Injection Molding Surface Finishes
In order to increase the appeal of a part, as well as improve its functionality and competitiveness, injection molding parts may require some surface finishing, which is usually accomplished by treating the mold surface.
Our standard mold finishes include the following:
  • SPI
  • VDI 3400
  • Mold-Tech
  • Bead Blasting
Types of Injection Molding Surface Finishes
SPI Finishes
The SPl is that Society of the Plastics Industry sets standard for plastics industry in the United States that identifies the surface finish of plastic parts.
SPl specifies twelve grades of finishes divided into four categories, from mirror to matte. Each grade specifies production requirements, with the rougher the surface, the larger the number, and the smoother the surface, the smaller the number.

With grade #3, 6000 Grit Diamond Buff .Typical surface roughness 0.012-0.025 μm (Ra). Suitable for high optically transparent Lens / Mirror parts.
With grade #6, 3000 Grit Diamond Buff .Typical surface roughness 0.025-0.05 μm (Ra). Suitable for high transparent plastic parts.
With grade #15, 1200 Grit Diamond Buff .Typical surface roughness 0.050-0.100 μm (Ra). Suitable for High-to-medium, non-optical lenses polish parts.

With 600 Grit paper polish .Typical surface roughness 0.05-0.10 μm (Ra). Suitable for medium polish parts.
With 400 Grit paper polish .Typical surface roughness 0.10-0.15 μm (Ra)). Suitable for medium polish parts.
With 320 Grit paper polish .Typical surface roughness 0.28-0.32 μm (Ra). Suitable for Med – Low polish parts.

With 600 stone polish .Typical surface roughness 0.35-0.40 μm (Ra). Suitable for low polish parts.
With 400 stone polish .Typical surface roughness 0.45-0.55 μm (Ra). Suitable for low polish parts.
With 320 stone polish .Typical surface roughness 0.63-0.70 μm (Ra). Suitable for low polish parts

Dry Blast Glass Bead to a satin finish. Typical surface roughness 0.80-1.00 μm (Ra).
Dry Blast #240 Oxide to a dull finish. Typical surface roughness 1.00-2.80 μm (Ra).
Dry Blast #24 Oxide to a dull finish. Typical surface roughness 3.20-18 μm (Ra).
Open SPI finishes Details
VDI Finishes
VDI 3400 Surface Finish (known as VDI surface finish) refers to the mold texture standard established by the German Engineers Association. The VDI 3400 surface finish is primarily machined by Electrical Discharge Machining (EDM) , It can also be achieved via traditional texturing methods such as SPI.
VDI 12
With 600 stone low-polish finish, surface roughness 0.4 μm (Ra).
VDI 15
With 400 stone low-polish finish, surface roughness 0.56 μm (Ra).
VDI 33
#24 oxide dry blast dull finish, surface roughness of 4.5 µm (Ra).
VDI 36
#24 oxide dry blast dull finish, surface roughness of 6.3 µm (Ra).
VDI 18
Glass bead blast satin finish, surface roughness of 0.80 µm (Ra).
VDI 21
#240 oxide dry blast dull finish, surface roughness of 1.12 µm (Ra).
VDI 24
#240 oxide dry blast dull finish, surface roughness of 1.60 µm (Ra).
VDI 27
#240 oxide dry blast dull finish, surface roughness of 2.24 µm (Ra).
VDI 30
#24 oxide dry blast dull finish, surface roughness of 3.15 µm (Ra).
VDI 39
#24 oxide dry blast dull finish, surface roughness of 9.00 µm (Ra).
VDI 42
#24 oxide dry blast dull finish, surface roughness of 12.5 µm (Ra).
VDI 45
#24 oxide dry blast dull finish, surface roughness of 18 µm (Ra).
Opeen VDI 3400 Finishes Details
Mold-Tech Textured Finishes
Mold-Tech is divided into four series, categorized by serial number and texture depth. The most popular are the Mold-Tech A series in fine to coarse matte finishes. Mold-Tech requires a variety of techniques to complete, from finishing to laser etching to chemical etching. Mold-Tech mold texture is rougher than SPI finish and therefore requires a larger draft angle, it is recommended to add 1.5° of draft angle for every 0.001" of texture depth.
Mold-Tech Injection Molding Finishes:

Mold-Tech A Finishes
NO. Texture Depth (Inch) Texture Depth (mm) Minimun Draft (°)
MT-11000 0.0004 0.01016 1
MT-11010 0.001 0.0254 1.5
MT-11020 0.0015 0.0381 2.5
MT-11030 0.002 0.0508 3
MT-11040 0.003 0.0762 4.5
MT-11050 0.0045 0.1143 6.5
MT-11060 0.003 0.0762 4.5
MT-11070 0.003 0.0762 4.5
MT-11080 0.002 0.0508 3
MT-11090 0.0035 0.0889 5.5
MT-11100 0.006 0.1524 9
MT-11110 0.0025 0.0635 4
MT-11120 0.002 0.0508 3
MT-11130 0.0025 0.0635 4
MT-11140 0.0025 0.0635 4
MT-11150 0.00275 0.06985 4
MT-11160 0.004 0.1016 6

Mold-Tech B Finishes
NO. Texture Depth (Inch) Texture Depth (mm) Minimun Draft (゚)
MT-11200 0.003 0.0762 4.5
MT-11205 0.0025 0.0635 4
MT-11210 0.0035 0.0889 5.5
MT-11215 0.0045 0.1143 6.5
MT-11220 0.005 0.127 7.5
MT-11225 0.0045 0.1143 6.5
MT-11230 0.0025 0.0635 4
MT-11235 0.004 0.1016 6
MT-11240 0.0015 0.0381 2.5
MT-11245 0.002 0.0508 3
MT-11250 0.0025 0.0635 4
MT-11255 0.002 0.0508 3
MT-11260 0.004 0.1016 6
MT-11265 0.005 0.127 7
MT-11270 0.004 0.1016 6
MT-11275 0.0035 0.0889 5
MT-11280 0.0055 0.1397 8

Mold-Tech C Finishes
NO. Texture Depth (Inch) Texture Depth (mm) Minimun Draft (゚)
MT-11300 0.0025 0.0635 3.5
MT-11305 0.005 0.127 7.5
MT-11310 0.005 0.127 7.5
MT-11315 0.001 0.0254 1.5
MT-11320 0.0025 0.0635 4
MT-11325 0.003 0.0762 4.5
MT-11330 0.002 0.0508 3
MT-11335 0.002 0.0508 3
MT-11340 0.003 0.0762 4.5
MT-11345 0.003 0.0762 4.5
MT-11350 0.0035 0.0889 5.5
MT-11355 0.0025 0.0635 4
MT-11360 0.0035 0.0889 5.5
MT-11365 0.0045 0.1143 7
MT-11370 0.004 0.1016 6
MT-11375 0.004 0.1016 6
MT-11380 0.004 0.1016 6

Mold-Tech D Finishes
NO. Texture Depth (Inch) Texture Depth (mm) Minimun Draft (゚)
MT-11400 0.002 0.0508 3
MT-11405 0.0025 0.0635 4
MT-11410 0.0035 0.0889 5.5
MT-11415 0.002 0.0508 3
MT-11420 0.0025 0.0635 4
MT-11425 0.0035 0.0889 5.5
MT-11430 0.007 0.1778 10
MT-11435 0.01 0.254 15
MT-11440 0.0005 0.0127 1.5
MT-11445 0.0015 0.0381 2.5
MT-11450 0.0025 0.0635 4
MT-11455 0.003 0.0762 4.5
MT-11460 0.0035 0.0889 5.5
MT-11465 0.005 0.127 7.5
MT-11470 0.002 0.0508 3
MT-11475 0.002 0.0508 3
MT-11480 0.003 0.0762 4.5
Opeen Mold Tech surface finishes
Bead Blasting Finishes
Bead blasting is a process for treating the surface of an object. It involves projecting spherical or bead-shaped media onto the workpiece surface under high pressure, with the impact of the media leaving a uniform finish on the part to complete the part surface treatment. bean blasting is commonly used to treat metal parts, molds, plastics, glass and other materials to create an excellent surface finish.
Mold Steel Treatment
Mold steel treatment can increase the strength, hardness and toughness of the mold, extend the life of the mold, and also increase its surface properties including wear resistance, corrosion resistance, friction coefficient, fatigue coefficient, etc. It is an essential processing technology for high-performance injection molds.
Our standard mold finishes include the following:
  • Heat treatment
  • Vacuum Carburizing
  • Thermal refining
  • Quench
  • Vacuum nitriding
  • Annealing
  • Tempering
  • Carbonitriding
Injection Molding Surface Finishes Design Tips/Considerations
Design tips/considerations
Plastic material
High-gloss mold finish does not mean high-gloss injection molded parts, but is also determined by other factors, such as molding materials, molding process, part design, etc. For example, for molds with the same surface finish, the brightness of ABS and PC plastic parts is higher than that of PP and PE.
Mold steel
Typically, high-gloss surface finishes require higher grades of mold steel. For example, S136H (HRC 50-55) and NAK80 tool steel (HRC 40-43) are often used to produce SPI A2 mirror surface finish, rather than P20 (HRC 30-33).
Areas with tight tolerance requirements need to be masked or plugged to prevent surface treatment from affecting the tolerance.
Higher mold hardness will increase processing time and post-processing time, affecting overall cost and delivery time, and needs to be evaluated overall.
Bead Blasting
When using sandblasting for surface finish treatment, the thin-walled areas of the mold should be specially treated to prevent deformation.
Bead Blasting
Branch gas channels are not conducive to the forward flow of gas, and small differences in conditions between the two branches will lead to differences in air flow resistance, resulting in different distributions of the same gas expected in the gas channels.
Mold steel
Glass fiber or other mineral filling materials in the plastic part material will cause strong friction on the mold surface during molding, causing irreversible wear. Therefore, when treating the mold surface, a coarser finish should be considered to cover molding stripes and other defects. At the same time, a mold material with a heat treatment hardness of HRC 45 or above should be used.
Mold steel
It is not recommended to use sandblasting for surface treatment on the mold surface formed by plastics containing glass fiber (such as nylon + glass fiber), as it is easy to be worn. It is recommended to use VDI texture or mold-tech leather texture to increase durability.
Reviews from Our Customers
A customer’s words have a more substantial persuasion than a company’s claims. We have served hundreds of satisfied customers and here are some reviews they give us.
Their engineers were a big help in prototyping our electronic device enclosures through microscopic laser surface texturing optimization. Continuous suggestions for improvements are also helpful, they are a very innovative injection molding company. We will have more cooperation on injection molding projects
David Moon
Vice President
Their engineering experts provided significant assistance in our material selection. The modified plastics they provide have been proven to be durable and environmentally friendly in delayed aging tests. With such a high-quality and capable injection molding supplier, it is impossible for us not to strengthen cooperation.
Carl Harris
Pruchasing Manager
Their accurate Moldflow analysis simulation greatly helped us avoid some mistakes in the early stages of project development. They can help us develop completely standard injection molded parts production processes. This is obviously very beneficial to us. The key is that these services are free.
Tony Jones
The original texture of the mold was damaged and Attractive Plastics laser repaired it, and I didn't see any difference from the original, which we were happy with. Otherwise we will lose a lot of money and shipments will be delayed. They are a very reliable injection molding supplier.
Ben Holder
They provide more than 100 kinds of textures, which greatly enriches the appearance options of our products. Their experienced experts provided me with a lot of suggestions, whether it was product structure or appearance, color. While accelerating the process, it also provides great support for the success of the project.
Anne Zaremba
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Injection Molding Surface Finishes FAQs

What is surface finishes?

Surface finishes refer to the texture and appearance of the surface of a manufactured product. It is an important indicator reflecting the micro-geometric shape errors on the surface of parts. Some also refer to it as surface roughness, but that is not entirely accurate. In fact, Surface finish is composed of three distinct elements – roughness, lay, and waviness. it mainly describes the degree of unevenness on the component’s surface, which is composed of minor peaks, valleys and wavelengths. Surface finish is closely related to the fitting performance, wear resistance, fatigue strength, contact stiffness, appearance and other aspects of mechanical parts.

What surface finishes do you offer?

We provide over 100 surface finish options for your plastic products. The most common surface finish used for injection molded parts include SPI-SPE, MOLD-TECH, VDI, bead blasting etc.

What is SPI surface finishes?

SPI surface finish refers to the surface finish standard established by the Plastics Industry Trade Association (SPI). It classifies surface finish into 12 levels. A to D represent surface finish from rough to smooth.

What is the VDI 3400?

VDI 3400 Surface Finish (commonly known as VDI surface finish) refers to the mold texture standard established by Verein Deutscher Ingenieure (VDI), the Society of German Engineers. The VDI 3400 surface finish is primarily machined by electrical discharge machining (EDM). It can also be done through traditional texturing methods (such as SPI, laser).

Injection Molding Surface Finishes Resources
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