Plastic Finishes: Plastic Injection Molding Surface Finish

custom plastic parts, product development

Plastic finishes play an important role in manufacturing industry. The success of a product is heavily influenced by its aesthetics and tactile qualities in the field of product design. Plastics’ surface treatments have the potential to make or break a product’s appeal. They are a crucial component of the design process and have the power to elevate an ordinary product to a sign of more value.

In the design process, choosing the best plastic surface finish is a crucial choice. It can improve a product’s aesthetic and tactile qualities, enhancing its allure and attraction to customers. Our team of professionals at Sungplastic can help you select the optimal plastic surface treatment that precisely complements the goals and vision of your product.
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plastic finishes

What are Plastic Finishes?

Plastic finishes, also known as surface finishes or surface treatments, refer to a variety of processes and techniques applied to the surface of plastic parts or products to enhance their appearance, texture, and functional properties. These finishes are used to improve the aesthetics, durability, and overall quality of plastic parts. Plastic finishes can vary widely in their purpose and application, and they include:


  • Texture and Appearance Enhancement
    Plastic finishes can alter the visual appearance and tactile feel of plastic parts. They can create glossy, matte, textured, or patterned surfaces, depending on the desired effect.
  • Protection
    Some plastic finishes provide a protective layer that shields plastic parts from environmental factors like UV radiation, moisture, chemicals, and abrasion, thereby extending their lifespan.
  • Coloring
    Plastic finishes can be used to apply colors or patterns to plastic parts. This is particularly common in industries like automotive and consumer goods.
  • Functional Coatings
    In some cases, plastic finishes serve a functional purpose. For instance, anti-slip coatings may be applied to improve grip on plastic handles or surfaces.
  • Smoothness
    Plastic finishes can be used to create a smooth and polished surface on plastic parts, reducing friction and enhancing the overall feel.
  • Customization
    Plastic finishes allow for customization by incorporating branding, logos, or unique designs onto plastic products.

Why the Quality of Plastic Finishes Matters?

When it comes to the success of a product, design is undeniably paramount. However, it’s not just about how a product looks; perhaps even more crucial is how it feels in the hands of its users. Even a product with exceptional design can falter in the market if it lacks a pleasing tactile experience.

The exterior appeal, the surface’s quality appearance, and the tactile satisfaction it offers are pivotal factors that can tip the scales in favor of your product over a competitor’s. They influence the customers’ choice and their perception of product value.

Beyond aesthetics and feel, plastic surface finish serves a practical purpose. It can effectively conceal many of the tooling marks and imperfections left behind during the injection molding process. Elements like flow lines, weld lines, sink marks, and shadow marks become less conspicuous with the right surface finish or texture. Furthermore, a thoughtfully chosen surface finish can significantly enhance subsequent processes such as painting, as it improves paint adhesion. In essence, a part with a subtle surface texture is more receptive to and capable of retaining paint compared to a part with a perfectly smooth surface.

Crucially, plastic surface finish plays a pivotal role in enhancing the functionality of a part. Textured finishes, for instance, improve grip and ensure that the item feels right when held by the customer. The selection of the appropriate surface texture is an integral part of perfecting the overall product.

Types of Plastic Finishes

Common types of plastic finishes include painting, coating, polishing, texturing, anodizing, electroplating, printing, and more. The choice of finish depends on the specific requirements of the product and the desired aesthetics and functionality.
Plastic surface finishes can be achieved through two distinct methods, each offering its own advantages:

  • In-Mold Texture
    This method involves tooling the desired texture directly into the mold. It offers several advantages, including ensuring uniformity across all produced pieces, which can be essential for consistency in product quality. In-mold texture also reduces costs by eliminating the need for additional post-processing steps.
  • Post-Processing Applications
    Alternatively, achieving the desired plastic surface finish can be accomplished through post-processing techniques. These methods involve treatments applied after the molding process. Common post-processing applications include sanding, bead blasting, or etching. They are particularly useful when specific areas of the part require texturing or when a unique finish is desired.

In practice, a combination of in-mold texture and post-processing applications is often employed to attain the desired plastic surface finish. In-mold texture ensures overall uniformity, while post-processing steps can be used selectively to address specific areas or create diverse textures and finishes on a single part. This approach offers flexibility and allows manufacturers to achieve a wide range of surface finishes to meet their design and functional requirements.

Plastic Finishes vs. Texture

The final texture and appearance of a plastic part are determined by a combination of factors, including mold tooling, the inherent properties of the injected plastic material, and any subsequent post-processing steps. It’s essential to differentiate between texture, which pertains to the pattern within the plastic itself, and finish, which encompasses the overall visual and tactile qualities of the plastic surface.

Plastic surface finishes can generally be categorized into four primary types:

  • Dull Finish
    This finish is characterized by a rough and unpolished texture with minimal shine. Dull finishes are typically employed for internal parts, as they prioritize functionality over aesthetics. They are also well-suited for applications where paint adhesion is crucial.
  • Matte Finish
    Matte finishes exhibit a smoother texture compared to dull finishes and offer a modest level of shine. While they are often used for internal parts, they can also be employed externally if a subdued appearance is desired. Like dull finishes, matte surfaces are conducive to paint application.
  • Semi-Gloss Finish
    Semi-gloss finishes present a smooth and noticeably shiny appearance. They strike a balance between aesthetics and functionality, making them suitable for both external parts and internal components that require a sleek, friction-resistant surface.
  • Glossy Finish
    Glossy finishes are characterized by their exceptionally smooth and highly reflective surfaces. Depending on the plastic material used, they can even achieve a mirror-like appearance. Glossy finishes are primarily employed for external parts where an attractive, polished look is desired to enhance product aesthetics.

The choice of plastic surface finish involves a careful consideration of factors such as the intended use of the part, desired visual appeal, and functional requirements, to achieve the desired surface characteristics for their plastic products.

Classification of Injection Molding Plastic Finishes

Various organizations and companies have established their own grading scales for plastic surface finishes. In the United States, the Society of Plastics Industry (SPI) and in Europe, the Society of German Engineers (VDI) have widely recognized grading scales. For Sungplastic, the Yick Sang Standard is the benchmark for plastic surface finish classification. Yick Sang is the Chinese equivalent of renowned standards like Mold-Tech or VDI. Regardless of the specific grading scale used, they all share a common objective: to categorize plastic finishes based on their appearance and texture, ranging from highly smooth and reflective to more subdued and rough.

At Sungplastic, our team of experts can assist you in identifying the most suitable plastic surface finish for your product. Below, you’ll find our standard surface finish chart, offering a glimpse into our common surface finish classifications. Additionally, we are well-equipped to accommodate custom surface finishes tailored to your unique requirements.

Standard No Machine Mark: Tool marks are meticulously removed, resulting in a low-cosmetic surface.
SPI-C1: Achieved with a 600-stone finish, this is suitable for low-polish parts.
SPI-B1: Features a 600-grit paper finish, ideal for medium-polish parts.
SPI-A2: Boasting a Grade #6 Diamond finish, this is reserved for high-polish parts.
SPI-A1: With a Grade #3 finish, this level is akin to achieving a lens or mirror-like surface.
IM-1 Light Bead Blast: Requires a 1-degree draft angle and imparts a distinctive texture.
IM-2 Medium Bead Blast: A 1.5-degree draft angle is necessary, resulting in a medium bead-blasted texture.
IM-3 Heavy Bead Blast: This level calls for a 3-degree draft angle, producing a heavily textured surface.

These classifications offer a range of options to cater to various aesthetic and functional needs, ensuring your plastic products meet your precise specifications.

Custom Plastic Surface Finishes

At Sungplastic, we rely on high-quality steel molds for our plastic injection molding processes. These steel molds afford us the capability to directly integrate custom textures into the mold itself. In contrast, aluminum molds do not provide the same level of flexibility for customization. Indeed, when it comes to surface finish options, steel molds outshine aluminum molds, offering a broader spectrum of possibilities.

Steel molds, with their exceptional versatility, can be meticulously polished to achieve a remarkably smooth surface finish. This polished finish enhances the final product’s sleekness and aesthetic appeal.

Furthermore, steel molds open up a world of possibilities for custom surface finishes, including but not limited to:

Bead Blast: Adding a unique texture.
Etching: Creating intricate patterns or designs.
Matte Finish: Achieving a subdued, non-reflective appearance.
Leather Grains: Mimicking the texture of leather for a distinctive feel.
Geometric Patterns: Incorporating precise geometric shapes.
Graphics: Integrating graphics or logos onto the surface.

With steel molds, we empower you with a wide array of surface finish options, allowing you to craft plastic products that align perfectly with your vision and requirements.

Sungplastic’s Plastic Finishes Services

Our services include:
Plastic parts surface finishes and Metal parts surface finishes
Such as:
Teflon Coating
Powder Coating
Spray Painting
Color Matching
Pad and Silk Screen Printing
Grinding and Polishing
Sandblasted and Brushed

As a plastic injection molding manufacturer, Sungplastic has ample experience of plastic finishes.
If you need plastic finishes services, please contact us.

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