injection molding surface finish

Table of Contents

Surface finishes play a crucial role in the plastic injection molding process, impacting the appearance, functionality, and overall quality of the final product. In this article, we will explore different surface finishes used in plastic injection molding.

plastic injection molding surface finish

PolishedTexturedMachining SurfaceSecondary Finishes
High Gloss PolishMold Tech MT-XXXXEDM SurfacePainting
Technical PolishVDI VDI3400CHXXMilling SurfaceChrome Plating

Factors consideration for selecting the injection molded part surface finish

1, Plastic parts design. Wall thickness, draft angles, gate location, the design of ribs, bosses, and surface features affect the molded part surface finish.

2, Plastic material selection. Different materials have their own properties, like flow, shrinkage, and surface appearance. These properties affect the surface quality, texture, and overall look of the molded parts. We can not get the high gloss finishes on the material with lots of glass beads or fibers.

3, Mold steel selection: Mold steel has many properties that affect the surface finish of injection molded parts. These properties include hardness, polishing capability, corrosion resistance, machinability, and thermal conductivity.

4, Mold Design. Proper mold design can help minimize surface defects like sink marks, weld lines, and flow marks.

5, Mold Surface Finish. The surface finish of the mold cavity directly affects the surface finish of the molded part. A mold surface that is smooth and polished will create a glossy finish on the part. A texture mold surface will result in a matte or textured look.

6, Molding processing parameters. Factors such as injection pressure, injection speed, melt temperature, and mold temperature can impact the surface finish of the part. Optimizing these parameters can help achieve the desired surface finish while minimizing defects.

7, Secondary Finishes. In some cases, additional post-molding processes may be required to achieve the desired surface finish. These processes include painting, chrome plating, or metallization.

injection mold surface textures types

  • Glossy finish: This type of texture provides a shiny, reflective surface on the molded part. It’s commonly used for cosmetic parts, electronics housings, or automotive trim components.
  • Matte finish: A matte finish provides a non-reflective surface, which can help reduce glare and fingerprints. It’s often used in consumer electronics, automotive interiors, and other applications where a subtle appearance is desired.
  • Grain textures: These textures resemble natural materials like wood, leather, or stone. They can add a unique and aesthetically pleasing appearance to molded parts.
  • Geometric patterns: This category includes textures with repeating shapes or patterns, such as diamond or checkered patterns, which can be used for grip enhancement or visual appeal.
  • Custom textures: Companies can develop their own custom textures, logos, or designs to differentiate their products and create a unique brand identity.

Texture application methods

  • Chemical etching: This process involves applying an acid-resistant mask to the mold surface, exposing the desired texture pattern, and then using an acid bath to etch the texture into the mold. It’s suitable for fine to medium textures.
  • Laser engraving: This method uses a high-powered laser to etch the texture directly into the mold surface. It provides precise control over the texture pattern and depth, making it suitable for complex or custom textures.
  • Electrical discharge machining (EDM): EDM uses electrical discharges to create the texture pattern on the mold surface. It’s a useful method for creating very fine textures or for working with hard or conductive materials.
  • Machining Surface: This process uses cutting tools, such as CNC milling machines, to carve the texture into the mold surface. It’s often used for larger or coarser textures, as well as for adding logos or other custom features.

VDI3400 Draft Angel

VDI3400RaRzDraft Angel for PADraft Angel for PCDraft Angel for ABS

Mold tech Texture Draft Angel AB

MT - XXXXDepth (Meter)Draft AngelMT - XXXXDepth (Meter)Draft Angel

Mold tech Texture Draft Angel CD

MT - XXXXDepth (Meter)Draft AngelMT - XXXXDepth (Meter)Draft Angel

injection mold surface texture standards

There are several texture standards available, but the three most widely used are:

  • Mold-Tech (MT) Series. It has many textures, ranging from fine to coarse, and offers options for various applications. For example, MT-1100, 1100 represent the texture number.
  • VDI (Verein Deutscher Ingenieure) 3400. The VDI 3400 textures are classified into 6 main groups: VDI-0 (without texture), VDI-9 (gloss), VDI-18 (matte), VDI-27 (fine texture), VDI-36 (medium texture), and VDI-45 (coarse texture).
  • YS (Yick Sang) Series. It provides a range of textures suitable for various applications, such as high-gloss, fine, medium, and coarse textures. The textures are represented as “YS-XXXX”, with “XXXX” being the texture number.

SPI surface finish

The SPI (Society of the Plastics Industry) Injection Mold Surface Finishes is a widely recognized classification system used in the plastics industry to define the surface finishes for injection molded parts. The SPI standard classifies finishes into various grades based on the level of polishing or texturing applied to the mold surface.

SPI FinishManufacturing MethodSurface Roughness RaTypical Application
A1Grade #3 Diamond0.012-0.025Mirror Polish
A2Grade #6 Diamond0.025-0.05High Gloss Polish
A3Grade #15 Diamond0.05-0.1High Gloss Polish
B1600 Grit Paper0.05-0.1Fine Semi Glossy Finish
B2400 Grit Paper0.1-0.15Medium Semi Glossy Finish
B3320 Grit Paper0.28-0.32Normal Semi Glossy Finish
C1600 Grit Stone0.35-0.4Fine Matte Finish
C2400 Grit Stone0.45-0.55Medium Matte Finish
C3320 Grit Stone0.63-0.70Normal Matt Finish
D1 #11 Glass Bead0.8-1.0Satin Textured Finish
D2#240 Aluminum Oxide Blast1.0-2.8Dry Textured Finish
D3#24 Aluminum Oxide Blast3.2-18Rough Texture Surface

Selecting the right surface finish for your plastic injection molding project is essential for optimizing aesthetics, functionality, and product performance. By understanding the different types of finishes available and considering factors such as part design, material, function, and aesthetics, you can choose the best surface finish to meet your project requirements and ensure a successful outcome.