Hey all,
I’m interested in making jigs and mechanical assemblies and am curious what the most appropriate resin is. Let’s consider the lens polisher from the article at https://formlabs.com/blog/creating-camera-lenses-with-stereolithography/ . Is the most appropriate resin for such things still the Tough resin, or is Gray pro now a better bet? They seem to fill a similar niche. What would drive someone to pick one over the other for this application besides the color/translucency.
Grey Pro is more precise, repeatable print-to-print and less dependent on orientation for dimensional accuracy. It’s also a bit stiffer.
Tough is dimensionally less stable, especially it will creep when submitted to constant loads. It’s less easy to get straight thin long walls to come out actually straight with Tough than it is with Grey.
Now the big advantage of Tough and the reason why I keep using it alongside Grey is that it is truly less brittle. It takes compression and bending forces better, especially dynamic ones. Grey Pro is still quite brittle, more like the other Standard resins than anything else really.
One might think Grey Pro is easier to cure since it only takes 15mins, but these 15 mins have to be done at 80°C and the Cure takes AGES to get up to that temperature. Also the longer curing time of Tough allows for more flexibility (pun intended) in the post-curing and final mechanical characteristics of the parts.
If you have walls thicker than 4mm, Grey Pro is fairly sturdy. It will not survive a drop to the floor, but then neither will Tough in many cases. I went through several liters testing Tough without getting many useful parts from it. The deformation under load (or sometimes, under parts OWN load, just lying still) along with the ludicrously low glass temp (unprotected parts can start to deform at 40 degrees celsius). I also had warping during printing n many parts that was caused by those characteristics.
I would absolutely love Tough if they could make it a little more stable.
If the mechanical assembly needs to handle more stress under a short time span, then maybe still use the Tough, but for something that needs to last months/years the Grey Pro would be better. If you need to insert things, like the bearings in that polishing jig, then Tough would be better. You can do things like tapping threads in Grey Pro if you are careful, but any stresses or pressure carries the risk of things cracking. Painting and lacquering helps to make Grey Pro a little more stable when it comes to breakage.
I’m inclined to just use clear resin within it’s limitations, and use FDM nylon/ABS for parts that need to be more sturdy. I’ve had problems with detail and creep with tough, and buying a prusa mk3 instead of a form cure seemed like a better investment, given that they’re similarly priced.