[lcvette]

There's nothing you can do about lead error.... Short of going with $1000+ ballscrews. Like I said you need to be concentrating on removing stacking errors, not being concerned with screw lead error.

Stacking errors from too short of a calibration distance are far worse than lead errors.

[phomann]

I then used a DTI finger on the vice jaw and told the machine to move 0.635mm as I know that the indicator will move round to 5 on the indicator. It Is mathematically calculated so that is safe.

The machine moved slightly over the the 5 mark ( 0.6731mm). I calculated the error and it turned out to be 0.0254mm.

The above clearly shows that your calibration method is faulty. The error that you calculated is 4% (0.0254/0.635)
That equates to 4mm per 100mm travel. Clearly not correct.

If you want to calibrate the axis you'll need to do it over the full axis travel.

Cheers,

Peter

[onocyclone]

Ok I'll have another go tomorrow.

I can't cut anything now as the motor is ****ed ! Haha typical ! Anyone got a Spare ?!?

[phomann]

Also don't forget, you are using a 1/8 microstep drive. These 8 micro steps are not evenly spaced between the full step, they are all over the place.
Microstepping does not provide greater accuracy, just greater resolution. you should only be relying on the full step accuracy. In your case, the full step distance is 0.025mm or 0.98 of a thou.

Remember that the rotor in a stepper motor is held into position by the phase current in the 2 coils and also the detent force. You can think of it as being held in place by two springs plus a 3rd spring pulling it to the full step detent position.

If the 2 coils are not identical then the rotor position will not be in the correct position except at the fullstep position as it also has the detent force holding it there.

You can usually rely on the 1/2 step position being reasonably accurate with no force on the motor shaft. The worst error will be at the 1st and 7th step. The stepper drive is setting the currents in the motor based on the sine/cosine of the desired rotor position. One coil has almost full current, the other very little. Also as the rotor is very close to the fullstep position, the detent force is pulling it to the full step position. Adding the fact the two coils won't be identical and limitations in the stepper drive, the first microstep may not even move the rotor from the full step position.

Microstepping was introduced into steppers to smooth the motion at low speeds. It was not done to improve the accuracy of the drive, although many people use it when stating the accuracy of their systems.

With your closed loop steppers, have an encoder that will improve the accuracy. Even then, the accuracy is determined by the resolution of the encoder and how they use the encoder.

Just another source of errors that needs to be accounted for.

Cheers,

Peter

[109jb]

Did you even look at the graphs that | posted and the explanation that went along with it? If you had you would have understood that your new "steps per" numbers were lousy like shown in the middle graph with the green line. You should not be too far off from 320. If it is lower than 319.9, or higher than 320.1, then either you are wrong, or your screw is off more than 0.004" in 12" or 0.1mm in 300mm. That is roughly the tolerance of the screw.

The 378 steps per mm that you got recently indicates that if it were correct the screw would have an 18% lead error (378/320)-1=0.18. Do you honestly think the screws could be that bad? I know they are chinese screws, but even they are not that bad. That would equal lead error of 54mm if it continued over 300mm. Simply not possible.

You need to start reading and understanding what multiple people have been telling you over and over and over. If your motor was running I would tell you to set the steps per at 320, turn off the backlash comp, and run a part. I'd bet it would come out closer to perfect than all of your messing around with these settings has done.

[treyjugson]

Lol, why do people keep bringing up closed loop steppers? Try reading from the beginning, he shows pictures and links to what he is running and they are regular old 4 wire steppers, nothing closed loop about them, no encoders and just your basic stepper drivers. Haven't you confused the guy enough already? You can't even agree whose advice he should heed over and over.

[lcvette]

You're correct, I mistakenly thought he was someone I spoke with through email who purchased closed loop steppers. That member has the same machine as the OP and is at the same stages of his build. That's my fault for any confusion, apologies to the OP.

Treyjugson, clearly you are hurt and upset, it's pretty transparent in your posts. I do apologize if I hurt your feelings. I truly do appreciate you pointing out my error on the closed loop steppers. Good catch. Hopefully it will remove some confusion for the OP.

[lcvette]

Ok I'll have another go tomorrow.

I can't cut anything now as the motor is ****ed ! Haha typical ! Anyone got a Spare ?!?

There are a few motor options for your spindle. I have been a few directions here from a stock replacement motor, treadmill motor, and now a brushless DC. If I had it to do over again, I would go with a VFD and 56C frame inverter duty AC motor, 56C frame sizes can be had in 1.5hp-3hp. From others reviews and videos, the constant torque is pretty nice for these mills and gives a good bit more rpm range.

[onocyclone]

Would I have to make some brackets ? Or is it going to be a straight fit for a brushless DC motor ? Would like the mill a bit quieter ! Very noisy !

[lcvette]

Any new motor short of a direct replacement will need new brackets of some kind. Is your mill a belt drive or gear drive? Gear drives are noisy by nature, adding a belt drive conversion will quiet it down significantly.

[onocyclone]

Just tested the electrics and nothing is wrong with the fuse/controller. It must be the motor

Attachment 273868

[LeeWay]

Have you tried spinning the spindle to turn the armature in the motor to a different spot? I have found that some controllers like these need to start the motor slowly rather than jump to full speed.

[onocyclone]

Yes I've tried creeping it from zero and it's still not having it. Would powering the motor directly give me a better result ?

Cheers,

[lcvette]

Sounds like it's dead. Fairly new machine isn't it? Is it under warranty still?

[LeeWay]

You can test the motor with a clean DC power source. Just to see if it is the problem. It doesn't need to be high voltage. 12 VDC or 24 VDC should turn the motor if it isn't damaged.

[onocyclone]

Yes it is fairly new, Edith me extensively modding the machine do you think that they would still pay for a new motor and it not void the warranty ? I didn't change any of the motor settings in the control box.

[Fastest1]

You supported my argument perfectly.

The rolled screws have errors across there length. If you do your test over a different part of the screw, you will get a different error. So, which one do you believe?

Doing the calibration over an inch or two is a waste of time.

As I said, maybe ground screws is the answer of the screws are not accurate enough.

Cheers,

Peter

It wouldnt be the first time my argument has back fired ;-)

[lcvette]

Yes it is fairly new, Edith me extensively modding the machine do you think that they would still pay for a new motor and it not void the warranty ? I didn't change any of the motor settings in the control box.

I don't see why not, I mean as long as you were inside the RPM and tool capacity it states it is rated for I would say they should honor the warranty. They will be asking for a motor swap not sending the mill back and forth.

[109jb]

Yes it is fairly new, Edith me extensively modding the machine do you think that they would still pay for a new motor and it not void the warranty ? I didn't change any of the motor settings in the control box.

You converted it to CNC which at this point had absolutely nothing to do with the motor or motor control. They should absolutely warranty the motor and motor control.

[Fastest1]

Grizzly is pretty good about replacement of defective parts. They are well aware of the issues.