By Marshall Taylor
There are many options when it comes to finishing machined parts. Those options depend on the application of the component and the required material. Marvel Manufacturing has approved suppliers that can accommodate most finish and plating requirements. Below is a list of definitions of common finishing processes and terms that are used to describe them.
Terms
Buildup – The amount plating that is deposited above the original surface of the material.
Penetration – The amount plating that is deposited below the original surface of the material.
Thickness – This is the total thickness of the plating (penetration + buildup).
Blind holes – Holes that do not go completely through the part.
Distribution – This refers to how uniform the thickness of the plating is over the surface of the part.
Electroplating – Uses an electrical current to attract and bind the coating to the part surface. Only conductive materials can be electroplated.
Electroless Plating – Coating is chemically bonded to the surface of the part. No electrical current is used; therefore, the material does not need to be conductive.
Racking – This is the method that parts are held or fixtured during the plating process. Electroplating requires a contact point for the electrical current to flow through the part. This can sometimes leave a small “arc” point. It is suggested to specify on drawings where a suitable place to rack is, usually on a non-critical and non-visible position on the part.
*Plugging – Used to plugged holes that should not be plated. Usually these are rubber cylinders placed in smaller holes but custom plugs can be made for specific applications. These are often used to prevent plating in threaded holes and small holes with tight tolerances.
*Masking – Covers surfaces that should not be plated. Lacquer masking that is painted on or tape-like films are used to cover large or odd shaped surfaces.
*Note - Plugging and masking are typically a manual process. This adds to the cost of plating depending on the number of holes or surface area that requires masking.
Finishing Processes
Heat treat – Various processes used to make material harder..
Stress relief – A type of heat-treating process used to relieve the stresses in the material caused by the material manufacturing process. Useful when flatness or avoiding warping is critical.
Bead blast – Abrasive material such as glass beads that are blasted at high pressure onto the surface of the part. Creates a uniform matte finish. Can be used for material prep to remove rust and corrosion or to finish parts and remove tooling marks.
Tumble – Parts are rolled or vibrated in an abrasive media. This leaves a smooth uniform finish and helps to remove sharp edges.
Electropolish – Process that uses electrical current to smooth the microscopic ridges of a machined surface. This is often used when a very smooth surface finish is required.
Silkscreen – Used to print labels, markings, and logos directly onto the surface of a part with paint.
Laser engrave/etching – Used to permanently engrave markings and logos directly onto the surface of a part. This is often used for engraving part numbers after the plating process.
Plating/Coating
Anodize (Type II)
Hard Anodize (Type III)
Teflon (PTFE)
Cerakote
Paint
Powder Coat
Zinc
Black oxide
Passivate
Chem film
Electroless Nickel
Bright Nickel
Chrome
Gold
Silver
Copper
QPQ Nitride
Nitrocarburize
Would you like to meet us? Please call us at (208) 748-6600 or email sales@marvelmanufacturing.net.
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