The process of masking metal components so that areas such as gasket surfaces, internal & external threads and bearing surfaces has moved on from the days of a man with a roll of paper masking tape and a stanley knife laboriously cutting and sticking bits of tape here and there sometimes accurately but most times not.
Powder Coatings Ltd are able to offer comprehensive Powder Coating Masking advice for any requirements you may have, we source products from all the major masking suppliers as well as commissioning bespoke masking solutions for components that cannot be masked using off the shelf materials.
Powder Coating Masking is required for a variety of reasons;
- Parts that need to fit together: and have tight tolerances such as two tubes that form an assembly.
- Holes or recesses that have bearings fitted into them: Bearings are usually a ‘press fit’ and the inside diameter of the part that accepts the bearing must be the correct dimension.
- Internal or external threads: if a thread is coated with powder this will cause problems during the assembly process. Removing powder coating from tapped holes or threaded surfaces is extremely difficult and can waste a huge amount of time and slow down the assembly procedure after the powder coating process.
- Gasket surfaces: many machined components that fit together have surfaces that require gaskets or seals between the two components. The mating surfaces have to be kept free of Powder Coating to ensure that no leaks occur and that the components fit together precisely.
- Electrical Earthing: All metal electrical components or enclosures require an ‘earthing point’ This is an area of the component surface that has no coating applied so that an earth tag or connection can be fixed to the surface of the part ensuring the part can be used safely.
Masking Tapes; these are made of a polyester material that is usually 2 mm thick and able to withstand high temperatures of 200 + degrees centigrade. They are available in widths ranging from 1/8” up to 9”. The adhesive type is silicon based so it can withstand the heat and leaves no sticky residues when removed.
Die Cut Discs or rectangles; supplied on a roll these are small die cut discs/rectangles of polyester masking material that can be easily peeled off the roll and applied accurately to components.
Tapered Plugs; used to insert into holes the taper ensures a tight fit; they are able to withstand up to 200 + degrees centigrade so the parts can withstand the heat of the oven with them in situ and be removed after curing.
Caps; these are used to fit over external threaded parts or machined spigots while they are being coated. They are sometimes used to fit over threads and spigots after finishing so that the parts do not get damaged in transit.
Die Cut Shapes; in cases where specific areas of a component require masking and off the shelf die cut discs or rectangles are not suitable it is now possible to produce die cut shapes that exactly match the relevant area. Using CAD drawings the masking material producer makes a bespoke tool that exactly cuts the required shape using adhesive backed polyester sheet. The bespoke shapes are then applied to a roll of base material so that they can be peeled off as and when required and applied accurately to the relevant area that needs masking.
Bespoke Silicon Tubing; this is useful when a specific internal diameter needs to be free of powder coating and a stock item cannot be found. As long as the precise internal dimension is known an extruded bespoke silicon tube can be produced with the outside diameter of the tube exactly matching the inside diameter of the part that requires masking. The tube can be cut to the specific length required and fitted inside the component prior to coating.
Bespoke masking pieces; Certain parts have irregular shapes or multiple angles that need masking. We can commission bespoke masking pieces. A multi impression tool is produced that matches the exact shape of the area to be masked. Molten silicon rubber is injected into the tool and after cooling the bespoke masks are trimmed and ready for use.
Liquid Mask; An air drying masking film that can be applied by spray, brush or roller. After coating the mask can be peeled off and disposed of. This is an ideal way to mask irregular shaped surfaces and prototypes prior to bespoke masking pieces being produced.
Another important issue to remember is the information supplied by the customer to the powder coater. Very often Powder Coating Masking requirements are an ‘after thought’. The coater will be supplied the drawing or sample component and generally informally told that a particular thread or holes need masking. This is not very efficient and if not fully understood can result in parts that are not masked to customers’ requirements causing delays and unnecessary rejects. The best way to inform a coater exactly what parts or areas need masking is to produce a bespoke Powder Coating Masking Drawing and add it to the drawing register for the part. With Computer Aided Drawing Systems it is relatively easy to highlight in a different colour the specific areas, threads or spigots that do not require coating. The coater can attach this drawing to his Route Card so that all works personnel are fully informed about the specific masking requirements.
Contact [email protected] with any questions or requests for more information about Powder Coating Masking