Extruder gear miss alignment

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DrewPetitclerc
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Extruder gear miss alignment

Post by DrewPetitclerc » Mon Oct 29, 2012 5:04 am

I'm now after a new design flaw I've found in the extruder that I must admit I missed on my first design review and am embarrassed by.

This may only apply to some but if I've learned one thing from having worked on more than 12 UP! plus machines is each and every one is unique is small ways, so yours may vary.

The flaw is the extruder gear that is pressed onto the motor shaft is not aligned properly with the filament path, turns out a great deal of feeder problems are due to the simple fact that the extruder gear only catches an edge of the gear teeth when engaging the 1.75mm dia filament.
I found this problem when I was getting feed slippage even with my self adjusting pressure roller and on inspection of the filament that had be passed through I noticed the very small corner indents from the gear into the plastic when they should have been long full width tooth marks, when I disassembled the unit I found the gear had walked out to very near the end of the shaft and after pressing it back down to the flat stop on the motor shaft I noticed that it really is not in the right place to best utilize the full width of the gear teeth.

Since the filament slides along the face of the motor it only sees the outer edge of one side of the gear, and if the gear should slip even a small amount towards the end of the shaft and the filament diameter reduces you could get slippage, if you check the wear on your gear I'm willing to bet you will find the pattern is near the edge and not in the center were it should be.

This can be remedied by pressing the gear deeper into the motor so that the filament is gripped more in the center of the gear teeth, but to do this the gear will have to be pulled from the motor shaft and the flat on the shaft ground back a millimeter more and/or the gear bore will need to be recessed to make it press further down the shaft.

I hope this helps some of you and I hope the company will take notice and make a small design change for the better of all the newer machines.

Regards
Drew
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2012-10-28_12-43-48_932.jpg
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2012-10-28_12-41-46_299.jpg (50.26 KiB) Viewed 6813 times
Drew Petitclerc
Petitclerc Designs
Owner/Senior Principal Designer, prototype, tooling and test equipment design and 3D printing
http://flash-graphics.deviantart.com/
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mr6k
Posts: 327
Joined: Tue Feb 14, 2012 11:47 am

Re: Extruder gear miss alignment

Post by mr6k » Mon Oct 29, 2012 12:46 pm

Drew,

Thought this image might help users check their gear feed alignment.
The image shows where the gear has gripped the filament on a well aligned gear. To test go into maintenance, perform an extrude and then a withdraw. When the filament has been withdrawn you should feel a serrated section on on side of the filament near the end as seen in the image. To see it clearer, when using light colored filament, just rub a lead pencil over the serrations. I guess the gear of the test image is well placed as the serrations appear over a good 1mm of the material circumference. I guess in Drew's case the serrations would be over a somewhat smaller circumference.

cheers

Peter
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goopyplastic
Posts: 42
Joined: Mon Jul 30, 2012 5:53 am

Re: Extruder gear miss alignment

Post by goopyplastic » Mon Oct 29, 2012 6:25 pm

I purchased a replacement extruder stepper and it came just like your picture, maybe even worse. I didn't attempt to try and use it but instead let Afinia know and they cross-shipped me a new one that did not have this issue (was almost perfectly level).

Image

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