A350 Heated Bed Consistency?

Snapmaker 2.0
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In one of my other threads Achieving a good first layer A350
I explored bed levelling and my conclusion was that the magnetic print sheet is one the culprits in creating a large levelling delta.

I was following up on this thread and was going to re-test everything with my probe as I now have the serial port working on my MBP to use Luba as really wanted to compare the M420V outputs.

The first step was to check the heated bed (without print sheet). However, this leads me to some strangeness that needed to be investigated.

Steps

  1. Heat bed to 60C and leave for 15 minutes.
  2. Start manual calibration (3 x 3) and set bed to maintain 60C

Issue
Leaving the probe at point 1 (0,0) I noticed the probe would fluctuate a lot in value. See Video:

A quick hand test and the lower segment of the print bed feels warm but not hot. So I eventually found my IR Thermometer. I put on the magnetic print surface so it was all the same material type and not accidentally measuring metal bolts etc.

Now you can’t see the laser pointer. However, it is always within the bounds of the printable area. See Video:

You can see that the temperature varies a lot and in particular the lower-left area is way below other areas. The centre of the bed is measured at 58.8, the value doesn’t matter so much as long as it’s close to 60C. The point is the large delta around the surface.

Center 58.8
Lower Left 43.8 = Difference of 15C

I had expected a little tail off with temperature over the bed surface, although I was expecting a few degrees. However, in this case, I believe it must be a faulty unit. It may also as shown by the probe lead to adhesion and print issues with the varying impact on Z height.

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Very good observation. I took some measurements with my infra red temperature reader and also found considerable fluctuation in bed temperature. I am trying to ask around to see if others also have this situation or whether mine is faulty.

Apart from that I am also suspecting my magnetic bed as a culprit and have ordered a Creality glass bed to try instead in the hope that this may somewhat resolve the issue.

I have also tried to ensure that the printer as a whole is on a level surface since I reason that if the nozzle is not at a perpendicular to the level surface this may affect the way it lays down the layers.

Finally I am starting to think that the fan on my printer head is not working. I am not sure which Gcode (or Mcode) to send to turn it on and off without actually printing anything just so I can see if the wind from it can be felt with my hand. Do you have any information on this that you could share please?

Thanks.

3

Try M106 S255 to turn fan on full speed

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Would uneven bed temperature be the culprit in this case? I’ve had no end of problems getting the white PLA to stick. Upping the initial bed temp helped a bit, but you can obviously see it’s laying down layers very differently from one end to the other.

20200903_134314
20200903_1343144032×3024 1.23 MB

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Can you validate the temperature? I don’t think it would vary much over a short distance.