Worn out extruder gear?

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pyronaught
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Worn out extruder gear?

Post by pyronaught » Wed Sep 28, 2016 8:31 pm

I have a printer that has been running fine for a while and then just started failing to push the filament through at random intervals. It will stop, then start again and so on, leaving dead spots all over the print. The extruder gear will barely even grab the filament unless I have the tension wheel screwed all the way in to the point where the gap completely closes. Any thing less than that and I can pull the filament through the extruder by hand without much effort. Even with the wheel all the way in, I still don't see much bite on the filament as it comes out and it will still stop feeding at random intervals and then start again. The extruder gear is one of the newer fine toothed type and I'm wondering if maybe these are just subject to wearing out faster, or maybe the refurb machine I got had a used gear on it that had a lot of hours on it. It just seems like it has to be the gear causing the problem. I'm going to switch back to the coarser toothed gear since I've never had any problems with those. Anyone else ever had a gear wear out like this? My first printer from two years ago with tons of hours on it is still using the original gear, but this one I'm having problems with is only a few months old and probably only around 500 hours on it.
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pyronaught
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Re: Worn out extruder gear?

Post by pyronaught » Wed Sep 28, 2016 10:03 pm

Looks like it wasn't a worn out gear... I replaced the printed filament drive with one from a working machine and then it started working again with the normal tension gap. That narrows it down to either the tension bearing or the printed part. I'm printing a new v4 filament drive to check if it is the printed part. I really don't see how it could be the printed part though, unless there's a difference between the r2 vs r3 versions of the drive, since the original was an r3 and I replaced it with an r2. I find the r2 gives you a higher success rate when feeding in a new roll of filament mid-print. Something about the r3 makes new filament jam more often on the change-over.
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sthone
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Re: Worn out extruder gear?

Post by sthone » Thu Sep 29, 2016 1:46 am

I've had the same problem in the past... I think the printed drives just wear out.

My best guess is the bottom part where the bearing half of the printed drive joins the gear side just loses its stiffness over time and you really can't get a good tension anymore.

I came up with this modified design and it's been working great ever since. I don't even change my tension anymore it's been pretty much "set it and forget it" for me.

I bet once you print some new stock drives though you'll notice your problem go awhile.
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pyronaught
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Re: Worn out extruder gear?

Post by pyronaught » Thu Sep 29, 2016 2:14 am

Yeah, I printed a new drive and it's working fine now. I want to modify that drive so that the exit hole under the gear on the inside has a funnel lead-in. Just having a hole on a flat plane like it is has been plaguing me on feeding in new filament during a print when a spool runs out. If the end of the filament doesn't hit that hole dead-on then you get a jam and have to try and yank the filament back up through the gear to try it again-- meanwhile the extruder is printing air until you finally get it to feed. A funnel at the mouth of the hole should eliminate that problem.
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sthone
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Re: Worn out extruder gear?

Post by sthone » Thu Sep 29, 2016 3:15 am

Both the R2 and R3 versions look like they have a bit of a funnel to the bottom hole already I think the only difference with the R3 is it has the cut out on the left side to clean the gear with a brush.

When your changing/chasing filaments while running are the ends of both filaments cut at 90°?
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Re: Worn out extruder gear?

Post by jimc » Fri Sep 30, 2016 1:35 am

are you sure the pinion gear in the planetary box is not worn out? that is usually the thing to go ....atleast in the past. not sure what era the extruder motor is. it takes quite alot to wear out the filament drive. i do replace them maybe once a year though.

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pyronaught
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Re: Worn out extruder gear?

Post by pyronaught » Fri Sep 30, 2016 7:24 pm

jimc wrote:are you sure the pinion gear in the planetary box is not worn out? that is usually the thing to go ....atleast in the past. not sure what era the extruder motor is. it takes quite alot to wear out the filament drive. i do replace them maybe once a year though.

The outside gear is still turning when the filament stops feeding. I can flip the fan to the side to check it pretty easily, so I know it's not the internal pinion. Plus printing a new filament drive fixed the problem. I've got all refurbished machines, so I don't know what was replaced and what wasn't following what I'm assuming was a long period of in-house use by MakerGear. It could be the filament drive had a lot of miles on it over what I've personally printed on it.
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pyronaught
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Re: Worn out extruder gear?

Post by pyronaught » Fri Sep 30, 2016 7:28 pm

sthone wrote:Both the R2 and R3 versions look like they have a bit of a funnel to the bottom hole already I think the only difference with the R3 is it has the cut out on the left side to clean the gear with a brush.

When your changing/chasing filaments while running are the ends of both filaments cut at 90°?

I've tried cutting at both 90 and 45 and don't notice any difference. If you take the drive off and try just pushing a stick of filament through it, you will see that it catches on the bottom hole 50% of the time. So if there's a funnel there it is pretty ineffective and needs to be made larger.
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sthone
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Re: Worn out extruder gear?

Post by sthone » Fri Sep 30, 2016 8:16 pm

Strange.... the 90° cut usually does the trick as long as you keep both filaments butted up to each other during the feed.

Makergear does supply the step files on the Github page for the filament drive though so it should be pretty easy to just make the bottom opening a little more chamfered.

Looking back at my modified drive I think I did open mine up a bit more as well as fileting the openings edge too so maybe that's why I don't have any problems.

Either way it's always good to have a few spares on hand.
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pyronaught
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Re: Worn out extruder gear?

Post by pyronaught » Mon Oct 03, 2016 11:49 pm

After having a new feed jam about six times in a row I finally downloaded the step file for the v4 filament drive, r2 and modified it. There was a little bit of a funnel there, but not nearly enough. I about doubled the opening diameter of the funnel and will see how that goes.
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