A Catch Can that Failed on Infill

9 months ago, I was driving my pre-runner on RM-620, it was 6PM, and the sky was turning a golden color. I sat at a redlight for a while. It turned green, I pressed on the accelerator… and nothing, it had stalled out. An automatic had stalled out on me…

It couldn’t idle, I had to keep above 3,000 RPM to shift it into gear and couldn’t stop, or it would die on me.

I made it home, eventually. Read the codes, spent hours trying to diagnose the issue, no vacuum leak, or faulty sensors.

Then I took the intake off. My throttle body looked like it swallowed a gummy bear, and the intake piping was coated in oily grime. Blow-by mist had left me nearly stranded. I didn’t want that to happen again.

I had a 3D printer and an idea. First it started out as a PLA prototype for a catch can. Checking to see if the geometry was manufacturable. Then came the vacuum tests, the pressure tests, the flow tests.

It failed each one of them…

But I wasn’t going to solve micro-porosity in FDM additive manufacturing overnight. First, I needed a material that would actually work, not melt in my engine bay, not crack, not degrade with oil and chemical exposure.

I started testing nylons, PA, PPA, carbon fiber filaments.

The first PPA prototypes fell apart in my hands, the layers were splitting themselves apart. It may have been the most durable material, but the hardest to work with and get right and print reliably. What’s the point if I can’t even make the catch can?

Then the nylon prototypes, plenty of mistakes, 3D printed threads, hose barb inlets with insufficient wall thickness. It didn’t even have a drain plug.

But it worked, it held some vacuum, it warped but it was good enough to test on a real engine on a real truck. A pre-runner with 300k miles on the engine and enough blow-by to fill up a hot air balloon.

Then came refinement. Over-extrusion, heat treating parts in silica substrate, way over glass transition temperature. Larger volumes, more baffling, thicker hose barbs, an actual drain plug.

That’s the version that’s stuck, that’s the version that’s handled thousands of miles of torture for 4 months on a 300,000 mile truck that hits redline every other day

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