Z-axis skipping at start of print.

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helifrek
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Z-axis skipping at start of print.

Post by helifrek » Wed Mar 25, 2015 1:19 am

Hey guys,
My M2 has been printing happily for about 4 months now and suddenly the Z axis has started skipping on me right after the bed raises to the top and hits the limit switch. If I support the bed with my hand to keep it from dropping it does just fine. It seems like the Z motor just looses power for a split second. I haven't made any changes at all to anything. I am using S3D, haven't made any changes in there either.....
I am stumped.

Any ideas?

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jimc
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Re: Z-axis skipping at start of print.

Post by jimc » Wed Mar 25, 2015 1:32 am

either A: you need to lube the rods and bearings or B: the bed is raising and hitting the nozzle which will make the bed drop. the bed gap would need adjustment in this case

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insta
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Re: Z-axis skipping at start of print.

Post by insta » Wed Mar 25, 2015 2:54 am

helifrek wrote:Hey guys,
My M2 has been printing happily for about 4 months now and suddenly the Z axis has started skipping on me right after the bed raises to the top and hits the limit switch. If I support the bed with my hand to keep it from dropping it does just fine. It seems like the Z motor just looses power for a split second. I haven't made any changes at all to anything. I am using S3D, haven't made any changes in there either.....
I am stumped.

Any ideas?
One of my M2s does this as well, like the motor makes this godawful squealing sound and it drops about 6", then continues like nothing is wrong?
Custom 3D printing for you or your business -- quote [at] pingring.org

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jimc
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Re: Z-axis skipping at start of print.

Post by jimc » Wed Mar 25, 2015 3:06 am

yup nozzle contact or the resistance to raise the bed causes a missed step. as soon as you mis a step the weight of the bed just drops it like a rock. sometimes the bed goes all the way down, sometimes the stepper catches mid way and goes back up.

benavery
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Re: Z-axis skipping at start of print.

Post by benavery » Wed Mar 25, 2015 3:13 am

Perhaps check the lubrication of the z-axis leadscrew. It gets significantly more wear at the top last bit of the travel than anywhere else (unless every print you do is super-tall), so it might look nicely lubed upwhen you look at half-way up it - but the last little section perhaps not so much.

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helifrek
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Re: Z-axis skipping at start of print.

Post by helifrek » Sat Mar 28, 2015 1:12 am

Thanks for the tip guys. I have noticed there is a lot more resistance up towards the top of the z-axis, the bed doesn't fall anymore. Definitely needs cleaned up and lubed! I never really notice because my end g-code lowers the bed. Will clean it up and get back to you guys!

Thanks again!

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helifrek
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Re: Z-axis skipping at start of print.

Post by helifrek » Sat Mar 28, 2015 2:13 am

I think that fixed it! What is the best kind of lube to use on the Z-axis rod? The included stuff seems rather thick for that application.

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jimc
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Re: Z-axis skipping at start of print.

Post by jimc » Sat Mar 28, 2015 2:23 am

I use grease on the threaded rod and oil on the rods. I actually use 30w bar and chain oil on everything because its a little sticky and doesnt run down the rods

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