Bontech gears griding?  

Re: Bontech gears griding?

If someone could tell me please what the U shaped notch cut on the top of the mount is needed for?

Re: Bontech gears griding?

Looks like it's for access to the cleaning hole for the filament sensor that's behind the fastener - pull the little plug and blow out dust with compressed air per the manual.

Re: Bontech gears griding?

Bondtech's assembly documentation shows you should add lubrication to the gear and shaft:

https://drive.google.com/file/d/0B7A1MEUY39HCZmlFYW5oc3Rvcjg/view

Besides that, the Bondtech manual shows that the design is quite different on the original Bondtech extruder, putting the drive gears really close to the shaft outlet/bearing, which should make it stiffer. Also the secondary wheel and shaft are supported by a very stiff housing it seems.
Looking at the picture of the MK3 extruder, I wonder if it wouldn't have been possible to flip the gears and get the gear part closer to the shaft output of the motor. That would significantly reduce the leverage of the forces.

Only time will tell how durable the design of the MK3 is. In the best case this wear is a kind of "wear in" and will stabilize, but I wish we'd not have to deal with this issue at all...

Re: Bontech gears griding?

From what I can see in the earlier posted pictures is that the idler gear mount (PETG) is twisted from the spring tension causing only the gear edge tips to engage. The design and choice of material for some of these parts is questionable in my opinion. I have the ability and means to try improvements but for $800 this MK3 should be better quality.

A coworker got interested in 3D printing soon after I made my MK3 order before Christmas. He bought two similarly priced printers to the MK3. A Bibo dual extruder and a Qidi X-Pro dual extruder so he could do water soluble supports. Both those are well built but lacking some features that drew me to the MK3.

Was expecting a better first time experience!

Re: Bontech gears griding?

Finished assembling my MK3 last night and paid special attention to this part of the build. Wondering if the damage could have been from over tightening the screws with the springs? When I first screwed the idler down I screwed it all the way down and noticed that the end of the screws were sticking out the back of the part. Loosened it up and everything seemed fine.

Also, I did put a very fine amount of lithium grease on the gear teeth.

Re: Bontech gears griding?

Finished assembling my MK3 last night and paid special attention to this part of the build. Wondering if the damage could have been from over tightening the screws with the springs? When I first screwed the idler down I screwed it all the way down and noticed that the end of the screws were sticking out the back of the part. Loosened it up and everything seemed fine.

Also, I did put a very fine amount of lithium grease on the gear teeth.

I highly doubt that.

The way i check tension goes like this: I leave the screws pretty loose, to the point it wont grab the filament, then i start a print and slowly and carefully start tightening them until i get enough grip not to slip... thats it!! Any less and it would start to slip and grind the filament.

If that amount of pressure on the gears is enough for them to grind themselves... then something is wrong!

Re: Bontech gears griding?

Noticed a hint of what apperas to be rust on my MK3's gears as well, even if they're tightened according to the manual.

There's an interesting article over at E3D's blog about a similar problem, a good read.

Added a few dabs of grease on the gears, it seems to be a requirement (old school says "if it's metal on metal, lubricate it").

Re: Bontech gears griding?

...
Added a few dabs of grease on the gears, it seems to be a requirement (old school says "if it's metal on metal, lubricate it").

A Little Dab'll Do Ya!

Re: Bontech gears griding?

Has anyone contacted support over this?
I keep seeing more and more "rusted" Bondtech Gears in MK3s in other places (Facebook) and threads.

I am not sure what the stepper motor shaft is made from but i wouldnt want rust to spread to the stepper motor.

Re: Bontech gears griding?

Pre-assembled MK3. I just took a peek and I see the brown dust too. I'm going to put some lithium grease on it, but this isn't good.

Re: Bontech gears griding?

Just chiming in here that I'm also seeing signs wear on my gears.

Re: Bontech gears griding?

Ugh, the above post made me check my bondtech gears and they're showing wear and producing rust looking dust. I used a very thin amount of lithium grease during assembly to see if it would prevent this from happening. Obviously not.

Edit: Popped up a quick support session and Shane recommended to use PTFE grease or white lithium grease on the gear parts only.

Edit 2: Chat takes a while between responses. Shane recommended to check on the bondtech gears every so often and add grease as needed. If more wear shows up, start a chat and they'll replace them.