In this part of our regular series on FDM 3D printing materials, we’re looking at a very useful but unusual material known as HIPS.
What is HIPS?
As we’ve said, HIPS is a useful material in the world of FDM 3D printing but you’ll seldom find any trace of it on your completed printed item. HIPS stands for High Impact Polystyrene and is a lightweight material most commonly used as a dissolvable support structure for 3D printed ABS models.
If you imagine Polystyrene or Styrene as its also known, then you’ll know that this will evaporate when exposed to heat. This makes it a useful material for creating aluminium objects where the model is crafted in styrene, placed in sand and then the molten aluminium is poured into to replace it. This method is pretty low-tech but something that has been used by crafters for years.
HIPS also evaporates but not when exposed to heat. The liquid d-Limonene will completely dissolve HIPS when applied but has no effect on ABS. This makes it the ideal material to use as a temporary support structure.
How Does it Work?
Using HIPS and ABS as your printing materials will require a particular type of FDM 3D printer, or at least a particular type of extruder. We’re talking about dual-feed extrusion so the printer needs to either have this capability from the outset or have the adaptability to have it added.
A dual-feed extruder does exactly what it says and will feed two different filaments through the extruder during the same print. This type of machine is ideal if you want to either mix colours together in your print or to change colour at certain layers. You could of course add a pause command into the g-code of the print file and manually change the filament but a dual-feed extruder avoids all that effort.
When using HIPS, the g-code will need to be set to feed the ABS through to only print the 3D object and the HIPS to only print the supports. Once the print is finished, you would then place the entire printed object, including supports, into a jar or vat of d-Limonene and just wait for the HIPS to safely dissolve. The result is that you’ll have a support free 3D printed object without the tell-tale signs of the support contact with the object.
Pros and Cons
As always, we need to look at the good and bad points of using HIPS but hopefully the pros will generally outweigh the cons.
Impact and water resistant: HIPS is strong despite its dissolvability
Lightweight: Very lightweight which makes sense with the Polystyrene element involved
Dissolvable by d-Limonene: An easily obtainable liquid which works well at dissolving HIPS
Dual-feed extrusion: This is uncommon in most FDM printers so can require the need to upgrade
High printing temperature: Again, a specialist 3D printer may be needed to cope with the high working temperature
Ventilation required: HIPS can give off toxic fumes so a ventilated workspace is a must
There isn’t really anything else to add about the common uses of HIPS because, as an FDM 3D printing material, it only has one use.