[Grbl_Esp32 PR#49] Restored Spindle speed control code to make SPINDLE_PWM_MIN

Issue #49 | 状态: 已关闭 | 作者: gflaser-au | 创建时间: 2018-10-31

Current spindle speed control does not use min pwm define.
I have copied back the code from upstream and tested that it works on my machine.
Also added a conditional define in the cpu_map.h because min pwm must be defined, and the default config.h indicated it can be commented out to disable.
More Info:
Min pwm is important for co2 lasers because they have no output until around 10-12% pwm. Correctly setting the min pwm is important for engraving, especially when using M4 (dynamic power control) mode.
In this case, min pwm should be set to a value so that M3S1 will just start the laser to very faintly mark.
SPINDLEPWMMIN_VALUE setting is in count (not percent). A setting of around 25 will give approximately 10% PWM. (25/255*100)
Remember that the higher this value is set, the less total PWM resolution is available.

#1 – bdring 于 2018-10-31

@gflaser-au Are you using 20kHz for the laser power control? If so, what are your settings?

Do you think we could rewrite things to get more than 8 bits of range in most cases. It could be transparent to the user and calculated from the frequency.

#2 – gflaser-au 于 2018-10-31

Yes, currently I have simply set the pwm freq to 20kHz with no other changes, except a min pwm value – 17 counts as it turns out.
I do notice some perforation on the underside if the speed is higher and the power is only just enough to get all the way through. I’m going to test a higher frequency – up to maybe 60kHz (which was about what I was using on the nano – just to see of the laser is actually getting modulated somehow.
I can’t see how it could be given that at 3000mm/min, 20khz is a “period” of 2.5 microns – the perforations are more like 100-200 microns.
Potentially, it could be some other mechanical resonance – more likely.

#3 – bdring 于 2018-11-08

Tested on logic analyzer…nice work @gflaser-au

I started a wiki page to explain spindle stuff

Let me know if you have any suggestions for that page.

原始Issue: https://github.com/bdring/Grbl_Esp32/pull/49

[Grbl_Esp32 PR#49] Restored Spindle speed control code to make SPINDLE_PWM_MIN_VALUE work

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