Surface finish

SPI Surface Finish Chart: A1 to D3 Compared

One reference page for SPI A through D grades so buyers stop guessing which letter belongs on a drawing.

Surface finish

Map SPI letters to what the mold must deliver

Category search volume sits on SPI as a system, not on each letter alone.

SPI grades describe what the part should look like after ejection, not a resin property. The mold surface must be prepared to hit that reflection or texture.

When a print calls out A2 on one face and C3 on another, call out parting line constraints and draft before steel is ordered.

Specification

SPI grade on the drawing versus mold scope

Higher gloss grades consume more polish time and tighter process control.

Drawing only lists SPI letter

No parting line or side action note
Texture on one face, polish on another without transition plan

Drawing plus mold finish plan

Each face references SPI or alternate texture standard
DFM notes cover draft and shutoff for glossy areas

SPI grades

SPI surface finish chart (A1 to D3)

Use the chart to align cosmetic targets with mold polish or texture scope. NetProto does not sell finish as a separate SKU; it belongs on the tool and process quote.

Grade	Typical appearance	Tooling approach	Common use
A1	Mirror gloss	Grade A diamond polish	Lenses, high gloss caps
A2	High gloss	Fine diamond polish	Visible housings
A3	Medium gloss	Fine abrasive polish	Consumer electronics
B1	Medium sheen	600 grit paper	Low glare visible parts
B2	Low sheen	400 grit paper	Internal visible surfaces
B3	Matte sheen	320 grit paper	Hidden cosmetic surfaces
C1	Fine texture	600 stone	Low reflectivity faces
C2	Medium texture	400 stone	General purpose matte
C3	Coarse texture	320 stone	Heavy matte, hides flow
D1	Light blast	Dry blast	Utility covers
D2	Medium blast	Dry blast	Non cosmetic internals
D3	Heavy blast	Dry blast	Hidden functional surfaces