Development work by Mitsubishi Chemical Advanced Materials has enabled the injection-molding of pump-rollers for a high volume application using Ertalyte TX PET-P. These parts were originally machined from extruded bar stock shape of the same material by Mitsubishi Chemical Advanced Materials CMS’ sister company. The change to a more cost-effective processing method for the pump-rollers was needed since the production levels rapidly increased over the last few years. The pump-rollers molded by Mitsubishi Chemical Advanced Materials are principle components in the pump. Since their original design and conception, the pump-rollers have been produced from Ertalyte TX, an unreinforced semi-crystalline polyester (PET-P) with a solid lubricant filler. The material was chosen for its strength and stiffness, high dimensional stability, outstanding wear resistance and low friction coefficient. The material provides sustained performance under high-pressure and high-velocity conditions, and is ideally suited for applications involving soft metal and plastic mating surfaces.
Within the Mitsubishi Chemical Advanced Materials Group, a new technology to bond a thin strip of PTFE with a thermoplastic carrier in a single step overmoulding process has been developed and patented.
|The resulting product has a top surface which exhibits the excellent low-friction and chemical resistance properties of the fluoropolymer, yet is as mechanically strong as the thermoplastic carrier beneath it. Moreover, it provides the typical “design for assembly” freedom of an injection-molded part.|
Specific advantages of the new design include a reduction in the amount of PTFE used for each slide bearing - to just 10 percent or even less of the original volume - for significant cost benefits, and ease-of-assembly, while maintaining the required low coefficient of friction and self-lubricating properties of the PTFE strips when in contact with the mating surface.
|The properties of PTFE (polytetrafluoroethylene) are well-established: low coefficient of friction, self-lubrication, wide operating temperature range, and good UV and chemical resistance, to name a few.To date, however, barriers to its wider use have related to its processing requirements: a non-melt processable material, PTFE is produced as a stock shape which is costly to machine to the required size and shape. The material’s low structural strength is a further limiting factor for applications where toughness is required. Hence Mitsubishi Chemical Advanced Materials developed its Thin Film Fluoropolymer Technology (TFFT) to bond thermoplastic injection moldable materials to a thin film of PTFE. This allows for the use of PTFE only on the surface where its unique properties are required, while supported by a melt-processable plastic carrier, cost-effectively injection-molded in a more complex form or shape|
Mitsubishi Chemical Advanced Materials in Belgium received the drawings for two Techtron HPV brackets in 2009. The drawings of the brackets, which are used as a cable guide on a new passenger aircraft, came with the request to have a look at the possibilities to injection mold these instead of machining out of a solid plate.
Considering the annual amounts of parts and the fact that the two brackets were quite similar, we quickly understood that it was a far better option to offer a near net shape, that would be common for both parts; and out of which the final versions could be machined.
The finished molded part has a weight of 172 grams. This weight should be compared to the weight of the section of the solid plate which was previously used to machine this part, and which came to 652 grams. So clearly, in terms of cost : the molded part uses far less material, and needs less machining time, and therefore is a much more cost-effective solution.
This product clearly demonstrates what Mitsubishi Chemical Advanced Materials is capable of:
- we can advise our customers of what particular material they should use in their application (in this case it’s one of our QEPP proprietary materials)
- we can advise on the design of their product
- supply our customers with injection molded, near net shape parts, for machining to optimize the cost efficiency of the application
An additional advantage to our customer in this particular case is in the global nature of our Mitsubishi Chemical Advanced Materials organization. The mold for this product left Belgium (once optimization had been done and the first batch of products had been delivered) and relocated in the Reading facility (North-America). In the mean time the US facility was equipped with injection moulding capability. We did this to accommodate our customer as they wanted the molding to take place in the US for currency risk reasons.