Fast Iteration With 3D Printing

IdEA SFU is lucky enough to go to all kinds of interesting events where we interact with the public. At one event with SFU Surrey, we were lucky enough to hear from Matthew about his invention that would help prevent his little brother from becoming locked in rooms.


Like most good inventions, this once came from necessity. Matthew’s brother isn’t tall enough to twist door handles, so he’s become locked in rooms as some of the doors in his house swing and latch automatically. So Matthew and his dad heated up plastic in the oven and using pliers, he formed a stopper to fit in the door latch. Problem solved! The doors wouldn’t latch so his brother could easily push them open with the invention installed.


Some IdEA members met with Matthew and his dad and got to discussing 3D printing as a great technique to further refine the invention. Agreeing to meet later, I was brought in to help assist with the CAD for the prototyping process.


Seeing the excitement that Matthew and his dad had for the invention was really exciting. Not having much CAD experience before, we walked him through the workflow. Starting with a cross section of the stopper and extruding it out, we decided to add protrusions so that the stopper would be a tight friction fit in the latch, keeping in mind the flexibility characteristics of the PLA prototype.


We dimensioned the part after taking some measurements of the hole and sent the file to the printer. Matthew also got a quick rundown of how the 3D printer worked as it was easy to see it quickly building up the layers on the small part. Once it had cooled off and was installed, we hit the first snag. We couldn’t get the stopper out!


Back into SolidWorks, we began the first iteration. We added a hole to the stopper and also flipped the sides of the shape that would have the friction fit arms, as we determined that it would more universally fit different sized holes that way. Back to the printer with the still rudimentary shape, we ultimately added a slight curve to the friction fit arms to make it easier to install and remove for the second iteration. During these and future iterations, we got a feel for how PLA deforms in the thin shapes we were printing it in.


One of the first prototypes.


We also decided to turn the friction nubs into hooks and test that out, keeping in mind the lack of sharpness that the printer would be able to reproduce. A thumb hook was also added to make removal of the plug absolutely tool-free. Further yet, a slight curve was added to the latch facing side of the stopper so that the latch would partially engage. This prevented the door from swinging open accidentally, while keeping it easy to open. Truly a happy medium.


In the course of a few hours we printed six prototypes and got a feel for how the material performed as we made usability changes. It was really cool to lay the prints up beside each other so we could visualize the iteration process and think about the speed we were able to make changes at. I really hope we communicated how amazing that was to Matthew, since the speed we worked at wouldn’t have been possible without 3D printing.


In all it was a very fun few hours of real engineering, and a really unique experience for a kid in grade seven. While it would’ve been great to do a few more iterations, we felt that the stage we paused at was a good break point to take time and consider other designs and think about the product even more.

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