SL .25 Micro printerhead, proper tension?

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MrRemj
Posts: 10
Joined: Tue Oct 13, 2015 9:06 pm
Location: Seattle, WA

SL .25 Micro printerhead, proper tension?

Post by MrRemj » Sun Dec 30, 2018 4:50 pm

The stock printerheads (Mini 1.03/1.04) are pretty forgiving, but I've been having trouble getting a good tension on the filament feed for the Micro head - grinding off filament, where the filament can't feed anymore.

I've experimented with tight, loose, and everything between. Once I start seeing the filament bits in the metal herringbone gear, I abort and try again. (I managed to get halfway through a print, once, before it started grinding off.) I use the nut to gauge how tight the feeder is. (Looking at it from above, the nut moves away from the filament when you turn the dial clockwise, loosening tension.)

1. If it's a question of tension, where is your nut in the loose/tight spectrum?
2. If it's not a question of tension, what should I be experimenting with?

Thanks for any feedback, and I hope others get use out of the discussion.

Galadriel
Aleph Objects | LulzBot
Posts: 272
Joined: Mon Sep 25, 2017 10:23 am

Re: SL .25 Micro printerhead, proper tension?

Post by Galadriel » Mon Dec 31, 2018 10:51 am

This might be a matter of tension and if so a good way to find the best tension for the filament you are working with would be to completely loosen your idler, load your filament into the toolhead, preheat the toolhead to extrusion temperature, then extrude 10mm+ at a time and slowly tighten the tensioning screw until you start seeing a solid line of filament extrude out of the bottom of your toolhead.

It is also possible it could be a matter of a couple other things and to help narrow down if it might be other potential causes it would be helpful to get some more information. What filament are you trying to print with? (Type, brand, and diameter.) Along with the type of filament you are using knowing the settings being used would be very helpful. Also, could you post a couple photos of how your prints are coming out?

MrRemj
Posts: 10
Joined: Tue Oct 13, 2015 9:06 pm
Location: Seattle, WA

Re: SL .25 Micro printerhead, proper tension?

Post by MrRemj » Sat Feb 16, 2019 3:39 am

I straightened out the issue for awhile. (Coming back now to close this.)

Your solution of slow incremental feed is definitely a useful process.

For other people's data: I've been using up the last of my 3mm MakerGeek PETG, switching over to 3mm Filastruder PETG. I've been using a flat 230 degrees for extrusion.

It definitely feels like a different experience than the stock toolhead from the 1.04/1.03. The two knobs to adjust tension, super-easy to get right. The .25 SL, inserting the filament with the arm pulled back, wiggling a little to get seated deeper in, releasing the arm...extrude...and usually it feeds, otherwise repeat Galadriel's wise words of extrude a bit, slowly tighten the screw...

fastrobplus
Posts: 26
Joined: Thu Sep 27, 2018 10:57 am

Re: SL .25 Micro printerhead, proper tension?

Post by fastrobplus » Fri Mar 01, 2019 2:03 pm

I just got my printer back last night from Lulzbot support with the .25 toolhead and had the exact same issue. The tension screw was super tight and when I heated the toolhead, tried to extrude 5mm of the lulzbot green PLA they left in the hotend for shipping it quickly ground the filament to powder and fouled the gear teeth. After 2 hours of heating, cleaning, adjusting to get that initial PLA out, I eventually seem to have settled on just to the "looser" side of exactly halfway. I just printed two benchies successfully (in PolyLite orange PLA) though it feels like the printer operating right on the edge between feeding and grinding the filament.

I'm wondering if this has something to do with the nozzle creating back pressure. One of the reasons the printer was shipped in for repair is that I was having print quality issues. It turned out the factory had put a .5mm nozzle on the .25 toolhead by mistake. I didn't know that at the time since it never occurred to me. But I also didn't have the grinding issue at all with that nozzle. So assuming I get the same toolhead shipped back and only the nozzle was changed, this seems to be the culprit.

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