Custom PTFE? How to calibrate?  

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inf-57
(@inf-57)
New Member

Hello,
I'm installing the MMU2 on multiple printers, I'm replacing the PTFE tubes with capricorn tubes, but they're a bit longer.
How does the MMU2s know how long the tube is and how can I change it? 

Posted : 03/12/2019 12:16 pm
CybrSage
(@cybrsage)
Honorable Member
Posted by: @inf-57

Hello,
I'm installing the MMU2 on multiple printers, I'm replacing the PTFE tubes with capricorn tubes, but they're a bit longer.
How does the MMU2s know how long the tube is and how can I change it? 

The sensors should tell it when the filament makes it to the printer side successfully (the one that senses it entering the bondtech gears in the extruder).  It should not have to be calibrated any more due to that.  It is the S upgrade, I believe, that changes it.

Posted : 03/12/2019 5:33 pm
inf-57
(@inf-57)
New Member

@cybrsage

I removed the filament sensor in the extruder 😅

I need to replace it?

Posted : 03/12/2019 5:53 pm
david.a66
(@david-a66)
Honorable Member

yes, the MMU2s needs the chimney style extruder IR sensor to tell the MMU when the filament reaches the bondtech gears so the MMU can disengage

Posted : 03/12/2019 10:14 pm
gnat
 gnat
(@gnat)
Prominent Member
Posted by: @cybrsage
Posted by: @inf-57

Hello,
I'm installing the MMU2 on multiple printers, I'm replacing the PTFE tubes with capricorn tubes, but they're a bit longer.
How does the MMU2s know how long the tube is and how can I change it? 

The sensors should tell it when the filament makes it to the printer side successfully (the one that senses it entering the bondtech gears in the extruder).  It should not have to be calibrated any more due to that.  It is the S upgrade, I believe, that changes it.

Does it still? I thought one of the last couple of updates switched it back to a static length like the plain MMU2? I'm still on 1.0.5 myself as I subscribe to the "if it ain't broke..." philosophy.

I know with my way out of date firmware that a longer MMU -> Extruder PTFE length was possible as I threw a 1m tube in just to see what it would do. What I found is that while it did work, it didn't work well. The problem (confirmed by looking at the code at the time) is that it wasn't remembering the length between tool changes so each tool change went through a long process of "searching" for the IR sensor. Given the 1m length I was using, this added A LOT of extra time (one example jumped a 13 minute print to 45 minutes if I recall correctly).

What it would do is start to load normally with the "fast load" process. There is/was a value range set in the firmware for where it expected to have tripped the IR sensor. After getting to that point it would stop the fast load and instead start advancing in small increments until the IR sensor actually tripped.

I meant to submit a PR (I think I submitted a GitHub issue on it though) to make it store the newly determined length for future tool changes, but life got in the way...

If I ever get around to building an enclosure I want to move the MMU off the top of the printer and locate it in a more accessible location (and/or into a dry box to keep filament protected until it hits the extruder).

MMU tips and troubleshooting...
Posted : 10/12/2019 9:27 pm
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