Disabled filament sensor to print  

RE: Disabled filament sensor to print

I'm having the same issue. It did work well for one print but not others: https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-assembly-and-first-prints-troubleshooting/trouble-with-first-prints/#post-142077  

RE: Disabled filament sensor to print

Check to make sure you have the sensor in the correct row of pins on the board.  I had mine in the wrong spot so it wasn't sensing that I had filament loaded.

RE: Disabled filament sensor to print

I am having the same issue. Disabling the filament sensor also worked. I also found that the filament door was binding with the filament/sensor cap and removed the cap. Doesn't affect the sensor (it's disabled ) and the door is able to move freely to adjust tension on the filament. Yes I have updated firmware.

I would like to figure this out because I do have a MMU 2s ordered.

RE: Disabled filament sensor to print

I will check but could you be more specific about how you corrected your issue.

RE: Disabled filament sensor to print

Yeap, I'm finding the IR sensor to be far worse than the old laser was for me (bad enough that I'm going back and switching to the Butterworth extruder with the indirect sensor mod).

I believe that my issue is in regards to the MMU tower as I have seen complaints where the arm on the door has to be modified to more reliably trip the sensor.

RE: Disabled filament sensor to print

Some idiot ( me ) didn't have the sensor plugged into the main board correctly. Printing perfectly now!!! 

RE: Disabled filament sensor to print

I recently finished my mk3 to mk3s upgrade and can’t use the filament sensor because it again and again urges me to unload and reload filament while printing. I discovered that the IR status changes sometimes when gently touching the filament a few centimetres above the hole where it enters the extruder. I think this corresponds approximately to the pressure during the movement of the extruder in the x and y direction. I don’t know if this causes the filament unload/load action but I don’t have any other idea.

I reprinted the fs-lever to be sure to have an accurate object and I also printed the plug-aligner which was not part of my upgrade kit and then reassembled the whole thing. I double checked wiring, filament path, magnet position. At the first test print the unload/load action reappeared. This means that at the moment the filament sensor is of no use, I can only print with filament sensor off. I am using the latest mk3s firmware but the error happens with older versions too.

I never had any problem with the mk3 version so I already regret having done the upgrade.

RE: Disabled filament sensor to print

I corrected the error. I did not have the filament sensor plugged in correctly. It's hard to see in there with all of the other cables plugged in there.  I've printed several things successfully. Thanks for all the support.

RE: Disabled filament sensor to print

Also have this issue. It looks like the connections are accurate and fine. Disabling filament sensor works

/shrug

RE: Disabled filament sensor to print

Posted by: gnat

Yeap, I'm finding the IR sensor to be far worse than the old laser was for me (bad enough that I'm going back and switching to the Butterworth extruder with the indirect sensor mod).

I believe that my issue is in regards to the MMU tower as I have seen complaints where the arm on the door has to be modified to more reliably trip the sensor.

So I printed all the Butterworth parts (both MK3 and MK3S versions), but haven't switched. As a last attempt I re-printed the idler door for the MMU version of the sensor placement and found 2 things.

First is that now my gears are loose enough that I can manually insert and remove filament as I used to be able to do with my MK3 before the upgrade. Even with the tension bolt barely catching the door's nut I could barely insert the filament into the gears and was not able to push it farther. Now I can (with some resistance) push the filament all the way to the nozzle with the bolt set as it should be (flush).

The second is that I was able to sand the "flag" on the end of the door arm (it's a MMU thing) down to adjust it's trigger point so that it is nor more reliable.

Prior to reprinting the door I couldn't get a print to go through, since I have done about 6 solid days of printing both with and without the MMU with the IR sensor on and no errant run out events.

The MMU tower interacts with the IR sensor in a different manner, but the trouble the MMU people are having with the IR sensor sounds really similar to what you all are talking about. You can't easily get to the arm on the plain MK3S to fiddle with it though can you (for the MMU version it's just 2 bolts to pull the door and that's all we need to remove to fiddle with this)?

RE: Disabled filament sensor to print

My filament sensor also is not working, and on looking/probing pins. I have found the pivot arm that is suppose to block the beam in the IR sensor is not moving far enough to block it thus not allowing the sensor to detect that filament is loaded. Am still looking into how to fix this issue with my modified MK3 to MK3S. 😐 

RE: Disabled filament sensor to print

At first to clarify: My printer is a MK3S upgraded fom MK3 (without MMU). The filament sensor in the MK3 version never had any problems.

Prusa itself obviously knows that there is a problem with the MK3S filament sensor, they have an article about it here:
https://help.prusa3d.com/article/43mduc4zdn-filament-change-prompted-at-the-beginning-of-the-print#_ga=2.172577253.733291065.1551101755-1350821872.1543029894

I don’t know since when this article exists but it describes what I did before knowing their advice (and didn’t help anything).

Like @keith-m10 I also thought of the fs lever to be the problem. Looking on thingiverse I found two custom versions of this part and tried them both. It seems to me that the error occurs less often but it still persists and makes printing with activated filament sensor impossible.
https://www.thingiverse.com/thing:3567736
https://www.thingiverse.com/thing:3452597

In the Prusa-article mentioned above they say:

“The IR sensor value should be a stable 0 when there is no filament and a stable 1 as long as the filament is present.“

When watching the IR state on the LCD screen of my printer (support – sensor info) during a print I see the IR value toggling randomly between 0 and 1.

So for me it looks more like a problem of the sensor itself, definitely for me it is a disimprovement against the MK3.

RE: Disabled filament sensor to print

How did you calibrate the MMU to make it work without the IR sensor? I can't see the filament position on the gears now that the new filament door is in place. My IR sensor will only show 0, never 1, no matter where I shift it or what's in the feeder, so I'm assuming it's not working.

RE: Disabled filament sensor to print

Take a closer look at the connection. Use a magnifying glass if necessary. There are two sets of four pins, even with the orange spacer. The bottom four are the pins you want. Mine works great.

RE: Disabled filament sensor to print

Posted by: jeffrey.g3

How did you calibrate the MMU to make it work without the IR sensor? I can't see the filament position on the gears now that the new filament door is in place. My IR sensor will only show 0, never 1, no matter where I shift it or what's in the feeder, so I'm assuming it's not working.

If your IR sensor isn't working I don't think the MMU is going to behave. 

If you remove the filament does the IR sensor report 1? If not then there is an issue that needs to be sorted out. Assuming that it still report 0:

• Remove the idler door altogether and check again. If it reports 1 now, then the issue is the door and likely the flag/arm. Sand/file the tip of the arm a little bit at a time and keep reinstalling and testing with and without filament. 
• Remove the sensor from the tower, does it report 1 now? If so then there is something about how it was installed in the tower or how the tower was on the extruder. 
• If it still stays stuck at 0 and there is nothing in the sensor itself triple check the wires that they are both plugged in, oriented correctly, and it's in the correct slot on the main board. 
• If all that checks out and it's still showing 0, you might have a bad sensor. Contact support. 

RE: Disabled filament sensor to print

Hi,

I have just upgraded from MK3 to MK3S and have the same filament sensor problem. I printed all of the parts from the supplied G code and they all printed OK. My default filament is PETG so no problems there. I also loaded the MK3S firmware.

I found the link to the Prusa document showing how to troubleshoot the problem. This was akin to open heart surgery pulling most of the extruder appart so I decided to take a simpler approach. I remove the top extruder cover and then removed the IR sensor so that I could  see the operation of the filament sense mechanism. Everything was working OK. 

I measured the distance (with a vernier caliper) from the top  of the lever that blocks the IR sensor and then measure the distance from the top of the opening of the IR sensor channel, it was 1.5 mm. I then tested the IR sensor using a cable tie and it worked OK (checked status on Support screen). I noted that 1.5 mm was way too low for the IR sensor to be blocked.

I do not recommend doing how I went about trying to fix the problem but I will describe my procedure. Using a temperature controlled soldering iron with a chisel end set to 220dec C and I proceded to remove some of the material where the IR sensor board sits. I cleaned the mess with a small sharp chisel and managed to lower the board by about 0.5 mm. After fitting

RE: Disabled filament sensor to print

Hi, as you can see I am a new member and did not realise that pressing the "Save " button actually posts what I have written. When I came back to finish the article I pressed edit, finished the article then updated and found that non of my second half of the article were included.

Here is what I think I wrote:

After fitting the IR sensor I got a change of status when inserting a filament however it was unreliable. A I could not lower the IR board any further I decided to try and build up the activating lever. Using a smaller chisel end on my soldering iron set to 220dec C I deposited some PETG to the lever to build it up. This was a bit like icing a cake, using the chisel end to smooth the top and sides and using a small hobby knife to cut off any stringing. Now when I fitted the board I managed to get a solid signal however the position of the board was quite critical to ensure no change of state when I wriggled the filament. To solve this I only lightly tightened the IR mounting screw and fixed the board in its final operating position with hot glue. Now I get a positive state change when inserting the filament and it does not change when I wriggle it. I have since done a couple of test prints and the printer works flawlessly with the filament sensor "on".

I use my printer to make engineering components and I use PETG for the non structural items and Nylon (Taulman Alloy 910) for the structural components and it has operated flawlessly for hundreds of prints. That said my next comments are not as favourable.

I cannot believe that Prusa would design and release an extruder with a filament sensor that has such critical operational tolerances without having some adjustment facility as well as burying the sensor mechanics so deep in the extruder that only major dissassembly gives access to it.

I feel for others out there who may have the same issue with their upgrade as I see no simple solution to this particular problem  (ie not wrong firmware, not a faulty sensor, not wrong wiring, not a poorly printed part, magnets not reversed, no jammed parts, not wrongly assembled.......).

I hope this article is of value to those with sensor problems on their MK3S upgrade and those who are thinking of upgrading.

Hans