SPI Guidelines – Mold Polish

SPI standards are determined by the Society of the Plastics Industry for the plastic industry. Texas Injection Molding uses these SPI mold polish standards to specify mold polish finishes for multiple applications, guides, and finishes.

The below specifications provide guidelines for SPI mold surface finishes as provided by the Society of the Plastic Industry.  For more information visit Society of Plastic Industry.

SPI Standards

Guide

Typical Finishes

Typical Surface Roughness

A-1 Grade #3   Diamond Lens /   Mirror – requires 420 SS material 0.012 to 0.025
A-2 Grade #6   Diamond High   Polish parts 0.025 to 0.05
A-3 Grade #15   Diamond High   Polish parts 0.05 to 0.10
B-1 600 Grit   paper Medium   Polish parts 0.05 to 0.10
B-2 400 Grit   paper Medium   Polish 0.10 to 0.15
B-3 320 Grit   paper Med – Low   polish 0.28 to 0.32
C-1 600 Stone Low Polish   parts 0.35 to 0.40
C-2 400 Stone Low Polish   parts 0.45 to 0.55
C-3 320 Stone Low Polish   parts 0.63 to 0.70
D-1 Dry Blast   Glass Bead Satin   finish 0.80 to 1.00
D-2 Dry Blast   # 240 Oxide Dull   Finish 1.00 to 2.80
D-3 Dry Blast   # 24 Oxide Dull   finish 3.20 to 18.0


Glossy Finish

 Material

A-1

A-2

A-3

ABS Average Average Good
Polypropylene (PP) Not Recommended Average Average
Polystyrene (PS) Average Average Good
HDPE Not Recommended Average Average
Nylon Average Average Good
Polycarbonate (PC) Average Good Excellent
Polyurethane (TPU) Not Recommended Not Recommended Not Recommended
Acrylic Excellent Excellent Excellent


Semi-Glossy Finish

 Material

B-1

B-2

B-3

ABS Good Good Excellent
Polypropylene (PP) Good Good Excellent
Polystyrene (PS) Excellent Excellent Excellent
HDPE Good Good Excellent
Nylon Good Excellent Excellent
Polycarbonate (PC) Good Good Average
Polyurethane (TPU) Not Recommended Average Average
Acrylic Good Good Good


Matte Finish

 Material

C-1

C-2

C-3

ABS Excellent Excellent Excellent
Polypropylene (PP) Excellent Excellent Excellent
Polystyrene (PS) Excellent Excellent Excellent
HDPE Excellent Excellent Excellent
Nylon Excellent Excellent Excellent
Polycarbonate (PC) Average Not Recommended Not Recommended
Polyurethane (TPU) Good Good Good
Acrylic Good Good Good


Textured Finish

 Material

D-1

D-2

D-3

ABS Excellent Excellent Good
Polypropylene (PP) Excellent Excellent Excellent
Polystyrene (PS) Excellent Excellent Good
HDPE Excellent Excellent Excellent
Nylon Excellent Excellent Good
Polycarbonate (PC) Excellent Not Recommended Not Recommended
Polyurethane (TPU) Excellent Excellent Good
Acrylic Average Average Average