First Shot Samples Polished before the Buyer Ever Sees Them
Doctored T1 samples hide draft and thermal flaws through hand polishing; enforce raw steel T0 audits with continuous cavity telemetry before sign-off.
SPI Surface Finish Standards
Meaning
Classification systems define the visual and tactile texture of a molded plastic part by specifying the methods used to finish the mold surface. Using spi surface finish standards allows designers and molders to communicate clearly about the appearance of the product and the cost of the tooling. The standards range from high-gloss diamond polishes to rough stony textures created by sandblasting.
Finish Classification
Standards are divided into four main groups, each with three sub-levels of increasing coarseness. Group A finishes are produced using diamond polishing and result in a mirror-like surface that is required for optical parts or high-end consumer goods. Group B finishes use grit paper, Group C use stones, and Group D use dry blasting with materials like glass beads or sand.
Manufacturing Impact
Type of finish selected for a part directly affects the cost of the mold and the ease of production. High-polish finishes require many hours of manual labor and are easily damaged by the abrasive fillers found in some resins. Additionally, very smooth surfaces can sometimes cause parts to stick in the mold, requiring higher ejection forces or the use of mold release agents.
Visual Boundary
Utility of the standard is limited by the fact that the same finish will look different on different types of plastic. A matte finish on a dark resin may look much rougher than the same finish on a light-colored resin. Designers often use physical plaques that show the standard finishes on the specific material being used to ensure that the final product meets their aesthetic expectations and functional requirements before full production begins.