The advancements in polymer technology have resulted in myriad different plastics, each offering its own unique property. While some polymers are preferred for their strength, others may have specific resistance to certain chemicals, making it the material of choice in an industry where such chemicals are prevalent. A case in point of this is PPS (Polyphenylsulfone). PPS is a relatively brittle polymer, which usually requires a glass fibre reinforcement in order to maintain its structural stability. However, PPS is especially resistant to the chemicals used in pulp and paper industries, requiring that components used in the equipment for pulp and paper be made from this polymer.
While many properties have been tested and improved continually, it has always been the durability of the polymer that has remained a mainstay of its preference. Traditionally, OEMs and equipment manufacturers have always prided themselves on making products that can stand the test of time. Be it a car or a pair of shoes, quality and durability have always played the most prominent role in defining the industry leaders. However, this is suddenly changing.
Shortening product life cycles have started placing questions around the importance of durability. What use is a car that can stay fuel efficient and low maintenance over 10 years, if the consumer is going to buy a new car within 3 years anyway? Nowhere is this phenomenon more pronounced than in the electronics industry. Mobile phones, smart watches and even laptops are no longer needed for more than 18-24 months, before the consumer upgrades to a new variant.
The shortening of the life cycle has an impact on the input materials used. Devices no longer need high-performance materials, which are expensive and drive up the final cost of the equipment. Furthermore, with the ever-changing designs, a component needs to be made with as low an upfront cost as possible, since any one-time tooling and development charges cannot be amortized easily over volumes over time.
In the polymer space, this has created both a dilemma and an opportunity. Polymer components are typically of two variants:
- Injection moulded parts – where the part is made by injecting molten polymer into a die that has the final shape of the component needed
- Machined parts – where the part is turned or milled from a rod or sheet
Injection moulded parts are traditionally cheaper, when you only consider the marginal cost of making the part. Not only does the injection moulding use only as much polymer as needed, it also creates complex shapes within seconds and a single die may be capable of housing multiple cavities, so the process is high in productivity.
Machining is expensive, as you are effectively removing excess material from a rod or sheet. Furthermore, it is a length process that only gets longer as the complexity of the part increases.
Machining, however, wins against injection moulding on two accounts. For one, the cost of making the die can be both expensive and time consuming. Making a good die can often take over a month and cost upwards of US$1500 for a single die. In addition to this, the tolerances achievable on injection moulding are not always close. Once the die is made, if the part tolerances are not as per the drawing, either the OEM needs to accept the new dimensions as they are, or the component manufacturer must re-make the die, which is again expensive and time consuming. Machining, on the other hand, can easily attain tolerances of within 20 microns, if done properly. Furthermore, any change in drawing or revision only requires a simple modification of the programme on the CNC machine – which is free of cost and can be done in minutes.
So, even though machining yields a more expensive per-part cost, device manufacturers are slowly accepting that machined components are a better option for short product life cycle parts. Considering the mobile phone market operates on barely an 8-12-month product life, there is little time to invest in making a mould, testing the parts and moving to production. It is simpler for the OEM to utilise the expertise of a good machine shop, where both the polymer and the final component can be changed as required.
While machining is certainly taking off as a preferred option for making polymer parts, the grade of polymer has also been reviewed and revised accordingly. Polymers like PEEK, PCTFE and Polyimides are highly durable, but come at a steep price. For comparison, the price of PEEK would be nearly 20-40 times the price of cheaper polymers, such as Nylons and Polyacetal (Delrin). Considering that high-performance polymers offer, amongst other things, durability as a key property, there is a shift away from the more expensive plastics to those that offer lesser durability at a fraction of the price.
In our own experience, we have seen that while one part is running for an existing generation of equipment, another set of parts is already under development for the next generation. This pipeline allows the OEM the time needed to test and modify the parts as required, so that the time to market for the next generation of devices is shortened as much as possible. The ability to adapt and cater to this changing dynamic is based on a company’s capability to understand and work with many different polymers. Being able to take on a new polymer – based on what the client specifies – and immediately develop techniques to achieve the desired close tolerances on the same is a skill that is slowly acquired. By working with nearly 30 different polymers, Poly Fluoro Ltd. has developed a wealth of understanding on how each family of plastics behaves. This puts us in an ideal position to capitalise on the changing approach of today’s industries.