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I'm using a Prusa i3 MK3S printer. After ~8 months of printing PLA, PET-G, ABS I decided to buy some HIPS and print something with it. I cannot print >1 filaments at once, so I'm not using it as a support for ABS, I want to create some high durability working models, like gears, robot parts etc.

While the quality of my models is perfect, unfortunately their strength is disappointingly low. They easily undergo plastic deformation or break. I've tried lots of settings, some yielding better or worse results, but the problem is present regardless.

My settings:

  • Printer: Prusa i3 MK3S
  • Nozzle: Default 0.4 mm nozzle for Prusa
  • Layer Height: 0.2-0.3 mm
  • Temperature: 230-240 °C nozzle, 100-110 °C bed
  • Slicer: PrusaSlicer 2.0.0

I've read lots of tutorials regarding HIPS printing and they did not give me the answer to my question...

Am I doing something wrong or is it normal for High Impact PolyStyrene? At this point, the High Impact Polystyrene seems less High Impact than generic PLA.

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It might. If HIPS is a single material with consistent properties, it might have a narrower temperature range. Online references suggest up to 240 °C. Try that, then 245 and 250 °C. Maybe higher.

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  • $\begingroup$ Thank you, it worked $\endgroup$ – StLuke5 Jan 4 at 23:35
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You might try upgrading your PrusaSlicer to 2.1.1. I don't know if the "Prusa HIPS" setting got updated since your 2.0.0 but it's worth checking.

For comparison, PrusaSlicer 2.1.1 uses these settings for HIPS:

Filament:

  • First layer temp: 220
  • Other layer temp: 220
  • Bed temp, first layer: 100
  • Bed temp, other layers: 110

Cooling:

  • Fan speed: min 20%, max 20%
  • Bridges fan speed: 50%
  • Disable fan for first 3 layers
  • Enable fan if layer print time is below 10 sec
  • Other cooling settings same as for PLA

Advanced:

  • Max volumetric speed: 11

There's also custom G-code for HIPS setting M900 K10.

I, too, want to print actual parts with HIPS. For me, it's because HIPS the lowest density of all the commonly-available stiff-plastic filaments, which is great for printing lightweight model aircraft parts where every gram matters.

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  • $\begingroup$ If you are scraping for weight, consider foaming PLA! :-) $\endgroup$ – 0scar Jan 7 at 12:07
  • $\begingroup$ That foaming PLA is interesting... but really expensive. I'm amazed that it seems possible to make precision parts from a foaming filament. $\endgroup$ – Anachronist Jan 8 at 17:57
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The primary use of HIPS in 3D printing is to create sacrificial supports, which you're aware of. The material dissolves in lemon oil, making it popular for printing dense supports within complex shapes that can then be easily removed just by spraying the part down with Orange Clean.

I would not expect HIPS material sold for 3D printing use to have much if any strength, especially for moving parts. Outside 3D printing, most uses of the material are in expanded foam products like bike helmets, flotation products etc, and these applications require pressure-molding, which creates a higher-density object and hardens the foam's outer layer to make it tough enough for everyday use. Just extruding the stuff out into the open air gives you the same density (and strength) as a packing peanut.

If you want a styrene-type material that's strong, tough and relatively light, I'd stick with ABS. If you're looking for a challenge in a similar material, try nylon; it creates a lower-friction surface, is very tough but pliable, and its hygroscopy requires very careful handling of the filament (in some more humid climates, you have to feed it from a dry box through PTFE tubing straight into the printer; even the time out in the air between the box and the extruder is enough to get hydrolysis-related issues).

If you really want to print HIPS foam gears, the only thing I can suggest you try is an epoxy coating to give the object a harder shell while retaining the light weight. My wife does custom-applique vacuum tumblers (but who doesn't nowadays; my wife's making more money selling other people the supplies and equipment to do it), and her favorite stuff to use is Faux Rizzle; very durable, odorless, easy to mix and apply, and relatively inexpensive (many other art resins sell for about double what you can get FR for). Good luck to you.

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    $\begingroup$ Are you suggesting that HIPS filament goes to a foam when 3D printed? Probably the weakness is because of bad bonding. Might drying the filament and printing with a higher temperature be helpful? $\endgroup$ – cmm Jan 4 at 3:25
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    $\begingroup$ Don't forget POM (acetal/Delrin). Although I hear adhesion is hell. $\endgroup$ – R.. GitHub STOP HELPING ICE Jan 4 at 6:08
  • $\begingroup$ @cmm My first prints using this filament were even weaker, which was caused by bad bonding. The nozzle temperature was too low (220*C). The strength improved after increasing the temperature to 235*C. I don't know if increasing it even more will help. $\endgroup$ – StLuke5 Jan 4 at 9:08
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    $\begingroup$ @R..GitHubSTOPHELPINGICE Yes getting it to stick is not very easy, but possible, see "POM filament not sticking to the build plate?". Once mastered sticking it is great material for custom bearings. $\endgroup$ – 0scar Jan 7 at 12:15
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    $\begingroup$ @FarO I'm aware; edited to clarify that the absorption of moisture in itself is not hydrolysis. It remains that nylon is very hygroscopic and it's hard to dry back out, so a totally enclosed feeding system is recommended. $\endgroup$ – KeithS Jan 9 at 14:47

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