i need some advice for circles and sticking (Page 2 of 3)

@JustSomeGuyTN

Can you messre the bump yo have? Mine is abot 0.2mm

I think this is too much. When i print parts that have to fit together this will be a problem.

@JustSomeGuyTN

Would be nice if you could measure the bumps when you got a caliber. Thank you.

@Solidoodle Support

Can you please check if this is a common problem with the printers? I think there is something defectiv in my device.

These bumps are so annoying, I cant print parts that should fit together. Printing cubes is just fine but circles are a horror.

The rods on the y-axes are not parallel. The holes for the rods are not drilled prperly i think. Is there are way to adjust the parallelism?

I will also try to change the y-axes motor with the x-axes one. Maybe its a stepper problem.

What else could be going wrong?

I did try to use the new hysteresis fix (backlash) with the new M99 function, but it does have no effect on my prints. (Actually it gets worse)

thanks for your help

Kvirre, I believe it was the Y axis drive belt that I tensioned.  It's the stepper at the very back of the case that's screwed to the left side with four screws.

Kviree,

I made mine a bit tight.  Probably dropped the stepper down about 2 to 3mm down from where it was.

Most difference did the relocation of the stepper in the back.
Here are pictures of before an after.

Hard to see it from pictures though.
Just take the advice if you have this problem.

The one in the back.
Beside the z-offset screw

This is normal, and part of microstepping/steppers in general. 0.2mm is about 1 degree, which is less than a step on these steppers. http://www.micromo.com/microstepping-my … ities.aspx

So when you microstep, you don't have enough torque to overcome friction in the system.

You need to set up backlash to work around it, or use a bigger motor/stepper driver, or turn up the juice and provide active cooling on the Y stepper and driver.

Basically, it's part of buying a $500 printer.

Check out this video from Solidoodle's Vimeo account.

The firmware setting is 88 steps/mm, which without microstepping is 5.5 steps/mm.
1 step =  .18mm.  It seems like that should be good enough, but the motors are run at less than the rated voltage to keep them from getting hot enough to melt the ABS motor mounts.  This means they don't get the maximum torque, and maybe it isn't enough for the Y axis.

I don't know how much torque is required, or achieved, but the Y motor is rated for 2.8v and a holding torque of 30 oz.in which is well within recommendations at the reprap wiki.  Maybe a worthwhile test would be turning up the voltage on the Y motor driver a little and seeing if it will step .2mm.   Also use a dial gauge and see if hitting the .1mm button 10 times moves 1mm, even if it didn't move on every button press.

Something I've been thinking of doing is replacing the motors with steppers that have a 400 step/rev resolution.  I think this would improve the surface of the prints.  Maybe it would make them more accurate as well.

Hi Ian,

Instead of switching to a 400step/rev motor, have you instead considered moving to a DVR8825 motor driver? It will be able to tolerate higher temp, and can do better microstepping resolution.

That said, I'm asking you this, but I reason your answer might be "Sanguino can't run the stepper motors fast enough." I haven't looked into it, but I have no idea how the firmware calculates accelleration and so forth, but in certain ways (acellstepper library for arduino, for example), it can't do more than 4000 steps/second, and that's without the additional overhead that I'm sure the marlin firmware has for all the other things it's doing.

In several ways it will be an easier option to switch to DRV8825. If you do switch motors, make sure your new motors are of similar inductance. The motor "voltage rating" will be closely enough correlated with the motor inductance.  If the inductance is too high, then you will need a higher voltage power source to step the motors quickly enough (to get the current into the motor windings during fast steps.).

Also, I found your statement that the motor temp is kept down because of not wanting to melt the mounts as very interesting. I think I measured the outside of the motors to be 50-60 celsius. How hot do you think they can get before they're softening the motor mounts?  I understand abs gradually softens, but there must be a point at which everything is ok, and a point at which it'll accumulate into longterm damage.

My goal right now is to in one swoop implement an AC heated bed, and peltier modules on each of the motors, and just have a stand-alone arduino regulate the peltier modules on the motors. Peltier modules to cool the motors because I want to have a higher printer case ambient temperature (the hot side of the modules will help with that), and I want the peltier modules to help cool the motors in the situation of having a higher-temp ambient print case. If the peltier modules end up working very well, then I'll also be able to afford increasing the current on the motors, above what it is right now. This is especially relevant on the X axis which is part of the mounted extruder movement, though the Yaxis and Z-axis I could just upgrade to a bigger motor (since they're "unsprung")

Bouncing ideas back right now.  Hope it's not too much of a thread hijack. Seems relevant.

try to calibrate using this, http://www.soliwiki.com/Calibrate_Filament_Flow
also
measure the thickness of the z thickness of the ring and adjust the z stop screw clockwise to make thicker.  counter clockwise to make thinner.  .5mm or .020 inches per turn.