So after checking various sites, here's some things I've found as well regarding warping. It does point into a shear force issue.
There’s however quite some differences in the build plate temperature set-point and motivation for it to combat warping:
- Reduce warping by reducing the temperature difference between extrusion temperature and build plate: https://ultimaker.com/en/resources/158-print-not-sticking-to-build-plate
- Set build plate temperature to the heat deflection temperature (HDT): https://bootsindustries.com/heat-bed-3d-printing/
- Go for the glass transition temperature: https://ultimaker.com/en/resources/19537-how-to-fix-warping
- Interestingly, this site also mentions not to go too high with HBP temperature (at least for PLA): https://rigid.ink/blogs/news/3d-prints-warping-why-it-happens-and-how-to-prevent-it
Looking at my earlier prints, I tend to go for a too high heated build plate at first, as these show some inward deformation of the first layers:
Train of thought goes like this: the first few layers are kept above HDT, which causes a shearing force with each successive layer. With adequate build plate adhesion, this results in successive shrinkage of each layer added, but also the layers already deposited, as they are kept above HDT.
Warping did not really change by going from 99C to 85C, but the effect of inward shrinkage of the first few layers up until say 10mm did. Note that all points into the direction of a shear force related phenomenon.
The above also suggest there's an optimum HBP temperature to look for:
- not too high (causing inward deformation of the first few layers)
- not too low (causing too much cooling and going too much below HDT)
At least that’s what I found, but a might be wrong still there. I wonder if there’s support for this by observations from others?
Other measures to reduce warping (I think in order of importance):
- getting as best as possible adhesion to the build plate,
- reduce shear forces by setting lower infill, smaller bottom thickness, smaller wall thickness,
- prevent sharp corners,
- going as low as possible with the extrusion temperature to reduce temperature drop and related shrinkage.
For the curling thing at the top, I have not looked that well yet as what happens here exactly. It seems less of a inter-layer shear force phenomenon compared to warping?Edited by Guest
To fix the problems at the top of your print you need some fan. Just a tiny bit. The slowest where it reliably rotates is good. Around 30% on UM2 or 3% on UM3. If you do too much fan the layers won't bond well (not a problem with PLA). Bad layer bonding is not obvious until you break the part. It will break along layer lines. But if you enclose the machine and set the fan to minimum you should be fine.
The bottom corner curling/lifting/warping is a completely different unrelated issue. It is caused by upper layers cooling and pulling inward which rotates the corners up with tremendous force.
Keeping the bed at 105C helps because being above the glass temp means the ABS is more flexible and can warp the tiniest bit and yet still stick to the glass. This is MUCH preferred over the corners lifting off the glass.
Another trick is to make the filament stick like hell. ABS glue, rounded corners, brim, squishing the filament into the glass are all good ways to assure it WILL NOT COME OFF the glass.
260C is dangerously hot. Sometimes ABS will get all clogged in the nozzle and you have to take it apart. You don't want ABS at above 240C for more than a minute or so. Higher temps are worse (more likely to clog) but if you haven't had any clogs I guess your temp is fine. So once the nozzle is up to temp keep things moving/printing.
To really get your part to stick like hell to the glass I explain all the tricks in detail here:
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