Is that any different to the existing z wobble calibration software fix? There is also the "hysteresis" fix which kinda sorta worked, but really was about backlash (dunno where the hysteresis entered into it.. )
http://www.soliwiki.com/Calibration_of_the_Z_wobble ?

I had initially thought the hysteresis fix was what I wanted to deal with the backlash but found it had been pulled from the firmware.  After that, I tried looking into Skeinforge's lash settings.  But for whatever reason found that my Skeinforge install wasn't extruding (traced the path, but the E codes had very small values in them.)

When I came across the NoLash thread it suggested that Skeinforge's lash setting maybe wasn't implemented quite correctly.  So I didn't go any further down that rabbit hole and instead chose the more familiar burrow of converting code to C.  Which would work on Linux anyway ...

Yes, the link you posted to the calibration of z-wobble does in fact look to be what I had in mind.  Thanks for making me look at it - I was aware of it, but hadn't gone there yet...

Matt

Whilst backlash is present in the X/Y axis due to how the belt teeth interface to the pulleys, in reality its far more minimal than you get out of the Z-Axis. Unless you need extreme precision in the X/Y axis and very tight tolerances, I would consider it a nicety and not a neccesity in comparison to dealing with Z-Axis backlash.

If I can get the code ported over, I'd like to see if the Z-axis can be adjusted in the same way.  What I'm thinking, though, is that the Z-axis might be affected by periodic error (again, evident in telescope mount worms/gears).  In which case it might be possible to create the equivalent of a "pointing" model (where software adjustments are made to improve the pointing accuracy of a telescope) that is simply a function of the Z-axis coordinate.  Haven't really thought this one through yet though ...

Matt

How do you determine the amount of backlash in the x and y axes?  I did the z-wobble calibration that required printing 3 cuboids, but I haven't seen any x and y backlash calibration cubes.

I mounted a digital dial indicator onto the bed, such that I could move the extruder in the Y-direction 1mm at a time.  Then I wrote down all the readings as I used the "manual" mode in RH to move the extruder.  Did this going in forward and reverse for a few millimeters.  At the switch in direction, where there would have been a 1mm move if there were no backlash, there was instead a move of about .6mm.

I also recorded the indicator readings for all the nominally-1mm moves.

Did this routine 5 times and averaged the results to judge both backlash (thats where the .382mm came from) as well as what the true stepping rate was for the Y-axis stepper.

Because of the size of the dial indicator and my off-the-cuff clamping, I couldn't measure the x-axis in the same way (I need to find a way to bolt on a non-flexing flat surface to the extruder).  What I did instead was print 3 cylinders with 0, .1mm and .2mm settings for the X-axis backlash.  Then I eyeballed which one looked best.  That's the one you see in the picture.  FWIW, I've so far left the X-axis stepper at 88 steps/mm.  The Y-axis came in very slightly less than that - around 87.92 if I recall.

This was on an out-of-the-box SD3 (with only a firmware update).  So I'm sure things could be improved with the whole belt-tightening routine.  At the end of the day, though, I don't particularly care if the improvement is made in hardware or software as long as the end result is the same.

Hope this helps,
Matt

How do you determine the amount of backlash in the x and y axes?  I did the z-wobble calibration that required printing 3 cuboids, but I haven't seen any x and y backlash calibration cubes.

Print a 50mm object such as a long and thin rectangle then measure it... the difference +/- the 50mm's assuming calibrated wall thickness ("Extruder Calibration") is roughly your backlash.

The more precise method, is to print the Dial Gauge holder and use a Dial Gauge braced against the case or a block. Move the head in 1mm increments and ensure that you see 1mm changes on the dial gauge. Any deltas is once again the amount of backlash.

Whilst backlash is present in the X/Y axis due to how the belt teeth interface to the pulleys, in reality its far more minimal than you get out of the Z-Axis. Unless you need extreme precision in the X/Y axis and very tight tolerances, I would consider it a nicety and not a neccesity in comparison to dealing with Z-Axis backlash.

The before and after image is attached (y-axis backlash setting was .382 and x-axis was set to 0.  Note that I have not yet done any belt-tightening adjusts...)

The code is C# and requires .NET to be installed.  So this doesn't help me on my Linux box.  I've started porting it to C/C++ but admittedly am making slow process trying to match the code output of NoLash.

Hope this helps a bit...
Matt

Solidoodle's Vimeo calibration didn't work. So I changed X/Y Stepper motor cables while printer is working so that find out trim pot issue is exist. Result was same. Same bumps are made at top and bottom of circle. I think Y belt is still problematic.

How do you guys see this bumpy circle?

P.S
I think this topic should get 'sticky' mark. In consideration of the number of replies and views, there are many who having this circle problem I think.

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.

I did find out that when i tighten only 2 screw of the y-axes stepper the print gets better. When i tighten the lower left screw my y-aces rod is being bend real bad.
I think the chassis is bend.

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.

But it didnt help me. The problem still stays the same.

me again:)

I couldnt solve my "Circles have Bumps" problem so maybe someone can help.

Please look at the attached Picture for details.

After switching the X/Y Stepper motor cables and endstops with each other the "Bump" just flipped over to the righthand side.

This cant be a Backlash problem right?

When i print Circles in different sizes the "Bump" stays the same in shape but gets bigger in size=)

I am at my wits end, i dont now what to do. I already changed the Y-Stepper and the hole Belt-Pully system to a better HTD-Profile. I do have almost zero backlash in x, y, and z with 1mm steps only with small 0,1mm steps there is backlash of 0,1mm in Y.

Maybe it has something to do with the elektronics?

Thanks

breaker