Plastics Color Matching and Color Difference Detection Instruments Selection Guide

Color Management Challenges in Plastic Manufacturing

Identical color matching and detection devices greatly contribute to the quality of the plastic produced. Regardless of whether you manufacture plastic automotive parts, electronic devices, packaging plastic film, or plastic resin, color variations are unacceptable. Even the slightest variations cause production losses, the customer will refuse the shipment, and the company will suffer financial losses.

That is why color measurement and control in plastic production is so precise. Instead of the subjective color judgment by workers, color measurement devices are used to analyze color pointing, difference, and control for the production of plastics.

The color control starts from the basic materials in the form of color plastic resin granules, master batch, and color pigments and continues to the processes of injection molding, extrusion, and ends at the quality control. A good control system is the one that connects all production processes to ensure that all workers operate within the established parameters.

What is the Allowable Lab Value Error Range of Colorimeters for Plastic Products? How to Judge Pass/Fail in Color Matching Quality Inspection

The core of plastic color matching quality inspection is to adopt unified and reliable measurement conditions to quantify color difference within an acceptable tolerance range, reducing batch-to-batch color deviation and rework. This article provides reference for Lab value error ranges and ΔE comprehensive color difference criteria, and explains the operation workflow of color matching inspection, to help injection molding, color formulation and quality control personnel effectively manage batch color variation.

Understanding the Importance of Selecting an Appropriate Colorimeter in the Plastic Industry

Not all colorimeters are suited for measuring plastics. These materials can be opaque/transparent, semi-gloss/matte, have a variety of shapes, and can have a variety of textures (including granular). So, a colorimeter optimized for measuring color of paper or fabric may not provide consistent or reliable measurements of shiny plastic casings or color-pellets.

Choosing the wrong colorimeter will measure and record inaccurate color values, leading to poor color quality decisions; i.e. poor decisions will be made about whether to approve or reject certain batches of plastic products. Poor color quality decisions will cost money and negatively affect your company’s reputation among your customers.

Using the right colorimeter will eliminate uncertainty, measuring and color quality decisions will be speeded up, and the plastic purchaser will have a better ability to set and convey color standards to all customers and suppliers. This is especially true in the plastic exporting business where color standards are rigidly maintained, and the colorimeter used to measure color values must be of a high quality.

Determining What Is Important Considerations When Selecting a Colorimeter in the Plastic Industry

Before understanding what is targeted, ascertaining what needs to be achieved is vital. For example, a factory that produces components for toys will have a set of requirements that is unique, just as a company that is a supplier of plastic trims for the manufacturing of automobiles.

Thus a packaging business that deals with clear PET bottles (Polyethylene Terephthalate) will have different needs compared to a compounder who is providing masterbatch (which is a concentrated mixture of plastic and additives) to an end user.To begin measuring factors related to your workplace, think about what sort of plastic you will be measuring in your workplace, what types of surfaces you may need to measure (smooth, rough, curved, flat, etc.) and if you will need to measure transparent objects or materials. Finally, think about how many measurements you anticipate your team to take in a day.

Color Measurement in the Plastic Industry

In the plastic industry, colors are measured by CIE (Lab and LCh) color spaces. The main key value is ΔE, which indicates the total color difference of two samples.

Based on the results for ΔE:

● ΔE ≤ 0.08 indicates a  general quality control acceptance

● ΔE ≤ 0.03 indicates acceptance for the automotive or for precision molding

● ΔE ≤ 0.005 indicates acceptance in laboratory work and R&D

Additional features of the instruments are the measurement of multiple illuminants (D65, A, and F2) to measure in different light conditions. A color may appear the same in one light, but under different light conditions, it may look different.

Always Verify the Accuracy and Precision of the Device

In order to measure plastic quality control, select instruments with repeatability of ΔE ≤ 0.03 (or better). For optical geometry, D/8 integrating spheres are the best opt to choose for plastics in quality control.  These spheres offer SCI (specular component included, which is color) and SCE (specular component excluded, which is appearance) modes, which are essential for separating the appearance of color from visual color.  These modes are very important for all surfaces, whether they are matte, glossy, or anywhere in between.

Think About Portability and Practicality

For a production setting, your team needs a tool that will be practical on the shop floor. The simple, battery driven, and easy to use, portable hand held colorimeters, allow you to measure color directly at the product or assembly line. Operators with little or no technical training will find these easy to use because they have touch screens and one-click measurement capabilities.

For laboratory work, a more stable option is to select a benchtop model, which will allow you to have bigger opening options for bulk materials like pellets and powder. Modifying bench colorimeters with a bigger opening will also provide you with more flexibility for your testing.

Consider the Measurement Range and Flexibility

Different plastic products require different measurement setups. Below is a simple guide.

● 8mm aperture — common for most molded plastic parts, panels, and casings

● 4mm or 1×3mm small aperture — for small parts, buttons, connectors, and curved surface

● 50mm large aperture — for plastic pellets, masterbatch, and pigment powders

● The transmission mode is needed for transparent plastics like bottles, films, and light guides.

In the case that your factory processes more than one type of plastic, it is advantageous to the pocketbook to select a model that accommodates different sizes of apertures, eliminating the need to purchase multiple instruments for different applications.

Examine the possible Software and Data Management

Good software should have the ability to store standard colors, compare recordings from previous batches, create reports, and track color changes throughout the years. Some software have the ability to set tolerance limits and automatic notifications when the reading is out of the acceptable range. The best software is the one that is simple to learn and is able to export data to different formats.

Look into the calibration options

To keep an instrument working correctly, it must be calibrated regularly. Most colorimeters are calibrated with a white tile and a black trap. Some models can self-correct to stay within calibration for a longer time while measuring. You should also check how long the light source is expected to last and if there are people in your area to maintain the device.

Look at price, warranty, and support after you buy.

Portable colorimeters for simple and routine quality control are between $800 and $2000. Standard models with greater accuracy and more advanced software have a price range between $3,000 and $8,000. Specialized laboratory instruments sit above this.

Make sure to check the warranty and see if the manufacturer includes technical training, calibration, and software updates.

Color Measurements Standards For Textiles & Fabrics Industry

Color evaluation in fabrics and textiles industry requires the use of internationally accepted standards. For color difference evaluation, the measurement standards are usually in conformity with CIE No.15 and ISO 105-J03, while color fastness testing is in conformity with GB/T 8424.3 standards. Moreover, ISO 105 and AATCC are major contributors to the evaluation of fabrics in relation to washing, light and rub abrasion. The colors are defined based on the CIE Lab* color space and ΔE is the metric of the color distance between the samples. The measurement is performed under illumination of a D65 light source.

Color Measurement Devices and Tools for the Plastic Industry by 3nh

3nh covers many instruments that span various stages of plastic production.

● With ΔE ≤ 0.03, D/8 geometry and 8 mm aperture, the NH310 is perfect for injection molding and packaging lines.

● PS2080 is good for precise measurement of small apertures of 1×3 mm, ideal for electronic connectors, buttons and bent parts.

● TS2010 / PS2020 is good for masterbatch, pellets and pigment powder  measurement and has 50 mm wide apertures.

● With dual transmission and reflection modes, TS8260 / YS6060 can measure haze, transmittance, and the color of transparent plastics.

● TS8560 is laboratory-grade with ΔE ≤ 0.001. It can measure humidity and temperature and is great for high-precision R&D work.

Conclusion

Selecting the right colorimeter largely depends on the plastic type, surface and quality standard. Most factories would require a portable D/8 colorimeter with an 8 mm aperture, ΔE ≤ 0.03 and SCI/SCE modes. For laboratory work, transparent materials and pellets, specialized models can be used. To achieve high and consistent color quality, it is important to select the right instrument and be color consistent across your production line.

FAQs

Which colorimeter is best for measuring color of plastics?

It is best to use a D/8 integrating sphere colorimeter with SCI and SCE modes for most plastics.

What aperture size should I use for plastic pellets?

For pellets and masterbatch readings, 50mm large aperture is better for stability and representation.

Can one colorimeter measure both transparent and opaque plastics?

Yes, both transmission and reflection measurement modes are supported by the 3nh TS8260 or YS6060.

What ΔE value is acceptable for plastic quality control?

ΔE ≤ 0.08 is acceptable for plastic quality control, ΔE ≤ 0.03 is acceptable for plastic quality control precision work, and ΔE ≤ 0.005 is acceptable for laboratory use.

How often should a colorimeter be calibrated?

It is suggested that a colorimeter be calibrated prior to each measurement or at the beginning of each shift.

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