Tethys case study: 1,000 flexible TPU 90A parts for an industrial cooling vest
In short: Tethys, the French maker of active heating and cooling vests for industrial workers, needed flexible TPU cases that resist 95 °C, at pre-series volumes, as demand for its vests grew. 3Descu printed 1,000 TPU 90A parts in two orders, tuned the process to keep a functional air channel airtight, and proposed design changes that Tethys built into its next revision.
Who Tethys is and why its vests matter
Tethys builds wearable thermal regulation for people who work in heat and cold: steel mills, glass factories, construction sites, energy and logistics. Its vests circulate water through thin textile circuits and use Peltier (thermoelectric) modules to cool or heat the wearer. The company is based in Biot, near Sophia Antipolis, and positions its product as Made in France and Italy.
Founder and CEO Giacomo Saccone, PhD, spent years designing active thermal control systems for satellites at MIT, the European Space Agency (ESA) and Thales Alenia Space. Tethys applies that space-grade thinking to heat stress on the shop floor. Its Tempesta vest won the Preventica Bordeaux 2025 Innovation Prize in the personal protective equipment (PPE) category.
The challenge: flexible, heat-resistant cases at growing volumes
In March 2026, Tethys was printing its own TPU cases in-house. Volumes were rising, so the team decided to outsource them and sent us the files.
The requirements came straight from the product:
Heat resistance: the material had to withstand 95 °C
Flexibility: the cases had to stay "a bit flexible", so a rigid plastic was out
An airtight air channel: one family of cases carries an internal pipe, and air must flow from inlet to outlet without escaping through the walls
Volume: 500 parts in the first order, across five case designs
Tethys put function first. In the team's words, roughness on the pipe was acceptable "as long as it is still air tight".
The solution: process tuning around one critical feature
Choosing TPU 90A over a stiffer alternative
We print flexible parts in TPU 90A shore, which matched the grade Tethys already used in-house. Because TPU costs more and prints slower than rigid filaments, we also offered PETG with settings tuned for extra flexibility, and shipped PETG samples alongside the first batch. Tethys tested them, found them more flexible than standard PETG, and chose to stay with TPU for the final parts.
Setting layer height for an airtight channel
Tethys printed its cases at 0.12 mm layers, with a 0.2 mm first layer. Our standard for TPU is 0.2 mm, because finer layers raise the risk of nozzle clogs on long production runs. We agreed on 0.15 mm at 20% infill. Later, our tests at 0.2 mm showed no visible quality difference and no air leakage in the channel. Tethys shared its own slicer project files, so both teams worked from the same reference.
Accepting cosmetic marks, protecting function
The long-tube cases print with supports in places, so we told Tethys early that support marks and small surface deformations would show. We tested these cases on three printers with several profiles and sent photos before shipping. Tethys approved the visual result on one condition: the channel stays airtight.
Shipping in batches so assembly could start
We split the first order into three shipments. The first carried 40 complete sets, which let Tethys start assembling vests while the rest of the order printed. In the client's words, "having already almost half of the order allows us to start the production".
Reprinting what failed inspection
The case geometry needed more process tuning than a standard order: we ran more than five print profiles across our fleet. Tethys inspected every batch, and after the first two it listed the parts outside spec. We reprinted each of them at our cost, added extra parts free of charge, and closed the order with the full, correct quantity.
Feeding design changes into the next revision
After the first order, our production team recorded a short video with four design-for-printing suggestions. Tethys applied part of them to the next version and dropped the hardest-to-print case from the repeat order. Before the second order, our factory also spotted a thin wall around the internal tubing and stray spurs in the files. The cause was a CAD export to STEP; a direct STL export fixed it. Tethys then raised the case bottom wall from 0.6 mm to 1 mm.
The result: a closed order, a repeat order, parts in use
1,000 production parts in TPU 90A over two orders, plus PETG samples
First order closed with the full count and no further reprints needed
Repeat order in July 2026 with redesigned cases, including new short variants
Parts in service: most were already fitted in Tethys systems by late August 2026, with the rest set aside for prototypes
"The parts are looking good. Most of them were already used in our systems." Tethys engineering team
Where 3D printing fits in Tethys's industrialisation
Tethys designs its vests in France and manufactures them with partners in France and Italy. 3D printing gave the team pre-series cases while the design was still changing. Between March and July 2026 the case files went through several revisions, and each order followed the latest one with no tooling to rework. For a deep-tech company preparing industrial production, that means design changes cost a file update, not a new mould.
At a glance
Project | Details |
Client | Tethys, Biot, France |
Sector | Personal protective equipment, wearable thermal regulation |
Parts | Flexible cases for the vest system, including one with an internal air channel |
Technology | FDM |
Material | TPU 90A shore; PETG samples with flexibility-tuned settings |
Process | 0.15 mm layers, 20% infill |
Key requirement | Airtight internal air channel, heat resistance to 95 °C |
Volume | 1,000 parts over two orders |
Delivery | Partial batches so assembly could start early |
FAQ
Can a 3D printed TPU 90A part hold an airtight air channel?
Yes. In this project, the internal air channel of the Tethys cases stayed airtight at 0.15 mm layers, and our tests at 0.2 mm showed no leakage either. Each batch went through the client's own inspection, and we reprinted any part that did not pass.
Why choose TPU 90A over PETG for a flexible case?
TPU 90A bends and recovers, while PETG stays stiff even with tuned settings. We printed PETG samples with settings that made them more flexible than standard PETG. Tethys preferred the feel of TPU and kept it for production.
What layer height should you use for airtight TPU parts?
Start from the function, not the default. Tethys printed at 0.12 mm in-house; we print TPU at 0.2 mm to protect the nozzle on long runs. We agreed on 0.15 mm, then confirmed with tests that 0.2 mm kept the channel airtight.
What happens when 3D printed parts fail your inspection?
We reprint them at no charge and ship them as soon as possible. On this project, Tethys listed the parts outside spec after the first two batches, and the final shipment included every replacement.
Which design changes make TPU cases easier to print in volume?
Three changes from this project apply to most flexible cases:
Export STL directly from your CAD software when a STEP export distorts thin walls or adds spurs
Keep floors at 1 mm or more; a client test print with a 0.6 mm floor came out with a hole
Ask your print partner for a design-for-printing review before a repeat order
Does 3Descu manufacture the Tethys vest?
No. Tethys designs its vests and manufactures them with partners in France and Italy. 3Descu supplied 3D printed pre-series cases.
Print your pre-series parts with 3Descu
3Descu runs 200+ printers in an ISO 9001:2015 certified factory in Târgu-Jiu, Romania, one of the largest 3D printing factories in Eastern Europe. Upload your files at quote.3descu.com for an instant price, and an engineer reviews every file before production.
Comments