stepper motor over stepping than its actual position

[ajith]

Dear sir,
we have a glue dispensing machine controlled by Kstep. recently we changed the axis mechanical setup to timing belt rotated via pulley for axis movement.But we have been experiencing over stepping of the motor than the commanded position that is each time there is an increase in step around 1mm. The axis movement is smooth there is no jerk even though there is a positive shift in motor stopping. i have been attaching our machine image below.

There is Repeatability issues in our system.

[TomKerekes]

You might first determine if the problem is mechanical miss-steps or electrical microsteps.

If it is mechanical miss stepping then the offset will always be an exact multiple of 4 motor full steps (1/50th of a rev). How much would that be in linear motion for your system? In this case you might reduce acceleration and/or velocity to see if the program goes away.

The other common problem is with timing on the electrical step/dir signals. If there isn't sufficient direction setup time then the first step pulse might result in a microstep in the wrong direction resulting in an offset of 2 microsteps. There would be a chance for this each direction reversal and would accumulate.

I assume you didn't have a problem before you changed the mechanics? If so it would likely be something mechanical.

How often does it occur?

[ajith]

Dear sir,

I assume you didn't have a problem before you changed the mechanics? If so it would likely be something mechanical.

yes sir, it works fine in our old setup.

If it is mechanical miss stepping then the offset will always be an exact multiple of 4 motor full steps (1/50th of a rev). How much would that be in linear motion for your system? In this case you might reduce acceleration and/or velocity to see if the program goes away.

we have already tried reducing the acceleration and Jerk value.but we didnt reduced the velocity value.
lets assume that we need to stop the motor at 100th position after we teach the coordination from DRO value.But while running it in gcode it stops in 102nd position and again repeating the Gcode using m98 command the position keeps on increasing in mm.we also facing a problem that while running two stepper motor simultaneously the motor noise increased
.i think its low voltage issue when two motors run simultaneously.i have attached my voltage clamp setting image.our motors are power up with 24vdc.

How often does it occur?

it occurs in every cycle of operation.
our axis setup is so smooth that even a slight pull makes the axis to move freely.
may i know the relation between acceleration value, velocity Value and jerk. that is whether the value of acceleration is greater than the velocity in the trajectory planner.

the axis parameter works fine with repeatability while running each motor individually but it doesnt suit for running two motors simultaneously and we can increase speed to certain value above that it doesnt react because before reaching its max speed it reaches the specified position.may i know how to choose the acceleration velocity and jerk ratio.Can you help me with setting acceleration, velocity and jerk value and also setting Voltage clamp for ensuring repeatability of our motors.

[TomKerekes]

Hi ajith,

lets assume that we need to stop the motor at 100th position after we teach the coordination from DRO value.But while running it in gcode it stops in 102nd position and again repeating the Gcode using m98 command the position keeps on increasing in mm.

By "position" do you mean mm?

So I think you are saying when moving one direction 100mm it overshoots 2mm but when you move back it does not. How do you know this? Measuring or looking at the DRO? So each back and forth motion results in a 2 mm shift?

2mm would be 2 / 25.4 x 20000steps/inch / 16uSteps = 100 full steps. or 1/2 motor revolution? Can you see this?

i think its low voltage issue when two motors run simultaneously.i have attached my voltage clamp setting image.our motors are power up with 24vdc.

Voltage Clamp looks correct for 24V

What are the specs on your 24V supply?

What are the Specs on your Motors? Looks like KStep is set for 3.13A

Please post your Init C Program and the GCode you are running. Is it doing a Rapid move or a feed move?

our axis setup is so smooth that even a slight pull makes the axis to move freely.

What do you mean by this?

may i know the relation between acceleration value, velocity Value and jerk. that is whether the value of acceleration is greater than the velocity in the trajectory planner.

I don't understand what you're asking. But Velocity of 5 inches/sec and Acceleration of 1 in/sec2 means it would take 5 seconds to accelerate to max speed. That would be very slow acceleration.

[ajith]

dear sir,

By "position" do you mean mm?

kind of sir. i just mentioned it so that it is easier to describe the problem we are facing. Actually the DRO's value is in mm.

So I think you are saying when moving one direction 100mm it overshoots 2mm but when you move back it does not. How do you know this? Measuring or looking at the DRO? So each back and forth motion results in a 2 mm shift?

by measuring

What are the specs on your 24V supply?

i cant understand sir

What are the Specs on your Motors? Looks like KStep is set for 3.13A

in this above image i have marked two motor model number(1st motor model-1 no and 2nd motor model-2 nos totally three axis) which we have been using. PSM57HS2A81-2P we used this model motor for two axis in which motor coil is connected in parallel.

Please post your Init C Program

InitKStep3Axis - set45andOP1-ACC.c

(4.96 KiB) Downloaded 90 times

GCode you are running. Is it doing a Rapid move or a feed move?

Repeat 4 pts.ngc

(775 Bytes) Downloaded 92 times

our axis setup is so smooth that even a slight pull makes the axis to move freely.

that is without powering up the motor and if i slide the axis with hand. it slide freely .my question is whether the acceleration value should be lower than the velocity value in the trajectory planner.

2mm would be 2 / 25.4 x 20000steps/inch / 16uSteps = 100 full steps. or 1/2 motor revolution? Can you see this?

we didnt noticed that sir.

[TomKerekes]

What are the specs on your 24V supply?

i cant understand sir

what are the current specifications of the supply?

our axis setup is so smooth that even a slight pull makes the axis to move freely.

that is without powering up the motor and if i slide the axis with hand. it slide freely .my question is whether the acceleration value should be lower than the velocity value in the trajectory planner.

If the Acceleration value is equal to the Velocity value then the acceleration will occur in 1 second. It is normally greater than the Velocity value because most systems can accelerate in a fraction of a second.

2mm would be 2 / 25.4 x 20000steps/inch / 16uSteps = 100 full steps. or 1/2 motor revolution? Can you see this?

we didnt noticed that sir.

Is 1/2 revolution of the motor equal to 2mm of motion? If so, how can the position be off by 2mm and the motor not be off by 1/2 revolution?