GMW 6992 Visual Appearance Assessment

The “GMW 6992 Visual Appearance Assessment” standard, developed by General Motors Worldwide (GMW), is an engineering standard used to create a controlled and consistent method for evaluating the visual appearance of vehicle components and materials. This standard is particularly important for assessing whether parts meet General Motors’ intended requirements for appearance, color, surface, texture, gloss, and overall visual quality.

The primary goal of the GMW 6992 standard is to make visual assessments repeatable and consistent. Visual appearance can be subjective. Two inspectors might examine the same automotive component under different lighting conditions and arrive at different conclusions. Therefore, the GMW 6992 standard specifies controlled conditions for the following:

• Lighting
• Imaging equipment
• Viewing location and conditions
• Visual inspection
• Comparison with approved core standards or objectives.
• Assessment of changes in appearance after environmental exposure.
• Evaluation of color, brightness, texture, and overall appearance.

This standard is designed for components with appearance requirements and supports General Motors’ goal of achieving consistent appearance quality across its vehicles.

The GMW 6992 standard is applicable to a wide range of automotive components. Specifically, it defines applications involving interior, exterior, under-the-hood, and other components with appearance requirements. Examples include:

• instrument panels
• Door trim
• Console components
• Interior decorative pieces
• Seats and upholstery materials
• Molded plastic components
• Coated surfaces
• Painted components
• Decorative films
• Textiles and leather
• Exterior flooring
• Visible tissue or components with texture

The GMW 6992 standard is not just a color measurement standard. It can encompass various features related to overall visual appearance.

• Color: The evaluator determines whether the component visually matches an approved master or target. Potential differences include:
  • Lighter or darker
  • More or less saturated
  • Tone differences
  • Front/back surface differences for effect surfaces.

Color measurement can also be supported by instrumental methods. For example, accredited laboratories list this standard for color measurement along with ASTM D2244, SAE J1545, and ISO 3668 standards.

• Brightness: The amount and character of reflected light can affect whether two components appear harmonious. A piece might have the right color, but still look different because its brightness is too high or too low.
• Texture and pattern: Texture is particularly important for automotive interior materials. The evaluation may take the following into consideration:
  • Grain pattern
  • Grain size
  • Grain definition
  • Coarse/fine structure
  • Consistency between interlocking parts

This is especially important for molded plastics, synthetic leather, and other textured automotive surfaces.

• Overall appearance: Instead of evaluating just a single numerical color value, the evaluator considers the overall visual impression. This may include:
  • Surface smoothness
  • Color
  • Brightness
  • Tane
  • Metallic or special effects look
  • The relationship between adjacent components.
  • Visible production characteristics

A key concept in the GMW 6992 standard is comparison with an approved baseline or target. A component isn't necessarily judged simply as good or bad. Instead, its appearance is compared to a defined reference. This approach is important because automotive components often need to visually function within a vehicle. For example, an instrument panel component and an adjacent trim component might be made from different materials.

Lighting is one of the most important elements in visual appearance assessment. A material may appear different under the following conditions:

• Daylight
• Fluorescent lighting
• Different artificial light sources
• Different perspectives

In conclusion, the GMW 6992 standard specifies controlled viewing conditions so that different inspectors and facilities can obtain more comparable results. This standard includes references to lighting such as D65 daylight and cool white fluorescent (CWF). This is particularly important for materials with metameric behavior, where two colors match under one light source but appear different under another.

Meanwhile, the evaluator's skill is also important. This standard includes an appendix regarding color perception ability for personnel performing color evaluations for material color development and part appearance approval. This demonstrates an important principle: visual inspection depends not only on equipment and lighting, but also on the skill of the person performing the evaluation.

The GMW 6992 standard can also be used to evaluate changes in appearance between control and exposed samples. For example, a material might be exposed to:

• Exposure to artificial weather conditions
• Exposure to UV rays
• Exposure to heat
• Exposure to moisture
• Other environmental conditions

The exposed sample can then be compared to an unexposed control sample to determine if its visual appearance has changed.

The evaluation process generally follows these steps:

• Component preparation: The test sample or production component is prepared according to the relevant component specification.
• Reference identification: An approved master, target, or control sample is selected.
• Checking the viewing environment: The specified lighting, viewing equipment, and environmental conditions are established.
• Component inspection: The evaluator examines the part from appropriate viewing positions and angles.
• Appearance comparison: The part is compared to a verified reference.
• Evaluating differences: Color, brightness, grain structure, texture, and other appearance characteristics are considered.
• Saving the result: The appearance status and relevant observations are documented.

The exact equipment, lighting configuration, acceptance criteria, and evaluation requirements are included in the GMW 6992 standard.

It is important to distinguish visual evaluation from purely instrumental color measurement. A spectrophotometer can provide numerical color data, but a numerical result does not always describe the complete visual impression of an automotive component. For example, two parts may have similar measured color values ​​but appear different due to gloss, grain structure, texture, orientation, or special effect behavior. Therefore, GMW 6992 provides a framework for controlled visual appearance evaluation, while instrumental methods provide quantitative supporting data.

The GMW 6992 standard is important because appearance is a quality attribute visible to the customer. A component may meet dimensional and mechanical requirements, but still be unacceptable if it looks different from surrounding components. This standard helps suppliers in the following areas:

• To reduce subjective self-assessments.
• Establishing consistent audit conditions.
• Improving color harmony
• Checking grain and texture consistency.
• Evaluating the appearance after aging
• Improving consistency among suppliers.
• Supporting view approval
• To reduce differences in vehicle interior/exterior appearance.
• To create a common language for appearance assessment.

In conclusion, the GMW 6992 standard is particularly valuable for automotive suppliers because it provides a common basis for determining whether a component visually meets its intended appearance and whether different components meet the required vehicle compatibility.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services in accordance with the GMW 6992 standard.