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Colour Uniformity in Plastic Injection Moulding

Colour uniformity in plastic injection moulding is more than just an aesthetic concern; it is a vital part of product quality. In this article, we'll unravel the complexities of different colour systems used in injection moulding and the importance of specifying colour tones numerically.

Whether you’re a designer, manufacturer, or just curious about the world of plastic parts, this insight will provide you with the knowledge to ensure colour consistency in your projects.

Colour Systems in Plastic Injection Moulding

In plastic injection moulding (IM), the application of colour goes beyond mere appearance. It signifies brand identity, function, and quality. Several colour systems are available to help manufacturers achieve precise and consistent colouring.

  • Pantone Matching System (PMS): Widely used for branding strategy and marketing, PMS allows for exact colour matching across various materials.
  • CIE L*a*b System: A colour-opponent space that quantifies colour sensations, enabling precise colour communication and control.
  • RAL Colour System: This is a European colour standard used mainly in architecture, construction, and industry, known for its comprehensive and accurate colour representation.
  • HSB (Hue, Saturation, Brightness): A cylindrical-coordinate system representing colour in terms of human perception.
  • RGB and CMYK: These systems are commonly utilised in digital printing and display, focusing on red, green, blue, and the combination of cyan, magenta, yellow, and black.

L*a*b Colour System in Plastic Injection Moulding

The L*a*b colour system, also known as CIE L*a*b, stands at the forefront of precision in colour representation. It operates on three dimensions: L* for lightness, a* for green to red, and b* for blue to yellow.

CIE L*a*b* Colour Space
CIE L*a*b* Colour Space

By quantifying colour sensations, the L*a*b system creates a standardised colour-opponent space, making it indispensable for industries needing exact colour matching.

A vital benefit of the L*a*b system is its device-independent nature, meaning that colours remain consistent across different devices or displays. 

Its mathematical foundation ensures that any colour within human vision can be described, a crucial aspect in plastic injection moulding where colour precision is paramount.

Various online tools like this fix sensor are available for converting colour values to the L*a*b system.

The RAL Colour Standard in Injection Moulding

The RAL colour system, stemming from the German Reichs-Ausschuß für Lieferbedingungen, is a widely recognised European colour standard. With over 2,300 colours, it’s extensively used in architecture, construction, and injection moulding industries.

RAL colour palette
RAL colour palette

Unlike the L*a*b system, RAL focuses on categorising colours into collections, like Classic, Effect, and Design. It’s renowned for its accurate colour representation, particularly in industrial applications.

Comparative Analysis: L*a*b vs. RAL

While both systems have their unique strengths, comparing them reveals distinct differences:

  • Universality: L*a*b’s mathematical approach makes it more universal, while RAL’s categorised collections cater to specific industries
  • Precision: L*a*b offers device-independent accuracy, whereas RAL’s physical colour representations may differ across devices
  • Application: L*a*b is broader, while RAL is often favoured in European industrial contexts

The choice between L*a*b and RAL depends on the specific requirements of the plastic injection moulding project. Understanding their intricacies will help select the system that ensures colour uniformity, satisfying technical demands and aesthetic preferences.

Red round injection moulded parts
Red round injection moulded parts

Achieving Colour Uniformity in Plastic Injection Moulding

Design Tips for Colour Consistency

When it comes to maintaining colour uniformity in plastic injection moulding, the design stage plays a critical role. Here’s how to make it work:

  1. Material consideration: Understanding the material’s characteristics is crucial, as different engineering plastics react differently to colourants
  2. Colourant selection: Utilising high-quality colourants that match the polymer used helps achieve consistent shades
  3. Simulation and prototyping: Testing colours through simulation and prototypes ensures that the final product will match the desired tone
  4. Consider environmental impact: Different lighting conditions and environments can affect colour appearance. Design with the end-use environment in mind

Selection Guide for Uniform Colours

Choosing suitable materials and methods is paramount for colour uniformity in injection moulding. Here’s a guide to follow:

  1. Understand the project requirements: Identify the exact colour specifications and the intended application of the part
  2. Choose the right colour system: Select between systems like L*a*b or RAL based on the project’s needs and industry standards
  3. Select appropriate colourants: Work with suppliers who provide industry-certified colourants, ensuring quality and consistency
  4. Consult with professionals: Engage with experienced engineers or colour specialists who can guide you in achieving the exact shade
Injection moulded orange corner brackets
Injection moulded orange corner brackets

Sending a Sample to the Manufacturer: A Must-Do Step

A practical and often overlooked solution to ensuring colour uniformity is sending a sample to the manufacturer. This sample, a 50 x 50 mm flat surface, can be a cut piece of material from a targeted colour or a part you’d like to match with newly manufactured parts.

This practice of sending a sample to Xometry or the respective manufacturer allows for precision in colour matching. It eliminates guesswork, reduces the risk of inconsistencies, and ensures that the final product aligns perfectly with the customer’s expectations.


In the multifaceted world of plastic injection moulding, colour uniformity is more than a visual aspect; it symbolises quality, brand identity, and customer satisfaction. 

Through a detailed understanding of colour systems like L*a*b and RAL, meticulous design planning, strategic selection, and sending a sample to the manufacturer, achieving precise colour tones becomes an attainable goal. 

These principles, rooted in technical expertise and collaboration, ensure that the final product resonates with the desired vision, paving the way for success in any plastic moulding endeavour.

Xometry provides a wide range of manufacturing capabilities, including plastic injection moulding and other value-added services for all of your prototyping and production needs.

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