This Smartrap is losing steps only in the x-axis,

(Matt Urich (Redleader36)) #1

This Smartrap is losing steps only in the x-axis, can you guys help me figure out why?

It’s an older Smartrap with spectra line instead of belts. The controller is a Sanguinololu with genuine Pololus running a half-year old version of Marlin. The motors are all 1.8°/step. The issue I am having is a very consistent missing step when I print objects with bridging around 2" or wider in the X axis. It’s hard to pin down, but it seems to only happen when there is bridging, and in some cases corrects itself on layers there there is no gaps. The part in this picture printed without issue when I rotated it to print wide in the Y axis. Here is my Marlin configuration:

Can anyone give me any suggestions? I’m thinking this issue is way too consistent to be backlash or anything loose (or maybe anything mechanical). Also, the way it corrects itself is curious.

(Thomas Cox) #2

Tighten your belts?

(Matt Urich (Redleader36)) #3

@Thomas_Cox as I said above, there are no belts. I’m running spectra line. Also, if my line were lose, why would it correct itself and why would it only be a problem on wider prints?

(Thomas Cox) #4

@Matt_Urich_Redleader ​ At this point I would start there and continue with the basics of troubleshooting until I had my answer. You could also boost the motor current and lower acceleration values.

(Kevin Billett) #5

I do not think spectraline is a reliable method for mechanical drive motion period. You want better precision, go with good belts or the best is still lead screws.

(Jonatan Pipping) #6

Could it be that it’s correcting itself by hitting the endstops?
My first thought is that it’s skipping when attempting to achieve the higher travel speeds, but that would give the same symptoms as needing to tighten the belts: it doesn’t explain the correction. Autocorrection could be a separate phenomenon, and in that case: raise the motor current.

(erik vdzalm) #7

This is not caused by missed steps. (Unless you have a very high resolution).
Most of the times this is caused by slipping pulleys.

(paul wallich) #8


(Matt Urich (Redleader36)) #9

Nobody got it. The reason I’m losing steps is my X and Y motors are switched (and so are the endstops). It only happens on wider parts because the printer is crossing the Y_MAX_POS limit on what I thought was the X axis. Apparently I’ve also learned Cura, Pronterface, and OctoPrint sideways.

(Danut Lipsa) #10

You are loosing steps from two reasons. Spectra line is running directly on motor shaft and there is no good grip and will slip. Or acceleratin is too high. I had same issues when tested with spectra line.

(Michael Scholtz) #11

What is your non printing moves speed relative to your printing speed. If it’s much faster could slip when moving. I converted mine to belts right off the start. I posted a 16t pulley on thingyverse under redsalamander. Print 2 of those and convert to belts.

(Michael Scholtz) #12

@Ian_Lewis3 post a new topic. Asking at the end of someone else’s discussion won’t get you answers.