Grbl Controller

Grbl does not have native support for SCARA. But I intend to convert a cartesian gCode file into a format that will fool grbl.

I have an old Laser controller but it only supports grbl up to v0.9. The latest is v1.1, in this version the spindle on/off and spindle speed (PWM) pins have been swapped.

I thought I would buy the latest Laser CNC controller as I would like to use grbl v1.1 (my old Laser uses grbl v0.7 and is not compatible with later grbl versions).

Here is the controller I am using (except my is covered with labels):

It has a built in power on/off buttons which are quite handy:

As my laser module has a built in power supply and only needs PWM, but this gives you the idea:

I am currently using a 12v 2.5A plug pack but I suspect this will be inadequate for both the motors (0.64A per phase, there are 4 phases) and the Laser (1A).

GRBL Set Up

Surprisingly GRBL did not work "out of the box", Basically, "$1=25" shut down the motors after doing a move. It confused me as I am used to the motors staying on.

Other than that, I set the steps/mm ($100 ans $101) to steps/degree ($100=17.778 and $101=17.778). The stepper motors are 0.9 degrees per full step.

The stepper drivers where set (hard-wired) to 1/16 micro-stepping.

Next is to step up the laser model. Nothing to do here (I think), the spindle speed range is 0 to 1000 (i.e. 0% PWM to 100% PWM).

Power Supply Upgrade

Bought a 12v 9A power supply.

The controller seem more quiet but hard to tell.

The laser works.

Under-Damped (i.e. over shoot) Motion

The arms suffer badly from under-damped motion.

This is seems to be a common theme!, and micro-stepping does not help (makes it worse).

How to solve? Gearing and half stepping, PID, or physical damping?

• Gearing and half-stepping is for the next planned generation of SCARA.
• PID is not really practical via Grbl.
• So perhaps a felt washer between the arms?

AlanX