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

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

Post by Jules » Wed Mar 16, 2016 3:28 am

sthone wrote: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. :lol:
:lol: :lol: :lol: Several! ;)

Can't blame 'em though.... I ain't wild about hairspray either! (But for those who seriously hate the hairspray.....look into PEI. Stuff's fantastic, and nooooo hairspray or glue.) In the Modifications section of the forum.

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

Post by jsc » Wed Mar 16, 2016 4:12 am

Why do people hate glue stick so much? No overspray, no mess, works great, super cheap and easy to source. I know jimc says it doesn't work for him, but I'm just going to say he's doing it wrong.

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

Post by Jules » Wed Mar 16, 2016 4:18 am

jsc wrote:Why do people hate glue stick so much? No overspray, no mess, works great, super cheap and easy to source. I know jimc says it doesn't work for him, but I'm just going to say he's doing it wrong.
I've never been able to do it right either......too heavy a hand, i guess. 8-)

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

Post by Matt_Sharkey » Wed Mar 16, 2016 3:35 pm

thin layer with the glue is key, and its the pinnacle of lazy, I hardly wipe the dust off my bed now (don't worry i still do.) you can see any glue that has been pulled up and easily apply more over that section.

I will sympathize with the bare glass people though, nothing beats the convenience of the parts falling off when it cools. but the frustration of when the parts falling off while its hot....that's another thing.

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

Post by sthone » Wed Mar 16, 2016 4:15 pm

Matt_Sharkey wrote:thin layer with the glue is key, and its the pinnacle of lazy, I hardly wipe the dust off my bed now (don't worry i still do.) you can see any glue that has been pulled up and easily apply more over that section.

I will sympathize with the bare glass people though, nothing beats the convenience of the parts falling off when it cools. but the frustration of when the parts falling off while its hot....that's another thing.
Yeah I just do two light coats, one left to right and then the other on top of that front to back. My parts pop off when they cool with glue, unfortunately they been taking chucks of glass with them lately too :shock: I should probably use some Kapton tape.
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dramsey
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Re: When is it appropriate to use the bed fan w/PLA?

Post by dramsey » Wed Mar 16, 2016 7:32 pm

Well, the weird thing is that I've made dozens of successful prints on bare glass, and suddenly things aren't sticking...

So this morning I lowered the bed temp to 60 and the extruder temp to 205 as suggested here, coated the glass with glue stick, and tried to print four Ford key fobs. They're in a vertical line from the bottom to the top of the bed.

The first one printed fine. 2 and 3 showed increasing amounts of curl. The first 6 or so layers of #4 printed fine, then the entire fob came loose and was dragged around the bed for the remainder of the print.

The _only_ thing I've changed recently is removing the fan guards on the extruder and bed fans. I can't see how this could possibly make a difference.

If I had to guess I'd say it's a bed leveling problem, with too much clearance toward the rear of the bed. But I don't see why that would change suddenly. Guess I'll get out the feeler gauges.

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

Post by jsc » Wed Mar 16, 2016 8:00 pm

Everyone has the same experience as you with bare glass, I think. Works great for a while, then stops. If you want to stick with it, you will have to take it off and clean it to within an inch of its life. Dishwashing detergent, dry carefully, acetone to remove any trace contaminants, handle with gloves, etc. Seems like a lot of work to me.

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

Post by dramsey » Wed Mar 16, 2016 8:29 pm

Here's an image showing the problem I'm having. The foreground fob is the good print; you can see the edge of the background fob pulled away from the bed during the print. Although the print finished, the fob is distorted.

Image

Does this look like a typical "poor bed adhesion" problem?

EDIT: Actually, that does look like a first-layer adhesion problem, doesn't it?

Image

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

Post by Jules » Wed Mar 16, 2016 8:45 pm

Yep. See the ring area? That's thin compared to the bulk of the fob....very small surface area to attach it to the bed. It's going to cool off faster than the fob, and the difference in cooling rates pulls it up towards the fob, breaking the seal. Little bit of glue or hairspray will hold that down. (Bare glass just doesn't work for long. Try the PEI, you'll lurve it.) :lol:

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

Post by dramsey » Wed Mar 16, 2016 9:27 pm

But for PEI I'll need the aluminum bed, right? Already talking to Jim about this...

Btw, would a raft be of any help?

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