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Extruder Drive - spring tension

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Hi community

I know there's lots of threads about this already, but I didn't find anything about my particular problem. So here it is:

Assembling my UM, I noticed the part where it says "the spring should be about 11 mm long" (not the actual formulation but I guess you know what I mean).

So I screwed the thing in until the bolt couldn't be turned any more. My guess is the bolt just reached the end of the thread.

Still, my extruder drive spring is like 15-16mm long.

The printer works finde, didn't have any serious problems yet. The tension seems pretty stiff, but still I'm curious whether this is normal or not.

I'm using the UM version shipped in July 2013 (for now I guess it's the newest one).

I took the bolt with the length it said to (30mm).

So, what should I do? I could just use a shorter bolt and get my 11mm. But then I don't know if there would be too much tension because there's quite some pressure on the plastic parts already and I don't want to break anything.

Btw, I also noticed that the Extruder drive motor can't be locked onto the wooden part tightly. The bolts are too long...

(I noticed that when the motor started to vibrate and roar like crazy)

Is there something off with the assembly instructions? I feel like I should have used shorter bolts but I'm sure I used what it said in the description.

Thanks for the help!


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Still, my extruder drive spring is like 15-16mm long.


Can you send a photo? This area of the UM changed in the last 6 months. But are you sure you are measuring the spring length and not some other distance? Also 11mm is the length with filament in the feeder *and* the feeder closed onto the filament.


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I had a lot of problems with the Extruder Drive. I had the feeling it did not press into the PLA hard enough to get enough 'grip' and a lot of prints were lost.

I fixed it by sanding out the U shaped part were the spring pushes into. I sanded the bottom of the U to give it a bit more range. I also sanded the parts of the black plastic part that pushes into the wooden part of the extruder part. This way the little wheel that pushes into the PLA has way more drive so it gives you way more range in tensioning the spring. If I can press in the wheel with a force of 15kg I get no failed prints anymore. Too hard and it will jam, too light and it won't push any PLA through.

Hope that helped!


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Also, this sounds a little obvious but make sure you are measuring the distance between the areas where the spring makes contact; not the end of the screw to the bottom of the spring.

And when you are trying to screw it down to achieve high tension, you may have a similar problem that I did. When I began to turn it, the nut turned with it. In order to stop this and to overcome the high static friction, you must press really hard when you are screwing it with the screwdriver and at the same time, use something to hold the nut in place. As for your motor screws, use shorter screws? there should be extras. You only need 3 or 4 mm of thread inside the motor from the screw to avoid stripping. Hope this helps.


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