Functions like ‘dynamic sealing’ and ‘dynamic bearing support’ of shafts, pistons and rods are increasingly handled by high-performance plastics. Requirements like sealing higher pressures or supporting shafts and guiding pistons in various systems require heavy-duty materials like compounds based on Moldflon and PEEK.
The sealing of higher pressures in systems like high-pressure gasoline injection pumps or the bearing support of shafts and guiding of pistons in electro-hydraulic braking systems, for example, can only be achieved by materials that are resistant to particularly heavy loads. In plastics engineering, this challenge is met by the development of new compounds based on Moldflon and PEEK.
Two examples serve to illustrate how the use of high-performance plastics results in viable solutions for special automotive applications. The use of multi-functional components made from plastics or plastic composite systems in automotive applications enables the number of assembly components to be reduced and to thereby provide more economical solutions.
In the second example new PTFE manufacturing and processing techniques in the hose, tube and casings sector are described. This process enables new applications in the area of casings for cables and lines used in new transmissions.
Friction bearings and guide rings
The composition of Moldflon largely corresponds to that of conventional modified PTFE, albeit with very good properties for friction bearings. The Moldflon friction coefficient is nearly identical to the PTFE friction coefficient combined with reduced cold flow and increased pressure stability. Due to its universal chemical resistance and extremely high temperature stability as well as low wear Moldflon is the ideal basic plastic material for friction bearings.
Due to proprietary compounding the materials can be specifically tailored to suit the users’ parameters or the parameters incorporated into the material by using fillers. This advantage resulted in the development of the friction bearing compounds Moldflon MF 40002 and MF 40003. Examples of applications for Moldflon friction bearings other than in the area of brake systems include:
- Transmission friction bearings and axial thrust plates
- Friction bearings in gear pumps
- Friction bearings in exhaust gas recirculation valves and EGR systems
- Friction bearings in valves for controllable cooling circuits
- Bearings in steering systems / steering column adjustment systems
- Friction bearings in seating systems and much more
Self-lubricating high-pressure Moldflon-PEEK friction bearings / guide rings from MF 40002 are suitable for ABS/ESP piston pumps in braking systems. In electro-hydraulic ABS/ESP piston pumps, in addition to seals, guide and back rings made from PTFE compounds have been used for many years, among others. Today’s pump generations require longer lifecycles as well as higher dynamic pump pressures. Specially developed materials based on Moldflon and PEEK fulfill these requirements.
Another advantage of Moldflon is its lower deformation under load. The respective assembly components such as friction bearings and guide rings are either machined or produced by injection molding technology, depending on the geometry and required tolerances. Moldflon-PTFE not only offers the technical advantages associated with improved pressure stability in this case but, due to the modification, enables use of the cost-efficient manufacturing method of injection molding, which is particularly suitable for large-volume production.
3D-molded casings in passenger car transmissions
3D-molded PTFE and Moldflon casings are used to route cables in modern passenger car transmissions. The casings serve to protect cables and lines in the transmissions from damage and wear. A special 3D-molding technique allows small bending radii and thus defined hose and cable routings to be achieved. All 3D-geometries can be produced in large volumes by means of a partially automated manufacturing process.
Since Moldflon is slightly stiffer than PTFE it is used particularly for small bending radii to avoid creasing. In addition, PTFE and Moldflon offer the advantage of chemical resistance to transmission fluids and, even more importantly, of temperature resistance in the typical automotive temperature ranges from -40°C to +150°C. These 3D-molded casings are usable for other applications as well, for example wherever tubes, hoses and casings with high temperature and extremely good chemical resistance are required.
Outlook for multi-functional components / complete systems
The manufacturing method of injection molding that is highly economical for large volumes and the weldability of Moldflon-PTFE opens up new opportunities of using multi-components and composite systems.
Moldflon is very suitable for combination and bonding with other plastics and metallic materials. Injection molding technology makes it possible to design and offer 2-component parts as well. This provides the design engineer with new degrees of freedom. In addition, the total number of components required may be reduced.
With in-house material and component development and in-house CAD design capabilities, Elring Klinger Kunststofftechnik offers all the prerequisites expected of a system supplier to both tier-1 suppliers and OEMs.
The author, Klaus Hocker, is key account automotive, at Elring Klinger Kunststofftechnik in Bietigheim-Bissingen.
