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X axis skipping steps

Posted by croak3r 
X axis skipping steps
December 27, 2017 09:06AM
Hi guys,
I'm having an issue with my printer skipping steps on the x-axis. I thought the driver was overheating so I lowered the voltage and added a fan, but that did not solve it. I also tried lowering the jerk setting from 20 to 10, but thats not helped either. Bed seems to move smoothly and I have played around with the belt tension too.

It doesnt always seem to skip steps either. I have tried printing test cubes and other small objects but they come out fine, but when I try to print a new mount for my hotend every new layer skips further away from the original position.
Can anyone recommend what could be causing this issue?
Re: X axis skipping steps
December 27, 2017 09:40AM
If your X-Axis has a belt you may need to increase the tension.
Re: X axis skipping steps
December 27, 2017 07:48PM
Try lowering acceleration as well as jerk. Otherwise, check if the rails move smoothly etc.
kr_
Re: X axis skipping steps
January 03, 2018 03:33PM
This means your steppers are skipping steps. I've had this happening for various reasons, some being linked.
1 - Driver over heating : add a heat-sink and set the current below manufacturer's specifications. There are tutorials for this.

2 - Too high acceleration and jerk : this produces shocks, especially on sharp trajectory changes. Patterns like this can also be seen if these are too high : "echoing effect". Try lower acceleration and lower jerk.

3 - Resonance : your printer has natural frequencies and mode shapes. You're likely to hit one when doing repeated short and fast moves, like during some top fills. When the moves frequency matches a natural frequency, while moving in the same direction than the corresponding mode shape, the moves get amplified. Try lower speed and /or lower acceleration and lower jerk. Tightening belts as suggested, rigidifying the structure or reducing mass help too.

4 - Bumps : Bumps can appear and increase layer after layer. This is the trickiest to avoid when trying to print decently fast. I've seen them forming mostly while doing infills. It can be caused by too much plastic coming out of the nozzle. Calibration problem can do that. Also plastic leaking out when not required (Bowden or soft plastic with too little retraction). Highly reducing the speed during "bumpy layers" avoids them occurring or smoothes them out.

5 - Warping : The plastic often warps upwards when doing overhangs. This can be solved by placing appropriate supports or sometimes be smoothed out by slowing down. It can also warp from bad bed adhesion. I'm preventing it by printing a skirt and heating the bed.

Steppers have a higher torque at lower speed, so slowing down can give enough torque to not skip steps when cases 3 to 5 occur. Reducing acceleration and jerk leads to reduced speed too for short moves. I also noticed my printer going easier through cases 4 and 5 with reduced Āµstepping.

I found 3 and 4 too tricky to avoid 100% while trying to print fast, which led to lots of failed prints, mostly day long ones... This pushed me to upgrade my steppers to closed loop ones Misfittech Smart Stepper
Re: X axis skipping steps
January 04, 2018 09:12AM
Thanks for all the replies and apologies for the late response. Turns out that it was a lose belt that caused it. My printer is an acrylic frame Prusa style and the front frame where the belt mounts bends quite a lot and causes lots of vibration, which i'm sure added to this. I've jammed a piece of wood in there to keep it stiff for now. My plan is to change over to an aluminium extrusion frame like the AM8 design.

Now that problems solved another has appeared though. My printer is not extruding enough filament (i think) once it gets to a part of a print which requires a lot of movement without extruding. I thought it may be a retraction issue, but the problem still happens with it disabled.

EDIT: Ok so this is kinda stupid, i just realised it's not the x axis i was talking about it's the Y (bed) axis. guess that would have helped.

Edited 1 time(s). Last edit at 01/04/2018 02:02PM by croak3r.
kr_
Re: X axis skipping steps
January 04, 2018 02:39PM
I've had that happening for various reasons too:
1 - Insufficient heatbreak cooling. The plastic was getting soft and expended before the heated block and less came out, especially after non printing moves. I added a fan.
2 - Too much retract, but you tried that one
3 - Bad nozzle assembly. There was a gap between a tiny PTFE tube's extremity and the heated block.
4 - A slipping extruder drive gear. I used a MK8 and increased the pressure on it.
5 - Extruder skipping steps. I reduced friction in various ways and reduced Āµstepping
6 - Leaking plastic during travel moves. I tuned retract (speed and length) and slightly reduced the temperature.
7 - Overestimated plastic advance per step. You would have the problem all the time tho, and external dimension slightly smaller because of thinner walls. I measured the wire advance to tune the setting.
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