As one of the UK’s leading acrylic engineering firms, NCA Ltd work with a range of tools and equipment to ensure that our engineered components meet both our exacting standards and those of each client. In today’s blog we focus on an element that is used within our production, acrylic polishing, and how this step within the process ensures that the final product is fit to leave our fabrication plant. We will also outline the two main types of finishing that we use in our plastic polishing services: manual and mop polishing and vapour polishing
What is acrylic polishing and why is it important?
For however accurate and precise fabrication methods can be, unevenness and blemishes across the surface of machined plastics can occur such as saw marks, blemishes or scratches. Of course, this is not ideal because of two main reasons. Primarily, the finish itself is not aesthetically pleasing to look at and is not uniform. And secondly, the non-uniform finish is undesirable because it can also make bonding the piece difficult. Acrylic is polished in order to forgo such issues resulting in beautifully crisp and neat edges that can be properly and uniformly bonded. What’s more, depending on the specifications and requirements of the project, when high levels of optical clarity, vapour polishing (also know as super-finishing) is used to achieve the required level of optical clarity.
What is mop and manual polishing?
Acrylic, like many other engineering plastics, can be mop or manually polished by hand to help improve the surface finishing, remove scratches and create an even finish on the surface improving its appearance. Before polishing is undertaken, it is vital to have a decent machined finishing on the piece to make sure that dimensions are maintained.
Mop polishing uses a variety of mops and cloths at various levels of abrasiveness and specialist abrasive solutions that work by removing a layer of the surface material to leave a polished finish. Depending on the amount of parts and the shape of the parts being polished the process can either be done by hand or through automated machines and processes. Generally speaking, small quantities and unusual shapes will be mop polished by hand whereas large, more uniform shapes will be automated.
What is vapour polishing?
Vapour polishing is another method of polishing plastics that, like mop and manual polishing, aims to reduce the roughness of the surface and improve the optical clarity of the plastic.
Vapour polishing works at a microscopic level and leads to incredible optical clarity. It is done by using the volatile gas of Weldon 4 solvent which is highly reactive to the surface chemistry of polycarbonates. In a controlled environment, Weldon 4 solvent is heated to its boiling point creating vapours that are sprayed across the surface of the piece. The plastic then melts at the surface, filling in the minute scratches (the roughness), which quickly solidifies once the gas is no longer present creating an even and clear finish.
Typically vapour polishing is used on materials which require a high level of optical transparency such as lenses leading to improvements in both the internal and external surface finishes. Vapour polishing has the advantage of being able to polish internal, detailed features such as threads, apertures, channels and sample inspection areas that would be impossible with manual polishing.
Below is an interesting comparison of both polishing methods by one of our favourite Youtube channels ‘Applied Sciences’ who tries out a combination of different polishing techniques.
In next week’s blog, the start of a new series, we will be exploring our machining capabilities in a range of industries starting with chemical processing. For more information on our acrylic and engineered plastic polishing, contact our team via email@example.com or 01928 790209.