Prusa MINI - Varying temperature across heated bed
 
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Long Dog Workshop
(@long-dog-workshop)
New Member
Prusa MINI - Varying temperature across heated bed

Hello, 

 

Received my MINI in August 2020 and have thoughtfully enjoyed it, however since the beginning, I have had trouble printing on the forward 1/4 of the bed with poor adhesion and issues with the auto-leveling consistently raising in this area. I have confirmed the bed is level to the nozzle/probe by checking all measurement points manually with a piece of card stock to confirm the distance isn't an artifact of an uneven bed. After that, I measured the surface temperature of the bed when heated to 60degC. What I found was a large variance on the 1/4 I have been having issues with (photo below).

 

I am not familiar with the architecture of the Prusa heated beds (first Prusa Machine), so I was curious if this is a common issue, or potentially a faulty heating surface? Would the surface of the bed have an effect on the MIDNA measurements?

 

Any input is greatly appreciated. 

 

 

Posted : 15/01/2021 3:34 am
JPLau001
(@jplau001)
Eminent Member
RE: Prusa MINI - Varying temperature across heated bed

Check that there is no air draft over the front 1/4 of the heated bed. Air drafts can cause significant drops in the surface temperature of the MINDA probe and parts of the heated bed. Try fully enclosing the printer in a temporary box and testing again to eliminate air drafts as a cause of the detected temperature drop.

Also use a straight edge to confirm that your Heated bed and steel plate are flat and not bowed so that the front of the steel plate has bad contat at the front 1/4 of the heated bed.

Please note - the temperature sensor in the MINDA probe is only meant to compensate for the detection height drift due to the temperature affecting sensitivity of the MINDA probe. 

Posted : 15/01/2021 4:36 am
Gordon W
(@gordon-w)
Reputable Member
RE: Prusa MINI - Varying temperature across heated bed

@jplau001

There is no temperature sensor in the Minda probe (that's been the root cause of many of the early problems people had with the Mini.)

@geoff-vangemert The problem could be airflow, but ~10deg seems like a big delta. If nobody else has ideas I'd have a chat with Prusa Support via the web chat. I'm thinking there could be a problem with one of the tracks on the heater, or possible a poor connection to the heater, but they'd be able to help diagnose and send spares if they are needed.

Posted : 15/01/2021 1:06 pm
Bernard
(@bernard-2)
Member
RE: Prusa MINI - Varying temperature across heated bed

 

Posted by: @geoff-vangemert

Hello, 

 

Received my MINI in August 2020 and have thoughtfully enjoyed it, however since the beginning, I have had trouble printing on the forward 1/4 of the bed with poor adhesion and issues with the auto-leveling consistently raising in this area. I have confirmed the bed is level to the nozzle/probe by checking all measurement points manually with a piece of card stock to confirm the distance isn't an artifact of an uneven bed. After that, I measured the surface temperature of the bed when heated to 60degC. What I found was a large variance on the 1/4 I have been having issues with (photo below).

 

I am not familiar with the architecture of the Prusa heated beds (first Prusa Machine), so I was curious if this is a common issue, or potentially a faulty heating surface? Would the surface of the bed have an effect on the MIDNA measurements?

 

Any input is greatly appreciated. 

 

 

Did you ever figure it out ? I'm having the same problem definitely not a draft.


 

Posted : 06/02/2024 12:55 pm
JoanTabb
(@joantabb)
Veteran Member Moderator
RE: Prusa MINI - Varying temperature across heated bed

Try raising  the bed temperature to 70c...

To improve adhesion try wa shing the build plate with dish soap and water. Rinse with hot water. Dry immediately with plain paper towels 

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Posted : 06/02/2024 1:12 pm
Paul beard
(@paul-beard)
Trusted Member
RE: Prusa MINI - Varying temperature across heated bed

Seeing much the same on a well-loved MK3S I just acquired. If I had gridded temp chart like OP, it would show the same trend, if not the same values. The front edge has low temps and low adhesion/part loss. A small job in the center works great: many pieces spread across the bed don't work so well. I decided the same advice — raise the temp to 70° — was the right call before I read this. 

Posted : 09/02/2024 5:31 am
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