The gloss of a part is an important factor in the visual appearance and perception of the quality of a part. It also affects the look of the texture, especially on fine matte finishes. If the gloss of the part is dull, the texture may appear less deep, and if the part is glossy, the texture may appear deeper than it really is.
A number of factors impact gloss, and the gloss on the mold itself may not translate onto the part for a number of reasons. We¡¯ve assembled the information found below over the years and through testing, and are supplying it here to help guide you in assessing what can or cannot be adjusted to alter the gloss of your part.
DETERMINING FACTORS FOR GLOSS ON A PART
1. Type of plastic being processed.DETERMINING FACTORS FOR MOLD SURFACE GLOSS
2. Cavity temperature.
3. Core temperature.
4. Material temperature.
5. Material composition.
6. Pack pressure (hard pack) - this is a major factor.
7. Material color.
8. Texture type - leather versus matte.
9. Cycle time.
10. Material thickness.
11. Transfer point from high to low pressure.
12. Clamp pressure.
14. Material weldments and knit lines.
15. Venting (and lack of it).
16. Part design.
1. Mold material (type of metal).
2. Mold hardness.
3. Blast media (glass bead, aluminum oxide, size of blast media).
4. Pre-gloss mold finish (polish, texture matte, etc.)
5. Mold finish pre-etching.
6. Welded areas.
7. Porosity in the steel.
8. Cutter marks, cutter burns, EDM scale.
9. Steel streaks or segregation lines.
Although only a small portion of the factors that affect gloss are within our control, we need as much information as possible from you regarding the gloss you want to achieve. OEM¡¯s often supply a gloss number related to a 60 degree gloss meter. If we know the type of plastic being shot, we can usually supply a gloss on the surface of the tool that will approximate their gloss specification.
If you mold a part and the gloss is not exactly what you want, it is possible to adjust the gloss. The data provided above indicates that the molding parameters chosen have a lot more impact on the gloss than most aspects of the texturing process do.