Microform Precision divides our cosmetic requirements into four categories: A, B, C and D. A is the highest and consequently requires the most effort to attain. Likewise D is the lowest and will be the fastest and cheapest option. For most applications, either B or C would be advisable. Choosing the most appropriate cosmetic class for your application will help to ensure a finish that will be pleasing to your end user without increasing the time and cost beyond what is needed. Following are a series of the most relevant excerpts from Microform Precision’s cosmetic inspection criteria.
Class B: Class B finish is a quality finish with only minimal imperfections. A Class B finish is the most common finish for exterior surfaces. It is normally specified on surfaces such as external covers, panels, and parts that are fairly prominent.
Class C: Class C finish allows more imperfections than Class A or B. Class C is often specified for interior surfaces not readily visible, surfaces that will be covered by another part when assembled, or surfaces which the Customer feels do not need to meet a high cosmetic finish. This Class is generally used for parts or surfaces which are not viewed after installation or viewed only for service.
Class D: Class D finish might be used when cosmetic appearance is not important. With a Class D finish, all imperfections are permissible provided they do not impair the function, safety, structural strength, environmental, electrical or dimensional requirements of the part; part is usually never viewed.
Viewing Time and Distance
|Class A||12 inches||6 sec/ 12″x12″|
|Class B||16 inches||4 sec/ 12″x12″|
|Class C||16 inches||3 sec/ 12″x12″|
|Class D||24 inches||2 sec/ 12″x12″|
|Imperfection||Class A||Class B||Class C||Class D|
|Blister*||3 x .010||5 x .010||5 x .020||**|
|Burr||None||None||10% of mat. Thickness||**|
|Chip*||None||None||1 x .030||**|
|Crater||3 x .010||5 x .010||5 x .020||**|
|Dent||None||None||1 x .030||**|
|Ding||3 x .010||5 x .010||5 x .020||**|
|Grainy Coating/Orange Peel*||Minimal||Light||Moderate||**|
|Gouge||None||None||1 x .030||**|
|Mar||3 x .010||5 x .010||5 x .020||**|
|Pinhole||3 x .010||5 x .010||5 x .020||**|
|Pit||3 x .010||5 x .010||5 x .020||**|
|Scratch||3 x .010x.125||3 x .010x.25||Moderate||**|
|Specks||3 x .010||5 x .010||Moderate||**|
|Forming Stress Marks||Minimal||Light||Moderate||**|