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RapidDirect SPI Surface Finish Services
Enhance the quality and aesthetics of your plastic parts with our SPI surface finish services, providing a range of finishes to meet your specific requirements.
What’s SPI Finish?
The SPI finish is an American surface finish standard system set by the (Society of the Plastics Industry) and used to classify the surface texture of plastic injection molds
The SPI finish standard covers 12 SPI grades of polish finishes ranging from a high-gloss, mirror-like finish (A1) to a rough, matte finish (D3). Using the SPI standards, manufacturers can meet the requirements for aesthetic and functional qualities of plastic products.
SPI Surface Finish Chart
| SPI Finish Standard | Finishing Method | Finishing Look | Typical Surface Roughness Ra (μm)) | Steels Recommended |
|---|---|---|---|---|
| SPI A1 | 6000 Grit Diamond | Super High Glossy finish | 0.012 to 0.025 | S136 (54HRC) or 8407(52HRC) |
| SPI A2 | 3000 Grit Diamond | High Glossy finish | 0.012 to 0.025 | S136 (54HRC) or 8407(52HRC) |
| SPI A3 | 1200 Grit Diamond | Normal Glossy finish | 0.05 to 0.10 | S136 (300HB) or 718H |
| SPI B1 | 600 Grit Paper | Fine Semi-glossy finish | 0.05 to 0.10 | 718H |
| SPI B2 | 400 Grit Paper | Medium Semi-glossy finish | 0.10 to 0.15 | 718H |
| SPI B3 | 320 Grit Paper | Normal Semi-glossy finish | 0.28 to 0.32 | 718H |
| SPI C1 | 600 Grit Stone | Fine Matte finish | 0.35 to 0.40 | 718H |
| SPI C2 | 400 Grit Stone | Medium Matte finish | 0.45 to 0.55 | 718H |
| SPI C3 | 320 Grit Stone | Normal Matte finish | 0.63 to 0.70 | 718H |
| SPI D1 | Dry Blast Glass Bead | Satin Textured finish | 0.80 to 1.00 | 718H |
| SPI D2 | Dry Blast | Dull Textured finish | 1.00 to 2.80 | 718H |
| SPI D3 | Dry Blast | Rough Textured finish | 3.20 to 18.0 | 718H |
Plastic Materials for the SPI Surface Finish
SPI surface finishes can be applied to various plastic materials, including ABS, PC, PP, and PS. The choice of plastic and SPI finish depends on the final product’s application, aesthetic requirements, and functional properties. Different plastics respond uniquely to the polishing process, so selecting the appropriate material and finish is essential for achieving the desired result.
Glossy Finish
| Materials | A-1 | A-2 | A-3 |
|---|---|---|---|
| ABS | Average | Average | Good |
| ABS-PC | Average | Average | Good |
| PC | Average | Good | Excellent |
| PMMA | Excellent | Excellent | Excellent |
| PP | Not Recommended | Average | Average |
| HDPE | Not Recommended | Average | Average |
| LDPE | Not Recommended | Average | Average |
| HIPS | Average | Average | Good |
| PBT | Average | Average | Good |
| TPE | Not recommended | Not recommended | Not recommended |
| PA+GF30 | Average | Average | Good |
Semi-Glossy Finish
| Materials | A-1 | A-2 | A-3 |
|---|---|---|---|
| ABS | Good | Good | Excellent |
| ABS-PC | Good | Good | Excellent |
| PC | Good | Good | Average |
| PMMA | Good | Good | Good |
| PP | Good | Good | Excellent |
| HDPE | Good | Good | Excellent |
| LDPE | Good | Good | Excellent |
| HIPS | Excellent | Excellent | Excellent |
| PBT | Good | Excellent | Excellent |
| TPE | Not recommended | Average | Average |
| PA+GF30 | Good | Excellent | Excellent |
Matte Finish
| Materials | A-1 | A-2 | A-3 |
|---|---|---|---|
| ABS | Excellent | Excellent | Excellent |
| ABS-PC | Excellent | Excellent | Excellent |
| PC | Average | Not Recommended | Not recommended |
| PMMA | Good | Good | Good |
| PP | Excellent | Excellent | Excellent |
| HDPE | Excellent | Excellent | Excellent |
| LDPE | Excellent | Excellent | Excellent |
| HIPS | Excellent | Excellent | Excellent |
| PBT | Excellent | Excellent | Excellent |
| TPE | Good | Good | Good |
| PA+GF30 | Excellent | Excellent | Excellent |
Textured Finish
| Materials | A-1 | A-2 | A-3 |
|---|---|---|---|
| ABS | Excellent | Excellent | Good |
| ABS-PC | Excellent | Excellent | Good |
| PC | Excellent | Not Recommended | Not recommended |
| PMMA | Average | Average | Average |
| PP | Excellent | Excellent | Excellent |
| HDPE | Excellent | Excellent | Excellent |
| LDPE | Excellent | Excellent | Excellent |
| HIPS | Excellent | Excellent | Good |
| PBT | Excellent | Excellent | Good |
| TPE | Excellent | Excellent | Good |
| PA+GF30 | Excellent | Excellent | Good |
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FAQs
The VDI 3400 Standard is a German guideline that specifies a series of surface textures for plastic mold tools. It provides a classification system for surface finishes, similar to the SPI (Society of the Plastics Industry) finish standards commonly used in the United States.
The VDI 3400 Standard categorizes surface textures based on numerical codes and descriptions, allowing for consistent communication and specification of desired surface finishes in plastic molding applications. By adhering to this standard, manufacturers can achieve the desired aesthetic and functional properties in molded plastic parts, ensuring consistency and quality across production processes.
To judge the surface quality of a mold, use optical interference technology to assess if the surface has accurate geometry and the absence of long wavy undulating patterns, which can indicate surface imperfections. After mirror treatment, visually inspect the surface for scratches, holes, or other defects that could affect the appearance and quality of the final part. Ensure the surface is smooth and uniform, without blemishes or irregularities, to produce high-quality molded parts.
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