Mr Handy

I have been working in the background on setting up my own CNC for long, and now seems a good time to share about it…

Meet Mr Handy

Mister_Handy

Named after the famous utility robot from Fallout, my CNC’s purpose was to be able to process small designs on not-so-hard materials, like acrylics, wood, or even aluminium, but not steel.

But my main goal was to engrave PCB with it, to speed up prototyping without having to use the old and dirty exposing/etching techniques.

My setup

00097.MTS_snapshot_00.22_[2015.05.15_08.54.52]-1

I used the Microcarve MV3 as the fundation of my CNC. It’s a very good product, with a good and sturdy design, and above all, John from Microcarve is really a very nice guy, always available to help his customers on the dedicated forum.

I added three basic 3V/3A chinese stepper motors, along with some Gecko G251X stepper drivers, and a KRESS FME 1050 milling motor with its custom mounting block.

For the main G-Code hardware+software solution, I chose the Planet CNC usb controller and software, because:

  • it seemed a good alternative to the old looking mach3 or linuxCNC softwares,
  • the software screenshots looked good, the hardware documentation was clear
  • it was a USB connected hardware solution (why in the world in the 21st century are still CNC people using some parallel interface !?! It’s a complete mistery to me)
  • The solution was fairly priced.

I made a custom controller box and a remote control jog, adjusted the settings, measured the backlash precisely, and I was good to go!

P1050925-100104.MTS_snapshot_00.13_[2015.05.15_08.56.08]-1

00099.MTS_snapshot_00.15_[2015.05.15_09.52.32]

PCB Engraving

P1060032-1Engraving a PCB is not an easy task. The copper thickness is about 14mils, that is 0.035mm, and then under, you have fiberglass, which is a material that quickly wears engraving bits. The engraving bits have an angle of 30° or 45°, so if you’re engraving too deep, the trace width will be quickly larger than planned.

And the copper boards surface, as your CNC base, is not perfectly levelled, so trying to engrave without taking that into account leads to immediate failure.

Making PCB engraving an everyday routine requires a precise CNC solution with advanced features, like being able to warp G-Code on a curved surface (your copper board surface), and to be able to quickly transform/map G-Code onto a rotated surface (using a webcam for example), to achieve 2 sided engraving without pain.

Software tools

I used Eagle PCB to route the board and export the Gerber and milling files.

Those are then imported into CAMBAM, a sort of Swiss-Army-knife software for CNC needs, that allowed me to precisely define the engraving/milling tasks, before generating some G-Code for each PCB side.

The G-Code is then finally imported to the Planet CNC software for processing.

2015-05-15 08_43_34-1 Board - E__microchip_dev_dir_eagle_stuff_MUTA_operator_mk1_v4_operator.brd - E 2015-05-15 08_42_40-CamBam+  operator.sol2015-05-15 08_41_16-CNC USB Controller - E__microchip_dev_dir_eagle_stuff_MUTA_operator_mk1_v4_opera

Failure is part of the process

51bApmm4DILThe planet CNC Mk2/4 hardware controller is a good product, well designed and documented.

But the software is not as well thought and built. With it, using the advanced features required for 2 sided PCB engraving (Warp and Tranform) has been a real nightmare for me. I have spent nights and days trying to fix the problems I encountered, without success.

Some of the problems I encountered came from the difficulties I had to understand how the software was built/thought. Some others came from bugs I encountered, or regressions introduced by new versions. The only people able to help on the forum was the author, but I guess he had other priorities.

As a result, I ended up spending too much time on this, breaking so many bits and wasting copper boards… In the end, I managed to engrave only ONE 2 sided PCB, without being able to reproduce it! (T_T)

Added to the fact that the Planet CNC hardware controller is locked to its software, you can’t switch to Mach3 or LinuxCNC, it’s a dead end for me.

So yes, failure is part of the process, and now I know I can use Mr Handy for basic milling tasks and machining, but PCB engraving was a bad idea. I’ll go back to dirty PCBs services for that !