IR Trigger height suddenly changed a lot



  • I had a print running overnight, and it went to the noodle fail. After that event the trigger height of my ir probe went from Z1.66 to Z4.85.
    I see no physical damage to the probe, and while the plastic coating on the capacitor in between the IR bulbs and the IR sensor did get torn at one point, that happened months ago and has had no effect on performance.

    The probe triggers at values over 500, which is expected. Its like nothing is wrong, except that the trigger point suddenly moved. Any ideas?


  • Moderator

    What was the cause of the noodle fail? Did the print head come into contact with the print and maybe jostle it loose?



  • I have been looking for exactly that. I cant find anything wrong. The print had a layer shift, i could see a blob that hung up the nozzle enough that it was then airprinting the supports and it was all spagetti time after that. But that did not seem to make the nozzle, hotend, mount, or sensor loose. At the moment i have recalibrated to this new larger offset and I am going to see if a print works fine with it in this state. But it sure seems wacky.



  • 0_1551990907802_0307191426_HDR.jpg
    Here we are printing with a recalibrated z offset of Z4.956
    This is the same part, after i resliced it and double checked all my settings. Hopefully it works. Its a 9 hour print.


  • administrators

    Have any of the IR components at the bottom edge of the sensor board become contaminated with filament?



  • @dc42

    i never thought of that. what is a safe way to clean them? I dont think there is actually plastic stuck on there, but there was contact between the sensor and some heated up molten plastic. I could see how some kind of contamination would cause a difference in refraction on either emitter or receiver and make it trigger at wrong height


  • administrators

    You can clean them using a cotton bud moistened in isopropyl alcohol.



  • @dc42 I have encountered a problem much like this. My machine has been flaw less for the last 1000 hrs of print time. I went to start another print this morning and the IR sensor triggers at 20mm above where it is supposed to be. I tried the recalibrate and i get nothing but error messages. I am stumped, I did not do any updates or change any settings.0_1553533624827_Current set up.JPG 0_1553533638033_Probe set.JPG 0_1553533692452_g code error.JPG 0_1553533768486_config 3-25-19.g


  • Moderator

    @billsrf Have you tried cleaning the sensor as DC42 suggests above?



  • @phaedrux yes, i even change the sensor and getting the same results. No matter where it is at, it moves 10 mm down towards the build surface and stops.



  • For what its worth, I also cleaned the sensor and got essentially no change. After further testing I have also found that the sensor is making increasingly large errors as well. Basically i have to watch the first bit of the first layer and baby step it a bit to get it right each time.



  • @dc42 , @jkaechler yes exactly! now when i run HOME.ALL, it moves to the center, dives 10mm , the sensor triggers at 200 mm from the build surface. This is crazy. it has been perfect for 1000= hours now i cant figure it out. reloaded firmware and config.g same thing again.2_1553547133616_homeall.g 1_1553547133616_config 3-25-19.g 0_1553547133615_homez.g


  • administrators

    Is your IR sensor the older sort with through-hole phototransistor and IR diodes, or the new sort with surface mount ones? If it's the older sort, then you have probably had a collision and one of those components has been bent into a different position. If it's the newer sort, then perhaps it has developed a fault.


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