Dec 3, 2015 | By Alec

When startups and even established businesses in the 3D printing community introduce new products, they are always trying to be slightly original in one way or another but ultimately all follow a same set of principles. That’s we were very pleasantly surprised by the approach Formlabs took last summer to introduce their Tough Resin. Instead of having some engineer talk about properties or list comparative charts or show 3D printed examples, they took the most ridiculous route they could: they built a fantastic, needlessly complex and large Rube Goldberg machine that does absolutely nothing but break glasses and shoot confetti, but still achieves the purpose of showing what the material is all about. We really enjoyed it, and fortunately they just revealed more about the building process behind this fantastic machine.

To remind readers, a Rube Goldberg machine is a machine that relies on a large number of unnecessary mechanical steps involving marbles, weights, pulleys and sometimes even candles and pieces of string to accomplish something seemingly useless. It’s something out of a cartoon, really. This cool machine by Formlabs is visible above, and perfectly showcases that Tough Resin creation can definitely withstand lots of pressure, strain and friction. When released in June, I was already imagining building such a machine myself, but it obviously takes a lot of effort and material to 3D print something even slightly complex, and the behind the scenes look at the building process fortunately confirms that time and energy are required in abundance.

For in fact, eleven engineers worked on this project, each working on different mechanical aspects of this useless, but so useful machine. ‘To celebrate the launch of our latest resin, Tough, we gathered a toolkit of engineers to help build a 3D printed Rube Goldberg machine. Inspired by the Japanese children’s series Pitagora Suichi, we wanted the machine to be fun, surprising, and also showcase the properties of Tough Resin: durability, strength, and impact-resistance,’ they say of the creation.

So what’s what in the video clip? Well the machine starts off quite simply, with a laser-cut see-saw platform by Ava Chen. The resin bottle is used as a pivot, and a small 3D printed snail is just added to get everything moving. The real 3D printing fun begins at the following level, where a bunch of gears are used to pass the marble along. These were designed by Matt Keeter. ‘I designed a generic gear in Antimony, my homebrew open-source CAD package, then used the template to make gears of different shapes and sizes,’ he says of the design. ‘I was very happy with our strategy for closing the circuit: we put copper tape on the pipe, then relied on the (conductive) ball to close a circuit and start the gears turning.’

The marble then reaches what was perhaps my favorite part: the three hammers smashing glasses to illustrate that Tough Resin can withstand a serious punch. This step was designed by engineers Gagandeep Singh and Sven Werhmann, and was perhaps the most difficult step – how do you get those hammers to stay upright and be released by something as insignificant as a marble? ‘It was incredibly hard to develop a system to allow the hammers to fire with the small weight and size of the steel ball. We were able to do some calculations and use some free body diagrams to find the optimal pivot point for the hammers,’ they say. In the end they had to do a lot of test runs with the hammer, resulting in lots and lots of shattered glass everywhere – who says work can’t be fun?

The next step is less visually impressive, but more so in engineering terms. Featuring a deconstructed drill, it shows that the resin is tough enough to be drilled into. The entire rig holding the drill upright was designed by Hugh Medal and Dmitri Megretski. ‘Having many of the parts printed in Tough Resin really made the difference, allowing the drill-rig to keep trucking through multiple trial runs,’ they say. ‘I knew I wanted something with a bit of old-fashioned cast-iron machinery flair, so I offset the faces on the cradles to make a decorative raised area. I also modeled the holes for the clamp screws slightly undersized, in order to drill them to final size and tap them to receive screws. I needed something strong enough to hold up the entire drill, and not break under the twisting forces while driving the screws.’ Much of the parts were 3D printed in the Formlabs draft mode, for quick 3D printing.

The marble then moves on to perhaps the most impressive 3D print: the chain and sprocket pulley. Designed by Darian Zigante and Valentin Trimaille, it emphasizes the mechanical wear properties of the material, but to us also emphasizes how fantastic the prints look. But as you can imagine, 3D printing a chain link is quite challenging. It was finally 3D printed in a few separate parts that doubtlessly needed a bit of post-print processing to get the parts moving smoothely. ‘The most exciting part in the entire making-of had to be when the chain and sprocket lifted the build platform for the first time. Seeing an entirely printed mechanical system, full of moving parts, on that scale, was very cool to watch,’ they say of the results.

Moving on to the spoon tower and elevator, this section was designed by engineer Adam Lebovitz. ‘I wanted to show how shatter/fracture-resistant this resin is as compared to our Standard Resin. I also wanted the demonstration to be visually interesting. To keep the theme and continuity of the rolling steel ball going, I decided the ball should be what causes the pieces to flex,’ he says. And in that he easily succeeded.

The finale, finally, features a loop-de-loop through which a ball is propelled. If you were thinking, like we were, that it is quite unlikely to generate that much force with a simple pushing motion, you’re right: a magnetic force cannon is used to supply the necessary power for a 3D printed ball to reach the finish line. ‘Our station uses magnetic force to propel a 3D printed ball through a loop-de-loop made of PVC pipe. The ball drops at the end of the pipe, hitting the mousetrap and setting off the confetti cannon,’ engineers Clark Anthony and Meg Maupin say. As a whole, the machine is a very impressive engineering feat, though we are especially glad to learn it was as huge a design effort as we feared it would be, even for the experienced Formlabs.



Posted in 3D Printing Materials



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