383Mazda
Member
- Joined
- Mar 10, 2014
- Location
- North Texas
This got a lot of attention on FB so I figured I'd make a post.
TLDR:
I 3D printed and installed bushings for an IPD torque rod on one side of my 240 wagon on 6 Apr 2025 @ 144xxx miles. I drive around 5000 miles a year, so we'll see how long they last.
Back story:
Last fall I noticed a torque rod hanging down when my wife pulled into the driveway. The chassis end bolt had come lose and backed out, and I lost the metal sleeve and one of the bushings. Unfortunately IPD doesn't sell components to their kit and I didn't want to spend $100+ just for a single bushing and sleeve, so I figured I'd try printing one. (IPD did get a hold of me and made a more than fair deal for a replacement kit - they really went above and beyond!)
I had installed these in fall of 2023
Chemical stuff:
My initial design was just a straight copy of the IPD bushing, I had to print a handful to get the ID/OD just right. I used Polymaker TPA 95A filament. Interestingly they measured the same on my informal durometer test. No, these were not tested to ASTM 2240 standards; yes, it's a valid back-to-back comparison of the poly bushing and the TPU bushing.
TPU is short for Thermoplastic Polyurethane. The difference is that poly bushings are a thermoset polyurethane. Thermosets and thermoplastics are like brownies and fudge - once brownies are "cured" (baked) the batter has gone through a chemical change that can't be reversed (thermoset). Fudge though can be reheated and reshaped, from pouring into a mold to hardening no chemical process takes place (thermoplastic). The melting / printing temp for this filament is around 210 - 230ºC. However, the "Vicat Softening Temp," where plastics begin to soften and deform under load, is 80-100ºC. I've never measured how hot bushings get, but I imagine I'll be able to keep them under 176ºF even in the Texas summer.
3D printing:
Once I had the size figured out I decided to put grease grooves in the final design:
However, I noticed voids in the slicer with the grooved bushings. The slicing software draws the walls first and then the infill. I used 100% concentric infill since I figured that'd be the strongest pattern for a bushing, but those voids are going to be weak points. If these fail quickly, I'll print a smooth set and try them out as well.
I also used "align" seams on the grooved design, and "random" seam on the smooth ones.
I'm using a Bambu Lab X1 Carbon for the prints. I fooled with the settings and was able to print all 4 at the same time with zero stringing. I did not anneal these with any post heating process - that's another step I could explore depending on how long these last. Some people like to put their functional TPU prints in an oven at 80ºC for a while to strengthen the part. I'm sure this would fool with demensionality which is why I didn't bother with it. I'll post my recipe parameters is anyone wants them.
Installed on 6 April 2025 on the pass side Torque Rod, front and back. Start the timer...
TLDR:
I 3D printed and installed bushings for an IPD torque rod on one side of my 240 wagon on 6 Apr 2025 @ 144xxx miles. I drive around 5000 miles a year, so we'll see how long they last.
Back story:
Last fall I noticed a torque rod hanging down when my wife pulled into the driveway. The chassis end bolt had come lose and backed out, and I lost the metal sleeve and one of the bushings. Unfortunately IPD doesn't sell components to their kit and I didn't want to spend $100+ just for a single bushing and sleeve, so I figured I'd try printing one. (IPD did get a hold of me and made a more than fair deal for a replacement kit - they really went above and beyond!)
I had installed these in fall of 2023
Chemical stuff:
My initial design was just a straight copy of the IPD bushing, I had to print a handful to get the ID/OD just right. I used Polymaker TPA 95A filament. Interestingly they measured the same on my informal durometer test. No, these were not tested to ASTM 2240 standards; yes, it's a valid back-to-back comparison of the poly bushing and the TPU bushing.
TPU is short for Thermoplastic Polyurethane. The difference is that poly bushings are a thermoset polyurethane. Thermosets and thermoplastics are like brownies and fudge - once brownies are "cured" (baked) the batter has gone through a chemical change that can't be reversed (thermoset). Fudge though can be reheated and reshaped, from pouring into a mold to hardening no chemical process takes place (thermoplastic). The melting / printing temp for this filament is around 210 - 230ºC. However, the "Vicat Softening Temp," where plastics begin to soften and deform under load, is 80-100ºC. I've never measured how hot bushings get, but I imagine I'll be able to keep them under 176ºF even in the Texas summer.
3D printing:
Once I had the size figured out I decided to put grease grooves in the final design:
However, I noticed voids in the slicer with the grooved bushings. The slicing software draws the walls first and then the infill. I used 100% concentric infill since I figured that'd be the strongest pattern for a bushing, but those voids are going to be weak points. If these fail quickly, I'll print a smooth set and try them out as well.
I also used "align" seams on the grooved design, and "random" seam on the smooth ones.
I'm using a Bambu Lab X1 Carbon for the prints. I fooled with the settings and was able to print all 4 at the same time with zero stringing. I did not anneal these with any post heating process - that's another step I could explore depending on how long these last. Some people like to put their functional TPU prints in an oven at 80ºC for a while to strengthen the part. I'm sure this would fool with demensionality which is why I didn't bother with it. I'll post my recipe parameters is anyone wants them.
Installed on 6 April 2025 on the pass side Torque Rod, front and back. Start the timer...
