Ensuring quality beyond the injection moulding process
BP&R sat down with Gabby Day, communications manager at Pentagon Plastics, to discuss Pentagon's post-moulding procedures for adding features, maintaining quality control, and alignment with sustainability goals.
How does Pentagon Plastics' experience with "filled and unfilled thermoplastics" translate into benefits for their clients (e.g., wider material selection, better product performance)?
Pentagon has been processing high engineering grades of thermoplastic materials for more than fifty years and the use of fillers greatly increases the choice of materials available to our customers and can provide advancements to the final function of the finished product.
Materials with glass filler offer benefits of improved strength, structural rigidity, and dimensional stability. Glass-filled nylons also have lower moisture absorption and are therefore less prone to taking in moisture compared to unfilled nylon, which can help ensure greater dimensional stability and reduce the risk of part failure in high-humidity environments. Material selection is largely based on the parameters surrounding the end use of the plastic component and the environment in which it will be used. The versatility of thermoplastic materials is advancing all the time which offers customers and their design engineers a wealth of options.
We are also using materials with carbon or steel fillers that make them semi-conductive. This can be useful in environments where static electricity can be an issue, providing Antistatic & ESD protection, preventing electrostatic discharges. Some conductive plastics are also used in Electromagnetic Shielding, reducing EM interference.
Pentagon’s breadth of processing knowledge delivers multiple benefits to customers, sound material advice within the design stage coupled with optimal mould tool design that is aligned with specific material behaviours and properties. Our optimised injection moulding processes allow for manufacturing efficiencies that lead to repeatable quality products delivered with efficient lead times.
Have you encountered any recent advancements in plastic materials that have significantly impacted your approach to injection moulding?
In line with the modern environment and the hard focus on sustainability within the polymer industry, the current crop of recycled materials that are available are much better than the products of a few years ago. Benefiting from much greater consistency allowing for a repeatable process in the moulding machine. This in turn increases our confidence in offering them as an alternative to traditional virgin polymers. This is particularly attractive to customers who want to be more environmentally sustainable or are simply looking for ways to reduce costs on high-volume parts. Although our approach to injection moulding remains consistent this advancement in recycled material options does enhance the polymer industries offerings.
In terms of Pentagon's process Beyond the Mould, could you walk us through the process of post-moulding and how you ensure quality throughout?
Processes beyond the mould are secondary operations to the injection moulding of the part, usually carried out for component features that are not compatible with the moulding process but are necessary to the finished product or to keep some of the initial cost out of the mould tool. This includes things such as drilling or insert fitting, milling, trimming and light assembly. Within the department quality checks take place every 1-2 hours whereby sample components that are being worked on are taken by the quality inspectors, checked, and measured using equipment such as co-ordinate measuring, callipers, micrometres, pin/thread gauges, and custom-built product specific jigs or gauges.
The results are then recorded and monitored; this enables the quality team to see if overtime any changes have occurred and maintains consistent accuracy of post moulding operations. The strict quality processes allow us to capture, report and rectify any quality concerns before they become an issue that may impact fulfilment of a customer order.
Pentagon Plastics recently acquired a Deltron CNC Coordinate Measuring Machine from Vision Engineering. Could you elaborate on the specific features and functionalities of this equipment and how it will contribute to your quality assurance processes?
Pentagon operates under ISO9001:2015 standards spanning both mould tool manufacture and plastic injection moulding and quality is vital throughout our manufacturing processes. The recent investment in to the Deltron CNC Coordinate Measuring Machine advances our quality process to the next level for mould tool manufacture. The compact machine brings high level measurement accuracy and repeatability directly to the shop floor allowing the technicians to check their own work at every stage and to produce extensive reports when required. Saving measurable amounts of time on the existing manual processes this state-of-the-art technology will predominantly be used for electrodes, cores, cavities, and other tooling components it will deliver greater accuracy for quality checking. The investment will support the reduction of tool manufacturing lead times and reduce the additional resources for reworking or remaking items.
The Deltron features fully sealed recirculating bearings delivering four key benefits: no dirt ingress, no gearbox, no compressed air, and smooth fast operation. This helps deliver exceptional accuracy, simplicity, and reliability. The system will allow us to perform high accuracy measurement supported with bespoke generated reports, run automatic measurement programs, and allows offline programming. Having the ability to import DXF, STEP and IGES files will further aid the process and simplify the measuring of component parts.
This will be a real asset to the shop floor.
How do the properties of different thermoplastics affect the design and processing parameters for injection moulding?
Properties of thermoplastics are a key factor when designing an injection mould tool and the tool designer must take into consideration multiple factors that can vary greatly from polymer to polymer. The main ones to consider are camping force requirements, shrinkage, corrosive or abrasion properties, and mould temperature.
Depending on the chosen polymer and size of product the clamping force required to successfully mould the component can vary greatly, materials such as Low-Density Polyethylene require low force, while Polyether Sulphones and Polysulfones could require 13 times more clamping force. This will affect what press size is needed to mould the component in production.
Shrinkage affects the physical size of the mould form and is a key consideration when designing a mould tool. Even within the same range of polymers they can vary due to different factors one such factor being additives, or fillers. Fillers such as Talc and Glass fibre are common in materials and much like clamping force the shrinkage of materials can vary greatly so it is important to know not only the polymer that is to be moulded, but the specific material grade as well.
Due to the chemical construction of some polymers and the additives, the tool designer may need to choose specific grades of tool steel for construction of the inserts to maximise the life of the tooling. Polymers such as PolyVinyl Chloride (PVC) release corrosive gasses during processing which can chloride steels with lower chrome content (non-stainless). While some materials require high hardness tool steels due to the abrasive properties or those of fillers that are added.
Processing properties of the polymer dictate what temperature the tool needs to maintain during moulding. Some polymers require very cold tools, this is achieved by running chilled water through the tool and inserts, while others can require heating over 200°C, which is often achieved with hot oil or sometimes on smaller tools electrical heaters built in.
As concerns about sustainability grow, how can the use of thermoplastics be integrated into the injection moulding process while maintaining part quality and performance?
By working with experienced mould tool manufacturers such as us, sustainability in plastic injection moulding starts with mould tool design. Mould tool design is a complex area and by working with experienced and expert tool designers your tool can be designed with minimised waste in mind at every stage of the manufacturing process.
Considering optimal cavitation, cooling, and ejection systems that best align with the product material specification will mitigate the generation of plastic waste in the moulding process. With the continuing advancements in recycled polymers and their improving compatibility with the plastic injection moulding process there is tangible ethical progress for the plastics sector. Here at Pentagon, we are excited to be taking this journey in the next chapter of plastics processing and its contribution to wider environmental and economic sustainability.