PEEK Manifolds - High Precision Components for Fluid Control Systems

Within the polymer space, PEEK (Polyetheretherketone) is considered one of the most robust materials. Not only does PEEK exhibit tensile strengths in excess of 100Mpa, but it can withstand compressive loads of over 300Mpa, making it tough enough for high-load, high-wear, and high-RPM applications where mating materials of steel can be used without fear that they will wear out the PEEK component. These properties can be further enhanced with the addition of carbon and glass, both of which give a sizeable boost to the overall strength of the material, while also making it more thermally stable.

PEEK seals and valves are commonly used in applications where high temperatures and loads are involved. While seals are relatively simple to machine, PEEK valves can prove challenging, especially if multiple ports of entry and exit are specified. It is likely that a turn-mill centre or a vertical milling centre are needed to make valves of consistent dimension and quality.

An even bigger challenge that the valve is the PEEK manifold, which is usually machined from a solid block, with each of the six faces of the block having its own set of holes. The manifold is essential in many fluid transfer applications. It is designed and machined is a way that allows it to sit within the system, and ensure not only that the fluid conduits all align perfectly, but that no leakages take place during operation. PEEK being a very chemically resistant material, the manifolds are highly durable across a range of fluids and substances and will hold their dimensions even with large variations in temperature.

Machining the PEEK manifold is a challenging task. For one, the PEEK stock shape for machining needs to be moulded into a block form. Most commercially available PEEK stock shapes are sold as round bars. This can prove highly wasteful when the final form is rectangular, especially as PEEK is an expensive material. Even technically speaking, machining a round bar into a rectangular shape places significant internal stress on the polymer. Considering PEEK has a tendency to build up stress the more it is machined, such a route will necessarily cause the final component to crack at some point during its operation.

In contrast, Poly Fluoro uses in-house moulding to make a rectangular block that is as close to the final dimension as possible, thereby minimising the excess machining, while lower the cost. The addition of glass or carbon is also vital. Again, commercially available grades would be made using Virgin PEEK. However, the increased thermal stability of PEEK when filled with glass or carbon makes it essential in applications where high variations in temperature may be expected.

Once the moulding is done, the key step is to machine. Again, considering tolerances can be as close as 10 microns, a 4-axis or 5-axis machine is essential to minimise the number of operations needed. However, more important than the dimensions themselves is the handling of the material. Even with reduced machining as compared with a round bar, there is every chance that as the block is machined, the internal stresses will build up. Hence, care must be taken in annealing the block, not just after moulding, but between operations during machining as well. 

As you can see, the end product, if done properly, can be rather pleasing. The PEEK manifold is a very challenging part. Getting it right is not something everyone can do. Moreover, our control over the entire process – from moulding, to blending, to machining – allows us to ensure that the final properties – both for the material as well as dimensionally – are always best-in-class.

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