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Stepper motors miss stepps

Posted by hokanp 
Stepper motors miss stepps
August 18, 2017 10:28AM
Hi
Have an CoreXY printer with Nema 17, A4498 stepper drivers and Ramps 1.4.
2 motors become hot + 100 degrees. I lowered the voltage on the stepper drivers down to 0,42.
Motors now about 50 degrees BUT now it skip stepps.
What to do?
BR
Re: Stepper motors miss stepps
August 18, 2017 04:08PM
What kind of motors are you using? What sort of guide rails and bearings? How big is the mechanism? How heavy is the X axis?

If things are misaligned, the motors will struggle to move the mechanism. Make sure the mechanism can move easily without the belts in place. Next put the belts on tensioned loosely and make sure the mechanism still moves easily. Tighten up the bets and see if things start to bind. If you over tighten the belts you put a lot of lateral force on the bearings and guide rails. If they flex it will cause problems.

Pictures of the printer would help...


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Stepper motors miss stepps
August 18, 2017 10:19PM
Hi
There are no problems with the mechanism, Everything moves easily. It is an CoreXY with 3 mini Wheels on all Y-zaxle and 4 Wheels on X-axle.
Nema 17.
The problem is that in idle the motors temp is about 50 degres.
Can it help to increase the voltage, from 0,42 to 0,5?
When it was at 0,69 the PLA melted.
BR
Re: Stepper motors miss stepps
August 18, 2017 10:53PM
If the mechanism moves easily and the motors are slipping, the motor torque is too low for the speeds/jerk/acceleration settings you are using. Increasing the motor current can get you a little more torque, but as you have discovered, it also gets a lot more heat. You must either reduce speed/acceleration/jerk or get higher torque motors. Since you've provided no information about the motors or the printer there's no way to know if the motors are capable of making the mechanism do what you want it to do. Start by decreasing the acceleration and jerk- try 300 mm/sec^2 and 2 mm/sec^3. Print at low speed to start- try about 30 mm/sec. Once you have that working, increase the acceleration, and speed in small steps. Once you have found the limits there, start adjusting the jerk upward. As you increase acceleration and jerk, you'll see ringing in the prints go from small to more severe. Use a number that provides satisfactory print quality.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Stepper motors miss stepps
August 18, 2017 11:46PM
Hi
I am going to try to lower to acc and speeds.
Steppermotors: NEMA 17.
Lock at attachments.
BR
Attachments:
open | download - 20170819_083832.jpg (200.6 KB)
open | download - NEMA.PNG (17.7 KB)
Re: Stepper motors miss stepps
August 19, 2017 07:35PM
You have a 12V motor. Not good, especially if you are using a 12V supply. You want to get lower inductance motors- look for motors rated for about 2A at 1-3V. The motor drivers control the average current in the motors- rated voltage doesn't bear any relationship to power supply voltage except that it is normal to operate steppers at 5-20X their rated voltage in order to keep torque up at high rotation speeds.

Edited 1 time(s). Last edit at 08/19/2017 07:38PM by the_digital_dentist.

Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Stepper motors miss stepps
August 19, 2017 11:52PM
Hi
That I didnĀ“t know. OK, I order new motors 2,55V and 1.7 Amp.
I have 2 12 V PSU.
I am up and running with the printer. Temp on the motors about 60 - 70 degrees.
Thank you for your help
BR
Attachments:
open | download - 17HS4417L20P1-X2.pdf (89.8 KB)
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