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.
Is it possible to use sugar somehow?
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.
Projets do this commercially.
Using UV curing rather than ABS.
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?
wonder what the melt point is for the plastic used for water soluble fabric (used in machine embroidery)?
Doesn’t High-Impact Polystyrene give off some pretty nasty fumes?
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.
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.
Agreed in general. 50C flashpoint is a bit of a concern.
But if you carefully calculate the fuel air ratio, as it approaches that concentration, you can have a match ready to clear it out in no time.
I wonder more about what the plastic is breaking down into than the effects of the solvent used.
Pulsejet heated reflow oven running off waste solvents and hydrocarbons anyone?
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.
PVA not PLA and as I mentioned in another reply, the current formulations of PVA on the market for hobby printers don’t print all that well and don’t work with ABS.
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.
PLA turns white with Acetone. And it’s hard to dissolve large quantities of ABS into acetone (I tried)
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?
Might work, as long as you kept the water at about 15 Fahrenheit.
At that temp it’s called ice, not water. ;)
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.
you can have liquid water (@atmospheric pressure) down to 0 F with the right salt, ie ammonium chloride. 1:1 ratio to water.
You’re too smart for me, yes, it was my way of saying, water in it’s liquid state, probably isn’t hard enough.
Use brine, not pure water. Brine freezes at 0 F (actually, that IS the 0-point defination for the farenheit scale).
actually you can take water BELOW 0-F by a few degrees with a saturated brine.
There are spools of PVA filament out there. My understanding is that works well, and it melts in a bath of water. No solvent needed.
White glue right?
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).
Okay, thanks…
Maybe some digging through this patent and references might allow us to figure other water soluble alternatives…. http://www.google.com/patents/US4331576
Particularly handy for cheapskates if we can brain out something that will work in a modified glue gun extruder…
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.
This technique would be perfect for the 2 color 3d printers that have come out recently. I hadn’t thought about one of the colors being just a temporary support structure.
This is what interests me about multi-color extruders: the ability to print a soluble support material. Color is a secondary application to me :D
Is this the stuff to get to dissolve HIPS?
http://www.amazon.com/d-Limonene-PURITY-Citrus-Solvent-Dlimonene/dp/B009SSGW48/ref=sr_1_3?ie=UTF8&qid=1362253340&sr=8-3&keywords=limonene&tag=651998669-20
Hello,
Does HIPS absorb humidity like PVA.
regards
Mohammed