Baking my Cookies...

As you can see from the attached photo, I'm currently baking the bottoms of my prints.

This only happens on long prints like the Prusa plates or Wallace Base ends.

Shorter prints don't brown like this. (Looks worse in person, Photo makes it lighter...)

Currently, my sensor is mounted on the top of the glass near the back edge.

The machine is reporting 95c. When I noticed the browning I turned it down to 85c.

I didn't want to go much below that for fear of the print letting go of the glass.

I'm guessing that the temps I'm seeing arn't correct.

What's the best way to check the temp? What would I have to buy?

Should I re-position my sensor? at this point puting it under the heatbead would be a major chore. (spray insulation...)

Other sugestions?

Looks Like your printing in PLA

Typicly people print PLA with a bet temprature more like 60 - 65 degrees,

Rob

Do you heat your extruder before printing? I find that if I leave the extruder hot with out it running, the first layer of the next print is discoloured and probably not doing my extruder any good :-/

I use PLA and bed temp of 55-60. I was using lower than that (50-55) and printing fine, but then Adrian came over and reset my bed to a higher temp and I guess I should listen to him as he kinda knows what he is talking about

Nope. That be ABS.

I heat the bed to temp, then hit print just after the hotend reaches temp.

As I said, small prints don't discolour. Only on long prints do I see the bottem layers getting glossy and brown.

On a side note. I just did a mideling length print. After about 20 layers, I dialed back th bed temp to 85c again. (My PLA wont stick unless bed at 92-95c)

The print came out fine, But it wasn't on there for as long as the others.

Hey Komb,

Could the burning have something to do with that fancy glassware your using on the bottom? Do you have a long print done on Kapton tape?


Regards

As the only capton I have is 6.5mm wide... No.

I'm thinking it's improper temp reporting by the sensor, but the glass Trevet could be a contributing factor...

I'm on a nother print right now. I was called away while the bed was heating, and had forgotten to re-set it to 95c.

Since it had been heating a while, I decided to try printing on it as that temp(85c). Worst that could happen is I throw away another line drawing.

Surprise, It's sticking! Will have to see if any corners curl when done.

This print is smaller that the last two, so much shorter run time than the tosted prints.

However, if this works, I'll have to try the long prints again.

I just tried printing Prusa V2 plate 2.

Ran from 1:20pm to 8:00pm.

Ended unhappily as nozzle stopped extruding.
(Can the ptfe liner get too hot in a J-Head?)

As you can see from the first pic, the bottom layers started getting glossy and brown.(pic 1)
More so tword the center of the build area. Heat defomation also seen near center. (pic 2)

I'll be looking into the J-head tomorrow.

As for the Travet glass, I'm going to try stripping the paint off of it and see if that makes a difference. The painted surface gives a nice satain finish on the bottom. Where the paint got scrapped off (Head crash...Ouch...) I get gloss.

If anyone else has seen this before or has other ideas, I'm all ears ... or eyes even.

Update!

The spray foam I had under the heat bed was turning brown, and I had finaly aquired fiberglass insulation I had originally wanted to use.

So, While I was at it, I moved the thermister from the top edge of the glass to the center under the heat bed.

Result, Bed temps can now be run at recomended settings, and no baking!

As for stripping the paint off. It was hard to do, and I can't get anything to stick to the bare glass...

Thankfuly I had spares.