Door sensor calibration failure  

RE: Door sensor calibration failure

The door tensioning screw shouldn't be fully tightened. Loosen it off until the metal rotary section of the door sensor just poke through the hole. 

Open and close the door yourself and adjust so that you hear the sensor click around an inch or so before the door actually seals closed. Once you have it at the location begin the door calibration wizard with the door closed. It will ask you to fully open the door......then close the door with your fingers in between. If it asks to you turn the tensioning screw at this point, do it, but then close the door again with the fingers in the way each time - not fully closed. It should then pop up and inform you it is successfully calibrated. 

Mine kept failing as well initially, but it was my error as I went reading it properly and not placing my fingers in between the door! lol

RE: Door sensor calibration failure

I figured it out. I had to back out the screw and the door sensor to the point where it didn’t click. Then I did the calibration procedure. It first asked me to tightened until the door sensor clicked. Then it went to the hand procedure. With a hand in between, the door sensor is NOT supposed to click. The whole calibration procedure is meant to get the door sensor to trigger as early as possible. I had the sensor adjusted too far forward during the initial install so the door sensor clicked even with a hand gap. Of course, the tutorial didn’t know that since it assumes the sensor is protruding minimally, so it kept on asking me to tighten.

I recommend during assembly to start with the sensor NOT clicking to allow the calibration process to do its job. Similar to the Nextruder gear calibration. 

RE: Door sensor calibration failure

Thanks for summarizing! It failed 2x for me, but then went through and I had no idea what I did "right".
Now I know.

RE: Door sensor calibration failure

Posted by: @langjai

I figured it out. I had to back out the screw and the door sensor to the point where it didn’t click. Then I did the calibration procedure. It first asked me to tightened until the door sensor clicked. Then it went to the hand procedure. With a hand in between, the door sensor is NOT supposed to click. The whole calibration procedure is meant to get the door sensor to trigger as early as possible. I had the sensor adjusted too far forward during the initial install so the door sensor clicked even with a hand gap. Of course, the tutorial didn’t know that since it assumes the sensor is protruding minimally, so it kept on asking me to tighten.

I recommend during assembly to start with the sensor NOT clicking to allow the calibration process to do its job. Similar to the Nextruder gear calibration. 

This is what I had to do as well.

RE: Door sensor calibration failure

I had the same thing. Skipped the door calibration. Then wen to the info menu to look at the door sensor. And it was detecting closed/open. So loosed the screw, and pushed the sensor back until it would just detect closed when the door was closed. Ran the calibration again, and it passed immediately.

RE: Door sensor calibration failure

Just bought a Core ONE (assembled), and problems started right from the first moment:

- The unit arrived with a bent door, making it impossible to close properly.
- The door sensor doesn’t detect when the door is closed, even when forced shut.
- Tried door sensor calibration, but it fails every time. The display message keeps asking to loosen the screw, I even removed it completely, yet the message still appears.

For a €1300 pre-assembled unit, I really didn’t expect this kind of experience.

I also tried printing some supports using PLA Galaxy Black Prusament, but the results were terrible: poor bed adhesion, lifted corners, and completely warped supports. Using the same settings on my Prusa Mini, the prints came out perfectly fine.

Additionally, the chamber temperature reading seems off: the printer shows 25°C, while an external sensor inside reads only 21°C.

I’ve already reported these issues to support and am now waiting for a solution.

Overall, quite disappointed so far.

Any ideeas on how to fix the door sensor until the repy from support?

RE: Door sensor calibration failure

Posted by: @cristi-2

Just bought a Core ONE (assembled), and problems started right from the first moment:

- The unit arrived with a bent door, making it impossible to close properly.
- The door sensor doesn’t detect when the door is closed, even when forced shut.
- Tried door sensor calibration, but it fails every time. The display message keeps asking to loosen the screw, I even removed it completely, yet the message still appears.

For a €1300 pre-assembled unit, I really didn’t expect this kind of experience.

I also tried printing some supports using PLA Galaxy Black Prusament, but the results were terrible: poor bed adhesion, lifted corners, and completely warped supports. Using the same settings on my Prusa Mini, the prints came out perfectly fine.

Additionally, the chamber temperature reading seems off: the printer shows 25°C, while an external sensor inside reads only 21°C.

I’ve already reported these issues to support and am now waiting for a solution.

Overall, quite disappointed so far.

Any ideeas on how to fix the door sensor until the repy from support?

I would suggest disabling the door sensor in the firmware. Getting the screw for the switch in the correct position to pass calibration is tricky so I simply disabled it. 

As for PLA prints, I'm assuming you are opening the top vent? Also the chamber temperature is correctly displayed, just confusing to interpret. For PLA the chamber needs to off. The first number is the actual temperature inside the chamber and the second number is the nominal temperature which in this case is "0" The internal chamber temperature will be a few degrees higher than room temperature because the bed and the hot end are heating the air inside the chamber,. 

As for poor adhesion, which bed are you using? Is it clean? PLA will warp for larger prints. 

RE: Door sensor calibration failure

I appreciate your suggestion, but buying a brand-new printer only to disable a feature as the first step doesn’t make sense to me.

For the PLA prints, I did open the vents — I’ve read the manual, and I know this is required. I’m using the standard Smooth PEI Print Sheet, and yes, it’s clean. As mentioned, the same object with the same settings printed perfectly on my Prusa Mini.
Regarding the temperature, I placed a Zigbee temperature sensor inside the chamber, right above the bed. It reports only 1–2°C higher than room temperature, while the printer shows about 5°C more, which seems inaccurate.

After running more tests, I’ve noticed additional strange issues:
- PLA blobs forming at the nozzle before printing, which ruin the first layer.
- Poor adhesion between Prusament PLA filaments (tested with Galaxy Black and Pineapple Yellow) when changing materials mid-print.
- Unusual noises when the print head moves opposite the door — it sounds like metal scraping.

I’m documenting all these problems for another support case.
At this point, I’m seriously considering returning the unit as defective, since it definitely doesn’t feel like the “unbox and print” experience it’s advertised to be.

As I said, I have a Prusa Mini from at least 4 years and never have this type of issues.

RE:

The thermistor for the chamber is at the back in-between the chamber fans. To compare you need to measure the temperature from there.

Also, the PLA you are using, has been put in a dryer recently? What you are describing are classic signs of wet filament. 

For the unusual noises, this is (probably) cabinet resonance. Try loosening the 4 screws on either side of the gantry connecting the gantry to the bearing holder. Move the gantry manually front to back several times and tighten the screws. 

RE: Door sensor calibration failure

I’ve moved the sensor closer to the fans and will share the new readings once I have them.

The PLA I’m using is brand new — it came with the printer. I’ve never had to dry new filament before, only older ones. I do have a good filament dryer with two slots, so to rule out any moisture issues, I’ll dry it and test again.

Normally, if humidity were the problem, I’d expect to hear small popping noises or see uneven extrusion on the printed part, but everything looks fine in that regard.What I don’t understand is why the same filament prints perfectly on the Prusa Mini without any of these issues.

RE: Door sensor calibration failure

Try opening the door as well. PLA is ironically not easy to print on a Core One.

Also, make sure the heatblock assembly is correctly inserted all the way into the heatsink. T

he problem with brand new filament is that you never know what condition it was in when it was sealing in the factory. I always dry my filament after opening a new box. For example, here is a brand new roll of Prusa PC-CF straight from a vacuum sealed bag (on the left) and the same after drying it for 6 hrs. The roll was only 1 month old when it was manufactured vs the date I pulled it out of the bag to print it. 

RE: Door sensor calibration failure

Wanted to add, the whole point of the door sensor is to comply (I believe) with EU safety regulations. I just find it a nuisance so the very first thing I did was to disable it. 

Further, the difference between your mini and the Core One is that the C1 has an all metal hot end plus it's enclosed. Extra care is needed for printing low temp filaments like PLA. It's also important to keep in mind that vendor profiles are not necessarily accurate. I always run temperature and flow calibrations (using OrcaSlicer) when I'm dealing with non-Prusa filament.