Replacement Key Fob
Replicating, Improving and Prototyping a Key Fob:
It seems like it was just yesterday that my parents handed over the keys to my first car, a 1997 Subaru Outback in 2006. Over the last 12 years I have taken the car coast to coast from Oregon to Maine. However, one part of my car that did not survive the adventures was the key fob. A few years ago, the loop on the key fob broke that attaches the body to a key ring. Without this attachment method, I threw it in a drawer and unlocked my car the old-fashioned way with the twist of a key.
Recently, I came across the fob when cleaning up my drawers and could not remember why I stopped using it. I convinced myself that the fob must have malfunctioned. However, I decided to try it out and my doors opened with a click. Now thrilled with the prospect of using the remote again I hopped online to search for a replacement. Ultimately, I discovered that Subaru had discontinued the fob model and that all the used replacements listed for sale online also had a broken loop. That is when the engineer in me kicked in. Why not just make one?
The first step was to grab a pair of calipers and begin to model the plastic shell of the key fob. All I needed to do was 3D print out a new case because the key fob internals still worked. After a bit of time in CAD, I matched the internal mounting dimensions for the PCB and the buttons and designed new snap hooks to clamp the PCB firmly in place.
After this initial mock up, I decided to 3D print the
initial design on Goddard’s new Form2 SLA printer due to its speed and accuracy.
After printing and post processing, the new body snapped together with an audible “CLICK”. Surprised that things were going so smoothly, I threaded the for onto my key chain and was back in business. About a day later, I was back to square one when the loop on my new body broke just like the part from Subaru. I tried to match dimensions as close as I could and realized I should have made the loop slightly thicker to support a metal reinforcement.
After a failed print and a bit of resin cleanup, I made a
prototype that functioned perfectly but after a day when I dropped my keys while struggling to open a door I realized I needed a better material, the “Clear” material from form labs was simply too brittle. One option that jumped through my mind was cast urethane molding, but because I only needed one it didn’t seem to make sense to put in so much effort for a couple of pieces.
Ultimately, I changed material to a Form Labs engineering grade material called “Durable”. The material is less dimensionally accurate and I lost some resolution in my inlaid text, but for the past few weeks my key fob has had no problems.
All in all, it took 3 rounds of prototyping and a few broken cases, but I am very happy with the result and have much less trouble unlocking my car with an arm full of groceries!
It seems like it was just yesterday that my parents handed over the keys to my first car, a 1997 Subaru Outback in 2006. Over the last 12 years I have taken the car coast to coast from Oregon to Maine. However, one part of my car that did not survive the adventures was the key fob. A few years ago, the loop on the key fob broke that attaches the body to a key ring. Without this attachment method, I threw it in a drawer and unlocked my car the old-fashioned way with the twist of a key.
Recently, I came across the fob when cleaning up my drawers and could not remember why I stopped using it. I convinced myself that the fob must have malfunctioned. However, I decided to try it out and my doors opened with a click. Now thrilled with the prospect of using the remote again I hopped online to search for a replacement. Ultimately, I discovered that Subaru had discontinued the fob model and that all the used replacements listed for sale online also had a broken loop. That is when the engineer in me kicked in. Why not just make one?
The first step was to grab a pair of calipers and begin to model the plastic shell of the key fob. All I needed to do was 3D print out a new case because the key fob internals still worked. After a bit of time in CAD, I matched the internal mounting dimensions for the PCB and the buttons and designed new snap hooks to clamp the PCB firmly in place.
After this initial mock up, I decided to 3D print the
initial design on Goddard’s new Form2 SLA printer due to its speed and accuracy.
After printing and post processing, the new body snapped together with an audible “CLICK”. Surprised that things were going so smoothly, I threaded the for onto my key chain and was back in business. About a day later, I was back to square one when the loop on my new body broke just like the part from Subaru. I tried to match dimensions as close as I could and realized I should have made the loop slightly thicker to support a metal reinforcement.
After a failed print and a bit of resin cleanup, I made a
prototype that functioned perfectly but after a day when I dropped my keys while struggling to open a door I realized I needed a better material, the “Clear” material from form labs was simply too brittle. One option that jumped through my mind was cast urethane molding, but because I only needed one it didn’t seem to make sense to put in so much effort for a couple of pieces.
Ultimately, I changed material to a Form Labs engineering grade material called “Durable”. The material is less dimensionally accurate and I lost some resolution in my inlaid text, but for the past few weeks my key fob has had no problems.
All in all, it took 3 rounds of prototyping and a few broken cases, but I am very happy with the result and have much less trouble unlocking my car with an arm full of groceries!