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kmsd

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  1. **STOP: Printing PC usually requires modifications to the printer. At the ambient temperatures needed for PC printing, the plastic printer parts inside the enclosure need to be printed out from annealed PC or at the very least annealed PLA. Do not even think about keeping any electronics inside of the heated enclosure. Do NOT run steppers above 60C ambient without cooling. To actively cool the steppers use local Peltier coolers or water cooling blocks from the PC scene. Before reprinting your printer parts, anneal sample parts to confirm their heat resistance and necessary scaling. No good results can be had without putting good work into it all - it doesn't have to be expensive, but must understand every step of the process and verify each as you go. Any LED strips used inside the enclosure must be ran at 25% duty cycle for thermal derating reasons. Verify performance of any adhesives used to attach anything inside the enclosure - anything stick-on will likely fall off. Use mechanical means of attachment (screws, clips, etc.)** Bed adhesion is *not* the problem - only a *symptom*. It's OK to print PC on acetone cleaned glass, on PEI, painter's tape, etc. The problem is the internal stresses within the print, as it cools to an inadequate ambient temperature. PC print environment requirements, in my experience, are as follows: - parts <1x1in - 115C first/140C subsequent bed, room ambient temp, - parts <0.5in thick - 115C first/140C subsequent bed, 50C ambient, - all parts - 115C bed & ambient, but anything in the 100-140C range should work with same bed and ambient temps. Bonus: parts come out annealed if you slowly cool down the enclosure and bed after the print. For the first two scenarios, in a 12V system the bed will slowly warm up to 140C after the first layer is finished, that's normal and not an issue. I print PC between 285C and 300C, depending on extrusion width (the wider the hotter). In ambient above 100C there is absolutely no issue with bed adhesion. I've printed PC on corrugated cardboard that way. Without additional heating, using only the bed as the source of heat, the enclosure is unlikely to go above 60C unless it is quite small. Apply one or more of the following workarounds then for larger prints to succeed. But those only make sense for particular prints that are close to succeeding and fail late in the print only! - Use white Hobbyking PC. Heat dissipation is controlled by color in the long infrared range, not visible color of course. But it turns out - at least for Hobbyking PC - that the white filament is also quite "white" in the micrometer infrared region. It will radiate heat away slower than the black filament. Again, the colors you can see with your eyes in the visible spectrum play no role whatsoever, it just happens that with Hobbyking PC filament in particular the visibly white one is also long-infrared-white. Other PC filaments may behave like that too - experiment to assess their performance. - Use very low infill (10-20%). It drives lower aggregate cooling stresses and may not have enough oomph to pull the print off the bed. - Use very high infill (75-100%) to thermally couple the print to the bed. The bed will then act to maintain sufficient print temperature to prevent warping. Center the print on the thermistor under the bed, and aim for high bed temperatures up to 150C. - Use adhesion improvement techniques, such as ABS slurry (PC binds well to ABS), PVA slurry, glue stick, etc. For proper PC prints at any size, without fuss, it's essential to monitor and actively control the enclosure temperature, and to have a separate enclosure heater, and to aim above 100C. Do not bother with trying to work around this issue by playing with bed adhesion: it's a war you will always lose, even if you happen to win a battle or two. Source: printed ~10kg of Hobbyking PC on a modified Prusa MK2S with a custom enclosure, including a 15x15x15cm test brick with 140C enclosure and 300C extruder.
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