When is it appropriate to use the bed fan w/PLA?

[dramsey]

I was trying some prints this morning that had previously worked perfectly, but had real problems with the edges lifting off the bed after a few layers.

It occurred to me that it was chilly-- room temp about 67 degrees-- and perhaps the bed fan was cooling the higher layers too much, causing them to shrink and pull the lower layers off the bed.

So I unplugged the bed fan and now the parts are printing perfectly.

I can see how the bed fan might be needed if you were rapidly printing small details, but how often is it really needed with PLA prints?

[sthone]

The bed fan is typically always used after the first layer with PLA. Edge curling might be a sign you are running to hot, what temp are you running at?

[Jules]

For PLA, it's needed a LOT. Any overhang will warp and curl up without adequate fan cooling.

You can also try increasing the bed temp by a few degrees, or using more adhesive, to compensate for the cold room. But if turning off the bed fan for that particular print helped, by all means, leave it off. (Just isn't necessarily going to work the same way for a different print.)

[dramsey]

The bed fan is typically always used after the first layer with PLA. Edge curling might be a sign you are running to hot, what temp are you running at?

Stock Simplify3D settings for M2 PLA: 70 degree bed, 215 degree extruder.

I've had a lot of success just printing on bare glass, but I s'pose I could go back to glue stick...

[dramsey]

For PLA, it's needed a LOT. Any overhang will warp and curl up without adequate fan cooling.

You can also try increasing the bed temp by a few degrees, or using more adhesive, to compensate for the cold room. But if turning off the bed fan for that particular print helped, by all means, leave it off. (Just isn't necessarily going to work the same way for a different print.)

There are no overhangs on this print-- just a bunch of Ford key fobs-- but I'll keep that in mind.

[sthone]

I've had a lot of success just printing on bare glass, but I s'pose I could go back to glue stick...

You need to use some kind of bed adhesion... Go back to the glue stick (or print on blue painters tape) and I bet you solve the problem.

[Jules]

Agree with steve though...you'd actually be better off if you do take the extruder temp down to about 205C, and don't increase the bed temp - that's plenty high. (Too high really....reducing that to about 60C might also be a good idea). Your current temps are okay, but running the extruder warmer contributes to the warping, because it takes longer for the PLA to cool. (The longer it takes, the more warp.)

[dramsey]

I'll try the lower temps and see how that works out...

[sthone]

Jules, have we been down this road a few time or what?

"How do I fix this problem?"
"This is what you need to do."
"OK thanks I try this instead."

Some people just love their bare glass.

[Slipshine]

I always had great luck printing pla on clean bare glass. The word there is "clean ". I had to clean with alcohol right before each print. If the glass didnt squeak while drying it wasnt good enough.

Frankly I was too lazy and went to glue stick,