Finishing Options for Machined Parts

Adding a finish to machined parts and enclosures is not solely about aesthetics; it also enhances protection and performance attributes.

At Protocase, we’ve got tons of finishing options to fit what you need, including a variety of finishes for machined parts.

In this blog, we will walk through the options for bare metal, anodized, and powdercoat finishes, so you can find the perfect fit for your project.

Why Add Finishing for Machined Parts?

A good protective finish can add layers of defense, ensuring longevity and performance under stress.

Secondly, finishing serves aesthetic and communication purposes. An aesthetically-pleasing finished part not only looks professional but can also communicate the identity of your brand as well as mention instructions or labelling connectors on your part.

Therefore, you should carefully consider finishing options during the design process.

Now, let’s take a look at the options that we offer at Protocase.

Bare Metal Finish or No Finish

Our most popular finishing options for machined parts are bare metal finishes or no finish, also called a stock finish.

For machined parts, no finish refers to the appearance straight off the machine, with visible toolpath patterns from the CNC mill or lathe tooling. These parts may also have minor surface scratches.

We offer three bare metal finishes: grained, vibratory and media blasting.

• Grained Finish: In this process, the part is de-burred and brushed to create a sleek, minimalist look with a linear grain direction.
• Vibratory Finish: The part is placed in a tumbler with an abrasive medium that smooths over the part, which minimizes toolmarks.
• Media Blasting: The part is deburred and cleaned, then sprayed with a steady stream of tiny glass beads via compressed air, creating a uniform finish and effectively removing tooling marks and scratches.

Design Considerations for Bare Metal Machined Parts

When applying a grained finish to milled parts, only the exterior surfaces can typically be brushed. Part geometry is important, especially if your part lacks easy-to-reach flat surfaces for brushing.

Anodizing

Anodizing is an electrochemical process that enhances the metal’s natural oxide surface, providing increased corrosion resistance and a decorative finish.

We offer anodizing as a third-party finish through our trusted suppliers. These partnerships allow us to bring your custom parts to life exactly the way you envision them, all while ensuring quick and efficient lead times.

If your project involves parts exposed to heat or electricity, an anodized finish ensures corrosion resistance. With its hard surface, especially when using Type III anodizing, it adds a durable layer that extends the lifespan of parts and protects against scratches and wear.

Design Considerations for Anodizing

Anodizing adds material to the surface, which can affect tolerances. Take a look at the following thickness ranges for Type II and Type III anodizing.

Powdercoat

Powdercoating involves electrostatically applying a dry, free-flowing powder to a part, which is then cured in an oven to create a hard, durable finish.

The two most popular types of powdercoats are polyester and epoxy, and each type has its advantages.

• Polyester powdercoating is the most common type, offering excellent value with great impact, mechanical and chemical resistance.
• Epoxy powdercoating is preferred for corrosion and chemical resistance, offering durability, hardness and strong adhesion to metals. However, its drawback is poor performance in exterior conditions.

Design Considerations for Powdercoating

Powdercoating will add thickness to a part, adding 0.003”- 0.005” to a cutout. So, ensure your design accounts for this increase and how it may affect the overall fit and function of the part.

Chemical Conversion Coating and Passivation

Keep in mind that we also offer processes that convert the surface of a metal part into a clean, protective layer with chemical conversion coating and passivation.

With either process, the finished part will be more resistant to corrosion and improve adhesion for subsequent coatings.

Some people don’t usually think of chemical conversion coating (also known as chem-film) as a finishing option. However, we recommend it as a pretreatment and for additional corrosion protection.

Part Markings and Graphics

We also offer permanent part marking options such as laser marking or engraving.

We can add graphics to your machined parts via silkscreen or digital print if required too. Adding graphics is a great way to communicate your brand or to add label cutouts for connectors and electronics.

Conclusion

Finishing your machined part is a balance between what looks good, what feels right, and what works well.

Understanding design considerations and the benefits of each type of finish will help you make the right decisions. This will result in machined parts and enclosures that are not only structurally sound but are also visually appealing, durable and meet your specific requirements.

We’re here to help you reach your project goals! If you’ve got any questions, just send us an email at info@protocase.com, and your dedicated Account Manager will get back to you as soon as they can!