1 Topic by Claghorn (edited by Claghorn 2013-12-15 00:10:08)

  • Claghorn
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Topic: So is this backlash?

I see lots of articles talking about backlash in here, but I'm not actually sure I really know how it shows up in a print. Is this an example?

http://home.comcast.net/~tomhorsley/hardware/solidoodle/problems/backlash.jpg

That's a photo of the back of the dalek I just printed. The model has an absolute flat surface with the hemisphere bumps on it. The printout appears to print a raised band on the flat part in the layers with the bumps. I've been guessing that this is the infamous backlash because the print head takes different paths when it moved out and back to print the bumps rather than going straight to print the completely flat surfaces, but just wanted to verify I have the name of this defect correct.

P.S. This is printed all in red, but it is weird how the flash had such an effect on the color - no actual multi-color filament was involved :-).

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2 Reply by FordGalaxie

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Re: So is this backlash?

If you use repetier host, go into the G-code tab.  It lets you view the entire model with each sliced layer.  If on that model it shows those ridges then its just the way that the model was produced.

3 Reply by Claghorn

  • Claghorn
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Re: So is this backlash?

The .stl file certainly has no ridges, I suppose the slicer could have added them, but that seems unlikely, and in fact, if I look at the gcode view in RH, I don't see any bands. I'm pretty positive they are printing artifacts, still wondering if the name of the artifact is "backlash" though :-).

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4 Reply by techbuilder2175

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Re: So is this backlash?

Can you take a couple more pictures from various angles?

It looks like it could be moire but I can't 100% tell from that photo since some parts of the photo are over exposed

Powder coated steel enclosure, 1/4" Surface grounded hardened aluminum plate, MK2A Heat bed, .200 Polished fused quartz plate, Machined quick change hot bed mount, E3D hot end, Ramps 1.4, DRV8825 stepper motor drivers

5 Reply by adrian (edited by adrian 2013-12-16 04:10:46)

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Re: So is this backlash?

Backlash if it occurs will be persistent on any directional change.

You measure it using a dial gauge against the frame. Move 10mm, then back 10mm and you should return to 0. If it goes to anything other than zero, then that is the amount of backlash.

Your problem looks like overshoot to me (I.e, velocity and acceleration too high for the distance, with some jerk issues for good measure (instantaneous acceleration)). Knock 10% off speed and try again.