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Baking with the heat bed  

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KaJashey
(@kajashey)
New Member
Baking with the heat bed

I had a made in china printer before my new Prusa I3 MK3S+. Sometimes I would temper PLA to get stronger more heat resistant prints. That is bake the PLA near it's glass temperature and cool it slowly to bond layers better, relieve internal tension, and crystalize it thoroughly. 

Instead of using an oven where it's hard to control the temperature I would use the heated and a cardboard box. The cardboard box would cover the part and trap heat. I would run code like this:

M84 ;steppers off
M117 Warming up
M190 R80
M0 S1800 Bake @ 80C 30min
M117 Cooling 80 -> 75
M190 R75
M0 S600 Bake @ 75C 10min
M117 Cooling 75 -> 70
M190 R70
M0 S600 Bake @ 70C 10min
M117 Cooling 70 -> 65
M190 R65
M0 S300 Bake @ 65C 5min
M117 Cooling 65 -> 60
M190 R60
M0 S300 Bake @ 60C 5min
M117 Cooling 60 -> 55
M190 R55
M0 S300 Bake @ 55C 5min
M140 S0 ; Bed off
M117 Done

I haven't done that with the Prusa but suspect I'd have some problems. Right now I have some older brittle filament that needs to baked at 50°C to dehumidify and restore it's elasticity. I'm trying to do some simple code like this:

M84 ;steppers off
M104 S0 ; Turn off the extruder
M190 R50
M0 S18000 Bake @50C 5 hours
M140 S0 ; Bed off
M117 Done

Instead of telling me what it's doing during the M0 command it says "wait for user". It will stay like that with the heatbed on 50°C, the extruder off for 30minutes then a safety routing kicks in and says "Heating disabled by safety timer". I looked through prusa's custom gcode to see if there were a different way to heat things. I tried to code around the timeout with a M113 command but had no luck so far.

Thankfully a half an hour or an hour is all that seems needed to get my filaments back with some elasticity. But does anyone have suggestions to get my heating codes cleaner for prusia? 

Posted : 25/04/2021 11:40 pm
Clarmrrsn
(@clarmrrsn)
Honorable Member
RE: Baking with the heat bed
Take a look in prusa gcodes,  https://help.prusa3d.com/en/article/prusa-specific-g-codes_112173/ 

M85 and M86

Although personally I thing heating a cardboard box for 5 hours is asking for trouble.

Surely for the price these sell for this is the tool for the job, and it will not burst into flames like
cardboard may in the case of a fault.

I have one myself and it works well,

https://www.aliexpress.com/item/1005001727757098.html?spm=a2g0o.productlist.0.0.5ba22906KgKUeY&algo_pvid=ec309620-416f-4326-8760-e59e4d82be9f&algo_expid=ec309620-416f-4326-8760-e59e4d82be9f-2&bts id=2100bdd716194212685024097ecac7&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_
This post was modified 3 years ago by Clarmrrsn

Tank you very much!

Posted : 26/04/2021 7:17 am
Clarmrrsn
(@clarmrrsn)
Honorable Member
RE: Baking with the heat bed

I now try and avoid filament getting damp in the first place, have started using reusable vacuum seal bags with hand pump, I did a review of them in the general discussion section.

They work well  but must say any time I have dried filament it has only needed around 30 mins in the dryer

Tank you very much!

Posted : 26/04/2021 7:20 am
KaJashey
(@kajashey)
New Member
Topic starter answered:
RE: Baking with the heat bed

Thank you Clarmrrsn. M85 and M86 look like just the commands I need. I don't need to cook anything for 5 hours anymore. Little 1/2 hour segments did it. I'm happy to have my Bake at 80 gcode recoverable.

I feel the cardboard box is safe. 50 and 80° are far below it's ignition temp and I haven't seen any physical change to the box even though it been used for this for a long time.

Posted : 26/04/2021 12:02 pm
Clarmrrsn
(@clarmrrsn)
Honorable Member
RE: Baking with the heat bed

@kajashey

Although cardboard certainly wont burst into flames at 50/60 degrees there are many other scenarios where this could occur, you are assuming everything will always run as planned, without fault.

Faults develop even in brand new printers run as per manufacturers guidelines.

Heat bed failure, loose connections on the 24V lines, are just a few examples that spring to mind, never mind the fact that Thermal runaway protection is not 100% guaranteed.

For the price of a £25 filament dryer I personally think this is crazy, putting a cardboard box over any part of a 3D printer is certainly not SAFE, it is rather concerning that you think this!!

I hope you have good house insurance 😳 

 

Tank you very much!

Posted : 26/04/2021 12:22 pm
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