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I recently upgraded to a Polypropylene print bed, but I haven't actually been able to complete a print.

Adhesion seems incredibly inconsistent, even on the same spot. Sometimes it goes down great, and sometimes it just curls up and clumps on the nozzle. I even cranked the temp up to 220 °C for the PLA and 70 °C for the bed in an effort to get it to stick for an initial layer, and it still isn't sticking.

Any tips? I've been cleaning with rubbing alcohol, but I don't know if there's any trick. Clean when hot? Cold? Let sit after cleaning before using? Is it just a matter of incredibly precise bed leveling?

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  • $\begingroup$ Before going into details of getting print to stick, first address the bed material in the question. Polypropylene (PP) bed? PP is very slippery (so difficult to get something to stick), isn't it PEI (Polyetherimide)? Or is it a Buildtak (or clone) bed surface? $\endgroup$ – 0scar Apr 18 at 13:53
  • $\begingroup$ @0scar I'm really not sure what you're asking, I meant Polypropylene bed material. This one specifically:link Is that what you were wondering? $\endgroup$ – dornadigital Apr 18 at 14:50
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    $\begingroup$ I asked because Polypropylene is an uncommon bed material, AFAIK it is only used when you want to print PP. Thanks for the link! $\endgroup$ – 0scar Apr 18 at 15:19
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If you are using PLA, 200 for the extruder sticks the best for me. The other issue with adhesion is the greater the difference between the extruder temperature and the bed the poorer adhesion. There are other things can help with this. Using a higher bed temperature for the first layer can help. A slower extrusion speed allows the extrusion to cool more before getting as long of a length to for the contraction force; thus improving adhesion.

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  • $\begingroup$ Problem is, even after I level the bed using thingiverse.com/thing:3235018, the filament still refuses to stick without additional adhesion. Even with a high temp. And going slow won't help, since the filament just bunches up around the tip. $\endgroup$ – dornadigital Apr 18 at 14:47
  • $\begingroup$ Have you tried putting a Kapton (polyimide) sheet on your bed? amazon.com/… $\endgroup$ – Perry Webb Apr 18 at 23:36
  • $\begingroup$ I use a glue stick. It works, but this plate was advertised as not needing additional adhesion. If it does, then I'll accept that as an answer and go back to a magnetic surface + glue. I'm just sick of banging my head against a wall. $\endgroup$ – dornadigital Apr 19 at 14:42
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When you updated the print bed, you may have affected either the manual or auto calibration of the bed height and bed leveling.

First layer adhesion is depends critically on an accurate first layer thickness, which depends on the bed height calibration. Adding or, perhaps more critically, removing any bed surface thickness could cause a problem.

With many forms of auto bed calibration, a sensor detects a steel or metallic reference under the surface. The thickness from that reference to the surface of the bed is not automatically detected or compensated. Changing the bed surface, even renewing the surface with another sheet of the same material, may alter the bed thickness enough to affect the adhesion fo the first layer.

If the bed is properly adjusted, the problem may be the surface of the polypropylene. I see that some instructions for cleaning polypropylene build surfaces suggest isopropyl alcohol and/or a mild soap solution. I find that with a PEI build plate, it is sometimes necessary to clean the surface with acetone.

Acetone is superior at removing oils and films from the surface and will do better than multiple isopropanol cleanings. I checked a table of chemical compatibility, and polypropylene is highly compatible with acetone, so a thorough cleaning will not degrade it.

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  • $\begingroup$ Nope, I remembered that part. Been using this thingiverse.com/thing:3235018 to try to level, but putting the bed close enough to stick leads to layers being pulled up as the nozzle travels. $\endgroup$ – dornadigital Apr 18 at 14:45

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