Protogenic comparative analysis of the relative flex of current SLA resins

Overview:  As rapid prototypers, we're often first to hear the new marketing claims of the SL resin suppliers, all claiming to offer the latest and greatest resins.  They all sound great at the onset, but we've learned that the resins often disappoint, and don't quite live up to the marketing claims.  At the same time, our Customers count on us to be experts at Stereolithography, and they frequently ask us to make SLA resin recommendations.  And so it's of vital importance that we develop a real-life, objective test, that we can use to learn about the relative performances of the resins, so we can make those recommendations based on our own personal experience, rather than the hearsay of a resin salesman, or misleading numbers on a spec sheet.

Our internal resin requirements have been, and will continue to be high accuracy, repeatability, short run time, and compatibility with our RTV molding processes.  Outside our walls, our Customers want SLA’s to be accurate, durable, robust, and “not brittle like the SLA’s I bought a couple years ago.”  To that end, we believe we have done a good job finding a balance between what’s been marketed as the “best” resin, and what actually works and performs well.  This study is a way to further develop our working knowledge of the various SLA resins that we run, so that our Customers can make more informed decisions about what SLA resin they choose to use in future projects.

The study: Design a test piece that will be run in every SLA resin, that will allow us to compare the “break points” of each resin, as well as a fixture that will flex the test pieces in a controlled and uniform manner.  Run the SLA samples, using the same “normal” process that is used for all Customer SLA’s, then compare each resin sample using the test fixture.  Perform the same test to each sample, record results.

Deflection test 1: Maximum deflection value.  In this test, pieces were run through the test fixture, forced in and out of each stage of deflection starting with the lowest deflection amount, then working up incrementally.  The 'fail point' of each resin was recorded as the deflection point at which the snap feature broke.  Two SLA's from each resin were tested, those results are below: 

Comments: The 10120 resin surprised us the most, by testing higher than the SL-5240 and SL-5260.  5240 is marketed as 'flex resin,' so it's interesting to see how it really doesn't flex as well as the general purpose resin (10120) and the water clear (10110). 

Deflection test 2: Repeatibility.  In this test, first determine a deflection amount that each sample is capable of doing, then count how many cycles each resin sample will do before breaking.  ''Down'' and ''up'' in and out of the test fixture was counted as two cycles, since the snap feature had to deflect two times.  The deflection amount chosen was .100'', and the cycles of each resin are shown in the table below

Comments: Again, the resin that surprised us the most is the 10120, since it is not marketed as a 'flex resin.'  The SL-5240 did well, but we expected it to based on our experience with the resin.  One other point worth mentioning is the 10120 appeared to 'creep' more than any other, meaning the snap feature didn't 'bounce back' to its original state between flexes.  The 5240, on the other hand, 'bounced back' more than any other resin tested.

Thank you for taking the time to read through this study, please let us know if you have any questions.  And as we add new resins, we'll run samples through the same test, then update our tables above so you'll always know how they compare.