Post Termination Asset Inspection and Tooling Clearance Verification Procedures
Verification of foreign-owned tooling clearance requires hard-stamped Chinese bailment marks, notarized site audits, and structured financial set-offs.
Spi Mold Finish Standards
Meaning
This industrial classification system defines the surface finish requirements and cosmetic appearance of injection molded plastic parts and the corresponding mold surfaces. Under the SPI mold finish standards, established by the Society of the Plastics Industry, finishes are categorized into twelve distinct grades, ranging from high-gloss diamond polishes to rough textured finishes. This standard is used globally and by Chinese mold makers to specify and verify the exact surface quality required for the finished product.
The standards apply to both the mold inserts and the resulting plastic components to ensure consistency across production runs. The classification system stops applying if the surface is treated with secondary processes, such as painting, plating, or chemical etching, which alter the surface texture after the injection molding process is completed.
Classification System
The implementation of spi mold finish standards involves selecting the appropriate grade during the product design and mold specification phases. The grades are divided into four main categories, with the A-series representing high-gloss finishes produced using diamond powder polishing, which are used for cosmetic parts like lenses or high-end enclosures. The B-series consists of semi-gloss finishes produced using ultra-fine sandpaper grit, which are suitable for parts requiring a clean, non-reflective appearance.
The C-series comprises matte finishes created with stone polishing, while the D-series defines textured finishes produced by dry blasting with glass beads or sand. The mold maker must use specialized polishing techniques and materials to achieve the specified finish on the mold steel. The inspector verifies the finish by comparing the mold surface and the molded sample parts to standard reference plaques under controlled lighting conditions.
Technical Boundary
Achieving the specified finish grade is constrained by the selection of mold steel and the geometry of the part. High-gloss finishes in the A-series require high-hardness steel, such as S136 or NAK80, which can be polished to a mirror finish without developing surface defects or pitting. Lower-grade steels or those with high carbon content cannot support high-gloss finishes and are limited to the C or D-series.
Furthermore, the part design must include adequate draft angles to prevent scuffing or drag marks during ejection, especially for textured or high-gloss surfaces. The mold maker must also ensure that the cooling channels are properly designed to maintain a consistent mold temperature, as variations in temperature can affect the replication of the surface finish on the plastic part. These technical limits require close collaboration between the designer and the mold maker.
Supply Chain Impact
Adhering to these surface finish standards reduces the risk of quality disputes and ensures that the finished products meet the aesthetic expectations of the market. When the finish grade is clearly specified in the contract and tooling agreement, the Chinese supplier has a clear baseline to follow, and the buyer has an objective standard to measure against during inspection. This clarity prevents arguments over subjective terms like high quality or smooth finish.
Conversely, failing to specify the finish grade can lead to the production of parts with inconsistent gloss levels, weld lines, or surface defects, resulting in high rejection rates and production delays. The use of these standards provides a reliable framework for quality control and enhances the overall efficiency of the supply chain.