3D Printed Supported Soluble HIPS: When to Use It and When Not To
This page explains how HIPS works as a soluble support material in dual-extrusion FDM printing, what it can and cannot dissolve away, and where the process stops being the right answer. Written for design engineers and buyers who need to judge a support strategy before committing tooling time.
What This Page Covers
Support removal is a geometry decision, not a material upgrade. Here is how to make that call.
What HIPS Does as a Soluble Support
HIPS stands for high-impact polystyrene. In FDM printing it is most often used as the support filament in a dual-extrusion setup, paired with ABS because the two share a similar print temperature and stick to each other well enough to hold an overhang but not so well that the interface fuses. The support is removed after printing, either by breaking it away or, in the case of HIPS, by dissolving it in d-limonene.
The point of a 3D printed supported soluble approach is that removal stops being a mechanical problem. Instead of reaching into a cavity with a pick and prying, the part goes into a bath. The support softens and washes out, leaving internal channels and re-entrant features that no hand tool could reach.
That is the capability to keep in mind. Everything else on this page is about the cost of using it. Dissolution takes hours, not minutes. D-limonene is not something you pour down a sink. And the nozzle, the slicer setup, and the part orientation all have to cooperate, or the support simply will not come out.
How the Print Is Actually Built
A dual-extrusion machine carries two filaments. The model material and the support material each get their own nozzle or share one with a purge between tool changes. For ABS plus HIPS, both print in a similar range, which is why the pair works. Temperature mismatch is the most common reason people abandon the combination.
The interface between model and support matters more than any other setting. You want enough contact to hold the overhang flat and little enough that the two do not weld. A typical starting point is a small air gap at the top of the support, with a denser interface layer underneath. Tune it per geometry, not per printer.
Orientation decides whether you need support at all. Rotating a part so overhangs face the build plate or sit below 45 ° from vertical can eliminate most of the support volume. Every cubic centimeter you avoid printing is time and solvent you do not spend later.
Purge and prime towers are not optional. When the printer switches from HIPS to ABS, a small amount of the previous material stays in the nozzle. Without a purge block, that residue ends up in the part wall as a visible streak. It also weakens the bond between layers.
Soluble HIPS Against Other Support Methods
Use this to pick a removal method before you pick a printer.
| Method | Best for | Main limit |
|---|---|---|
| Soluble HIPS | Internal channels, enclosed cavities | Hours in solvent; solvent handling |
| Breakaway PVA | Simple overhangs, low humidity shop | Sensitive to moisture; slow dissolve |
| Breakaway solid support | Open geometry, fast turnaround | Tool access required; marks surfaces |
| Printed-in-place design | Parts that can be reoriented | Not always possible with the function |
| CNC machining | Tight tolerances, structural parts | Higher setup cost per unique design |
Which Parts Suit This Process
Internal channels are the strongest case. A manifold with a curved bore that has to stay open, or a duct with a turn tighter than any tool can reach, is exactly where dissolution earns its cost. If a human hand cannot get a scraper in there, mechanical removal will not work.
Enclosed cavities come next. A hollow shell with a wall on every side needs something inside during printing to hold the roof up. HIPS fills that role, then leaves through a drain hole you designed in. Without a drain path, the solvent cannot circulate and the support stays put.
Parts with deep undercuts and re-entrant angles also qualify. These are the features that break away supports tend to tear or leave witness marks on. Dissolution avoids the marks because nothing is pulled off the surface.
Complexity of the cavity, not the outside shape, drives the decision. A visually busy exterior with no internal voids rarely needs soluble support. It just needs a better orientation.
Where It Stops Being the Right Answer
Thick support volumes dissolve slowly. A large block of HIPS hidden inside a part can take a very long time to clear, and the outer skin of the support can seal before the core softens. Design drain holes and keep support walls thin rather than relying on a soak that runs overnight.
Solvent access limits everything. D-limonene has to reach the support and the dissolved material has to leave. Long blind pockets with one small opening will not clear in a reasonable time. If your part looks like that, rethink the geometry before you print it.
Solvent is a real cost, not a footnote. It needs proper containment, it has a shelf life, and used solvent has to be disposed of correctly. A shop that prints two parts a month may find that cost hard to justify against a mechanical solution.
Tolerance is another boundary. FDM surfaces land far from machining tolerances. If a mating face needs ±0.005 mm or a bearing bore has to hold a press fit, print the shape for form and fit checks, then move to CNC for the finished part. We machine ABS, PC, POM, PEEK and HDPE to those numbers on 127 CNC machines, with 16 simultaneous 5-axis centers for the awkward angles.
Small feature size is the last limit. Walls under about 1 mm and pins under roughly 2 mm are fragile in FDM regardless of support strategy. Dissolving the support does not make a thin wall stronger. It just removes the thing that was holding it.
Common Questions
How long does HIPS take to dissolve?
It depends on support volume, wall thickness and how much the solvent can circulate. Thin lattice support with open drain holes clears far faster than a solid block behind a small opening.
Plan for hours rather than minutes, and agitate or refresh the bath if the part has long internal channels. There is no fixed number that fits every geometry.
Can I dissolve HIPS in water?
No. Water will not break it down. D-limonene is the usual solvent, and it needs to be contained and handled as a chemical, not a rinse aid.
Some shops use heated baths or ultrasonic agitation to speed things up. Both add equipment and both need ventilation.
Does HIPS work with PLA as the model material?
It is a poor pair. PLA prints at a lower temperature, so the two materials do not bond reliably at the interface, and the support either falls away during the print or welds in patches.
HIPS is normally matched with ABS or another styrenic filament. If your model must be PLA, use a different support strategy.
Will the dissolved support leave residue on the part?
It can leave a slightly tacky film if the part is pulled out before the bath is fully clear. A rinse in fresh solvent followed by air drying usually removes it.
On visible surfaces, do not rely on dissolution alone for finish. If the face matters cosmetically, plan a light sanding or bead blasting afterward.
Can a machined part replace a printed one with soluble support?
Often yes, once the design is frozen. CNC gives you the tolerance, surface finish and material properties that FDM cannot reach, and it removes the solvent step entirely.
The usual route is print for form and fit, machine for function. Upload the model and we return a quotation with DFM notes within 12 hours.
Do you need a drain hole in the part?
Yes, if the support sits in a closed volume. Solvent has to get in and dissolved material has to get out, so at least one opening is required and two is better.
A drain hole left in the final part may be acceptable or may need plugging later. Decide that at the design stage, not after printing.
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