ASA at the limits
I am trying to print a relatively large part (19 cm high by 20 cm wide by 10 cm deep), that needs to be relatively strong (25% in-fill), out of ASA (Filamentum) on my MK4. I have printed successfully with ASA before, but not such a large part and not with so much in-fill; the trick to avoid the print warping away from the heat-bed has always been to max the heat-bed temperature out at 120 C for the first layer, 95 C thereafter, and of course to have the printer inside an enclosure. That wasn't sufficient in this case: by about 5 cm up the print had warped away from the heat-bed at the edges and so failed.
However, I have now tried the ultimate: Pritt-stick on the heat-bed before printing. It turns out that the warping power of ASA is SO strong that it pulls the magnetic sheet away from the bed: the print got further, 7 cm up this time, and is still attached to the heat-bed, but the PE sheet came with it and the print failed.
What are my options to make this work?
RE: ASA at the limits
Thinking aloud here........... At that height above base are you really looking solely at bed temp/adhesion? I'd guess more at filament shrinkage so maybe keep a higher filament temp both during and after printing??
RE: ASA at the limits
Hmmm, yes, maybe you're right. See below a picture of the "Pritt sticked" attempt, the one that got up to 70 mmish tall. It does look as though all of the dimensions have shrunk towards either end. Maybe this is the kind of printing that really needs a chamber. I do have a heat lamp I could probably rig up in there...?
RE: ASA at the limits
I print ASA often but never encountered a part that warped strongly enough to curl up the steel plate. That said, I never made ASA parts 19cm tall.
As this is a Prusa MK4 (no inductive probe ), a glass bed possibly would be a solution. You just need to clamp the glass sheet to the bed frame with strong metallic clips at the front and the back. I think that setup would work OK ( provided the warping force isn’t so strong that it breaks the glass ! )
RE: ASA at the limits
> a glass bed possibly would be a solution
That's an interesting idea. I've found a glass bed that will fit but can't find any sign of any magnetic clamps: I have 20 mm neodymium disk magnets that I guess would do the trick...?
RE: ASA at the limits
It doesn't need to be magnetic clips, you can use bulldog clips or similar providing they don't restrict bed movement.
RE: ASA at the limits
> providing they don't restrict bed movement
Unfortunately the enclosure I have the printer inside doesn't leave any room to speak of around the printer so the clips would likely have to be magnetic to avoid fouling it.
RE: ASA at the limits
https://www.amazon.co.uk/dp/B08CQFYZ22/https://www.amazon.co.uk/dp/B08CQFYZ22/
And remove the arms
RE: ASA at the limits
Aha, yes, of course, remove the arms :-).
RE: ASA at the limits
Or use the clips on the std sprung plate and bedplate? 🤣
RE:
We had / have a similar problem with large ASA parts warping. Then we found out, that the real heatbed temperature of MK4 is far away from the set and indicated temperature.
We made measurements directly on the heatbed /no steel-plate installed with a calibrated touch-probe thermometer.
The result was (12 measurement-points across the heatbed):
Set / indicated temperature 100°C - measured tempertures 84 - 86°C
Set / indicated temperature 120°C - measures temperatures 102 - 105°C
PRUSA support was involved and very comitted and even did provide a brand new MK4 in exchange, but it showed the same problem so we did send it back.
For us this means, that the set and indicated heatbed temperature of MK4 is far away from reality.
PRUSA support told us, that a firmware-failure (heatbed thermistor factor) might be the reason for the problem and that a future firmware version maybe can solve the problem.
In the meantime as a workaround we artificially increase the heatbed temperature by 15°C - 20°C above the theoretical temperature. However at ASA and similar high temperature Filaments the MK4 is at (or better above) its limits as the required heatbed temperatures of 110°C (or even a bit more) for large ASA-parts cannot be reached at all.
MK4 is a rally good printer but this simple problem is annoying and limits the use of MK4.
At our other printers (other brand), the identical parts with the same ASA filament print well.
RE: ASA at the limits
Or use the clips on the std sprung plate and bedplate? 🤣
After writing in a hurry about a glass plate I realized that. You're right, of course. Why bother to get a glass plate if those clips can clamp the original steel plate as well...
Unfortunately it was too late to edit my original post to avoid the embarrassment. 😛
RE: ASA at the limits
> Then we found out, that the real heatbed temperature of MK4 is far away from the set and indicated temperature.
Very interesting: as others have indicated, I've not had problems printing with ASA before, but I've never tried to print such a large thing, and all of those previous attempts would have been on my MK3: I don't know if the problem you describe occurs on the MK3 or not.
RE: ASA at the limits
> After writing in a hurry about a glass plate I realized that. You're right, of course. Why bother to get a glass plate if those clips can clamp the original steel plate as well...
True, but it could still flex, it would depend where the ends of the print happened to lie in relation to the clamps on the flexible plate. Better to have it not flex at all I think.
RE: ASA at the limits
> Then we found out, that the real heatbed temperature of MK4 is far away from the set and indicated temperature.
Very interesting: as others have indicated, I've not had problems printing with ASA before, but I've never tried to print such a large thing, and all of those previous attempts would have been on my MK3: I don't know if the problem you describe occurs on the MK3 or not.
We had an MK3 before and did not face similar warping problems at the identical large ASA parts. Therefore we did not see any reason to measure the real heatbed temperature in relation to the MK3 theoretically indicated values.
Fact is, that with MK4 we have to increase the printbed temperature artificially by approx. 15C to 20°C above the theoretical values to receive the correct heatbed temperature, a good bed adhesion and minimum warping. As the problem is linear along the whole heatbed temperature range, other materials are effected by low adhesion because of unexpected / unwanted low heatbed temperatures also.
According to our experience, a super strong bed adhesion (glue) or stiff printbed (glass-plate) do not solve the warping problem as then the printed part itself cracks internally because of the temperature caused shrinking process.
The shrinkimg / warping process and resulting poor adhesion of the print in our view only can be reduced by adequate high heatbed temperatures.
As the heatbed temperature at our MK4 can be set to a theoretical max. of 120°C only, the real max. achievable heatbed temperature is approx 100°C only. And this is too low in some cases and for some filaments.
Again: MK4 is a good printer - and if PRUSA solves the heatbed-temperature problem, we are happy with it. But till then we print ASA and other temperature-sensitive filaments with our other printers