Motor torque

So I have been building a reprap and have been having problems with the motors and think I have isolated my problem. I decided to start my motors fresh so I set the firmware over and set the vref to around .5v. I took the belt off of my x stepper and connected it to my extruder driver(so I could get constant movement and adjust the pot). I set it to extrude for 100 and the motor didn't move. So I decided to up the pot until it started moving, I turned the pot and my motor started to move(vref=1.12)<-yikes! but the motor has very low torque and when it is moving, I can stop the shaft with my hand and it vibrates A LOT! but when the shaft stops moving the torque goes way up and I cannot turn the shaft at all. So I was wondering if anyone has any idea why this might be happening? I have also tried chaning the E axis value to 2 and 100 from 45 with no difference in motor speed:
#define _MAX_FEEDRATE {400, 400, 2, 45}
and
#define _RETRACT_ACCELERATION 2000 <--changed to 4000 and 500
I am not sure chaning either of these would make a difference but I tried them to see If making it slower would increase the torque. Unfortunatly it did not change speed of the motor therfore did not effect the torque either. Also if your confused why I am ching the E axis values in the firmware it is because I have my X axis motor connected to my E axis driver if that wasn't clear.
I have also tried chaning the steps per mm:
#define _AXIS_STEP_PER_UNIT {80, 80, 3200/(1.25),700} which does get the motors to move with torque but then my steps are all messed up because I have to set them to values like 20. So I am not really sure what to do next, any help is greatly appreciated cheers!
-Tyler Scofield

- The fact that when motor stops you can not turn the shaft by hand, that is absolutely normal, that is actually how it is supposed to work. What happens is that the stepper motor holds its position.

- The driver pot adjusts the peak current in the motor. It makes sense that when you do put it to minimum then motor does not have torque or does not move at all. You need to up it until the motor moves with the torque necessary for your system.

- Changing the MAX feedrate does not immediately upper the speed. If your MAX speed is 4000 and you order at speed 3000 then it accepts at 3000. Commands over 4000 will be executed at 4000 instead. This is what "maximum" word means.

- Retract is something that happens only at the end of an extrusion, that it tries to suck filament back. Something like you would try to spit then half way you stop and suck the spit back in mouth. Sry for the comparation, couldnt think at a better one.

- The E axis steps per unit value you talk about, steps per mm, that does not change the speed, it changes only the length the motor moves. You order a move 10 mm, if that value is incorrect it will move other length, like 15 mm or 5mm instead.

From what you say i do not see anything that would be obviously incorrect. I would say that things actually seem to work. About the torque, the potentiometer on the driver board adjusts that, and the formula between Vref and current peak is in the datasheet of your driver IC, look that up and check what sense resistors you have in order to figure out the exact formula, there are other posts in this thread that might help. About the speed, leave it be, the motor speed is either specified by the sender for travel moves or will be in the gcode file, or if you want to know more see the g-code reference on wiki and enter gcode commands manually specifying different speeds. For other configuration file you have to better read comments in the datasheet, these settings do exactly what they say they do. For example "steps per unit" does not have anything to do with torque. There are many sites with details about how to configure the firmware parameters, sry i dont have one to suggest, but you can search and i am sure you will find quite a number. Cheers, have fun.

Hello it looks like some of what I said was not very clear, When I was adjusting the pot on the driver chip I had to put it all the way to around maximum power around 1.2v vref to get the shaft to turn but even when I put it all the way up the motor still had no torque so I can't go any higher with the pot. I was saying this is weird because the motor has a lot of torque when it is not rotating but as soon as it starts to it loses all torque. When I was talking about steps per mm I didn't mean that it gained torque but rather that the motor was using it full torque. For example if I set the values really low on #define _AXIS_STEP_PER_UNIT {80, 80, 3200/(1.25),700} like down to 20 the plate moves with a lot of torque but the plate as expected will move farther than it should so this won't resolve the issue. Also when I set it really low the .1 and 1 jog need to be pressed multiple times to get the plate to jog anywhere.
I hope this clear up some of my miscommunication, I'm sorry about that!

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tyscof
Hello it looks like some of what I said was not very clear, When I was adjusting the pot on the driver chip I had to put it all the way to around maximum power around 1.2v vref to get the shaft to turn but even when I put it all the way up the motor still had no torque so I can't go any higher with the pot. I was saying this is weird because the motor has a lot of torque when it is not rotating but as soon as it starts to it loses all torque.

The Vref can theoretically go a long way, lets say up to 4.0v. But do NOT rush to get it all the way up because you get a chance to burn your driver. There is a relation between the Vref and the Peak current, you need to look up this exact relation, on the driver seller website or on the chip manufacturer website datasheet. This relation involves Rs which is sense resistors, two resistors on the driver chip that you must know the exact value, and depending on their value the overall relation can change dramatically. So look this up before making any changes. Also you could have some motors that are rated like 12v or so, which have high coil resistance like 30 ohms instead of 3 ohms, and if that is the case, after some point increasing vref wont help. So who knows what you got there, you need to look things up first, starting with that vref to peak current relation.

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tyscof
When I was talking about steps per mm I didn't mean that it gained torque but rather that the motor was using it full torque. For example if I set the values really low on #define _AXIS_STEP_PER_UNIT {80, 80, 3200/(1.25),700} like down to 20 the plate moves with a lot of torque but the plate as expected will move farther than it should so this won't resolve the issue. Also when I set it really low the .1 and 1 jog need to be pressed multiple times to get the plate to jog anywhere.
I hope this clear up some of my miscommunication, I'm sorry about that!

The "axis step per mm" does not affect torque in any way. This setting only determines the length of the move. If you set it to 10, it will move some distance, if you set it to 20 it will move double that distance, if you set it to 30 then it will move 3 times the initial distance, etc. Ofc if you set it to 0.1 then you will have to click it 100 times to move that same initial distance because 10=100*0.1. That is all. Nothing to do with torque really.

If smaller moves seem to be better, perhaps you have too high setting of acceleration or jog speed, and at long moves when it reaches the peak settings it fails, while at short moves it may not have time to reach the peak settings so it may seem better, but this scenario is already some kind of a stretch.

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The "axis step per mm" does not affect torque in any way. This setting only determines the length of the move. If you set it to 10, it will move some distance, if you set it to 20 it will move double that distance, if you set it to 30 then it will move 3 times the initial distance, etc. Ofc if you set it to 0.1 then you will have to click it 100 times to move that same initial distance because 10=100*0.1. That is all. Nothing to do with torque really.

I get that it doesn't effect the torque but when I set the values really low like 20 the motor will move and I wont be able to stop it like I could before. It has the torque that it should instead of the puny barley moving nonsense. Which is weird I don't see how it makes a difference, maybe has something to do with the motor needing more steps or the steps are screwy? Could this be a problem with my ramps or mega board? My motors are 12v aren't they supposed to be?

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If smaller moves seem to be better, perhaps you have too high setting of acceleration or jog speed, and at long moves when it reaches the peak settings it fails, while at short moves it may not have time to reach the peak settings so it may seem better, but this scenario is already some kind of a stretch.

This is what is really weird, if I set it super low all of the larger values like 1,10, and 100 will work(and like before it has the torque that the motor should) but the lower value like .1 will not move the plate... well it will but the plate wont move at all until I hit .1 like 3 times and then it budges once the same distance as the 1 jog. But if I set it higher then the motor will either not move at all or will only move on the .1 jogs and make high pitch noises for all the other values increasing in pitch the higher you go in jog vale 1,10,100. weird right?

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tyscof
I get that it doesn't effect the torque but when I set the values really low like 20 the motor will move and I wont be able to stop it like I could before. It has the torque that it should instead of the puny barley moving nonsense. Which is weird I don't see how it makes a difference, maybe has something to do with the motor needing more steps or the steps are screwy? Could this be a problem with my ramps or mega board? My motors are 12v aren't they supposed to be?

No, the motors are supposed to be any value 4-5 times lower than 12v. For example motors labeled 2.56v, 3v or 4v will be ok when supplied with 12v. If the stepper motor label says 12v and you supply them also with 12, thats not good: it may work, but poor performance.

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tyscof
This is what is really weird, if I set it super low all of the larger values like 1,10, and 100 will work(and like before it has the torque that the motor should) but the lower value like .1 will not move the plate... well it will but the plate wont move at all until I hit .1 like 3 times and then it budges once the same distance as the 1 jog. But if I set it higher then the motor will either not move at all or will only move on the .1 jogs and make high pitch noises for all the other values increasing in pitch the higher you go in jog vale 1,10,100. weird right?

No, not weird, actually its normal, if you set steps per unit small values like 0.1 and you order small moves, it will move an imperceptible distance or wont move at all. Because said value is supposed to be bigger. Thats normal.
And the noise changes because of microstepping changes the coils, one coil is at some% and the other coil is at other% sort of speaking the coils are "fighting" each other in order to balance the rotor somewhere in between them. Again, normal.