LinuxCNC configuration for the CNCDudez 2012 Desktop Mini Muscle CNC Machine
The machine is very similar to the "Mini Muscle MK2 Routing Machine" that CNC Design Ltd now sell: http://www.ukcnc.net/index.php/products/mini-muscle-mk2-routing-machine/
But I bought "Option 1" which only included the aluminium frame. I bought and built the electronics seperately myself.
http://www.ukcnc.info/forums/showthread.php?1202-Stepper-motor-heat-sinks
Even though the motors we use on the CNC Mini Muscle Machine are rated at 4.2 amps I set the driver at around 3.7 amps to play safe. So even going slow speeds where the current is at it's peek then they should still not get to boiling point as such.
Configuration for the microsteping driver:
| DIP Switch | Setting | Meaning |
|---|---|---|
| SW1 | Off | 3.7 Amps |
| SW2 | On | 3.7 Amps |
| SW3 | Off | 3.7 Amps |
| SW4 | On | Full Current |
| SW5 | Off | 10 microsteps |
| SW6 | Off | 10 microsteps |
| SW7 | On | 10 microsteps |
| SW8 | On | 10 microsteps |
More information in the datasheet: http://cnc4you.co.uk/resources/CW5045.pdf
Timing settings:
| Setting | Value |
|---|---|
| Step Time | 2000 ns |
| Step Space | 8000 ns |
| Direction Hold | 5000 ns |
| Direction Setup | 5000 ns |
| Steps on | Rising Edge |
More here: http://wiki.linuxcnc.org/cgi-bin/wiki.pl?CW5045
I am using a HG08 Parallel Port 'breakout board': http://www.cnc4you.co.uk/index.php?route=product/product&product_id=300
All pins are inverted.
| Pin | Direction | Breakout Label | Linux CNC Description |
|---|---|---|---|
| 1 | Out | EN | ESTOP Out |
| 2 | Out | CKA | X-Axis Step |
| 3 | Out | CWA | X-Axis Direction |
| 4 | Out | CKB | Y-Axis Step |
| 5 | Out | CWB | Y-Axis Direction |
| 6 | Out | CKC | Z-Axis Step |
| 7 | Out | CWC | Z-Axis Direction |
| 8 | Out | CKD | Unused |
| 9 | Out | CWD | Unused |
| 10 | In | IN4 | ESTOP In |
| 11 | In | IN3 | Both Limit + Home X |
| 12 | In | IN2 | Both Limit + Home Y |
| 13 | In | IN1 | Both Limit + Home Z |
| 14 | Out | RLY | Spindle On |
| 15 | In | IN5 | Probe In |
Parallet Port breakout board datasheet here: https://github.com/njh/linuxcnc-cncdudez-2012/raw/master/docs/HG08.pdf
I am using 57HS82-3008B 2.2Nm Stepper Motors, wired in Bi-polar parallel mode. They are connected to the control box using 4-pin XLRs.
| XLR Pin | Description | Cable Colour | Stepper Motor colour |
|---|---|---|---|
| 1 | A+ | White | Red + Blue |
| 2 | A- | Yellow | Yellow + Black |
| 3 | B+ | Brown | White + Brown |
| 4 | B- | Green | Orange + Green |
Stepper motor datasheet here: https://github.com/njh/linuxcnc-cncdudez-2012/raw/master/docs/57HS82-3008B.pdf
| Mini XLR Pin | Description | Cable Colour |
|---|---|---|
| 1 | Shield | Shield |
| 2 | +5v | Red |
| 3 | Input Signal | Black |
Do not use Pin 1 / Shield as ground / 0v
Note that the pin-out of a mini XLR is slightly different to a normal XLR.
The PC I am using has a D945GSEJT motherboard with a Intel Atom N270 CPU @ 1.60GHz. Sadly I have had some trouble with high Jitter in the latency tests - this mainly seems to occur when doing other operations, such as transferring files and waking from sleep.
| Max Interval (ns) | Max Jitter (ns) | |
|---|---|---|
| Server Thread (1.0ms) | 1067369 | 76089 |
| Base thread (25.0us) | 61272 | 36490 |
While I could achieve some quite high velocities, without loosing steps, during testing using Stepconf, I experienced problems with stalling which using the main LinuxCNC interface. I have therefore decided to set my Base Period Maximum Jitter value to 40,000 ns.
I am also limiting the maximum velocity to 1800 mm/min (30 mm/sec). While testing the acceleration, I was unable to find a value that caused problems, so I have set all axes to 500 mm/s2 for now. I suspect that it may be possible to have a much higher value - I'm not sure how this would affect cutting times.
- Steps per revolution: 200
- Driver Micro-stepping: 10
- Pully Teeth (Z axis): 1.0 : 1.0
- Ballscrew Pitch: 4mm per revolution