How To: Setting the Filament Drive Tension Screw

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Jules
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How To: Setting the Filament Drive Tension Screw

Post by Jules » Mon Aug 24, 2015 10:33 pm

What! We have no write-up on this yet? :shock:

Setting the tension screw on the filament drive can be a bit tricky. You want the tension to be firm enough to just catch the filament and guide it through, without smashing it in any way, since that causes problems with jamming and stripping the filament.

The tension screw should never be cranked so tightly that the two vertical uprights touch - there is supposed to be a fairly even gap between those uprights of approximately 1.5 - 2.5 mm. That's just an estimate, you can't really measure it precisely, and you can't set the tension by measuring the gap. It's going to change slightly for different kinds of filament.

What you can do, is have a bit of fun playing Sherlock ( :P ) by examining the end of the filament that goes into the drive, and make adjustments based on what you see after you retract the filament completely.

Since a picture is worth a thousand words:
Filament Drive Screw Tension.jpg
Filament Drive Screw Tension.jpg (707.05 KiB) Viewed 10530 times
Both the first and the last conditions on the chart are preceded by no filament coming out. :shock: But if you have been printing along happily and you suddenly have nothing extruding, (accompanied by a thunking sound),it's a stone cold bet that your filament diameter has swung up and you've stripped it. Retract the filament, and re-measure the diameter. Look at the tooth marks and loosen the tension if needed. (You will probably want to cut the over-sized length out of the spool.) On the other hand, if you are loading it and it doesn't feed, but comes out easily when lightly tugged at the top, that's an indication that the screw might need to be tightened a touch. In any case, it is always safer (from a non-jamming standpoint) to reverse the filament out and look at the end before you tighten that screw. Deep tooth marks are a no-no.

This is what you are shooting for. These are PLA, but you want about the same "bite marks" on whatever filament you are printing. That's going to mean adjusting the tension when you switch from one kind of filament to another, PLA to PETG for example, or any of the softer filaments. (And even though it doesn't necessarily belong here - remember that the softer the filament, the slower you print/extrude it.) 8-)
Filament Ends.jpg
This is what you are shooting for.
Filament Ends.jpg (228.2 KiB) Viewed 10530 times
:D

Tip Update: I jump back and forth between PLA and PETG on a regular basis, and i was getting a little tired of having to adjust that tension screw. Sometimes i'd completely miss the mark and wind up having to go through several iterations to get it reset correctly. One of the guys had mentioned making a mark on the bearing to see if it was turning on another post, and I decided to put that idea to use for the tension screw as well. It's a tremendous time saver......

Once you have the tension set correctly for a particular filament, make a mark on the 12:00 position of the screw. For mine, PLA is marked in black Sharpie marker (not very neatly, but i'll fix it later). So anytime i'm printing PLA, i make sure that the black mark is in the vertical position on the screw.

PETG is marked on my screw in red Sharpie, so when i print PETG, i make sure the red mark is up at the top.

That's it, and it's super easy. Notice how close together the two marks are - you don't have to tighten things up much when you switch to a different filament. But that tiny bit of turning can make all the difference.
Attachments
Screw modification.jpg
PETG being printed 'cause the red mark is on top.
Screw modification.jpg (230.3 KiB) Viewed 10386 times
Last edited by Jules on Thu Sep 03, 2015 5:18 am, edited 2 times in total.

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insta
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Re: Setting the Filament Drive Tension Screw

Post by insta » Mon Aug 24, 2015 11:57 pm

I wonder if you couldn't make a printed "torque wrench". When the plastic deflects, you're tensioned.
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Jules
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Re: Setting the Filament Drive Tension Screw

Post by Jules » Tue Aug 25, 2015 12:04 am

insta wrote:I wonder if you couldn't make a printed "torque wrench". When the plastic deflects, you're tensioned.
Make it happen Obi-Wan! (Not sure i understand how it would work, but I believe!) :P

CCVirginia
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Re: Setting the Filament Drive Tension Screw

Post by CCVirginia » Tue Aug 25, 2015 12:36 am

Thanks Jules! This is a great tip and should be locked at the top.
What I didn't do is check it when I put in the PETG (Don't think that cracked it, but it wasn't set right).

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Jules
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Re: Setting the Filament Drive Tension Screw

Post by Jules » Tue Aug 25, 2015 1:09 am

CCVirginia wrote:Thanks Jules! This is a great tip and should be locked at the top.
What I didn't do is check it when I put in the PETG (Don't think that cracked it, but it wasn't set right).
No that probably wasn't what cracked it by itself, but if it had a hairline fracture that couldn't be seen, having too tight a grip on the PETG might have finished it off when it jammed. (ABS does crack while printing - it's why most of the folks here have switched to the PETG.)

My original ABS filament drive had a crack in it too - someone at the factory caught it and glued it shut and it worked for months until i printed the PETG replacement. But they might have missed that one - it would be hard to see in that corner. Not to worry, I'm sure they'll replace it. (You can keep that one for your spare and keep using the PETG one you printed, it looks fine.) :D

CCVirginia
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Re: Setting the Filament Drive Tension Screw

Post by CCVirginia » Tue Aug 25, 2015 3:47 am

Jules wrote: (You can keep that one for your spare and keep using the PETG one you printed, it looks fine.) :D
Except it jams, perhaps once I get a "McMaster-Carr 48 gauge wire High Speed Drill Bit # 3161A63" it will work better. PETG is rough, I suspect it is catching on the imperfect hole.

HOWEVER - I don't think the roller should be binding in any case!

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innkeeper
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Re: Setting the Filament Drive Tension Screw

Post by innkeeper » Tue Sep 01, 2015 1:03 am

Never seen that chart before, that is awsum, great write up!

STICKY!!!!

i'm a bit anal over the tension, i will back out the filament after i step it in a bit, to check the bite every time i change filament. I've found this is especially helpful if you change filament types often, or use different brands. .

only other thing id say is, if you do strip the filament, do clean the plastic off the teeth, it will save you headaches. The pieces of plastic stuck in the gear may cause you to skip or strip again even if things are set correctly. I've had limited success with using compressed air or using vacuum to get out the peaces. for me taking the nozzle mount off the stepper and cleaning it with a brush works the best for me.
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Jules
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Re: How To: Setting the Filament Drive Tension Screw

Post by Jules » Wed Sep 02, 2015 11:33 pm

Added a new little tip update to the original write-up that someone else might find useful. Saves a lot of time resetting the screw. :P

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