HingePliers (a metamaterials experiment)

by profhankd Sep 25, 2016
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Cool pliers! However, I think you have a misconception about metamaterials. These pliers are more accurately described as a compliant mechanism. Compliant mechanisms are mechanisms that are designed to deflect. Metamaterials are materials that are designed to have properties that are not found in nature, often repeating patterns or other man-made structures. The Hasso Plattner paper describes a metamaterial made of compliant mechanisms but metamaterials can do other things like affect optics, electromagnetism, fluidics et cetera. The term compliant mechanisms is more generally applied to other deflecting structures. and can do other neat stuff. Here are some examples from BYU, they do a lot of research in compliant mechanisms. The textbook Compliant Mechanisms by Larry Howell is also a widely used starter text for it. https://www.thingiverse.com/BYU_CMR/designs


I happen to agree that the "metamaterials" title is a bit much, but it's what the Hasso Plattner folks published it as, and I echoed their terminology (more than two years before any of the BYU_CMR designs you cite above were posted). In any case, a single object of a single material here is behaving as a rigid structure in most of the unit but also as a spring, and those are two very different behaviors at least marginally qualifying it as a metamaterial. The Hasso Plattner design doesn't really work; it requires way too much deflection over a small area, causing immediate fatigue failure or requiring a material like NinjaFlex which results in poor rigidity for the nose of the pliers. The span-free hinge and relatively minor deflection of the spring in my design are what make mine work with ordinary PLA, ABS, etc. ... and, to be technical, my hinge isn't really a compliant mechanism (it literally is a joint, but interfacing two regions of the same object) -- only the spring is.

In any case, the textbook you cite predates all of this and certainly the concepts of compliant mechanisms are very relevant to design of functional 3D-printed devices. Thanks for the reference. I had hoped that I would find a venue to publish on the pliers and various other "3D printing design for manufacturability tricks," but there really doesn't seem to be a scholarly venue interested in improving the utility of low-end printers... perhaps some of it could go to a "compliant mechanisms" venue?

Yeah, my advisor (I'm a mechanical engineering Ph.D. student) has published at least one paper 9see below) that uses parts printed on low-end FDM printers. Normally, the conference he publishes compliant mechanisms papers at is the ASME IDETC.

Stress-Limiting Test Structures for Rapid Low-Cost Strength and Stiffness Assessment
A. Katz, J. Nussbaum, C. P. Lusk, N.B.Crane
Published in: Rapid Protyping Journal (in press - December 2014)

They normally focus on the mechanics of compliant mechanisms itself though. You may want something in sustainable manufacturing and open source hardware like this post. https://www.thingiverse.com/thing:134081

Adjustable Laptop Stand
by jpearce

Interesting write up and innovative design.