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I'm having a lot of trouble printing polypropylene right now, and I think it may have to do with the conditions. I'm using a very thin coat of ABS on the base plate (just as you would do when printing with ABS) in order to promote sticking.

In this following first picture, I attempted with a 240°C tip and a 150°C bed (above PP's Tg). Oddly enough, one side actually looked somewhat decent while the other clearly had trouble sticking. The print speed on this was 1500 mm/min.

In the second picture, I was printing with the tip at 220°C and a 50°C bed. What's interesting in that print (you may be able to see it) is that the polymer extruded with little blips of material followed by a more stringy section, rather than a steady, even filament. (Print speed on this was 2100 mm/min)

240°C tip and a 150°C bed

220°C tip and a 50°C bed

Does anyone have suggestions for doing better prints with PP?

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Polypropylene CAN be printed with excellent results, you just need a good filament roll and good printing setup. A few days ago I read this topic and was kind of afraid of testing it, now I am so happy I tried it.

I am printing the PP filament from the brand Smart Materials 3D (search on google).

I am using a Prusa i3 Mk2, bed heated to 70ºC and hotend to 210ºC. I ventilate the printer as much as possible: room windows open and fan at 100% after second layer.

IMPORTANT: apply some cheap brown packaging adhesive strips to the bed, where the part is going to touch the bed, with adhesive facing down. I tried many other solutions but none worked.

enter image description here

I have printed so far at 20mm/s constant, with 0.2 mm layer heigth, 0.4 mm extrusion width, 0.8mm retraction, flow 125%. Still optimizing setings. Parts come out very nice, with good flexibility and amazing inter layer bonding. Density is a bit lower than ABS, so excellent, and impact resistance is awesome. Check some parts I printed today:

enter image description here

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  • $\begingroup$ Awesome hints, it worked like a charm! I almost gave up on PP after reading Ryan Carlyle's post (which is definitely helpful too), but in the end I had less issues than with ABS. Only thing I changed was 240ºC on hotend, but that may be due to a different manufacturer/material. $\endgroup$ – Elephantik Mar 16 '17 at 22:28
  • $\begingroup$ This should be the accepted answer! $\endgroup$ – Art Sep 4 '17 at 11:25
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Polypropylene is a bear to print. There's a good reason almost nobody does it. The main problem is that it's a semi-crystalline material, which means it doesn't follow the normal rules for warping prevention.

An amorphous polymer like ABS or PET is able to slowly flow or creep until it cools below the glass point, Tg. This means the stresses caused by thermal contraction will "shake out" above Tg and only start accumulating when the print cools below Tg and fully solidifies. That's why heated build plates are usually set around the glass point for amorphous materials -- there's minimal warping stress in the print at that temp.

However, when you extrude semi-crystalline polymers like PE or PP, crystallization starts as soon as the temp drops below the melt point, Tm. A crystalline polymer will not flow or creep at a rate that is meaningful over the duration of an FDM print, so thermal contraction stresses will simply build up more and more as the plastic is cooled farther below Tm. And there's a loooong way to go when cooling from Tm to room temp. As a result, you get HUGE warping stresses with these plastics compared to more typical FDM materials.

It is simply not possible to pick a heated bed or heated chamber temp that entirely eliminates the tendency of PP to warp. The normal rules we use for amorphous polymers don't apply. And, greatly compounding the problem, PP is a very low-surface-energy material with adhesion behavior fairly similar to wax. It doesn't want to stick to much of anything except itself.

High warping stress + poor adhesion = bad times.

So, the simple answer is, polypropylene does not have the correct polymer behavior to be favorable for FDM. You will always be fighting warping. Think carefully about whether you want to struggle with PP or switch to a more suitable material that could accomplish the same design goal for the printed part. Do you really need to use PP? PET blends have similar hardness and chemical resistance, nylon blends have similar toughness, and TPUs can handle living hinge applications. That covers most of the reasons you'd want to use PP.

If you absolutely must use PP, you're going to need to pull out ALL the tricks people use with traditional high-warp materials like ABS and PC and nylon.

  • Use a build plate made of a close relative of the material you're printing. For example, people have successfully printed HDPE on a PP build plate, so I would imagine that a HDPE build plate should work for PP.
  • Or, use a perfboard build plate with a raft so the initial layer will get embedded into the holes.
  • Or, use a coarse fibrous surface like stiff cardboard or fiberboard.
  • Get the build chamber enclosed and as hot as you can without damaging the printer. 50C is usually reasonable for motors, extruders, etc unless you have PLA printed parts to worry about. (Heated build plates only really help with the bottom 5-10mm of the print if the printer is not enclosed.)
  • Use helper disks / mouse ears on corners.
  • Really mash the first layer down onto the build plate.
  • Print low layer heights, like 0.1mm. Smaller layers mean the thermal contraction applies more shear stress between layers, and less of the large-scale aggregate bending stress that lifts corners.
  • Higher print speeds may also help due to some complex strain-crystallization effects, but that's only currently proven in nylon to my knowledge.

Another option, if it meets your functional requirements, is to use a fiberglass or carbon fiber composite PP. CFR and GFR plastics usually warp less than virgin plastics. The fibers have a low coefficient of thermal expansion, which makes the composite material contract less as it cools, which reduces warping stress. The most successful PP printing I've ever seen was GFR-PP. But that stuff is hard to find and may not work if the part needs to be flexible.

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First picture clearly shows that temperature was too hight, second one suggests too small extruding speed (too little) which is connected to your printing speed.

35mm/s is quite slow :)

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  • $\begingroup$ I've improved the print a little by increasing the print speed to up to 3500 mm/min, but I'm still having issues. I re-coated the baseplate with ABS, and adjusted the temperatures as well but still haven't got this optimized. Thanks for your suggestions, though I'm not out of the woods yet. $\endgroup$ – CuriouSir Apr 6 '16 at 18:45
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Yes. These settings work for Ultimaker as well. Set the printer to print PLA, and put brown tape on the bed under the print. Set the layer to 0.1 mm, set the initial layer to 0.1 mm.

Don't over heat the PP or when it cools it will shrink tons making it want to peel off. PLUS if you don't let the PP go below its Tg (80°C) by making the bed too hot it will stay molten and eventually stick to the nozzle making a truly pants print, and probably detach itself.

I have been making tiny detailed little components with PP this evening, just about to put 21 on to make and then off to bed!

Update:

Sorry, PLA settings on the UM is 210°C for Hotend. I am making round PCB spacers, so these are best with a 100% infill and a concentric fill pattern. Also, I recalibrated the platform with a very thin post-it note which is about 50% of the thickness of the UM calibration card. It makes sense to just get the PP soft enough to extrude, in fact I am seeing turbulence at the beginning when the extruder runs some material through the molten material has a curly cable appearance. Like this the material beds itself right into the tape. Lovely.

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  • $\begingroup$ Hi and welcome to SE 3D Printing! Thanks for posting an answer. However, it would be a very good idea to edit your answer and post the additional information in the answer itself, rather than the comments. Not only does this contain the information in one "block", but also comments are rather ephemeral and are generally used for queries, or clarification requests, and as such can end up being deleted. Many thanks :-) $\endgroup$ – Greenonline May 26 '18 at 20:01

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