To improve the ability of a metering pump to resist absorption of media, Freudenberg-NOK Sealing Technologies Simrit developed a unique diaphragm design for fluid handling applications, such as inkjet printers used in offices and homes. Freudenberg-NOK’s design replaces the traditional polytetrafluoroethylene (PTFE) foil with a perfluoroelastomer (FFKM) layer that is bonded onto fluoroelastomer (FKM) pump diaphragms to improve stroke length, reliability and durability in select applications.
In the printer application, ink particles were absorbed into the substrate of the PTFE foil, which then hardened during extended periods of machine shut down. These hardened particles created stress points in the PTFE, causing it to eventually break during movement. The elastomeric FFKM layer solved this problem, since it is not a sintered material, while keeping a high chemical resistance. Another advantage of the FFKM layer is its high flexibility in comparison to a PTFE layer, which is an added bonus to the ink contamination problem. The FFKM cover promotes longer stroke, higher pump frequencies and life because the diaphragm design is no longer limited by the flexibility and bending fatigue strength of PTFE.
The Simriz 481 and 491 materials are produced within the Freudenberg and NOK family of companies, which allows the diaphragm development engineer the distinct ability to work with the material development group to find a unique solution that creates a functional part. The Simriz materials are FFKM, which by definition means that they are chemical resistant, but are also resistant to bonding and adhesion to other surfaces, which is necessary to make a functioning diaphragm. For the engineering team, it was clearly recognized that a diaphragm purely made of FFKM would increase the costs to an unacceptable level, so a special manufacturing method was developed in parallel to bind a thin but accurate FFKM layer onto a FKM diaphragm.
Filed Under: Fluid power, Hydraulic equipment + components