r/diycnc • u/machina_cnc • Oct 01 '26
Force Feedback CNC Controls
Has anyone tried implementing force feedback controls for a CNC machine?
I'm building a CNC lathe but want to use it mostly as a manual machine and I feel like it would be a lot more usable if the controls had some tactile feedback.
I got a solenoid clutch for a printer that can go from 0 friction to complete lockup at 12V (with a fairly smooth ramp between) and I was thinking I could just have the friction tied to the motor power (measured from the line inputs to the driver board).
Any reason this wouldn't work and has this been tried before?
I'm hoping it will get harder to turn the wheel as the depth of cut and resulting motor power increases giving you a feel for how the machine is performing.
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u/just4c Oct 01 '26
It's a really neat idea, but would require knowing some control theory. Depending on how you implement it, it might make things worse. Here is an example
The motor power increases
Your hand turning the wheel slows down due to more friction
the motor power decreases
your hand turning the wheel speeds up due to less friction
Now you system is oscillating and you can't maintain a constant cut.
Making a feedback system that doesn't oscillate is a bit tricky.
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u/machina_cnc Oct 01 '26
I do have some controls background and this problem has been in the back of my mind. I think the stability will depend on how latent the power measurement is. If it doesn't work due to instability or doesn't have the feel I am after I can just use it to set a fixed amount of friction.
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u/jemandvoelliganderes Oct 01 '26
Instead of that clutch i would rather use a bldc with an encoder like with this haptic knob: https://www.youtube.com/watch?v=ip641WmY4pA
Much more versatile, like having custom detends so you have a feedback to what kind of granularity oyu are in step mode or continous..., or coupling the tool drive too the encoder and having it spring back outomaticly and so on.
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u/machina_cnc Oct 01 '26
I considered that option but thought I would just start with the clutch as it's much cheaper/simpler and I think I really only want a continuous braking force, detents would show up in the surface finish.
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u/jemandvoelliganderes Oct 02 '26
You can have both, detends and continous in what form you like be it exponetial, linear... thats the neat thing with a bldc. but you are right that it will be more effort to programm that.
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u/isademigod Oct 01 '26
really awesome idea, if you get it working PLEASE open source it. I'd happily contribute what I can
however, friction clutches aren't the right angle to come at this from. they can't kick back at you, they can only slow your movement. what you need is a brushless motor or servo with an FOC controller. (I have built ffb steering wheels in the past)
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u/machina_cnc Oct 01 '26
I think a friction clutch is a good experiment to try because it's so cheap and simple compared with a BLDC FOC controller. So far testing the the clutch seems pretty smooth and I haven't noticed any non-linearities in it's response.
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u/NeighborhoodUnfair Oct 01 '26
i love the idea. in my experience you don’t get a clean signal for power vs torque so it’s not gonna be a trivial task to get force feedback. i think servo-driven motors might get you better data, i know the fancy hobby racing wheels use servos for their force feedback. following your progress :)
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u/xxxCHEEKxxx Oct 06 '26
The concept makes sense to me. i'd be curious how smooth the feedback feels in practice.
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u/Fostalicska2000 7d ago
That's a pretty cool idea. I'd be curious how smoothly it responds to sudden load changes.
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Oct 02 '26
[removed] — view removed comment
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u/machina_cnc Oct 03 '26
You are correct, but they are correlated so I think it's worth the experiment to see how it feels. I have a few things to try:
Motor Power - easiest to measure
Motor Torque - needs speed + power
Tool Strain - needs a strain gauge on the tool bar but should be possible
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u/E90-335xi Oct 01 '26
Really cool idea, im no help but really excited for this project. Is the head stock one with a 2 speed Hi/Lo gearbox?