Z axis issue: wrong movement (layers)
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@zecchi
My fault , the line is actually the number eight. So the current is 1.7A. awesome.This is the link :
€ 21,62 20%OFF | Nema17 Stepper Motor 42 motor Nema 17 motor 42BYGH 1.5A 38mm 17HS4401 motor 4-lead for 3D printer CNC
https://a.aliexpress.com/BBHPrX2gL -
This is the response to M122 command:
If you see something strange ,please let me know.
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Everything looks good to me. I think it is mechanical though. I went through a similar ordeal with my own Z axis a while ago. There was a repeating pattern. It wasn't exactly like your pattern but similar in nature. I ended up tearing the entire Z axis apart and replacing many of the chinese belts, pulleys, idlers, lead screws with better quality alternatives as I suspected some eccentricities in the pulleys and possibly some misalignment or bend in the lead screws. I was able to get it mostly eliminated, but it could still be seen in certain lighting conditions, but more faintly.
Take it apart. Inspect everything. Roll the lead screws on a flat surface. Check the couplers and pulleys. Test the motors and feel how they move in your fingers. Try different motors.
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Is this issue dependent on layer TIME at all?
IE, if a series of layers take the same time, the pattern repeats evenly, but if the layers vary in time, the pattern has a different frequency?
I think it could be your bed heater heater model/thermistor settings. Are you using the same thermistor in your heat bed as for your hotends? Your config indicates this. I don't see any heater model parameters in your M307 command for the bed heater. This would be using the default heater model, which is based on an e3d V6, no?
Many heating elements can expand and contract, or rather distort and contort in different ways, causing the position of the Z axis to vary slightly. Better tuning of the heater could help, if this is the case.
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@Phaedrux said in Z axis issue: wrong movement (layers):
Roll the lead screws on a flat surface
This is absolutely ok. It has been my first test.
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@bot said in Z axis issue: wrong movement (layers):
Is this issue dependent on layer TIME at all?
I don't think so. Rather it depend on height of the model: different models same errors at same height.
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@bot said in Z axis issue: wrong movement (layers):
Are you using the same thermistor in your heat bed as for your hotends? Your config indicates this. I don't see any heater model parameters in your M307 command for the bed heater. This would be using the default heater model, which is based on an e3d V6, no?
Yes , I'm using e3d V6. I'll try to repeat auto-tuning of PID for the nozzle. Maybe the error is due by the instable temperature.
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@zecchi said in Z axis issue: wrong movement (layers):
@bot said in Z axis issue: wrong movement (layers):
Are you using the same thermistor in your heat bed as for your hotends? Your config indicates this. I don't see any heater model parameters in your M307 command for the bed heater. This would be using the default heater model, which is based on an e3d V6, no?
Yes , I'm using e3d V6. I'll try to repeat auto-tuning of PID for the nozzle. Maybe the error is due by the instable temperature.
Have you pid tuned the bed as well? Bang Bang mode on the bed could cause some up and down motion via warping and expansion.
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@Phaedrux I think it’s worse than that. The user seems to be using pid with the bed but using default parameters. This may not be worse than bang bang but it could very well be.
I don’t think the user understood what I was saying. Tuning the bed PID or trying bang bang was my suggestion, basically. I’m so bad at wording posts.
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@bot said in Z axis issue: wrong movement (layers):
The user seems to be using pid with the bed but using default parameters
Yeah , it is. I've never tuned the bed because I never use it (At least for now ).
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@zecchi Sorry about that. If you're not heating the bed that is clearly not a factor.
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Today I'll try the new z axes. I set up them yesterday. My last chance...
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And here we go!!
The problem were the two z axis.
Maybe it was due to the elasticity of the belts!!Thanks to all.
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Congrats on solving the issue.
A question out of curiosity, what did you change in your Z axis?
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@zecchi
Thank you for sharing.
So you wouldn't recommend short belts for driving the axis?
I was close to modify my HEVO in the same way.
By the way, have you designed the geared axis by yourself? -
@Dkos
I've replaced it in this way:
Actually there are other improvements to do (these lead screws are too short ) but for now it's ok
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All my printer is designed by me.
And yeah , belts are not a good solution for high loads. -
@zecchi Thanks for the info, I also have the same issue as you had (i think), but not as intense as yours and i am running my Z axis with a closed loop belt. I guess i will give the direct a try to see if the issue is going to be completely eliminated for me as well.
Cheers!
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So I'm guessing eccentric pulley leading to uneven motion.
