A suggestion to reduce warping when printing with ASA: add a copper plate  

A suggestion to reduce warping when printing with ASA: add a copper plate

I print quite a lot with ASA. I often have to create big peaces, latest are 242 mm long and 162 mm large, so the worst possible dimensions for what concerns the warping issue.

I made many trials:

- the famous lack enclosure, that used in a controlled temperature environment allows me to get 35°C quite constant inside the enclosure during printing

- brim/mouse ears, as large as possible (as you can guess, not much for a piece that is 242 mm long just by itself)

- skirts as high as the piece to be printed, to contain heat

- etc.

Each of them provided an improvement, at the end a got results acceptable, but still not perfect.

The final idea that I tried, is adding between the heated bed and the PEI sheet a pure copper plate 1 mm thick and 5 mm larger then the PEI sheet on each lateral side, along the x axis to be more clear.
I add a photo that may be better than my description:

Please note that I'm not saying that with such a system alone I was able to solve any warping problem, but just that adding also this to all the items already implemented above, I was able to get the further and final improvement that I needed, now my 242 mm long ASA prints have no warping at all !

For the reason, I can just guess, as I don't own a thermocamera to verify it: probably the bed themperature is not perfectly uniform. On lateral border, where the printing area is very near the print bed border, probably the themperature drops enough to cause some adesion problems with ASA. Being pure copper a great thermoconductor and being a bit larger than the PEI sheet, probably it's a good helper to make the temperature more uniform, so to keep it nearer the required 105°/110° C also so near the printing area border.

I bought this copper sheet in a local bricolage store (here for Italians). With it, paid about 35€, I was able to produce 2 copper plates for my MK3S.

It was a careful and quite long task cutting it to the right measure  without creating any warping on the copper sheet.

I also had to be very careful when trimming the edges, to avoid any additional thickness due to burrs from the cut.

When they were ready, I then left them well pressed for hours between bigger and thicker steel plates, to be sure that they were as flat as possible before applying them in the printer.

Holes for the screws in the upper side of the print bed, were done a big larger than the screw (I used a 4 mm drill tip), so that differences in heat dilatation between heated bed and copper don't create curvatures.

The result is that now I have asa pieces, 242 mm long, that are printed perfectly flat: no visible warp neither due to uneveness for the added copper plate, nor due to the ASA warping.

Copper does not interfere with magnetic fields and 1 mm of distance doesn't reduce enough the magnetic atttraction of the PEI sheets: I've already done about 20 prints in this way and the PEI sheet has always remained totally stuck in place.

I hope that this my personal experience can be helpful also for someone else!