Z axis "clicking" on z-hop

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

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Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.

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?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

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

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Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.

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.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

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

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Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.

One of the axes on my delta started clicking occasionally. It turned out to be a disintegrated bearing on an idler pulley.

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

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Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.

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

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Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.

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...

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

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

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...

Seven hours later I still have not gotten my 1204 ball screw nut back together. I truly hate these things. These cheesy three-race reciprocating ball screws are evil incarnate.

Nine hours later, assembled three times, always notchy. Either notchy to start with or (most likely) a ball dropped in a "gap" causing jams. I am a stubborn person, but I value my time more than a $21 purchasing mistake! Time to find a more quality product. Bother.

There has to be a better device than this...
DLC

Edited 1 time(s). Last edit at 02/29/2020 01:09PM by dlc60.

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Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.