Injection Moulding Surface Finish
Most tool shops have a range of predefined finishes for the tools. SPI is a standard, ranging from Polished (SDI A-1) to rough (SPI D-3). Generally the part will reflect the tool, however for high polish other factors such as resin choice and mould design are also important.
SPI (Society of Plastic Industry) standards
Injection Moulding Surface Finishing Service
Finish
SPI Standard
Finishing Method
Surface Roughness Ra (μm)
Non-Cosmetic
–
Manufacturers Discretion
–
Low-Cosmetic
–
Most Toolmarks Removed
3.20 (visible machining marks)
Light Bead Blast
–
–
1.00 to 2.80
Medium Bead Blast
–
–
0.80 to 1.00
Fine Matte Finish
C-1
600 Grit Stone
0.35 to 0.40
Fine Semi-glossy finish
B-1
600 Grit Paper
0.05 to 0.10
Super High Glossy finish
A-1
6000 Grit Diamond Buff
0.012 to 0.025
SPI Standard Guide
SPI Standard Guide
Finish
SPI Standard
Finishing Method
Surface Roughness Ra (μm)
As machined
–
–
3.20 (visible machining marks)
Super High Glossy finish
A-1
6000 Grit Diamond
0.012 to 0.025
High Glossy finish
A-2
3000 Grit Diamond
0.025 to 0.05
Normal Glossy finish
A-3
1200 Grit Diamond
0.05 to 0.10
Fine Semi-glossy finish
B-1
600 Grit Paper
0.05 to 0.10
Medium Semi-glossy finish
B-2
400 Grit Paper
0.10 to 0.15
Normal Semi-glossy finish
B-3
320 Grit Paper
0.28 to 0.32
Fine Matte finish
C-1
600 Grit Stone
0.35 to 0.40
Medium Matte finish
C-2
400 Grit Stone
0.45 to 0.55
Normal Matte finish
C-3
320 Grit Stone
0.63 to 0.70
Satin Textured finish
D-1
Dry Blast Glass Bead
0.80 to 1.00
Dull Textured finish
D-2
Dry Blast
1.00 to 2.80
Rough Textured finish
D-3
Dry Blast
3.20 to 18.0
SPI (Society of Plastic Industry) standards
If the surface finish you require is not listed, please speak to one of our design engineers using Live Chat or email [email protected]
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