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PLA printing on heatbed with blue tape warping due to fan?

Posted by Bishop 
PLA printing on heatbed with blue tape warping due to fan?
February 12, 2016 07:34PM
Recently I've been printing larger width items (like 70mm x 100mm) and started getting the edges lifting/warping off the heatbed. I use the blue painter's tape, but also heat the bed to 60 degrees. The PLA I use recommends between 210-230 so I stick to ~210. This was not a problem before but I have changed a couple of things in my printing practice and rather than wasting 20+ layers to find out through trial and error, I thought perhaps others may have some good tips.

First off I switched from Repetier to MatterControl, which I don't think should be an issue, except that I cannot set an "after first layer" temp controls unless done manually. With Repetier, I would drop the temp of both the heatbed and hotend by a couple degrees after the first layer.

Second, to help with bridges and overhangs, I built/remixed this fan shroud to cool the bridge as it was extruded: [www.thingiverse.com] . I need a fan on at least low to cool my extruder motor or it will overheat. With this shroud, it's pushing air around 35% speed throughout most of the print save for the bridges which should be higher.

3rd: I'm finally using coloured filament as I've done most of my experimenting/prints using transparent.

I'm suspicious that the fan cooling in the direction of the hotend, even at a low speed, could be counteracting the heat coming off the heatbed. And of course there is conflicting info on [reprap.org] as to heating when using blue tape or not. I could include images but the warping is fairly textbook.

Thoughts? Ideas? Comments?


Prusa XI3 printer
1.75 filament
0.4 nozzle
Slic3r / MatterSlicer
Repetier / MatterControl
Re: PLA printing on heatbed with blue tape warping due to fan?
February 16, 2016 08:35AM
Whats the surface under the Blue tape? Personally I only use blue tape when I'm printing without a heated bed since PLA tends to stick pretty well to Glass, and with the larger prints some hairspray does wonders.

If you are using glass, get some Hairspray, not moose stuff, proper high fix hairspray. I'm not sure 100% but if it has Vinyl in it that tends to be the best stuff to use.

Clean that glass, get everything off it and spray with a thin coat of the hairspray, you don't need much in fact if you put too much on you end up having to stick the prints and bed in the freezer to get them off.

If your using Aluminium, the same thing works but not quite as well I find.

Some people swear by watered down PVA glue or slapping some UHU Glu stick on, both of which I found worked okay, but hairspray and glass by far for PLA worked the best.

I also found disabling the fan on the first couple of layers helped as well.

See if you can get away dropping the temps too, my PLA sweetspot was 205, but every PLA is different.
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