Does anyone know what happens when an SLA or polyjet part is exposed to extreme heat? Will it melt like thermoplastic or will it burn like thermoset? I’m thinking about softening some parts up but don’t know if I should use a heat gun, flame, or just soak it in alcohol. Or maybe it can’t be done at all?
To deform or straighten SLA parts we use hot water – works with most SLA resins.
Thanks - ever try it with a living hinge?
yes, don’t.
you can however get a living hinge out of nylon sls.
spoonyd is right – don’t. We have made living hinges out of sheet vinyl, getting about 100 flexes before it splits. We have also used silicone rubber, it works very well but it is difficult to do and on small parts as it wants to return to its original position as soon as it is released. Objet has a new machine that will jet different durometer resins in the same build – may be possible to get some hinge action for a while but the low durometer stuff tares pretty easily.
Living hinges are the bane of model making.
i’ve also had success just cnc’ing living hinges out of polypropylene (with a little extra meat). They have a pretty ok life, and when they break you can weld them back together using a soldering iron. It gets the job done.
I’m not going to comment on SLA, not my line of expertise.
Living hinges don’t have to be your nemesis. If the right resin is selected, they are very successful and wear quite well. You just have to go with a flexible resin rather than a more rigid less forgiving one.
You don’t have to beef up the hinge area all that much if your using injection, good venting & even heat to ensure a good flow of material.
Would some of the urethane resins used in RTV molding be a better material for living hinges? doesn’t add that much to the cost if it works better… they might even be able to lay in some fiberglass before they mold to make the joint even stronger
As much as I’d like to give you an answer on that, I’m not very familiar with Urethane resin’s and their properties. Thermoplastic’s is more my specialty.
Someone years ago I talked with about urethane castings was suggesting that they could either mold or extrude the hinge in PP (can’t remember which) and then insert it in mold & cast the rest of the part around it. Seemed too risky to try it then but I always wondered if it could work.
No thermoset is going to be a good candidate for high-flex usage; I’d almost say a single one-flex usage. And molding an entire product of out “snotty” PP just to get a “free” hinge, may not be the best choice. Why not just mold a simple PP living hinge with a snap-in capture detail to lock it into the two adjacent parts? You would also have the freedom to modify the hinge if performance didn’t meet expectations; and being, essentially, a flat part, the tooling cost would be very low.
Co-molding the hinge into the parts is always risky … if the operator has a brain fart and improperly inserts a part, you’ve lost the two major components, and possibly damaged a tool.
Just curious phoenix, there are a lot of ejectors visible on that part. Is that due to the “thin-ness” of the part … to speed up cycle times?
Are you experiencing any cracking problems with those “square” corners in the openings, and at surface transitions?
Sorry for the delay in answering. I did not see your question till just now. I guess I should check that tiny box that says “notify me when a reply is posted” 
The placement of ejection is due to part thickness which is 1MM (.040) and a lack of draft due to the part design allowance.
No, we are not experiencing any cracking or deformation due to sharp corners. Unfortunately from a molders view point, the part design won’t allow the standard radius that seldom affects the resin flow. Besides meeting the design guidelines, the hinges have to be processed properly. The molecules have to be oriented along the hinge line for the hinge to have acceptable life, which is predicated some by the gate location.
I can not speak for the 3d Systems brand polyjet, but I know the Objet material (vero) will for sure warm when exposed to heat. Our rapid prototyping company is based out of Tampa, FL and it is a big problem during the summer. If you order a part from a service bureau, make sure it is not exposed to the summer heat. If so have it shipped in the afternoon via Priority Overnight. Objet Materials have been used for flow testing, but not for hot water! I had a client try run hot oil through it before asking me, bad idea!
SLAs are also somewhat sensitive. A typical SLA material will be about ASTM D 648@ 66 PSI 136 - 145 °F.
If you need, try getting a material called BlueStone. I can be used in aggressive thermal environments - up
to 250°C (480°F). Feel free to contact me if you need more info on this.
Otherwise there is also an FDM material that can withstand temps of 400F+.
Hope this helps.
Getting in on this one quite late. Objet Vero Gray will not deform when exposed to temperatures below 135 degrees F. Objet FullCure720 is used alot for flow analysis, but it’s heat distortion temperature is around 120 degrees F.