GRBL spindle RPM soft start

[stoltenkamp.scott]

Tweaked the default GRBL post to "soft start" the spindle.

According to SainSmart some of their controllers can fail driving a spindle to 20kRPM from a dead stop and should be eased up to full speed.

Specifically this combo:

GS-775M 24V 20kRPM Motor + Motor Noise Suppression – SainSmart.com

[Replacement] Parts and Accesories, Control Board for 3018-PROVer V2 – SainSmart.com

Should work for anything that uses the default GRBL post as well, but it's largely untested.

No warranties, use at your own risk.

You're free to do what you wish with the bit of code I added. The rest belongs to the GRBL/Autodesk folks who can do what they like with the whole thing.

(But if SainSmart, Autodesk, or the GRBL folks want to send me hats, I won't argue.)

[seth.madore]

This is cool! I've not looked at the output code yet, but does this only kick in once the commanded spindle speed is over a certain value?

[stoltenkamp.scott]

If you command 9kRPM in fusion and you have this enabled at 300RPM intervals for .5sec it should..

S300 M3

G04 P500

S600 M3

G04 P500

S900 M3

G04 P500

... etc

Since both properties are configurable itis aggressive as you want it to be.

It's the mfr's workaround for a very specific little 3018 style router controller/spindle combo where going from Spindle off to 20Krpm will fry the board, but it's useful elsewhere I'm certain, so I dumped it here.

[programming2C78B]

Wow. Sad that there's such bad hardware being used. Why doesn't the acceleration value just protect it? 

[stoltenkamp.scott]

This style of machine (3018's) are like a fledgling opensource router project.

In this specific instance it came with a 10kRPM spindle. Later on there was a 20kRPM spindle offered as an upgrade (generically, not specifically for this board but for the family of these little controllers,) and it showed no issues until it got in the wild paired up with this board and fried them (as I understand the series of events.)

The specific problem (to the best of my understanding) is that the spike in current going from 0-20kRPM can cause some component on the board to fry.

So, in this case the machine does what it's intended to fine. The spindle motor does also. But this combination CAN (not guaranteed to) have issues.

In this case it's somewhat like putting performance parts on a car. When you do so you probably should tweak the ECU otherwise you're gonna ruin something, or not see appreciable benefit from it.

I don't know if GRBL inherently has a soft-start-spindle function, but I assume if it did then there'd be a firmware update that would resolve this instead of having to rewrite a post. Personally, I don't think the issue is widespread enough to be of concern to the GRBL team, or the people making those specific boards, and it certainly falls outside of the original design of the 3018 project.