Reprinting broken filament drive

[CCVirginia]

Today I found that my filament drive was cracked , no idea why - perhaps it was when some cleaning filament jammed up. This crack was causing skipping at full speed.

Cracked drive

CrackedFilamentDrive.jpg (29.78 KiB) Viewed 8431 times

It was still working somewhat so I thought I would try printing one. The drive is in ABS as PLA would melt, but I have never used ABS and it didn't seem like the time to start experimenting. I have used PETG a bit and had it calibrated, so thought I would give it a try.

The print came out quite good.

New drive

FilamentDrive.jpg (35.67 KiB) Viewed 8431 times

I did have to add supports and found I didn't have exactly the right drill bit for the filament hole - but we make do.

After installing it and setting the tension so the teeth go in about 1/3 of the way I tried it, but it jammed. I found that the bearing the filament rides on was binding against the main drive. I was able to back off the pressure to get it to work, but it should not be binding. The print looks OK in this area

I thought perhaps this had to do with different shrinkage of PET, but I would think that would have the opposite effect. Any ideas why it would not work or if there is another model that would work better? I have asked MG for a replacement, but would like to know how to make parts. Perhaps ABS has to be used?

Thanks!

[jimc]

you can use abs or petg. the slot where the bearing goes needs to be cleaned out and very smooth. i know that gap needs support to be printed and supported horizontal overhangs with petg don't always print really clean. when you tighten that shoulder bolt down its just snugging down on the bearing. disassemble the thing and clean it out with an exacto knife and maybe some sandpaper. you really should not have to buy the plastic parts from makergear. aways keep one or two spares of ever plastic part on the machine.

[CCVirginia]

you can use abs or petg. the slot where the bearing goes needs to be cleaned out and very smooth. i know that gap needs support to be printed and supported horizontal overhangs with petg don't always print really clean. when you tighten that shoulder bolt down its just snugging down on the bearing. disassemble the thing and clean it out with an exacto knife and maybe some sandpaper. you really should not have to buy the plastic parts from makergear. aways keep one or two spares of ever plastic part on the machine.

Yup, I cleaned it out (twice), best I can tell it is not binding against any "grunge", but against the properly printed vertical side nearest the gear. This is not an easy area to get to so I could be missing something. It seems like the clearance is not sufficient for the bearing, could this be due to the V4 and the part model not being up to date?

By the way, where is the best place to get a proper sized bit to clean out the path without paying more for shipping than the part? I used a slightly larger (SAE) one on the top and a slightly smaller on the bottom.

I am still in me guarantee "grace period", so this is not costing, but I do want to be able to print parts - just didn't think I would need them yet!

[Jules]

Looking at your first picture at the top of the ABS drive - that looks like it cracked because the tension on that top screw was way too tight. On my drive there is a fairly even gap of between 1.5 mm to 2.0 mm showing between those two uprights. The gap on the PETG one that you printed looks about right from the front, but you can't really see how tight it is at the back where the screw is located. PETG is going to be more flexible than ABS - it won't crack, but it might be what is causing your binding problem if the screw is too tight.

Try measuring the gap with calipers at the top and see if it is much narrower at the back where the screw is. If so, loosen it up. Mine prints best with about a 1.8 mm gap at the screw, 2.0 mm or so at the front.

The teeth will just barely catch the filament - you don't need to really dig in for a full third of the strand. (And if you do need to catch that deeply in the filament for the filament to be forced in, then you likely need to ream out the hole more. The interior of that filament hole absolutely needs to be at least 2.0mm in diameter to handle occasional filament diameter swings, or you will get jams down the road. The hole needs to be perfectly even, smooth, and straight all the way through. (ie: It's worth the investment in the long drill bit, even with the shipping costs. Or you can try 2.0 mm fence wire, which i hear works too.)

Looks like a good print though, so it will probably do just fine with a little adjustment or two.

[CCVirginia]

Looking at your first picture at the top of the ABS drive - that looks like it cracked because the tension on that top screw was way too tight. On my drive there is a fairly even gap of between 1.5 mm to 2.0 mm showing between those two uprights.

It is tight because I had tightened it prior to realizing it was cracked, it had not been that tight but may have been more tight than you suggest. I also had the filament tangle and break a few days ago, perhaps it happened then. I have been printing with PLA but when I put in PETG it skipped, perhaps PETG has more back pressure.

I tried to print with the new one today, but it stopped feeding the filament and "scraped out" a portion. I don't know if this is due to the hole not being just right or the pressure not being sufficient. I have not seen a picture of an "ideal" amount for the teeth to dig in, base on other posts I thought it was more than you suggest. Here is the one that failed last night, which is as tight as I can go without the roller binding:

Filament with gear marks

Filament.jpg (31.37 KiB) Viewed 8391 times

Not a great picture, but you can see the teeth marks and where it stopped.

BTW: Thanks so much for your consistent support of this community!!

[jsc]

PETG does have significantly more back pressure, and will strip out if you try to print it as fast as you're used to with PLA. I banged my head for a considerable period trying to figure out why until I just decided to go slower.

[Jules]

Looking at your first picture at the top of the ABS drive - that looks like it cracked because the tension on that top screw was way too tight. On my drive there is a fairly even gap of between 1.5 mm to 2.0 mm showing between those two uprights.

It is tight because I had tightened it prior to realizing it was cracked, it had not been that tight but may have been more tight than you suggest. I also had the filament tangle and break a few days ago, perhaps it happened then. I have been printing with PLA but when I put in PETG it skipped, perhaps PETG has more back pressure.

I tried to print with the new one today, but it stopped feeding the filament and "scraped out" a portion. I don't know if this is due to the hole not being just right or the pressure not being sufficient. I have not seen a picture of an "ideal" amount for the teeth to dig in, base on other posts I thought it was more than you suggest. Here is the one that failed last night, which is as tight as I can go without the roller binding:

Filament.jpg

Not a great picture, but you can see the teeth marks and where it stopped.

BTW: Thanks so much for your consistent support of this community!!

Yeah those teeth are digging in way too much - loosen the screw up some. That scraping out is called "stripping" and it means the tension is too tight.

(I wasn't sure whether you had tightened that drive for the picture or not, which was why i hadn't said anything until now. ) It's really not necessary to dig into the filament much at all - if you are running it too tight, it might be causing a lot of the issues you are seeing. I'll see if i can find a shot of one of my ends and show you how little it actually takes to move that filament through. (And Jin is also right, slow the speed down when printing PETG.)

[jimc]

3600mm/min is about where you need your print speed for petg. Also keep in mind that compared to la most plastics are soft. Petg is def on the softer side. If your tension is too tight you will squish your filament into an oval and it will be too big to slide through the lower hole in the filament drive causing jamming. As jules said, that drive cracked from too much tenstion. It should not take much tension at all to grip filament. My tension bolt is only ever finger tight. I never have to use the hex driver on it. If your filament is stripping its from too tight or some other issue. Get yourself a 2mm drill bit from mcmaster.com, amazon or wherever. Prob wont find one locally. It needs to be a longer bit as well

[Jules]

Okay, I dug a few ends out of the trash and took a shot - these are PLA, but you should see about the same amount of "tooth marks" on any filament that you print. Probably about a 10-15% "bite".

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