METAL STAMPINGS FINISHING OPTIONS

When designing and producing precision metal stamping parts, engineers and project managers representing manufacturers, their suppliers, and metal stamping dies should discuss options for finishing parts to ensure optimal performance. Whether you need to suppress corrosion, improve appearance or smooth sharp edges, metal surface treatment is an important step in the manufacturing process and should be considered from the beginning.

Finishing options include:

· Powder Coating and E-Coating

· Plating

· Electropolishing

· Deburring

· Heat Treating

· Cleaning

 

Powder Coating and E-Coating

Paint is applied to the surface of the part, the most common are paint, powder and metal paint. Usually electric coatings or electronic coatings are used as anti-corrosion primers, and powder coatings are added for aesthetic reasons. Some applications, especially in the automotive industry, require two types of coatings.

Coating technology can achieve many valuable purposes:

· · Improve corrosion resistance

· ·Improve the appearance of parts

· ·Used as a primer to promote paint adhesion

· · Increase wear resistance

· · Enhanced chemical resistance

· · Increase wear resistance

· · Improve chemical resistance

· Reduce or increase the impact of friction

 

Plating

From large auto parts to miniature electronic parts, many custom metal stamping parts require metal plating. Electroplating is mainly used to improve the appearance of parts, inhibit corrosion, improve conductivity and/or extend product life.

You can specify electroplated layers of different thicknesses. Electroplating materials include precious metals, such as gold and silver, and non-precious metals, such as zinc and copper. The cost of the plating material can be an important factor in the total cost of the part. Taking into account the type of coating required, the design of the die itself should minimize material waste and improve performance.

Depending on the part and its function, electroplating can be performed at different stages of metal stamping production.

· Pre-plating the metal material before stamping, the price may be cheaper.

· Post-plating is carried out after manufacturing, and is usually used for parts that work in harsh environments or have visual appeal.

· When only a small part of stamping parts need to be electroplated, spot plating is mainly used for precious metals.

The types of metal plating processes include:

· Reel-to-reel plating

· Barrel plating

· Rack plating

· Zinc or zinc nickel electroplating

· Aluminum chromating

 

Electropolishing

Electropolishing removes the outer layer of metal and all contaminants by immersing the part in a tank containing a mixed chemical electrolyte and then energizing it. Frame electropolishing is used to make contact with complex metal stamping parts with tight tolerances. More economical overall electropolishing is used for small parts, such as fasteners and springs, which do not require the same consistency in material removal.

Electropolishing is used to:

· Enhance the part’s appearance

· Prevent corrosion

· Debur minor flaws

· Improve fatigue life

· Perform ultra-cleaning 

Deburring

Burr refers to the edges or small pieces of metal remaining on the part after stamping. Deburring is the process of removing excess material. Although the secondary operation is relatively easy, deburring is usually a critical step in installation.

Common methods for deburring metal stamped parts:

· A large number of deburring processes are barrel polishing and vibration polishing, which will tumble or vibrate parts in abrasive media and cleaning solutions. Both barrel polishing and vibration polishing can remove oil and other foreign matter, as well as sharp edges and burrs.

· Electropolishing is a more expensive option for microburr processing of complex parts. It can remove surface metal and provide a mirror-like finish. 

Heat Treating

The heat treatment process involves heating and cooling the metal, which changes the microstructure of the metal, thereby bringing out the physical and mechanical properties that make it more desirable.

Heat treatment allows the metal stamper to use softer steel alloys to manufacture more complex parts and still achieve the metal strength required for unique applications. The temperature to which the metal is heated and the cooling rate after heat treatment will affect the performance of metal stampings. The most common reason for heat treatment of metals is to increase the strength, hardness, toughness and corrosion resistance of parts.

Two main types of heat treating:

· The quenching or hardening process is carried out in a furnace, and different media (such as oil, salt or gas) are used to make the parts harder, more wear-resistant, and stronger, and then can be tempered.

· The annealing or softening process heats and cools the part, making it more ductile and reducing internal stress and brittleness. 

Cleaning

The metal stamping process will leave residues on the stamped parts, such as lubricants, metal shavings and dust, which may affect the function of the parts. There are many cleaning methods to remove contaminants and improve the appearance of parts.

Metal stampers usually provide a series of cleaning services in-house, but they may require other approved suppliers to provide highly professional cleaning services. In some cases, multiple cleaning operations may be required, either after stamping or after metal surface treatment, to ensure its optimal function.

Cleaning methods for metal stampings:

· Degreasing: aqueous or vapor degreasing

· Passivation: citric acid, nitric acid

· In-line spray or immersion cleaning

· Rinsing followed by a rust inhibitor

· Electropolishing

· Deburring

· Sterilization 

Evaluating Metal Finishing Options During DFM

Discussing the specifications and requirements of the stamper parts with the metal stamper early in the design for manufacturability (DFM) process can avoid unnecessary costs and delays in the metal finishing plan. High-quality precision metal stamping companies use internal resources and mature suppliers to provide professional metal finishing services. Working with experienced metal stamping engineers who are familiar with various finishing techniques can provide valuable insights and help you determine the most suitable finishing method for the final product.

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