PEEK is a high performance thermoplastic which is only used for highly demanding applications, since it is also very hard to process. At Injex we took the challenge to demonstrate that PEEK prototypes can be produced in as little as 24 hours.
Polyether Ether Ketone (commonly known as PEEK) is a premium-use engineering plastic used only when other thermoplastics won't do, because of it's high price and some complex manufacturing requirements.
It has an extremely high operating temperature, and has excellent mechanical performance as well as chemical and wear resistance. You can read more amazing things about PEEK and how to use PEEK for prototypes in our Knowledge Center.
Despite the hurdles, PEEK is commonly used in the most demanding industries from bearings and sensor housings in Aerospace to pipe seals in Oil & Gas. Further to that, PEEK is even used in highly sensitive applications such as medical implants and high-wear components like mixing paddles and valves in the food industry as it is also easy to clean/sterilize.
At Injex, we're always up for a challenge. That's why we decided to see how quickly we could take some of our new test parts into PEEK production.
To put it to the test, we developed three fairly complex CAD models for injection molding. Similar to parts we develop for industry, these parts have complex geometries, undercuts and very small but important features. We first have to analyse the CAD models for moldability, and then we design our first iteration of tools for the production team to work with.
Next we begin printing and machining the required mold components. Depending on the size of the models, this can take a number of hours. When the molds are prepared they then join the production queue and are injected on our in-house machines.
With this method, it's possible to have real prototypes injection molded and shipped the next day.
Processing PEEK plastic is difficult because it demands the highest temperatures of any common thermoplastic. At 360-400 degrees Celsius, any plastic components nearby will soften and even steel will begin to temper meaning that many steel hardening processes will be reversed.
Natural PEEK itself has a distinctive oatmeal or tan color. Due to the chemical and temperature resistance of the material, it can be difficult to add dyes or other additives without compromising datasheet performance.
Furthermore, when PEEK is injection molded it can cool too quickly resulting in a semi-transparent outer layer. This clear layer is more brittle than regular PEEK, and so in order to achieve optimal mechanical characteristics PEEK must be heat treated after injection molding.
Left: Testing the 3D printed tooling with Polypropylene (PP)
Middle: Prototype in PEEK immediately after injection molding
Right: Prototype in PEEK after heat treatment
Due to our agile production line we are able to test multiple thermoplastics and colours with the same tooling. Because of this advantage, we often test sequentially to determine the best molding characteristics for different geometries.
In some thermoplastics it can be easier to detect problems such as sink marks, flow lines, weld-lines (also known as knit-lines) and voids. We use this information to optimise the next iteration of tool design allowing for faster and more reliable production on demand.
For more details about when and how to use PEEK for prototyping, check out the article in our Knowledge Center.