How to define the surface finish for injection molded parts
Some companies have troubles to define what their product surface should be, or how to describe precisely what exactly they want to the injection mold supplier, mostly they will just say matt or polish, actually this is not clear enough to define the product surface, there are many standards for the polish or matt, and some unique patterns we call it texture.
Here is an overview of SPI-SPE standard for polishing surface
| SPI | Description |
Ra in µm (DIN) |
Definition |
| A-1 |
Diamond buff grade 3 |
0 – 0.025 |
For mirror or optical finishes. Most time consuming. Steel grade important to results |
| A-2 |
Diamond buff grade 6 |
0.025 – 0.05 |
|
| A-3 |
Diamond buff grade 15 |
0.05 – 0.076 |
|
| B-1 |
600 grit paper |
0.05 – 0.076 |
Removes all tool and machining marks. Provides good mold release. Light reflecting finish on molded part, some sheen. |
| B-2 |
400 grit paper |
0.10 – 0.127 |
|
| B-3 |
320 grit paper |
0.23 – 0.25 |
|
| C-1 |
600 stone |
0.25 – 0.30 |
Remove all tool and machining marks. Provides good mold release. Mute finish on molded part, no sheen. |
| C-2 |
400 stone |
0.64 – 0.71 |
|
| C-3 |
320 stone |
0.97 – 1.07 |
|
| D-1 |
Dry blast glass bead 11, 200 distance at 0.7 Mpa; 5 sec |
0.25 – 0.30 |
For decorative finishes. Often used for die-cast and thermoset cooling. Helps hide shrink marks and other imperfections. Dull, non reflecting finish on molded or cast part. |
| D-2 |
Dry blast 240 oxyde, 125 distance at 0.7 Mpa; 5 sec |
0.66 – 0.81 |
|
| D-3 |
Dry blast 240 oxyde, 150 distance at 0.7 Mpa; 5 sec |
4.83 – 5.84 |
Here is VDI standard for matt surface, Matt surface is created by erosion process, it is a light and even textured surface.
It can be also unique patterns, there are many standards, mostly popular and widely recognized are MOLD-TECH and YS
Knowing these standards, you are able to communicate professionally with your injection mold supplier, like ACO Mold.
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