What materials do we offer for CNC machining?
What’s the best material for machining your parts? Check out this side-by-side comparison of the strength, price and application for CNC plastics and metals (in a handy, printable poster).
Read articleInjection molding SPI surface finishes
Tables with the standard SPI mold finishes and material recommendations to achieve best results.
SPI Mold Finishes
Learn more about the Injection molding surface finishes, in the main article here.
| Finish | SPI* standard | Finishing Method | Typical surface roughness Ra (μm) |
|---|---|---|---|
| Super High Glossy finish | A-1 | Grade #3, 6000 Grit Diamond Buff | 0.012 to 0.025 |
| High Glossy finish | A-2 | Grade #6, 3000 Grit Diamond Buff | 0.025 to 0.05 |
| Normal Glossy finish | A-3 | Grade #15, 1200 Grit Diamond Buff | 0.05 to 0.10 |
| Fine Semi-glossy finish | B-1 | 600 Grit Paper | 0.05 to 0.10 |
| Medium Semi-glossy finish | B-2 | 400 Grit Paper | 0.10 to 0.15 |
| Normal Semi-glossy finish | B-3 | 320 Grit Paper | 0.28 to 0.32 |
| Fine Matte finish | C-1 | 600 Grit Stone | 0.35 to 0.40 |
| Medium Matte finish | C-2 | 400 Grit Stone | 0.45 to 0.55 |
| Normal Matte finish | C-3 | 320 Grit Stone | 0.63 to 0.70 |
| Satin Textured finish | D-1 | Dry Blast Glass Bead #11 | 0.80 to 1.00 |
| Dull Textured finish | D-2 | Dry Blast #240 Oxide | 1.00 to 2.80 |
| Rough Textured finish | D-3 | Dry Blast #24 Oxide | 3.20 to 18.0 |
| As machined | - | Finished to the machinist's discretion | 3.20 (with visible machining marks) |
* : SPI (Society of Plastic Industry) standards
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Material recommendations
Not every mold finish produces the same results with every material. Use the tables below as guidelines to select the right mold finish/material combination for your application.
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 |
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