In the manufacturing of mechanical parts, customers usually require the manufacturer to do surface finishes on metal parts. Do you know what the surface finish of metal parts is in the CNC machining services field? What are the types of surface finishes we are usually required to make? In this post, we are explaining about them. And you will get practical answers to these questions.
The definition of surface finish
Surface finish is also known as surface treatment. Then what is surface treatment? Surface treatment is a process applied to the surface of a material to make it better in some way, for example by making it more resistant to corrosion or wear. It is a process of forming an artificial surface layer on the surface of the base material. And the mechanical, physical and chemical properties of the formed layer are different from those of the base material. Please note the surface finish is necessary for some raw materials. Because the purpose of surface treatment is to meet the requirements of corrosion resistance, wear resistance, decoration or other special functions of the metal parts.
What type of surface finishes are there?
Generally, surface treatment is divided into two types. They are whole surface treatment and local surface treatment.
What is whole surface treatment?
The whole surface treatment is to apply the surface treatment process to all surfaces of the entire part. When we finish the process, all surfaces’ performance and appearance color on the metal part are the same. So there is no need to do a special mask and protection of the mechanical part. And the surface treatment factory can complete the treatment at a time. Of course, it’s relatively easy.
Let us take the parts in the above picture as an example. The part in the middle is of natural surface that is plain. However, the other six pieces parts are anodized in black color. The entire parts are in the same surface treatment. They are wholely surface treated in black anodizing.
What is local surface treatment?
While the local surface treatment is different. It refers to form a single treatment layer on the partial surface of a metal component but no treatments on the other remaining surface. Or two or even multiple surface finishes on one piece of metal component. Let’s say A treatment on a partial surface and B treatment on the other remaining surface. In a word, we applied both treatment A and B to the same component, and they are in different areas separately, not overlapping each other. One image is attached below for your better understanding.
From this picture, we can see that there are at least two surface treatments. On the inside surfaces, there is Yellow Alodine (A surface treatment) and black anodizing (B surface treatment) on outside surfaces.
What issues we should consider in local surface treatment?
For such a surface treatment requirement, it needs to consider the characteristics of both A treatment and B surface treatment. That is to say, before doing the second surface treatment, people need to find ways to cover and protect the surface of the previous treatment.
In the majority of cases, the machining service supplier has to do secondary processing of the part after the first treatment but before the second treatment. Therefore, it’s more complex and takes much more time and cost. Besides, we need to note that such surface treatment requires better professionalism and technical processing ability.
