Jason Middleton, Ray Products examines thermoforming and the future of medical device manufacturing.
Precision and safety are paramount in every facet of the medical industry; medical device manufacturers are always looking for processes that help them produce safe, durable and effective products at a reasonable cost – and thermoforming is at the top of the list.
Thermoforming 101
At its simplest, thermoforming is the process of heating a sheet of plastic until it becomes pliable, then using an aluminum temperature-controlled male or female mold to shape the material into a three-dimensional part.
There are two different methods of thermoforming: vacuum forming and pressure forming. In vacuum forming, the plastic sheet is stretched over a male mold and then the air inside the mold is vacuumed out, with the plastic retaining the shape of the mold.
The pressure-forming process adds 80–100 psi of air pressure to push the plastic sheet into the female cavity mold surface, providing very high detail and cosmetics on the outside surfaces of the molded part.
In both methods of thermoforming, the plastic is allowed to cool after being molded, which allows for a finished part with zero residual stress. Then, any excess plastic is removed with a six-axis, fully robotic trimming machine.
After trimming, further customizations can be incorporated – from aesthetic touches like silk screening and EMI / RFI shielding to the addition of functional hinges, handles and other hardware.
Thermoforming is an excellent method for manufacturing production quantities from the low hundreds to the high thousands; and the process ensures that no matter the quantity, the quality (and specifications) are the same in the first piece as in the last.
A cut above
So what does thermoformed plastic offer that other plastic manufacturing processes, like injection molding, don’t?
For one, thermoforming can produce very large pieces like MRI or CT enclosures, storage bins or other equipment like chairs and hospital beds. And while injection molding is excellent for small complex parts with very high volumes, similar details can often be achieved with thermoforming.
Thermoforming also has lower tooling costs and a faster turnaround than injection molding, plus equal (or sometimes better) aesthetics – unlike some injection molded parts, thermoformed plastic doesn’t need to be painted, although it certainly can be. That said, there are some scenarios in which injection molding is the best option.
When compared with other materials, like sheet metal or fiberglass, thermoformed plastic outperforms the competition on nearly every level.
Fiberglass, which can be very labor-intensive and expensive, is up to 35% heavier than thermoformed plastic, is not recyclable and is more susceptible to damage from UV and impact. Notably, fiberglass does not support the complex geometries and repeatability that thermoforming offers.
Sheet metal is still used in medical devices, but in many cases, thermoformed plastic is a better alternative. Sheet metal is heavier and more prone to scratching and denting. Unlike sheet metal, thermoformed plastic can be formed into complex shapes, does not amplify noise and is incredibly durable.
With a range of materials, finishes and textures, there is endless room for detailed customization in thermoforming – especially in the medical industry.
Thermoforming & medical devices
Sturdy, scratch-resistant and lightweight, thermoformed plastic is ideal for medical devices that see heavy use, like medical electronics, imaging enclosures, surgical device housings and sterile packaging.
But one of the key benefits of thermoformed plastic is its ability to contribute to the health and safety of healthcare environments. In addition to being easy to clean, thermoformed plastic can be constructed with antimicrobial-resistant properties built into the plastic, helping to increase hygiene and protect patients and health care workers.