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False Replace Filament Alarm  

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mike
 mike
(@mike-60)
Active Member
False Replace Filament Alarm

Two print jobs now (on my Core One) have resulted in a replace filament warning and subsequent stoppage of a print.  Both times at approximately 98% completion (4 hours 48 minutes into the print job).

In both cases there was lots of filament on the spool, and no issues with it moving freely.  Both prints used Spectrum Filament FlameGuard ASA 275.  

Why is this issue occurring?  I recalibrated the filament sensor before this last print and it still reported an out of filament alarm.  Do I need to disable the filament sensors now?  This is annoying, I shouldn't have to worry about this unless it is a real issue.

Best Answer by FoxRun3D:

A quite common reason for unexpected filament changes is an accidentally inserted filament change in the slicer by inadvertently clicking on the slider in the slicer preview. Your observation that it happens at the same time in the print makes me suspect that is more likely the cause of error than a mechanical issue.

Posted : 22/06/2025 9:05 pm
mike
 mike
(@mike-60)
Active Member
Topic starter answered:
RE: False Replace Filament Alarm

Since I'm now on my phone I can't edit the original post.   Another question, how does this sensor work?   Is this a photo sensor or a limit switch?   If it's the later, how has it been mechanically integrated that it detects filament?  If it's an optical sensor, what kind of sensor is it?

Posted : 22/06/2025 9:26 pm
Jürgen
(@jurgen-7)
Prominent Member
RE: False Replace Filament Alarm
Posted by: @mike-60

Another question, how does this sensor work?   Is this a photo sensor or a limit switch?   If it's the later, how has it been mechanically integrated that it detects filament?  If it's an optical sensor, what kind of sensor is it?

It is ultimately a photo sensor, but it does not sense the optical properties of the filament. The filament pushes against a steel ball, which in turn pushes a little lever, which inserts a black flag at its other end into a forked light sensor.

In this direction, it's all forced displacement, so it's hard to see how the mechanical part could fail. (If the lever were to jam, the ball should block the filament path and make inserting filament impossible.) A fault in the optical sensor or the wiring is more likely.

Unfortunately the side filament sensor is a bit awkward to get to. If you have purchased your printer as an assembled unit, I would let Prusa support deal with this.  

Posted : 22/06/2025 10:12 pm
mike
 mike
(@mike-60)
Active Member
Topic starter answered:
RE:

Wow, overly complicated.   A simple micro switch would accomplish the same thing and be less complicated.  Make a cam mechanism to drive the micro switch.  

 

I'm leaning towards a QC issue with the filament, as it's only with this brand I've had an issue with.   I'll try another brand and see if the issue carries over.   But I find it's also interesting that it's at the exact same time in the print that the issue occurs...hmmmmm

Posted : 22/06/2025 10:22 pm
FoxRun3D
(@foxrun3d)
Illustrious Member
RE: False Replace Filament Alarm

A quite common reason for unexpected filament changes is an accidentally inserted filament change in the slicer by inadvertently clicking on the slider in the slicer preview. Your observation that it happens at the same time in the print makes me suspect that is more likely the cause of error than a mechanical issue.

Formerly known on this forum as @fuchsr -- https://foxrun3d.com/

Posted : 23/06/2025 12:38 pm
2 people liked
mike
 mike
(@mike-60)
Active Member
Topic starter answered:
RE: False Replace Filament Alarm

Thanks, I will check this out later in the week and report back.

Posted : 24/06/2025 12:41 am
mike
 mike
(@mike-60)
Active Member
Topic starter answered:
RE: False Replace Filament Alarm

You are correct.  I accidentally added a filament color change just before the very top layer.  Thanks for pointing this out as a likely scenario.

Posted : 25/06/2025 10:28 pm
3 people liked
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