Author: Don Slusarczyk

Edition: Model Aviation - 2026/07
Page Numbers: 62, 63, 64
Park Pilot: 3D Printing

The external spool holder is required on the Bambu P1S printer when using TPU filament.

3D-Printed Tires
By Don Slusarczyk | don@slusarczyk.com

One of my recent airplane projects required 3D-printed tires. I had printed tires from thermoplastic polyurethane (TPU) in the past and found them to be more of a novelty because the TPU rubber was rather hard with a durometer of 92A, which is about the hardness of the heel of a dress shoe.

3D Printing figure 1
3D Printing figure 2

Tires printed with this material did not really have any “bounce” to them. Additionally, printing in TPU can be tricky. Printing speeds need to be reduced, the TPU can easily get jammed up in the gears of the extruder, and nozzle clogs can occur if there is too much retraction when printing.

On my Sovol SV06 printer, I had to reduce the spring tension on the extruder by loosening the knob half of a turn. This adjustment reduces the gripping force on the filament to help prevent it from getting wound up in the extruder gears. Some manufacturers have released even softer TPU filaments for better flexibility, but softer filaments make the gear-jamming problem even worse and generally require a printer with a direct-drive extruder.

Fortunately, a foaming TPU filament was developed to help solve some of these issues. Foaming filament means that the material expands when it prints, based on the temperature at which it is printed. The hotter the temperature, the more it expands; the more it expands, the softer the end product is. Foaming TPU has a durometer of approximately 92A before it is printed, and then, depending on the temperature and flow rate, the final printed part can be as soft as 55A. This means that “soft” or “firm” tires, or something in between, can be printed by changing the printing temperature and flow rate.

I bought my foaming TPU from 3DLabPrint, which sells it under the brand name of Flexi Light LW. It is sold as a smaller spool (330 grams), which at first might seem like a small-sized spool, but parts are typically printed with a 0.5 flow factor. The amount of filament that is used for a set of tires is rather small, so the spool will last a reasonable amount of time.

The Bambu Wiki page gives clear instructions on how to switch over to the external spool holder and get the filament loaded. For my slicer settings, Bambu Studios has a preset TPU filament profile, which I loaded and used as a starting point. The main settings to note are that the bed temperature is set to 35°C, the nozzle temperature is set to 235°C, the flow rate is set to 0.50, the retraction distance is set to 0.8 mm, and all of the printing speeds are set to 20 mm per second.

For the tires I was printing, the designer recommended a 0.2 mm layer thickness, five walls (or perimeters), 20% gyroid infill, and five top and bottom layers. I sliced the STL models, and it all looked good in the slicer except for one thing: the printing time. At only 20 mm per second, a pair of 2.5-inch tires was going to take almost six hours to print.

I sent the file to the printer and periodically checked on it because I was afraid that the nozzle would clog or that the filament would tangle. I was glad to see that no issues occurred during the print, and the tires came out looking quite nice. Once they cooled, I removed them from the build plate and gave them a squeeze. They felt like typical foam tires that are found in an ARF kit—nothing like the very hard TPU tires I had printed in the past.

If I wanted to soften them up a little, I could have increased the print temperature or reduced the gyroid infill and/or number of walls. Once the first set printed okay, I made a second set just in case I needed any spares down the road. A quick calculation showed that this set of custom tires cost only about $1.25, which is quite reasonable.

Overall, printing with foaming TPU was not any more difficult than my previous TPU printing experiences. On the Bambu P1S printer, no physical machine adjustments had to be made other than using the external spool holder instead of the AMS unit. For other printers, you might need to reduce the spring tension on the extruder to lighten the pressure on the filament as it is fed into the extruder. Just be prepared for long print times because of the slow speed that is required.

Lastly, once you are done printing, seal the TPU filament back into a plastic bag because TPU likes to soak up moisture, which can result in bad prints.

This set of 2.5-inch tires took a little less than six hours to print. They are close to 10 grams each and cost approximately $1.25 per pair to print.
This set of 2.5-inch tires took a little less than six hours to print. They are close to 10 grams each and cost approximately $1.25 per pair to print.
3D-printed hubs were used to complete the upper wheel set.
3D-printed hubs were used to complete the upper wheel set.
You can see the outer and inner perimeters and the gyroid infill in the slicer preview. Adjusting these parameters and the printing temperature will change the feel of the tire.
You can see the outer and inner perimeters and the gyroid infill in the slicer preview. Adjusting these parameters and the printing temperature will change the feel of the tire.
Flexi Light LW, from 3DLabPrint, comes on a 330-gram spool and is available in several colors.
Flexi Light LW, from 3DLabPrint, comes on a 330-gram spool and is available in several colors.

SOURCES