Soluble Support Structure Can Be Used With Any Extruder-based 3D Printer

One of the issues with extruder-based 3D printing is that it can be very difficult to print objects that have voids in them. You simply must have something to deposit the soft material on until it has a chance to harden. [Matt] found a solution which should work for any extruder-based printer (with one caveat we’ll get to in a minute). He prints a support structure out of HIPS then later dissolves it using Limonene. The image on the left shows the object soaking for 24 hours. The final project is seen beside it.

The only real problem with this technique is that it requires a second extruder. Since printers build objects by layers, switching material in a single print head isn’t an option. HIPS stands for High-Impact Polystyrene. It extrudes at the same temperature as the ABS (235C) and adheres well to a heated bed kept at 115C. ABS will be unaffected by the hydrocarbon solvent Limonene, except for the residual smell of citrus.

34 thoughts on “Soluble Support Structure Can Be Used With Any Extruder-based 3D Printer

  1. I am thinking paraffin wax as it has a lower melting point than ABS and is cheep / easily available. the model could be heated after completion and the wax would melt away and be reusable. ofc that is speculation I don’t have a 3D printer to experiment with yet.

    1. I wonder if this would work considering the ABS is heated to about 220C. If it gets extruded onto wax, would the wax support material melt underneath? Or would the ABS cool quickly enough that it wouldn’t be an issue?

  2. D-Limonene is biodegradable, but due to its low flash point, it must be treated as hazardous waste for disposal.

    Limonene and its oxidation products are skin and respiratory irritants, and limonene-1,2-oxide (formed by aerial oxidation) is a known skin sensitizer.

    1. I suspect that most people who are smart enough to do this are also smart enough to safely deal with solvents. Limonene is actually much safer to human beings than most other commercial solvents such as acetone and xylene.

  3. PLA dissolves fairly quickly in a warm water ultrasonic bath. No solvents and no residue to deal with. The uPrint we have at the office uses this method. Using HIPS and Limonene is a pretty novel idea though.

  4. I haven’t really played with PLA but it is my understanding that it doesn’t dissolve in acetone like ABS. So couldn’t people just print with PLA and use ABS as the support material, then dissolve the ABS in an acetone bath?

    Mind you I would much rather have the smell of Oranges than the smell of heated plastic add a more pungent solvent.

  5. Here’s a silly idea from someone who doesn’t have a 3-D printer yet: could you lower the model into water as it’s being made to give support to those naked horizontal layers?

        1. Depends on what’s been added to the water. Adding salt will lower the freezing temperature (I don’t know the mix ratios off the top of my head), and adding propylene glycol will certainly do it.

          My point is that it’s not difficult to get water down to 15 F without freezing it.

      1. after eventually finding out it’s Polyvinyl alcohol that’s used to make the water soluble fabric used in machine embroidery. suspect the meaning of PVA here is probably Polyvinyl alcohol, rather than Polyvinyl acetate (white glue).

    1. Tony Buser has experimented in the past with PVA and PLA printing and had some encouraging results but it still wasn’t a great system. The problem here is finding two materials that print well together. The PVA on the market right now doesn’t adhere well to ABS and has other printing issues. PVA is also expensive. HIPS and ABS print really well together and adhere perfectly until you try to tear them apart or dissolve the HIPS portion.

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