Precision Machining of Plastics
Although there is no definitive meaning of precision plastic machining, we see it as accurately and repeatedly producing challenging parts in terms of geometry, tight tolerances, finishes and optical clarity when required. Meeting these requirements on a daily basis requires high performance machines and tools, experience, robust and efficient processes, and a culture of only accepting the highest quality.
Precision machining plastics is very different to machining metals, and requires a different approach in terms of tools selection, cutting paths, numbers of passes, cutting speeds, pecking, reaming and multiple other factors. The first step to this is a precise heat treatment protocol for the plastics to pre-shrink the base material and de-stress it. Throughout the machining processes we also conduct many first-off inspections and annealing cycles to ensure quality is built into and maintained in all components. When dealing with transparent plastics such as Acrylic / Plexiglas / Lucite (PMMA) or Polycarbonate, any minor errors or marks are immediately visible, so visual inspection stages are built into the process at multiple points.
Final inspection using a mix of gauges, Coordinate Measuring Machines (CMMs), machine vision systems, stencil templates and bespoke inspection and test equipment are used to ensure 100% conformance to specification.
In additional to specialising in Perspex Acrylic / Rohm Plexiglas / Lucite (PMMA), Carville also heat treat and machine components in a wide range of engineering plastics. These include many standard engineering grade plastics such as polycarbonate or high performance materials such as Ultem (PEI) or PEEK. Carville are experts in a versatile range of techniques and methods of Precision Plastic Machining. Different materials present different challenges, for example precision machining of PEEK and especially POM (Delrin) requires specific strategies and deburring techniques to avoid issues such as burr flaps on cross drilled intersections.
Carville CNC machine a range of plastic materials, some examples are shown below:
• PolyMethyl MethAcrylate, (PMMA – Acrylic)
• PolyCarbonate, (PC)
• PolyOxyMethylene, (POM – Delrin)
• PolyPropylene, (PP)
• PolySUlphone, (PSU)
• PolyEtherImide, (PEI – Ultem)
• PolyEther Ether Ketone, (PEEK)
• Poly Vinlyc Chloride (PVC)
The above is not an extensive list. If you require a CNC machined component in an engineering grade plastic, please forward a manufacturing drawing to Carville for review. Drawings may be sent to email@example.com
Cross-Drilled Fluid Manifolds
Precision liquid or gas manifolds are an excellent method of fluid control for anything from simple to complex systems. Carville manufacture both simple and demanding cross-drilled manifolds from many different plastic materials and work with valves from all the world’s major valve suppliers. For more complex manifolds, we often recommend using diffusion bonded manifolds which offer many advantages over cross-drilled. See our article for more background.
CNC Turning Plastics
Carville have a wide range of turning centres including a number of modern, full CNC machines to tackle a huge variety of complexities, different diameters and lengths. We can produce products ranging from one-off, large venturi systems, through to high-volume, small precision parts for applications such as laboratory equipment. We also produce many finely toleranced and finished parts for high end fine writing components with very fine and bespoke threads.
CNC Milling Plastics
Carville have many milling machine tools, including multi-axis, high-speed, pallet loaders and large beds. Renowned for our high precision, quality and repeatability on some of the most complex parts, industries such as medical devices, life sciences and food and beverage trust Carville to get it right every time. Manufacturing volumes can range from one-off parts and prototype runs, through to high volume series production, with a recent project of 2,000pcs per day.
Carville use the latest CAD/CAM system from Autodesk to allow full design to manufacturing integration. For more information on our tools, see our Product Development information.
Tooling, jigs and fixtures for precision plastic machining
Due to the complexity of the products Carville manufacture, a considerable number require bespoke tooling and fixtures to ensure accuracy, repeatability and efficient production cycles. These can range from simpler work-holding solutions through to complex multi-part vacuum fixtures. We assess the need and cost for these at the quotation stage and produce all of these in house.
Heat Treatment of Plastics
Plastics heat treatment is a core part of the process to ensure tolerances can be maintained and to avoid cracking and crazing. Carville have a high level of expertise and experience in applying the optimum normalisation and annealing cycle protocols, adjusting for the specific materials, thicknesses and applications. We have multiple, in-house ovens to perform these heating processes, all of which have full data recording capabilities to ensure every process and batch is fully traceable. We also offer stand alone heat treatment of plastics as a separate service to our clients.