Super-PID new low-cost router speed controller

[ger21]

The unit I sent to you has 3 metres of shielded cable (2 core + shield) attached to the sensor. Sorry if I had known you needed 5 I could have supplied it that way! I have tested the sensor wire next to the router power and stepper wires and not seen any interference so far as it has numerous layers of hardware and software filtering for the sensor signal but like any device I can't speak for every case! You should not need to shield the router power wires as the phase angle system used doesn't generate the amount of nasty noise that some PWM spindle controllers do. Maybe I can check your build log photos and suggest a wiring scheme based on that?

3 meters might work. Since I plan on moving the Super PID to a future machine, I think I can mount it closer.

My bigger concern with the spindle power is running it with the stepper wires.

Looking at the last pic here, 3 meters may not be long enough, as it's almost 2 meters up the gantry side and across.

Another First Router

Then when a chunk of wood is mashed into the 5mm endmill the spindle speed drops down to stall

That looks safe.

Second video of that job, this time drilling the acrylic at 5000 RPM with a 1/8" standard drill bit...........

I didn't think that running at 5K will allow me to use drill bits much more safely now. I usually use a 1/8" router bit, but am limited to 1/2" depth. This will let me drill all the way through my 3/4" parts. Awesome.

[Al_The_Man]

Roman, Did you try the difference of using a bridge after the AC controller and feeding the motor with DC?
I notice that the Universal motor Treadmill controllers that have used this method with the Onsemi IC with feedback will control down to zero rpm?
I have one currently on a band saw.
Al.

[ger21]

Al, you have to remember that all the motors this will be used with are dependent on the spindle mounted cooling fan to keep them cool. He's already stated that cooling might be an issue at 5000 rpm.

Although I guess there are plenty of other applications that this might benefit.

[CarveOne]

Impressive Romanlini.

Heating of the router motor can be monitored with a thermal probe, and the corresponding current draw can be monitored with an ac current probe. There would be some sort of correlation between 5k rpm and every 5k rpm increment upward to 30k rpm that may not be linear. Each level would need to be run long enough for the router motor temperature to stabilize. It would be a useful chart to have for the more popular router models used on the DIY machines.

CarveOne

[ger21]

I believe he said that motor heating (and current draw) will vary depending on the load. With a light load, it may not even get hot at 5K rpm.

[CarveOne]

I believe he said that motor heating (and current draw) will vary depending on the load. With a light load, it may not even get hot at 5K rpm.

That's true, but it would still be a good idea to have some measurements rather than something less subjective like finger tests for heat on the router case while cutting something. If 5k is the only point of concern, then maybe a no-load, medium load, and heavy load test may be enough to see how much change there is to be expected from a particular model router.

CarveOne

[Al_The_Man]

That's true, but it would still be a good idea to have some measurements rather than something less subjective like finger tests for heat on the router case while cutting something.
CarveOne

The majority of commercial CNC spindles have have either a thermal switch or a thermistor attached to the stator, probably would not be difficult to incorporate that if turns out to be needed.
Al.

[RomanLini]

Gerry- I don't think you will get problems between the router power leads and your stepper driver leads, BUT if you want to use shielded cable then by all means. The spindle sensor needs a 2-core cable plus shield, any good quality stereo microphone cable will work as they are well shielded and rated for high flex cycles.

Al- My original protoype unit (see post#1 above) used bridge rectifier (ie full wave DC) and IGBT with numerous PWM and phase angle systems tested. There is no benefit and for the final design I settled on the phase angle system for price and proven reliability and it actually has much less audible and RF noise than PWM systems.

Re the treadmill motor, these are always designed for very high torques at low RPM. Total opposites of router motors that have light weight armatures and are optimised for best powerband at 20000+ RPM. There's really not a lot of options to get better performance out of a router, believe me i've been tuning it for weeks... This is about as good as it gets.

CarveOne- Thanks! Heating really is not that big an issue. As you can see in the video cutting oval pockets with 5mm endmill, the power to the router goes from 10% to maybe 15%, this is a tiny amount of router heat and WELL within the cooling capacity of the router fan at 5000 RPM. The air pumped out of the router under this type of use is barely above room temperature. In any case where you are running the SuperPID at lower speeds than you currently run doing similar cutting work there will be LESS heat that you are currently getting including less bearing heat. I'll ask Val about changing that warning on the SuperPID.com page as I think it is giving people the wrong impression. Please don't stress too much about heating until you test it out for yourself doing some normal sane type cutting loads.

That is a good point about concerns at 5000 RPM, this is the most difficult RPM for the reason that the router itself was never designed to work well at 5000 RPM. What you will find at 5000 RPM if you try to take a ridiculously heavy cut is that rather than overheating the router will probably experience oscillation as the Super-PID tries to squeeze power from the rotuer that it is just not capable of producing at 5000 RPM.

Again I don't want to give people the impression that this is a problem, the Super-PID is capable of getting amazing low speed performance out of the router but there are finite limits to how well a 25k router can ever be made to work at 5k! If you need to drill steel with a 3/8" drill bit at 5000 RPM this is not the way to do it. Buy a big cast-iron drill press.

Al- Re the thermal sensor it's slightly different to commercial spindles. They only have multiphase windings in the stator and permanent magnet rotor so it is easier to do that. With a router, the stator field windings don't get very hot, the majority of the heat will be in the armature windings. An air temp sensor would be easiest and probably the smartest.

I am open to suggestions re a heat sensor or something but really people need to try these out, see that their routers can be run at lower RPMs with *less* heat and wear than they are currently getting for the majority of tasks and then go from there. At this point I just don't see it being needed as my router is running cooler, quieter, more precise etc. It would always be possible to cook a router through inappropriate use whether it has a PID or not.

[CarveOne]

I'm in no way suggesting that the Super PID be changed to include a temperature monitoring display function. Only that someone test it and have a chart or curve available to show what is happening at the lowest usable speed. That speed may be different for different routers. (?)

I would expect that under normal loads, at low rpm the current drawn will be less, and there is less heat to be to be dispersed by the fan anyway.

CarveOne

[RomanLini]

It's all good, please keep the comments coming I very much respect your opinion and it gives useful insight as to how people who are experienced in CNC routing perceive the unknown product re potential benefits/problems etc.

The idea of a temperature sensor and temperature shown on the display is actually a good idea. Maybe for a future version of the Super-PID it could be added without adding too much cost to the product and it would add value and perceived value. It's an idea that I would not have had myself, but now with your (and Al's) input it is now under consideration, so thank you both.

Re the Mach3 control, thanks Gerry I read through the Mach3 PDF and at this point it looks like the Mach3 PWM output could drive the Super-PID speed control, but not at linear RPM so there would be some user input needed to tell the PC to send out X PWM to then make the PID run at Y RPM. I'll keep looking into this.

In the meantime if anyone has cutting tests etc they would like to see I will have the video camera for a few more days.

[Al_The_Man]

Al- Re the thermal sensor it's slightly different to commercial spindles. They only have multiphase windings in the stator and permanent magnet rotor so it is easier to do that. With a router, the stator field windings don't get very hot, the majority of the heat will be in the armature windings. An air temp sensor would be easiest and probably the smartest.

I am thinking about DC spindles with wound field, the temp sensor is buried in the stator and being as these are shunt wound motors the heat IS generated in the rotor, but paradoxically they monitor the stator, as it is hard to monitor a rotor.
But with the router motors having the same current in both field and armature, I would have thought they would heat about equal?
Al.

[RomanLini]

Sorry Al I thought you were talking about VFD spindles! Series wound universal motors like routers generally have less than 20% of the applied voltage dropped by each series winding and the field windings have a larger cooling area. Generally with failed power tools it's the armature or commutator that goes first rather than either field winding.

If a motor is being operated well outside its safe operating area the whole thing will get hot. With forced air cooling the exhaust air will give a pretty good idea of the overall motor heat I think.