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Comparison of decoration techniques in plastics processing

In the field of plastics processing, the decoration of plastic parts plays an important role. It is not limited to aesthetics; it also meets functional needs, such as protection against scratches, UV rays, or graffiti, as well as product differentiation. Today, there are many decoration techniques suited to the demands of different market sectors.

Summary Table of Different Types of Decorations in Plastics Processing:

Technique
Principle
Visual Appearance
Advantages
Disadvantages
Typical Applications
Mold Texturing
Texture applied directly in the mold (chemically or mechanically) Here are the classification methods: VDI 3400: Uses a numerical scale from VDI 0 to VDI 45. Higher values indicate a rougher surface. SPI: Classifies finishes from A1 (very glossy) to D3 (deep matte), based on polishing method. Charmille: Finishes obtained by Electrical Discharge Machining (EDM), often used to create specific textures on molds.
Matte, textured, leather-like, sandblasted, technical
Durable, economical (no post-injection step), hides defects and fingerprints, gives a “premium” appearance
Cannot be modified after injection
Visible parts, dashboards, housings
IML (In-Mold Labeling) / IMD (In-Mold Decoration)
Insertion of a decorative or functional film into the mold before injection
Printed, glossy, matte, holographic effect, transparent
Integrated into the part, high precision, resistant (wear, scratches), very high level of customization
Higher mold cost, longer injection cycle
Touch interfaces, complex decorations, home appliances, automotive
Painting
Application of paint after injection
Custom colors, matte or metallic effects
Custom finish, possible contrast
Requires surface preparation, prone to scratches if not varnished
Casings, design components, high-end finishes
Varnishing
Application of a protective varnish: UV varnish: fast curing, excellent resistance. Matte, satin, or glossy varnish: adapted visual finish. Anti-graffiti varnish: especially useful for publicly exposed parts, allows easy cleaning of marker or paint traces.
Transparent, satin or glossy
Protects against scratches, UV, solvents, humidity
Additional cost, sometimes requires multiple layers
Urban furniture, design parts, public equipment
Pad Printing / Screen Printing
Pattern printing: Pad printing (via tampon) -> curved or complex surfaces Screen printing (via stencil) -> flat surfaces
Fine, precise, two-color or monochrome
Low cost, fast, precise
Susceptible to wear
Logos, pictograms, symbols
Laser Engraving
Direct marking into the material via laser
Very fine, discreet, engraved, sometimes contrasted
Permanent, no disposable materials, precise
High initial machine cost, not suitable for all materials
Serial numbers, codes, permanent logos

Comparison of Finishes Between VDI and SPI:

Finish
VDI
SPI
Ra (µm)
Method
Very smooth
VDI 12
A1
~0.40
Diamond polishing
Satin
VDI 18
B2
~0.80
Paper polishing
Matte
VDI 24
C3
~1.60
Stone polishing
Very matte
VDI 33
D2
~4.50
Sandblasting
Rough
VDI 45
D3
~18.00
Heavy sandblasting

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