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Z axis "clicking" on z-hop

Posted by dlc60 
Z axis "clicking" on z-hop
February 11, 2020 02:40PM
I have a RepRap Cartesian printer that is "old school". I built it from a friend's design, and have upgraded many parts. The X-axis moves on a rails whose gantry moves on the Y-axis rails and the Z axis is three ball-screws, two of which are paired with steel rods and whose ball-screws rest in bearings on the bottom and are "free" at the top. The third screw is the driver and is attached to a stepper at the top of the printer and rests in a bearing on the bottom. These are all straight and "true" and without the stepper, the bed moves freely up and down. They are all joined by a circular belt.

Here is my question. Lately I have noticed that there is an audible "click" or "clack" whenever a print does a z-hop during a retract. The sound comes from the ball-screw that is attached to the stepper. The noise does not occur when the z-height is changed for a new level, only when it goes up-and-down during a retract. As far as I can tell, everything is still working as well as it ever did, but this new noise has me worried that something is about to fail, something has changed. I have checked my set-screws and they are all tight and the shaft adapter also seems snug to both the stepper and the ball-screw.

What could this be? What do you think is changing?

Any insights are appreciated!
DLC


Kits: He3D K200 Kossel, Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head
Scratch: Large bed Cartesian, Linear slide Delta, Maker-Beam XL Micro Delta
Re: Z axis "clicking" on z-hop
February 11, 2020 02:46PM
When you do lift on retract the Z axis reverses direction very quickly...Is it the sound of the balls banging into each other inside the nuts?


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Z axis "clicking" on z-hop
February 11, 2020 04:31PM
Quote
the_digital_dentist
When you do lift on retract the Z axis reverses direction very quickly...Is it the sound of the balls banging into each other inside the nuts?

Hmm, I suppose that it could be that. It did not do this before, so I suppose that I am looking at a "bearing cleaning" and oiling job. Which is a drag, because it is basically a complete tear-down of the Z-axis mechanics and another re-alignment session for the bed hardware. Ick. Well, replacement, repair or refurbish, it is all the same tear-down!

Thanks,
DLC


Kits: He3D K200 Kossel, Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head
Scratch: Large bed Cartesian, Linear slide Delta, Maker-Beam XL Micro Delta
Re: Z axis "clicking" on z-hop
February 11, 2020 04:52PM
I wouldn't tear anything down- I think that it's a normal sound based on the motion. Inside each nut there are a bunch of balls in a tube that runs from the top of the nut to the bottom. As the screw moves the balls recirculate through the tube. There is some extra space in there to allow the balls to move freely without scraping on each other too much. When you quickly reverse the screw, the balls shift in the space and bump into each other, hence the clicking sound.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Z axis "clicking" on z-hop
February 11, 2020 06:29PM
Quote
the_digital_dentist
I wouldn't tear anything down- I think that it's a normal sound based on the motion. Inside each nut there are a bunch of balls in a tube that runs from the top of the nut to the bottom. As the screw moves the balls recirculate through the tube. There is some extra space in there to allow the balls to move freely without scraping on each other too much. When you quickly reverse the screw, the balls shift in the space and bump into each other, hence the clicking sound.

OK. I wonder if I changed a setting that shortened the minimum extrusion before a retract was done and it made the jumps quicker, causing me to notice something that I hadn't before. Hmm.

thanks,
DLC


Kits: He3D K200 Kossel, Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head
Scratch: Large bed Cartesian, Linear slide Delta, Maker-Beam XL Micro Delta
Re: Z axis "clicking" on z-hop
February 14, 2020 01:26PM
One of the axes on my delta started clicking occasionally. It turned out to be a disintegrated bearing on an idler pulley.
Re: Z axis "clicking" on z-hop
February 24, 2020 10:16AM
Quote
etfrench
One of the axes on my delta started clicking occasionally. It turned out to be a disintegrated bearing on an idler pulley.

Yup, I have seen that. A cheap 608ZZ bearing on my Y-axis belt did that.

DLC


Kits: He3D K200 Kossel, Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head
Scratch: Large bed Cartesian, Linear slide Delta, Maker-Beam XL Micro Delta
Re: Z axis "clicking" on z-hop
February 24, 2020 10:25AM
The problem has gotten progressively worse, I don't think that the Z layer is coming back correctly on a Z-hop. Prints that have lots of hops have gaps appearing, weakening them. When running "vase mode" with no Z-hops I can see layer variations that are semi-repetitive. I think that the bearing in the drive screw is degenerating. Fortunately I have found a replacement "bearing" for the 8mmID/12mmOD ball screws that I am using. I cannot easily replace the entire ball screw because it is custom made, so this is a less expensive ($22) way to test the theory. It will still be chore to pull the screw, replace the bearing (without losing any balls!) and re-level the bed, but what I have now is not usable, so...

BTW, anyone with experience have any tips for installing a new ball screw bearing without losing any balls? (Yeah, I know, lets keep the teenager humor to a minimum...)

DLC


Kits: He3D K200 Kossel, Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head
Scratch: Large bed Cartesian, Linear slide Delta, Maker-Beam XL Micro Delta
Re: Z axis "clicking" on z-hop
February 24, 2020 12:20PM
I've done it a few times. Keep the whole thing vertical, and spin the nut up to the end of the screw, and try to keep it under control so you can take the balls out one by one. I used antimagnetic stainless steel tweezers to grab the balls. Keep a jar of degreaser handy to drop the balls into as you retrieve them. Putting them back is always harder than getting them out...


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Z axis "clicking" on z-hop
February 25, 2020 05:24PM
Quote
the_digital_dentist
I've done it a few times. Keep the whole thing vertical, and spin the nut up to the end of the screw, and try to keep it under control so you can take the balls out one by one. I used antimagnetic stainless steel tweezers to grab the balls. Keep a jar of degreaser handy to drop the balls into as you retrieve them. Putting them back is always harder than getting them out...

it would be nice if there was a reliable way to just spin the new one onto the screw. I will try that first, then the tedious way, which is how i have done it in the past.

Printers are constant maintenance headaches, they eventually all need repair or updating. I am planning a Duet upgrade on this guy. Arduino/Marlin and Octoprint are not particularly reliable or consistent. Cheap, but not all that good.

DLC
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