 

I usually test materials with a gcode file of straight horizontal lines milled at different feed rates. I think the milling bit currently in it is getting a little blunt now; edges of polycarbonate parts require a little clean up where they used to need none.

David Clarke could tell you more about what he did with the electronics, I only have a cursory understanding of that.

-- 

David (H)

[Chunky]

Hi Marcus,
I've got a very similar CNC machine (but just 200 x 300mm bed) and have also used the Nottingham hackspace one a few times.
I've done a bit of PCB drilling and also PCB milling, with OK results. Check out my short blog post:
http://www.re-innovation.co.uk/joomla15/index.php?option=com_content&view=article&id=181:making-pcbs-with-a-cnc-machine&catid=48:blog&Itemid=75

Unfortuneately my router motor has recently burnt out (The brushes wear out really quickly and then sometimes the motor stalls and burns out). Hence I'm waiting on sorting out a replacement.

As David mentions, I also have problems with noise from the motor being transferred to the steppers. More details on how I fixed it are here:
http://www.re-innovation.co.uk/joomla15/index.php?option=com_content&view=article&id=107:cnc-machine&catid=48:blog&Itemid=75

Basically the machines seem pretty robust mechanically, but the electrical side of things leaves a bit to be desired.

Let us know how it goes.

Regards,

Matt

[David Clarke]

Hallo Marcus.

I have done some work on the CNC electrical system, as David Hayward
(nachimir) has said.

I will email you the details in over the weekend.

Tsch�ss.
David Clarke.

cix:Mail/NottingHack:5600