Ox CNC Status

The Hackspace Visual Arts
1

Hi All,

I had a quick play around with the new CNC recently.
I just thought to post some observations I’ve made so far

I’ve also started to put some docs together here:

Soft End Stops

The CNC has electrical endstop switches for homing (which is awesome).
I had a feeling that the software limits within grbl may have needed a bit of tweaking. As it turns out the software limits were disabled when I looked.

I’ve now enabled the software end stops and increased the values a bit.
For x and y the machine now stops just a couple of mm away from the electrical switch during normal operation.
For the Z axis it’s now set to stop the machine when traveling downwards just before the carriage collides with itself. Which is good since the z travel is increased due to the spoiler board being lower down when Greg and Ian fitted it to the table.

Stalling

One problem I have spotted is when running g-code for circles from jscut or laserweb, because there’s a lot of G1 G-Code’s it seems to run for a while, stop for a few seconds, start again etc. Sometimes when it stops it requires a click of the “Cycle Start” button to get things going again under chillipepr.

I’ve ruled out wifi being an issue by trying it with ethernet.
Also I’ve checked the baud rate which is 115200.

There’s a couple of quick options

  • First try bypassing the rpi1 serial proxy and try connecting to the grbl board directly over usb (I didn’t get around to trying that yet)
  • Next (if everyone is okay with it) try updating the firmware to 1.1 from 0.9j.20150811
  • If that doesn’t fix it, then perhaps discuss alternatives like a cramps / beaglebone / machinekit board.

I think the below relates to the use of arc’s but what I’m actually using it lots of G1 codes

Many Thanks
Richard

2

Just to follow on the above
I’ve now moved one of the tie-wraps on the machine that was causing the cable trunking to catch and rub against the homing switch.

Grbl has now been updated to 1.1 which now supports increasing the feedrate up to 200% of the original value while milling.
When using chillipepr make sure to use this link http://chilipeppr.com/jpadie (this is in the docs)

I’ve updated / copied / pastes some documentation to here:
https://HACManchester.github.io/Tools.OxCNC/
This should cover the actual milling.
But I still need to write some stuff on the generating the G-Code part (such as using JSCut)

One thing we have discovered is that the Rpi is maxing out on it’s CPU useage when acting as a serial proxy. So we need to replace that with a Pi3. For now the update to grbl seems to have reduced the stalling a bit and made it more usable.

Also it looks like the stepper drivers are a bit underpowered for the motors, I think Alegro ones at about 1A but the motors should be able to operate up to 2.8A. Just something to bear in mind if trying to mill metal etc.

Many Thanks
Richard