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Surface Finish 101: An Overview of Plastic Surface Finish Chart

A process that involves the use of a machine to impose characteristic irregularities on the surface of its product. Constant use tends to cause the product to wear down over time. This is usually due to the high friction that builds up between the surface of the product and the surface it is being used on. If you want to know why surface finish is important to your product, this guide is for you. Read on for a complete understanding of surface preparation.


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Plastic Surface Finish: What is it and why is it so important?

The plastic surface finishes chart provides information on different finishes that can be applied to plastic parts. These finishes can enhance the appearance, improve the surface feel, or provide additional functional properties to the plastic parts. The surface roughness chart typically includes details such as the name of the finish, the roughness measurement in microns, and the recommended applications for each finish.

Plastic Surface Finish Chart

The plastic surface roughness chart guides the various finishes applied to plastic parts. The chart lists the name of the finish, the roughness (in microns), and the finishing method and SPI standard.


1. Smooth or Polished Finish – Grade A

This is the highest level of glossiness and provides a shiny and reflective surface. It is often referred to as a diamond finish due to its high level of clarity. It will not have a clear texture and will scatter light rays due to the fine-grain buffing paste and random directional rotary polishing procedure, resulting in a very glossy finish. Ra surface finish chart for Grade A as below.


Finish

SPI standard

Finishing Method

Typical surface

roughness Ra (μm)

Maximum gloss finish

A-1

Grade #3, 6000 Grit Diamond Buff

0.012 to 0.025

Standard gloss-finish

A-2

Grade #6, 3000 Grit Diamond Buff

0.025 to 0.05

Low gloss-finish

A-3

Grade #15, 1200 Grit Diamond Buff

0.05 to 0.10


2. Semi-gloss Finish - Grade B

This finish has a moderate level of glossiness, providing a slightly lower level of shine compared to a gloss finish. It is less reflective but still offers a smooth and polished appearance. Ra finish chart for Grade B as below.


Finish

SPI standard

Finishing Method

Typical surface

roughness Ra (μm)

Excellent 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


3. Matte Finish - Grade C

This finish has a low level of glossiness and appears dull or flat. It does not reflect much light and offers a non-shiny, velvety appearance. Matte finishes are often chosen for their ability to hide imperfections. Ra surface finish chart for Grade C as below.


Finish

SPI standard

Finishing Method

Typical surface

roughness Ra (μm)

Fine Matte finish

C-1

600 Gritstones

0.35 to 0.40

Medium Matte finish

C-2

400 Gritstones

0.45 to 0.55

Normal Matte finish

C-3

320 Gritstones

0.63 to 0.70


4. Textured Finish - Grade D

This finish involves adding a textured pattern or design to the surface of the plastic. It can vary in roughness and adds a tactile element to the appearance. Textured finishes can include patterns such as grains, bumps, or grooves. Ra finish chart for Grade D as below.


Finish

SPI standard

Finishing Method

Typical surface

roughness Ra (μm)

Satin Textured finish

D-1

Dry Blast Glass Bead

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


The Importance of Plastic Surface Finish Chart

There are different surface finishes for plastic. The plastic Surface Finish Chart helps us in the following ways and more:


  • The plastic Surface Finish Chart ensures clear and accurate communication between different parties involved in the manufacturing process. It helps avoid confusion and misinterpretation when discussing surface finish requirements. It also helps ensure consistency and reproducibility in the quality of plastic parts across different production runs or suppliers.

  • The specified surface finish chart has a clear standard of surface roughness and other information. It can help us understand different plastic surface finishes, which can achieve the desired aesthetic and functional qualities for the plastic parts being produced.

Plastic Surface Finish: Surface Finish Conversion Chart

The base material of a plastic part can affect the choice of injection molding surface finish. Different plastics have different properties, such as hardness, shrinkage, and thermal expansion, that can influence the quality and appearance of the surface finish.

Base Material in Plastic Surface Finish

Here are some properties of the base materials as below:

  • Acrylic

Acrylic is a transparent and rigid plastic that can be polished to a high gloss.


  • Nylon

Nylon is a tough and flexible plastic that can resist abrasion and impact.


  • Polyester

Polyester is a strong and durable plastic that can withstand high temperatures and chemicals.


  • Polyethylene

Polyethylene is a soft and flexible plastic that can be easily molded and recycled.


  • Polypropylene

Polypropylene is a lightweight and versatile plastic that can be molded into various shapes and colors.


  • Polyurethane

Polyurethane is a flexible and elastic plastic that can be molded into various forms and textures.


  • PVC

PVC is a rigid and durable plastic that can be used for various applications and environments.

Surface Finish Conversion Chart for Plastic

The following table shows the surface finish conversion chart of plastic.

Rating

SPI Finish

1-Good
2-Average
3-Not suggested
X-N/A

A-1

A-2

A-3

B-1

B-2

B-3

C-1

C-2

C-3

D-1

D-2

D-3

Plastic


Acrylic

1

1

1

2

2

2

2

2

2

3

3

3

Nylon

3

3

2

2

1

1

1

1

1

1

1

1

Polyester

3

3

2

1

2

2

1

2

X

1

1

1

Polyethylene

X

3

3

2

2

1

1

1

1

1

1

1

Polypropylene

X

3

3

2

2

1

1

1

1

1

1

1

Polyurethane

X

X

X

X

3

3

2

2

2

1

1

1

PVC

X

X

X

X

3

3

2

2

2

1

1

1

Bonus >> Richconn Offers Outstanding Surface Finish Services!

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At Richconn, we offer the best CNC surface finish services. Coupled with an experienced team of experts, we believe that our customers can receive their plastic machined parts promptly and have confidence in the quality of the products.


  • Fast and Simple Online Quoting

Richconn offers fast and simple online quoting. Our customers can easily obtain quotes for their machining projects without the need for complex processes.


  • Reliable Delivery

Moreover, Richconn ensures reliable delivery of the machined parts to customers. Our customers can expect their orders to be shipped promptly and arrive in a timely manner. This reliability in delivery helps customers plan their production schedules and meet their project deadlines effectively.


  • Strict Production Process

Throughout Richconn’s machining process, rigorous quality control measures are implemented to ensure accuracy and consistency. Any deviations from the specified requirements are identified and addressed promptly.

Conclusion

The plastic surface finish chart shows clear information on different surface finishes. As we know, selecting the proper injection molding surface finish for your plastic product has several advantages. However, you need to do so as early as possible in your design process. This is because a surface finish will impact your tooling process and other decisions. Therefore, it would help to work with a plastic injection moulding expert to help you understand the chart and ensure you make the right choice. Contact the experts at Richconn today!


Contact the experts at Richconn today! We offer a variety of surface finishes, including blackening surface treatment, electrophoresis finish, and diverse CNC machining surface finishes to meet your specific needs. Additionally, if you're seeking cost-effective material options, explore their selection of cheap CNC materials. For those needing specialized plastic machining services, Richconn is also a CNC plastic machining factory ready to assist with your project.

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