Filament Drive Pinion gear slipping on shaft

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airscapes
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Filament Drive Pinion gear slipping on shaft

Post by airscapes » Thu Dec 19, 2019 11:07 pm

Not sure the cause, be it the grease I packed in the gear box or what but:
I printed and replaced the filament drive housing with on off thingivers that was altered to tighten up the filament path for flexible as I was having issues with the Ninjaflex not consistently extruding. In hind sight it may have been the gear problem I am about to explain.
The new drive housing has a filament path of exactly 1.75 which I cleaned out with a 1.75mm drill bit, I did not open it up to 2mm like the stock unit.
It worked well with NF and I got the parts printed that I needed. I then wanted to print something else in PLA and grabbed a old roll of MakerGeek filament. There was apparently a bend in it and it jammed after just a minute. After some head scratching I realized the stepper was running but the filament gear was not turning. After pulling the drive and gearbox off I found the pinion gear had slid down the shaft of the stepper. I was able to pop it off with a pick, clean all the grease off and inspect for cracks. There is no damage and support did not know if this was press fit or something else. I did a search here and found one post suggesting it is held on with adhesive. So I put it back on with a drop of CA and it is currently printing.
The question is: Is the CA the correct product? Anyone ever run into this, any other suggestion other than replace everything?
Picture is the gear when the unit was first removed.
pinion gear.jpg

thunderbt3
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Re: Filament Drive Pinion gear slipping on shaft

Post by thunderbt3 » Thu Dec 19, 2019 11:17 pm

The gear is slip fit onto the shaft. Green loctite is what you need to get back rolling.

I would first clean everything very well to isopropyl alcohol to make sure the gear hasn't cracked. Apply a bit of green locktite to the shaft and slip the gear back on. It takes about 24 hours to fully cure.

airscapes
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Re: Filament Drive Pinion gear slipping on shaft

Post by airscapes » Fri Dec 20, 2019 1:59 am

Did all that, cleaned and inspected, just use CA rather than locktite, only have the medium strength stuff from HF and didn't know if it would be too thick to do any good. If it comes loose again I will use the locktite.
Thanks for the info!

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ednisley
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Re: Filament Drive Pinion gear slipping on shaft

Post by ednisley » Fri Dec 20, 2019 1:43 pm

airscapes wrote:
Fri Dec 20, 2019 1:59 am
just use CA rather than locktite
Cyanoacrylate adhesives are brittle and have poor shock resistance, which the pinion desperately needs.

Threadlocking adhesives tend to be more resilient, although high-strength versions set hard.

However, if the pinion has worked finger-loose, then no adhesive can secure it to the shaft against the motor torque.

Installing a new pinion from MG is really the only way to go.

airscapes
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Re: Filament Drive Pinion gear slipping on shaft

Post by airscapes » Fri Dec 20, 2019 5:15 pm

I ordered one to have on hand as I didn't hold much hope that the CA or locktite will work. I would have assumed it was a light press fit not held in place by adhesive. Also a little disappointed that support could not tell me how that gear was affixed. The person who answered did not know and asked one of the builders. Since this is a complete unit purchased from china they did not have knowledge of the gears installation.
After cleaning I looked at the inside of the bore under high magnification and it appeared to have remnants of a chemical bonder as it was kind or white in places. No cracks or missing metal. It did slide on with finger pressure..

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ednisley
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Re: Filament Drive Pinion gear slipping on shaft

Post by ednisley » Sat Dec 21, 2019 2:25 pm

airscapes wrote:
Fri Dec 20, 2019 5:15 pm
a complete unit purchased from china
To a good first approximation, all electronic & electromechanical components come from halfway around the planet. That's a rant for another time, but just the way things are.
slide on with finger pressure
Yeah, that one's dead.

If you don't have trouble ramming the pinion in place, it's too loose: it should be a very tight fit.

airscapes
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Re: Filament Drive Pinion gear slipping on shaft

Post by airscapes » Sat Dec 21, 2019 4:35 pm

CA is holding, but have not had anything jam, just printing little 2 walled squares playing with Prusaslicer 2.1.1 which seem like it will be the software to use in the coming year(s) Liking the results better than simplified 3D ver 4.01.. Not sure that S3D has much of a future.. seems like they were bought by someone with no clue..

airscapes
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Re: Filament Drive Pinion gear slipping on shaft

Post by airscapes » Sat Jun 06, 2020 6:53 pm

Update: I tried to install some old Makergear PLA which is hard as a rock (going in the trash now) and it stopped the extruder, spinning the shaft in the pinion gear. I had purchased a replacement gear from MG knowing this would happen at some point.. took off the motor, pulled off the old gear and guess what the new gear .. "Spun right round like a record, baby Right round round round" If your old enough that will be stuck in your head for a while :D
So I used blue lock tight with the old gear as it at lease fit snug..
Guess I had better order an entire assembly which really bothers me. Maybe when this comes loose again I will sand the shaft with some 320 wet/dry and use JB with the new gear.. should be enough clearance between the shaft and gear for the JB Weld to lock them together..
I am open to other ideas on fixing the gear to the shaft, if there is something better than JB Weld
Doug

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ednisley
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Re: Filament Drive Pinion gear slipping on shaft

Post by ednisley » Sat Jun 06, 2020 10:33 pm

airscapes wrote:
Sat Jun 06, 2020 6:53 pm
use JB with the new gear
Although I'm a big fan of JB Weld, it's probably the wrong hammer for the job, because epoxies depend on a mechanical joint you don't get with a shaft, even a sanded one.

Threadlockers are designed to lock threads, not smooth-ish shafts to pinions. Some info from the Loctite people may be helpful:

https://www.henkel-adhesives.com/us/en/ ... ckers.html

However, you can get "retaining compounds" designed for shafts:
https://www.henkel-adhesives.com/us/en/ ... ounds.html

The label has long since worn off my bottle of green shaft lock, but I think it's something like 648.

If you've got an arbor press or drill press to shove the pinion on, get everything lined up / fixtured first, clean the shaft & bore with acetone to get rid of oils, anoint the shaft with Magic Juice, ram the pinion in place, then wait a day for it to cure.

Do, however, be careful of the cured adhesive:
https://softsolder.com/2012/04/26/ouch/

airscapes
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Re: Filament Drive Pinion gear slipping on shaft

Post by airscapes » Sat Jun 06, 2020 11:26 pm

Ed the issue is the new pinion gear will drop right on, no pressing need, spins like a fidget spinner. Hole in gear is bigger than the shaft.. .01-02mm maybe more.. Was hard to get a good measurement with the caliper. Will you magic juice work on that?

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