KFLOP Spindle Control with PWM Converter?

[Tim G]

Hi Tim,

Very good.

Is there an encoder on the Spindle? If so, that could be used as feedback to make the speed very accurate as well as maintain speed under load.

If not, you could make a lookup table or formula to determine the PWM as a function of desired speed.

Do you know how to use Microsoft Excel? Command like 16 different PWM settings (in 16 count increments) and measure the corresponding RPMs. Enter in Excel, plot, and ask Excel to fit a 2nd order trendline to it and see how well it fits. If it fits well, put the formula in to your Spindle program.

Sadly, no encoder on this spindle. I'll have to see if I can figure that out. If so, how would I enter than in the spindle program?

I did notice that when I have the potentiometer on the converter set high enough to actually reach 10v, all of the spindle speeds are high by over 1,000rpms (sometimes over 1,500) aside from 23,000 and 24,000 rpm speeds, which are pretty accurate. If, however, I adjust the potentiometer so the 10,000 rpm speed is accurately reached, then all of the speeds are very accurate, within 50 rpms of the requested speed. The problem is the spindle tops out at 21,600 rpms and will read that whether you request 22,000, 23,000, or 24,000 rpms. It basically makes the PWM converter top out at 9v instead of 10v. I don't have any bits that require over 22,000 rpm, so I'll probably stick with this setup for now, but it's a bummer the top speed cannot be reached. I'm tempted to try adjusting it so that 10v can be reached again and using the Excel method to establish a function, however, since the curve is accurate right up until the last few speeds, I'm worried it won't create a usable trend line for me. I also noticed that when it was set for the higher voltage and the rpms were over 1k rpms high for each speed, they were less consistent, with some being 1200 rpms over, some just 1000 rpms, and others nearly 1,500 rpms over. It wasn't a steady change either, which made the differences a bit confusing. Overall, I think having it adjusted for 10v made it less accurate across the board. Wish I had an encoder:)

[TomKerekes]

Hi Tim,

I think the C Program assigned to the S Action should have a factor in it to convert RPM to PWM counts.

So try setting up the converter board to output a full 10V and adjust the factor in the C Program to make the RPM match.

Post the C Program you are using for the S word and we can help.

[Tim G]

Hi Tim,

I think the C Program assigned to the S Action should have a factor in it to convert RPM to PWM counts.

So try setting up the converter board to output a full 10V and adjust the factor in the C Program to make the RPM match.

Post the C Program you are using for the S word and we can help.

Thanks! I managed to create some other problems for myself in the meantime... Posted another thread about a Screen Editor issue I'm having. If I can get that figured out, I may give this a try to dial the speeds in a bit better. Really appreciate all of your help on this.