1 Topic by paramite12

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Topic: Z-axis problems

Whenever I'm doing prints I end up with these squished out layers every once in a while and then the part ends up shorter than it is supposed to. Is the z-axis not moving as it is supposed to? How can I check this? I have a heavily modified SD3. I recently upgraded my power supply and the extruder. I have never had trouble with the z-axis until now. I'll post pics tomorrow once my part is done which appears to be messed up. Has anyone else had any similar problems to this?

2 Reply by grob

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Re: Z-axis problems

Pics will help, but your instincts sound right. Try running it manually up and down and listen for funny noises at any point. If it shudders/clicks anywhere the stepper might be missing steps. If not, there's something else going on! e.g. how consistent is your filament?

A couple of low-involvement / generally helpful anyway options:
* Tune v-ref for the z stepper driver (usually gets ignored as there's plenty of overhead, but still...)
* If it's getting squeaky anywhere you can add lubrication (3-in-1; sewing machine oil or similar does well) to the thread
* Make sure the stepper drivers and board are cooled (fan?) - even though the z axis only moves once a layer, the driver is usually always powering the coils to hold in place.

SD3. Mk2b + glass, heated enclosure, GT2 belts, direct drive y shaft, linear bearings, bowden-feed E3D v5 w/ 0.9° stepper
Smoothieboard via Octoprint on RPi

3 Reply by paramite12

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Re: Z-axis problems

Thanks for the advice, it could probably stand to have some lube put on it. I think I figured out what was causing it though. I had a kind of filament funnel thing that was attached to both of the rods that the print bed rides on. I believe it was squeezing the rods together just enough to make too much friction for it to move properly. I removed it and it seems to be printing normally again.

4 Reply by grob

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Re: Z-axis problems

Aha, yes - the bushing friction is quite sensitive to force like that.
Glad to hear you've sorted it out!

SD3. Mk2b + glass, heated enclosure, GT2 belts, direct drive y shaft, linear bearings, bowden-feed E3D v5 w/ 0.9° stepper
Smoothieboard via Octoprint on RPi

5 Reply by paramite12

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Re: Z-axis problems

Unfortunately I didn't sort it out sad It's still doing it. My print failed about 10mins from the end of a 2 hour print. I attached pics of the first one I tried that ended up being bad. Those are supposed to be circles and instead they are all smashed and messed up.
I removed the funnel thing and then put lubricant on the rods but it didn't help. In fact, after I put the lubricant on it messed up almost immediately. What should I try first?

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6 Reply by wardjr

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Re: Z-axis problems

A fan on the board will help cool the steppers.  Adjust the VREF  for that stepper and put a little oil on the threads.  Clean up the rods if they are all gooped up with grease just a dab is all you really need.

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7 Reply by grob

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Re: Z-axis problems

wardjr wrote:

A fan on the board will help cool the steppers.  Adjust the VREF  for that stepper and put a little oil on the threads.  Clean up the rods if they are all gooped up with grease just a dab is all you really need.

Agreed - the z axis shouldn't be having this much trouble; the motor should have plenty of oomph. How is it when you run it up and down manually for a while? Any strange noises?

SD3. Mk2b + glass, heated enclosure, GT2 belts, direct drive y shaft, linear bearings, bowden-feed E3D v5 w/ 0.9° stepper
Smoothieboard via Octoprint on RPi

8 Reply by pirvan

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Re: Z-axis problems

Here's another question to the OP.  Are you using Z lift on retraction?  Try disabling that and see if your problems go away or get less pronounced.

Usually the Z motor doesn't get a ton of work, only drops the bed once every layer, but if yo use Z lift, it could be working quite a bit, and it looks like it's getting progressively worse during the build.

Another thing to look for is wobble in your bed during printing.  Does your print bed appear to move side to side during prints and does this side to side wobble get worse as the bed gets lower?

To print or, 3D print, that is the question...
SD3 printer w/too many mods,  Printrbot Simple Maker Ed.,  FormLabs Form 1+
AnyCubic Photon, Shining 3D EinScan-S & Atlas 3D scanners...
...and too much time on my hands.

9 Reply by paramite12

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Re: Z-axis problems

I'm not using Z lift and the problem is actually pretty random. Those pics show one that gets worse as it goes, but I have also printed things that start off bad, go back to being fine, and then get bad again.
My bed doesn't seem to wobble, but the threaded rod does. It's always been like that though and it used to work fine.
It doesn't seem to make any strange noises when I move it up and down. Maybe a bit of struggling some times?
How do I adjust the VREF?

10 Reply by paramite12

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Re: Z-axis problems

I tuned the trimpot on the stepper controller a bit and that seems to have fixed the problem. It also made it a lot less loud. Thanks for your help everyone!