Proper Filament Tip Diameter After Unloading - MK3S+ & MMU2S
 
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Tom De Winter
(@tom-de-winter)
Active Member
Proper Filament Tip Diameter After Unloading - MK3S+ & MMU2S

I'm seeing about a 5% failure rate on filament changes. I think the tips are too large causing it to hang up at one of several points during load or unload.

Attached is a photo with dimensions of a typical tip after an unload. The fat area is 4.5mm long and 1.96mm diameter. This is the Prusa silver filament supplied with my printer. I'm using numerous brands (all PLA) and the problem exists on all of them.

I'd appreciate any thoughts on solving this.

Thanks

Posted : 03/12/2022 4:14 pm
Tom De Winter
(@tom-de-winter)
Active Member
Topic starter answered:
RE: Proper Filament Tip Diameter After Unloading - MK3S+ & MMU2S

I went back through the complete MMU build and filament path with a great attention to detail. I didn't find any problems. I disassembled the hotend and thoroughly cleaned the nozzle and heat-break. There was some baked junk inside, probably the result of leaving preheat on too long (?). I set the tensions on the MMU and extruder lighter than I had been running them. The MMU screws were set level with the housing and the extruder with the screw tip flush with the nut.

Meanwhile I finished my Lack V2 Enclosure so I put the printer in the enclosure with the spools and Prusa buffer on top of the lid.

I then ran a torture test with 5 color changes per layer. It cycled through all five colors for a total of 1250 color changes. The first load of #2 failed. It had a completely square tip. Assuming that this caused the misload I prepared this tip and the remaining three with a more rounded end and restarted the print. 

This time it ran flawlessly through all 1250 filament changes.

At times several of the colors would back straight through and out of the buffer instead of curling inside. On the fuller spools this created loops coming off of the reels. I rigged some temporary fixes. Now I've printed a check valve and filament guide for each color. 

 

Posted : 09/12/2022 9:21 pm
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