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Fussy Robox OR haunted/unlucky/dodgy filament

Rob Spray
(@reallymadrob)
Eminent Member

An odd situation; After a break of a few days I tried another print with some PLA (eSun Yellow) which failed almost immediately (a handful of layers in) as the filament had broken/snapped before the extruder. I can understand the breakage -  it's cheap filament and it has happened before. But when I discarded a few cm of filament and went to reload it takes up but stops before it gets to the head - part way down the tube. Many other trims and retries are the same... a quick check/clean of the exit switch on the extruder made no difference.

Other filament, both CEL and eSun, loads without problem. I can also advance the yellow stuff all the way to the head using the status page controls but the printer won't do it itself so it doesn't recognise it as ready to print.

The filament seems quite uniform - 1.75-1.77mm when measured and it was working well until it didn't anymore.

Any ideas? Help and advice appreciated :-)

Rob

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Topic starter Posted : 10th December 2015 12:55 pm
BHudson
(@bhudson)
Former USA Robox Support Moderator

@reallymadrob It sounds like you have wet filament. Based on your testing, I would discard that filament and not use it anymore. If the CEL filament works as designed, I would look to the issue being with the filament. I have had issues with third-party filament that I just don't have with CEL Filament. Generally the cheaper the filament the more issues I have had. I am unsure of the actual reason; this is just a general correlation I have noticed.

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Posted : 10th December 2015 3:39 pm
Rob Spray
(@reallymadrob)
Eminent Member

It's the first time I've had this particular problem - previously the most difficult filament was CEL Red PLA towards the end of its reel. Other 3rd party filaments are loading fine too. So while I don't mind setting scrap filament aside it would be nice to know what the printer is objecting too. The choice here was down to colour not cost :-)

There appears to be no fundamental problem with detection or feed. The printer is just 100% accurate at detecting this filament and not advancing it to the head. When I've had feed problems before they have been slip related and this one doesn't - so presumably it's confusing the index wheel (which appears free and operational) or the exit switch (which wasn't clogged) which I've gathered can wear out of spec?

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Topic starter Posted : 10th December 2015 4:15 pm
Rob Spray
(@reallymadrob)
Eminent Member

As a bonus: I gave the yellow a rest and tried another filament. Loaded no problem, purged and printed without issue. When I went to eject it did it all except stopped short as it reversed out - same kind of possible as the yellow was stalling on the way in.

Is this the side effect of a flakey position sensor or deluded motion sensor?

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Topic starter Posted : 10th December 2015 11:58 pm
BHudson
(@bhudson)
Former USA Robox Support Moderator

@reallymadrob If your extruder has not had the new filament detection sensor installed, there is a chance that this is starting to wear and cause the issues. You can tell by looking at the extruder - if there is a half-circle opening in the back of the extruder you have a new one. Otherwise, I would look at getting the extruder refurbished to see if that will help. You can also uncheck the "Detect loaded filament" option to see if that will help.

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Posted : 11th December 2015 12:46 am
Pete
 Pete
(@pete)
I am Pete Admin

There is a tick box in the settings to "Detect loaded filament" if your Loaded switch is intermittent you can ignore it using this tickbox, this is a bandaid for the problem, not a fix. The fix is as Ben suggests.

You can see the feedback from your Loaded switch in the Diagnostics page. It should be constantly True when filament is loaded past the extruder gears and False when the filament is outside the extruder gears.

The automatic loading feature uses this button to detect filament for many reasons. When loading the button becomes true for the first time so the extruder feeds for a known distance to reach the head.

For official support please create a support ticket using this link www.cel-robox.com/support/

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Posted : 11th December 2015 11:31 am
Rob Spray
(@reallymadrob)
Eminent Member

@bhudson The extruder has the half-circle opening, so I guess it's a new one :-) It should be good as it's only been back for a couple of weeks from an extended spa treatment but...

Swapped to spare, old type, extruder and now the yellow loads up... I guess we have a clue :-( I'll try some more swaps and check it wasn't just a hiccup.

I did have the 'detect loaded filament' unchecked as I wondered if it would make the handling of 3rd party filaments less annoying. My Robox seemed very inclined to forget what's loaded. Changing the setting didn't appear to cure the 'short' load problem.

 

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Topic starter Posted : 11th December 2015 7:57 pm
BHudson
(@bhudson)
Former USA Robox Support Moderator

@reallymadrob If you have a new model extruder sensor switch there should be no reason to have the "Detect loaded filament" box unchecked. The new style switch is more sensitive than the old one and should be much more reliable as it takes less force to activate. I still think it is a problem with the filament. Is the filament actually round? Could it be slightly ovoid in cross-section, meaning that it turns in the extruder and doesn't trip the sensor?

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Posted : 11th December 2015 8:19 pm
Rob Spray
(@reallymadrob)
Eminent Member

@bhudson I agree it must be down to a difference in the filament. My concern, because life with the printer hasn't been faultless, is that the acceptance threshold may not be correct.

When I measured the filament it didn't run out more than .03mm which I thought was surprisingly good. those are only spot measures but I also tried loading the filament in different orientations to investigate the effects of curl and deformation. In the past my nemesis has been filament feed problems but there's no such problem here, manual feed works fine - in and out. It would be a lot less tedious if there was an unloading speed out button :-)

One thing I've suggested in the past is that it would be useful, to know more about the printer's 'thought' process. Here I don't know what it considers to be happening, I think the load switch is oscillating. I'd guess the index and switch only detect undersize? The filament appears to only go slightly over size and some filaments that load don't fully unload so I wonder if there's some 'behaviour' around the sensor?

The yellow filament is just completing a 2 hr print, so it isn't utterly flawed. Though there is some whiskering which makes it look as though I should re-cal the head for this filament.

Rob

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Topic starter Posted : 12th December 2015 11:53 am
BHudson
(@bhudson)
Former USA Robox Support Moderator

#reallymadrob The index wheel detects only if filament is moving. It is a simple contact wheel with an optical sensor. If the indication on the index wheel does not change value in the right time after an extrusion command is given, the software flags the "Filament not moving as expected" error and starts attempting to solve the issue.

The filament exit sensor is a switch with a sensor flap. If the filament pushes the sensor flap in far enough to close the switch, the printer knows filament is loaded. If the switch stays open, the printer assumes no filament is loaded.

By using these signals in combination, the software determines if filament is loaded or not, where the end of the filament is relative to the extruder exit switch, and if the filament has run out.

I would not recalibrate the head for different brands of PLA; they should all be relatively the same viscosity. If you are seeing stringing, I would look for material buildup on the head or I would assume your filament is wet.

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Posted : 12th December 2015 6:54 pm
JeffB
(@jeffb)
Eminent Member

Can the index input be removed so as to continue printing in a known safe environment

 

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Posted : 7th May 2021 10:26 am
Mike
 Mike
(@17bt)
Prominent Member
Posted by: @reallymadrob

The yellow filament is just completing a 2 hr print, so it isn't utterly flawed. Though there is some whiskering

@reallymadrob

Try dropping your PLA temperature by 5-10°C, as different colours heat up differently :) That should reduce the whiskers or stringing. It might be better to use small retraction test model off thingiverse to dial the temperature in, rather than look at a whispered 2 hour print. I’ve always found eSun filament to be good quality. 

Mike

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Posted : 8th May 2021 7:27 am
BHudson
(@bhudson)
Former USA Robox Support Moderator

@jeffb The firmware expects the index signal, so no, you cannot remove the sensor and still have the extruder operate as intended. You may be able to set the slip threshold high enough to get this to work temporarily, but I would not trust it for a long print. 

If you are seeing problems with your index sensor, you should open a support ticket or otherwise look for a fix. Generally the index sensors are very reliable, but they may need to be cleaned from time to time. If you are getting filament slip errors, you will need to look into what is happening and why to solve the issue. 

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Posted : 8th May 2021 11:56 pm
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