Creating a smart lock - 3D Printing

Back in the days before CAD software, drafting technicians would draw on large pieces of paper. This required pencils, erasers, t-squares, and much more time compared to today. It all changed in 1982 when the AutoCAD was released.

Bringing the drawings to reality was however a different story. Plastic injection molds are used in order to achieve the speed and cost efficiency required by the highly competitive market. These molds are made of a very strong metal and cost between 10.000 EUR 200.000 EUR to manufacture depending on the strength and sophistication. Imagine, having to build these molds to later find a mechanical error. This is a complex process and until very recently this was an endeavor only highly capitalized and experienced companies could pursue. It is not so much today, with the adoption of 3D technologies.

3D printing technology helps considerably at developing and designing high tech products like Keymitt Smart Lock. See here how we did it in our article Keymitt Design Evolution Explained.

Drafts and computer simulations weren't enough to understand all the product and it’s manufacturing issues. Thanks to 3D printing we’ve managed to see the Keymitt in physical form, test the mechanical features, and feel the materials to be used. Having it in our hands helped us understand better it’s ergonomics and adjust things where needed.

We used Fused Deposition Modeling (FDM), Selective Laser Sintering (SLS) and Stereolithography (SLA) at various stages in the development.

The first in line, and the go-to prototyping printer we have is our Ultimaker 3. It uses 2.85mm filaments of polylactic acid (PLA), commonly called plastic.

An FDM model is robust, and can withstand higher temperatures and mechanical wear and tear. The layer thickness used by and FDM 3D printer isn’t that fine however it is very well suited for testing rough ideas and making spare parts.

Additionally we used SLA/PolyJet printers where the focus is on final product realism, smooth surfaces and fine feature detail. Polyjet’s finer layer resolution is made possible through its use of liquid polymers, which are jetted in liquid form and then cured through exposure to ultraviolet light. SLA produces parts in a layer by layer fusion using photochemical processes which light makes the tough resin to link together to form a solid structure. Stereolithogrpahy is a very fast way to create almost any design, from mechanical parts, prototypes to computer hardware.

As the components passed through the first prototyping phase it was also necessary to see how they fit together. SLA/Polyjet gives us very high accuracy which allowed us to analyze the draft angles and tolerances highly relevant for the injection moulding later on. Also it produces semi transparent models which just look so cool! One drawback though is that it is hard to achieve the necessary mechanical rigidity and such models are not suitable for demos as the edges break and surfaces are grippy.

SLS brought us the closest to the intended results from plastic injection molding. It is a technique that uses laser as power source to sinter powdered material (typically nylon or polyamide) in our case polyamide. Aiming the laser automatically at points in space defined by 3D model it binds the material together to create a solid structure as our device’s mechanical parts.

Unlike the other two technologies, this kind of printer is big, expensive to acquire and to maintain. It can however sinter parts on a large scale in a relatively short time. We used a local SLS service provider for such work. Models produced using this technology were of high accuracy and great mechanical strength. We could do real life tests, and after being painted, we also used them as demos at trade fairs, like the ones at CES 2019 : Keymitt Smart Lock at CES 2019.

3D printing enabled us to iterate fast through the design of our hardware. Without this, it would definitely take more time and capital to reach our goals. It is important to know the difference between technologies as each of them is useful at different times during the development. Such prototyping approach, once mastered, can turn ideas into reality really fast - much faster than before.