Materials: Dissolvable Support Filament

Guy Fraser edited this page Jun 3, 2017 · 8 revisions

Dissolvable filaments allow you to 3D print more complex objects, but you'll need a dual-extruder to use them:

  • One extruder is devoted to your primary printing material (eg. PLA or ABS)
  • The other is devoted to the dissolvable support material (eg. PVA or HIPS)

PVA

PVA (Polyvinyl Alcohol) is primarily used as a support for PLA. When placed in water, the PVA will dissolve away leaving just the PLA. It's not the easiest filament to work with, however.

Storage

By design, it absorbs moisture - so keep it wrapped up with some silica gel desiccant in a sealed bag when not in use.

Many brands also seem to be UV sensitive, as well as heat sensitive. Keep in a cool dry place out of direct sunlight.

Consider creating one of these, or even one of these.

Slicing

Most modern slicers will allow you to specify which extruder (or Tool / print head) to use for various aspects of the print which should suffice for basic use of PVA (eg. rafts, supports, etc). Remember that PVA is more easily removable, so you might want to use tighter settings than usual for your supports to get the best print possible.

If you're looking to use PVA in more advanced ways, for example creating "impossible designs" (like this), the general approach is to use the same process as you would when printing with two different PLA filaments - usually that means having two models loaded in to your slicer, and selecting which extruder to use for each model.

Pre-print

Pro Tip: Start by printing a PVA raft and just a couple of layers of your PLA object - and get that working first before worrying about other stuff, otherwise you will end up going round in circles.

The PVA raft should stick to the bed, and be clean and tidy. The PLA should stick to the raft, and have a well defined outline and fill.

PVA extrusion is usually erratic in comparison to PLA, it will likely take lots of experimentation to get it extruding reliably - don't give up! Try increasing extrusion rate, and/or decreasing print speed when printing the PVA. If you increase the extrusion rate, remember to check and tune the retraction rates.

Part of the problem with the extrusion is that the PVA won't be printing the whole time. If you've done multi-extruder printing before, this will be obvious - but for me using PVA was the first legitimate reason to use multi-extruder printing; and it's not just the PVA that will need tuning for correct extrusion - you'll need to tune your PLA extrusion as well, particularly if it's not printing infill or ooze shields properly.

PVA often struggles to adhere to other surfaces, including PLA:

  • If you have a heated bed, use it - a temperature of 40-80°C should help, depending on which PVA brand you're using.

  • Alternatively, try using hairspray or glue (ideally PVA-based) to make the bed stickier

  • A PVA raft can solve lots of frustration while you're tuning your settings

  • Reducing PVA print speed when printing supports usually helps too

Printing

Most brands are overly sensitive to ambient temperature. For best results, open your printer enclosure to let excess heat out. Conversely, don't get it too cold either - if your printer has a filament cooling fan, turn it off because if the printing PVA cools too quick it becomes brittle and won't adhere to whatever it's being printed on.

Keep a close eye on the print. It's not just the PVA settings you need to get right, but also the PLA settings that work alongside them:

  • You will often find one or both extruders are oozing too much between tool changes; using an ooze shield should mostly mitigate this issue

  • Even with an ooze shield, you should still try and tune your tool change retraction rates to prevent the nozzles from drooling in the first place

  • On the first few prints it might help to have some long tweezers to hand so you can quickly pluck unwanted mess from the print area

Post-print

PVA dissolves in water - but it's a bit messy and can take a while. Pull or cut away some of the excess PVA first to reduce time and mess. Warmer water will make it dissolve a little quicker, especially if given a few stirs from time to time, but avoid using hot water that could cause the PLA to warp.

Note: After dissolving the PVA, the remaining PLA object will likely have some water in it, even if there's no noticeable holes.

PVA isn't great at bonding to PLA. I personally found that a PVA raft would easily detach and with some patience I could also remove all the supports without damaging my printed object. This way I can drastically reduce the amount of time taken to dissolve any remaining PVA.

HIPS

HIPS (High Impact Polystyrene) is most commonly used with ABS. When placed in a solution of D-limonene, the HIPS will dissolve away leaving just the ABS.

While it's easier to work with than PVA, it can't be used with filaments that are affected by D-limonene, such as PLA.

Alternatives

You can often avoid the need for overhang supports by making your overhangs incline at >45° angle - modern slicers and printers are usually able to handle those without the need for supports.

Some other filament types can be dissolved, but often require nasty chemicals - here's a summary of the methods I'm aware of:

  • PVA dissolves in Water
  • HIPS dissolves in D-limonene
  • ABS dissolves in Acetone
  • PLA partly dissolves in Ethyl Acetate, fully dissolves in Weld-On #5
  • PEEK dissolves in conc. Sulphuric Acid (note: using PEEK as a support material would be insane)

There are other ways to create 3D objects to consider - such as CNC milling machines, SLA printers, etc.

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