Door Stop
Overview
The very first time I left my cat at home for a long weekend, she ended up playing with a toy under the bathroom door. Upon coming back a few days later, I see she has closed the door on herself and locked herself in the bathroom. Fortunately, her litter box was in there, but her food and water were not. While there are solutions out there for this, a door stop on the floor just becomes another toy, and most other retention systems require permanent mounting. This was an apartment, and I didn't want more holes to patch when I moved out.
So I decided to make a door stop that fits on the upper corner of the door. It would act as a bumper, if the door closed, it would remain open enough for her to squeeze in the gap with her paws to open it.
Analysis & Design
The first design was bulky; I overestimated the angle I needed to keep the door open, and the overhang on the 3D print didn't come out as nicely as I had hoped. But it worked. So I used it a few times until I could redesign it.
Then I went to iteration two. This time I made it in two plastic parts that squeezed the top of the door for a better fit. If I was going to injection mold this, it would have been one part, but with the 3D printing, I needed two to avoid the overhang. My apartment also had the door bumpers at the top corner, so I needed to consider that in my design and allow for clearance.
It worked out, but there was a flaw. It was rigid plastic, so the fit wasn't as flexible as I wanted, and it would rub and bump on the door and door frame, leaving behind marks. I knew I needed it to be flexible. So I invested in a direct extruder for my 3D printer because the Bowden extruder would jam up and not print with flexible filament. I also bought a spool of 60 Shore A TPU filament.
I got to redesigning. This time I made it three parts, but two of the parts were identical. I made it so the clearance for the oddly placed bumper was on both sides to make it more universal and reduce the unique part count. These front and backs were made out of the TPU I just got. The middle was a rigid plastic frame. To put it together, I settled on self-threading screws that secured themselves into the middle plastic component.
Process & Images
An exploded view of the three-part door stop design, highlighting the rigid core and two flexible TPU outer parts.
The final assembled design, showcasing the integrated screws and clean, minimalist aesthetic.
Results
I was able to solve the problem by designing a non-permanent door stop that still allows the cat to enter or exit a room. The final design is a three-part assembly that uses both a rigid plastic frame and flexible TPU components to provide a secure and non-damaging fit. The final design also gives clearance for the apartment's existing bumper to not cause any friction or issues.