What do we mean by Plastic Polishing?
Perspex Acrylic and Rohm Plexiglas can be polished to a clear glass like finish. Other plastics, such as Polycarbonate, can also be polished to achieve an improved cosmetic or surface finish.
Plastic polishing requires time and will require additional manufacturing costs. These additional costs may be appropriate for applications such as lenses and light guides, however, they may not be required for industrial engineering components which do not require optical properties or are hidden inside a larger assembly.
What results can be achieved by polishing?
Carville attend exhibitions throughout Europe and the USA. We display acrylic component parts that have been produced to individual customer specifications but carry a high level of internal and external surface finish. We regularly receive comments that our finished components look more like works of art rather than CNC machined engineering components. Customers are often surprised by the quality of the surface finish that can be achieved on a fully heat treated and diamond machined acrylic, plexiglas or plastic component part.
Where do we start?
A machined plastic component will have witness marks left by the machine tool. The type of tools used, along with the speeds and feeds applied, will influence the quality of the surface finish achieved.
Improving the surface finish of a machined component by polishing requires the removal of additional material after the completion of the machining operations. If a component does require a high quality surface finish, it is important that the machining operations applied will allow the end result to be achieved.
Carville have manufacturing procedures that ensure good material handling and a high level of machined surface finish. We aim to achieve the best possible machine finish on our component parts and will use a combination of high speed steel and diamond tools with the correct clearance angles. The correct tools, along with the correct speeds and feeds, will achieve the best possible surface finish and minimise the requirement for post machine polishing of acrylics or other plastics.
Page 4 of Carville’s product brochure shows 5 components which are dimensionally identical but have been produced using a combination of different machining and polishing techniques. This offers a useful guide and assists engineers to identify their requirements and to allow the addition of manufacturing notes to drawings which have a common understanding.
What are the Polishing Options?
When polishing is necessary, there are a number of ways to polish Perspex Acrylic, Rohm Plexiglas and other engineering grade plastic materials to achieve the end customer’s required internal and external surface finishes. These techniques will vary depending upon the actual component part and the final application.
Plastic polishing techniques for acrylic lenses and light guides are different from those applied to produce a luxurious finish to a high end writing instrument. Carville have developed a number of acrylic and plastic polishing techniques to achieve the required internal and external surface finishes for each customer application. These techniques may include:
Acrylic and other engineering plastics can be polished to improve the surface finish and appearance. Acrylic polishing requires the removal of material and it is essential to achieve a good machined finish before polishing to ensure critical dimensions can be maintained.
Mop polishing requires different grades of mops or clothes used in conjunction with abrasive soaps which will remove surface material and leave high quality polished finish on acrylic and other plastics.
The type of mop polishing process applied will be subject to the volume of parts required. When volumes are low, mop polishing will be a manual process with each part individually finished by hand. For higher volume components, such as writing instruments, Carville will apply mechanised mechanical polishing techniques.
Super Finishing (Vapor / Vapour Polishing)
Super finishing is a term used to describe Carville’s vapour polishing processes. Vapour polishing can be used to enhance component features on materials such as acrylic or polycarbonate. Vapour polishing is ideally suited to the polishing of small features such as apertures or threads and offers improvements to internal and external surface finishes
Can Carville Super Finish or Vapour Polish my Components?
The Vapour polishing process can be used to improve the cosmetic appearance and transparency of components, however, the results will be dependent upon the quality of the original parts. If a part has a very rough surface finish, the end results will be variable.
All Acrylic and Plexiglas materials processed by Carville are fully heat treated prior to and after machining. Components which have not been fully heat treated will have internal stress and can be damaged by the vapour polishing processes.
Carville do offer to Vapour polish components produced by other companies, however, this service is offered on a best endeavour basis and is subject to the quality of the components supplied.
When processing components produced by other companies, Carville will heat treat the free-issue components, clean the parts, perform the vapour polishing process and then clean the parts again before packing for dispatch.
Flame polishing requires the surface of the acrylic or plastic material to be heated sufficiently to create material flow. Material, in a liquid state, will flow and this results in a smoother finish. Flame polishing will result in uneven heat distribution and material stress. Introducing stress to the materials such as acrylic may result in future stress cracking, crazing and component failure.
Flame polishing is a lower cost technique and is typically used in applications such as the manufacture of acrylic signs or point of sales goods. Flame polishing is not ideally suited to engineering grade components and is not a process used by Carville.