PLA print warping on heated bed
I am trying to print the 3 jaw lathe chuck on Thingiverse. This specific piece is the scroll.stl, but it applies on every big piece. The print material is (transparent) PLA, that I print on custom glass bed, which is heated by a regular heated bed at 65 °C. However, my print is warping on the external edges of a solid 2 mm for a 85 mm diameter print.
I didn't use the cooling fan. And I don't have an enclosure to keep the warmth inside the printing area. The nozzle temperature is around 200 °C.
What could be wrong?
The printer is a slightly modified Prusa i3 MK2.
Use an adhesive between the glass and the print such as glue stick, strong hair spray or a dedicated product like 3DLAC to prevent warping.
i get that if my printing room is windy. If I put a couple pieces of cardboard along the printer to block some/most of the breeze it gets better. You don't need a full enclosure, but try stacking some books or something along the flank and see if it helps. It might also just need more hairspray; your glass looks pretty clear instead of frosty.
Glass is not a great conductor of heat. If you have an IR temperature meter, put some masking tape on the bed and measure it. You might need to increase the heater temperature to keep the glass hot enough.
@dandavis That is a good point. I didn't know that I needed to add hairspray on the glass. I though that the cleaner it was, the better it is. Thus, I tend to clean it with windows cleaner. But my room is not windy, and the flat tends to be quite hot with everything. But I could try to make a small enclosure. I think I neglected how imported it is.
@cmm Indeed, that is a good point. However, I tried with higher temperature before, and I add sign of too high temperature, as the first layers where "swollen", thus I reduced a bit the temperature. But the conduction to the glass in my setup is really poor. I should try to improve it! I am not sure how I would do that though...
Several things I've done to stop warping when it occurred:
Use a wider brim.
If the brim isn't sticking, use a higher bed temperature for the first layer.
If the brim comes up only on one side or warping is only on one side, make sure the bed is level.
Slowing down the print will keep you from having as long of a strand cooling down. This will lower the contraction force and reduce warping.
A hotter bed temperature will reduce the temperature difference between the extrusion and the bed, thus reducing the contraction force.
200 °C is a good temperature for getting PLA to stick. I've tried lower extrusion temperatures to reduce the temperature difference between the extruder and the bed, but this decreases adhesion to the bed and is counterproductive.
Well, I didn't put any brim as I thought the surface didn't need it. But I can indeed increase the temperature of the first layer. And reducing the speed of the print is a good idea. I also think that increasing the temperature of the bed is a good idea.
The sides will bulge if you get the bed too hot. That's why people use a hotter temperature on the first layer. Larger prints can have hotter beds because the longer print time for a layer allows it to cool more.
Glass is tricky. Try using a glue stick. It makes the problem getting it off more than keeping it on. Magigoo and Aquanet also come highly recommended for glass. Another thing would be printing with a raft. Raft's stick pretty well, and most prints stick to a raft, and those prints won't lift. A third trick would be using an extrusion multiplier on your first layer only. As far as slicer tricks go, check to see when (if at all) your cooling fans turn on. usually, fans will turn on about 12-15 layer into your print. Any earlier, and they may peel. Bed level, although crucial to have to some degree of accuracy, is somewhat nullified when a raft is used.
Hope that helps!