SPI Standard Description Finishing method Surface roughness Ra (μm)

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C-2 Matte Finish - Medium 400 grit stone 0.45 to 0.55
C-3 Matte finish - coarse 320 grain stone 0.63 to 0.70
Textured Class D
The roughest surfaces are typically surfaces with a sand texture for products that need to have a certain visual impact and tactile feel. Fine stone powder is used to smooth these rough finishe forex datasets before they are randomly dry-blasted with glass beads or aluminum oxide, producing a smooth, non-directional surface finish. These textured surface treatments are applied to thermoset industrial components and are suitable for items such as consumer product handles that have a satin or dull textured finish that improves grip. For this purpose, it is widely used in consumer products, industrial parts, and automotive components.

D-1 Light texture Dry Glass Bead #11 0.80 to 1.00
D-2 Medium texture Dry sandblasting #240 Oxide 1.00 to 2.80
D-3 Heavy texture Dry sandblasting #24 Oxide 3.20 to 18.0
SPI places more emphasis on the level of polishing than on the patterns. The result of SPI mold finishes varies depending on the type of material used in the injection molded components. This has a significant impact on the degree of SPI achievable. Designing parts with sharp corners, complex geometries, and stainless steel parts is an important factor. undercuts helps manufacturers choose the appropriate surface treatments based on product needs. Parameters involved in the molding process, such as cooling rate, injection temperature, and pressure, impact the surface smoothness.

VDI Injection Molding Surface Finish Texture, Advantages and Applications.
VDI 3400 or Reference VDI 3400 the standard set by ( Verein Deutscher Ingenieure ), the society of German engineers. The standard contains 45 texture gradations. Initially, electrical discharge machining (EDM) is used to process the 3400 textures for creating plastic molds. That is why they are sometimes referred to as EDM textures. The changes in electrical adjustment gave the roughness of the EDM process. Given the extent of the texturing areas, the surface quality of the texture in this case could not be as uniform or hard as expected. Recently, mold producers have resorted to chemical etching to obtain VDI 3400 textures after polishing the molds to obtain uniform texture surfaces. However, traditional texturing methods such as grit, stone and sandpaper can also be used to achieve this texture.


VDI 3400 is a more economical and efficient method for large components and large texture areas, such as vacuum cleaners, calculators and other similar items.