Warping problem

Hi guys,

I only have a warping problem when printing very large pieces, and only at the very corners.
What to do to avoid this...?
It's not a sticking problem, I even have problems to remove parts from the heatbed. Almost have to wait until it reaches room-temperature to remove parts(but that is not a problem, because I use spare glass sheets during printing)

Prusa Mendel
Bed 60° (Glass - 100% degreased)
Between Y-carriage and heatbed a thick layer of insulation(neoprene)
Hotend (185/195°)
PLA(no brand)
Nozzle : 0.35
First layer speed 70%

Thanks

Chris

Edited 1 time(s). Last edit at 07/24/2015 04:39AM by chriske.

That's a common problem, and hard to eliminate completely. My suggestions:

- Shield the printer from draughts
- Is the warping worse in one direction relative to the hot end fan? If it is worse behind the fan, then check whether there is any backwash from the fan.
- If you are using a print cooling fan, try turning it off except when bridging
- If possible, use rounded corners on your designs instead of square corners

Edited 1 time(s). Last edit at 07/24/2015 06:41AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks for the reply,

Done all that, I have two exact the same printers. One with a fan cooling the peek, the second one no fan, but there is no difference at all, both have the same problem.
And indeed rounded corners is not much of a problem. But some designs I can't change...pity...

And again it's only while printing larger parts, say almost filling completely the heatbed. Printing smaller parts I never have that problem at all. Printing very small parts I always add a brim, but for very large parts there is not enough room. And what's strange from time to time(not often) there is no warping at all even with larger parts.

Chris

Not much more I can suggest, except to use a larger bed (so that the temperature stays higher near the corners of your print), or an enclosure to increase the ambient temperature.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Larger bed, I thought of that to but I do not print very often larger parts than 185x185mm. In fact all my projects are based on a standard printer with 200x200 heatbed.
This very moment busy designing and printing a rather large telescope. All printed part, fitting on that 200x200 mm bed, has to be assembled ending up with a large instrument(but that's off topic...;-) [www.thingiverse.com])