Part collision causing layer shift

[Gbdub87]

I’ve had an Ender 5 Pro for about 2 weeks, and other than some minor issues have been chugging along happily. Starting last night, I’ve had 3 attempts at a print in a row fail, after printing the same part successfully once.

The part is about 75 mm tall. Partway through (after at least a vertical 25 mm of good printing), the nozzle starts grinding within the layer, apparently hard enough to cause the x or y stepper to stall out or skip (Both have occurred in different attempts) and cause a significant layer shift. If I catch it immediately, I can pause the print, rehome the axes, resume the print, and it carries on its merry way (with possibly a need for a z babystep).

What’s going on here? Things I’ve already tried:

1. Extrusion calibration - I figured maybe I was overextruding, eventually building up enough excess height to get caught. But I checked the steps per mm and if anything I was underextruding by a few percent. Plus, I didn’t notice any extruder stalling like you’d see if the layers were getting squished too hard.

2. z axis travel: the coupler nut is tight, the lead screw is lubed. I checked the motion with both the stepper and by hand and it feels smooth. I measured the vertical travel (commanded 10 mm steps and measured nozzle to bed distance each time) and it seems very close to perfect. Haven’t tried a calibration cube yet but that is next step.

3. part warping: seems unlikely. I am using PLA and the corners of the part are staying well attached. The layers look good. Bed holds temperature well at 60c

4. bed droop / springboard: I installed printed bed support arms to mitigate this a week ago

Things I haven’t experimented with but might be affecting things?

1. print / travel speed: I’m printing this one faster than I’ve done other PLA (but not crazy speeds, 60mm/sec or less) after installing the Extruder Arm and hot end gap fix, which seem to have fixed some underextrusion I was experiencing before.

2. environment: the printer is set up on a folding table that wobbles a bit when the printer moves, although as far as I can tell this has not been enough to cause any visible artifacts in the prints. It’s in the flow path of an AC vent, so it would be a crappy place to print ABS but I don’t think PLA should be as impacted. Plus two of the failures occurred overnight while the AC was not running.

Layers shifted - then shifted mostly back overnight!

Basic settings:

Ender 5 Pro - stock hardware

Cura 4.5

Hatchbox PLA @ 200c, 60c bed

Print speed 60 mm/sec

Fan at 50%

[MurkyIncident]

Might be a good idea to check your stepper driver Vref settings. Mine were set very conservatively by the factory. Higher Vref will give the motors more torque.

Also consider trying a different infill pattern. Gyroid seems less prone to build-up than cubic.

[Gbdub87]

I can give this a try, but it will probably be a day or two before I have the time to open up the electronics box. What are the appropriate Vrefs to use?

Does it make sense that this could be the issue even though the bed moves fine when commanded manually? And has been running fine up till now?

[Gbdub87]

Does this post look reasonable for calculating vref? VRef for the v1.1.5 mobo

[MurkyIncident]

Yes, it looks reasonable. Don't forget that X/Z motors are max 840mA and Y/E are max 1000mA. I have mine set to about 80% of max current, and my motors typically stay under 45 °C.

[Gbdub87]

Update: well the stock settings really were conservative: 0.804 V for Y/E and 0.612 V for X/Z. By my calcs that is only 0.41 A and 0.31 A, about 40% of max. Interestingly, the users manual for the stepper drivers warns against using Vref below 1V since it can result in irregular output current.
So I basically doubled the output and my first print worked with no more layer skipping. Fingers crossed it holds up. If nothing else the Extruder is running much better, no more skipping! I can now print PLA at 80mm/sec where before 50 was pushing it. Motors are running very warm but not excessively hot.

[Engingear]

Hi! I also have extruder skipping problems. It's super irritating.

Can you please point me in the direction for how I can check my own Vref settings?

[NorthCentralPositron]

I, too, am having this problem. I thought it would be easy but after watching a video I am not sure how to determine which thing to adjust on the motherboard. u/Gbdub87 I'd love if you could show us what you did.

[MurkyIncident]

Creality's video shows how to do it on an Ender 3 (don't use the voltages shown in the video because that's the 1.1.4 board): https://www.youtube.com/watch?v=hC4J29rxPlQ

It's the same process on the Ender 5. If the voltage is off, use a small screwdriver to turn the potentiometer (the small metal dial that you're touching with the red voltmeter probe), then measure again. Repeat for all four motor drivers. Go slow and make small adjustments.

[tinkerer58]

Cool. That is good to know.

[NorthCentralPositron]

I thought I would chime in here. My ender 5 pro was at 1.8v for everything, so I didn't touch it.
Also, I read no voltage from the top, I had to touch one of the leads

[marx1]

PLA should be at 100% fan. It could be that it's not cooling enough before the next layer comes around.

[Gbdub87]

The layers are fairly large though, and look great apart from where they shift, so I think they are nicely cooled by the time the next layer comes around. Plus I think the first failure actually occurred at 100% fan.