z axis jammed 4000 steps

I'm trying to calibrate z axis 4000 gives me accurate movement

using marlin firmware changing Z to 4000, test without using z home I can increment up and down 10mm a click in repetier. As soon as I home, the motors jam with a continuous noise, as if they are trying to turn but cant. after using emergency stop only way I can rehome is to lower z steps
3100 homes ok
3200 jammed

Has anybody experienced this, why is it doing this. Is it possible to home at a reduced steps?

I don't use Marlin, but it sounds to me that you have one or more of the following problems:

- Z homing speed set too high
- Insufficient Z motor current, probably because if you have two Z motors then RAMPS encourages you to connect them in parallel, which is a bad idea (series is better for most stepper motors used in RepRaps).

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

#define HOMING_FEEDRATE {50*60, 50*60, 2*60, 0} // set the homing speeds (mm/min) {50*60, 50*60, 4*60, 0}
#define DEFAULT_AXIS_STEPS_PER_UNIT {80.00,80.00,4000,1000}
#define DEFAULT_MAX_FEEDRATE {500, 500, 5, 25} // (mm/sec)
#define DEFAULT_MAX_ACCELERATION {9000,9000,100,10000}
#define DEFAULT_ACCELERATION 3000 // X, Y, Z and E max acceleration in mm/s^2 for printing moves
#define DEFAULT_RETRACT_ACCELERATION 3000 // X, Y, Z and E max acceleration in mm/s^2 for retracts


I changed the homing feedrate from 4*60 to 2*60 It lets me home ok, when I try moving 10mm, Printer stopped due to errors

Acceleration of 3000 mm/sec^2 is unnecessarily high for the Z axis. I'd crank it down to 500 or less and see if the problem doesn't magically disappear.

I had the same issue with the i3 I just finished and started up with Marlin. I lowered max feed rate for the Z axis from 5 to 2 and had the same idea as dc42 with the Z axis current. Haven't gotten around to checking that vref yet. If your not farmiluar on how check vref, the steps are on the Pololu stepper driver board page. I offer this note though, not all stepper motors are created equal. My old i2 has motors that were designed to opperate at like four or six volts instead of twelve; therefor, to keep them from running hot due to over current I had to set my vref lower. They do their job just fine at this lower vref. I have hundreds of succesfull prints to prov for it. In my opinion, if your motors run hot then something isn't set up correctly or they are out of spec in some way.

The voltage rating of the motors is not important except that you want them to be as low as possible because that implies low resistance which also usually implies low inductance. The current determines the torque they produce and the motor driver uses PWM to limit the average current to the set value. Operating from higher than rated voltage increases the speed at which the current rises in the coil. It is perfectly normal to operate steppers from supply voltages 5-20X their rated values.

12V steppers would not work very well with a 12V power supply feeding the drivers.

So would this support my finding that my motors performed fine with a lower than reccomended Vref?

Quote
the_digital_dentist
The voltage rating of the motors is not important except that you want them to be as low as possible because that implies low resistance which also usually implies low inductance. The current determines the torque they produce and the motor driver uses PWM to limit the average current to the set value. Operating from higher than rated voltage increases the speed at which the current rises in the coil. It is perfectly normal to operate steppers from supply voltages 5-20X their rated values.

12V steppers would not work very well with a 12V power supply feeding the drivers.

When I said "higher than rated voltage" I was referring to the power supply voltage, not Vref. Vref is used to set the average current through the motor.

The motor's torque spec is based on a specific current. That current results in the maximum allowable motor temperature, usually around 60-65C. So, if you run a motor continuously at its rated current, it will get hot. If you don't need all the torque the motor is capable of delivering, because the load is light, you can reduce the current which in turn reduces the heat.

Part of the definition of the "load" is the mass the motor has to move, how fast it has to accelerate it, how much friction there is, loading due to gravity, etc. All factor in to the required motor torque. If you limit acceleration, have a low friction mechanism, low moving mass, you can use a small motor near its rated torque which will run warm or hot or you can use a larger, high torque motor at reduced current/heat.

Yes, let me be clear, my motors do get warm as in run above room temprature. By hot I was referring to your finger refuses to stay on them when you touch them.

You will find some old post around here saying that their motors run hot and it's OK. I consider this to not be OK because as far as I know this kind of heat stress leads to break down.

Quote
the_digital_dentist
When I said "higher than rated voltage" I was referring to the power supply voltage, not Vref. Vref is used to set the average current through the motor.

The motor's torque spec is based on a specific current. That current results in the maximum allowable motor temperature, usually around 60-65C. So, if you run a motor continuously at its rated current, it will get hot. If you don't need all the torque the motor is capable of delivering, because the load is light, you can reduce the current which in turn reduces the heat.

Part of the definition of the "load" is the mass the motor has to move, how fast it has to accelerate it, how much friction there is, loading due to gravity, etc. All factor in to the required motor torque. If you limit acceleration, have a low friction mechanism, low moving mass, you can use a small motor near its rated torque which will run warm or hot or you can use a larger, high torque motor at reduced current/heat.

DEFAULT_ACCELERATION - Reduced both to 500
DEFAULT_RETRACT_ACCELERATION
DEFAULT_MAX_FEEDRATE changing this from 5 to 2 solved my problem
Setting multimeter to vdc X0.65v Y0.64v Z0.65v E0.58v

Thanks for your help

Oh, I meant to say earlier...

Note, some of those setings are in mm per MINUTE and others are in mm per SECOND. BIG difference there.