Visual testing (VT)

Detecting external features - simple, standardized, and non-destructive

visual testing is the fundamental method of non-destructive testing and is based on the targeted visual assessment of component surfaces. The goal is to identify visible deviations from defined quality characteristics and to evaluate them systematically.

Depending on the inspection requirements, the inspection is performed directly with the human eye or using optical aids such as magnifying glasses, endoscopes, videoscopes, or technoscopes. Crucial to this process is inspection lighting and magnification defined in accordance with standards, which ensures reproducible detection of surface characteristics. Parameters such as illuminance, viewing angle, and inspection distance are determined in accordance with applicable specifications.

During the inspection, the component surface is systematically checked. For example, surface condition, damage, cracks, pores, contaminants, or assembly conditions are evaluated. The assessment is based on defined defect catalogs, drawings, reference samples, or customer specifications.

For hard-to-reach areas, indirect methods are used, such as optical extension via endoscopy. In safety-critical applications, the visual testing can also be supported by photographic documentation or digital image analysis.

visual testing allows for an immediate assessment of the component’s condition without interfering with the material. It often constitutes the first inspection stage within an inspection plan and complements other non-destructive testing methods by quickly and efficiently identifying obvious surface features.

Which defects or features are inspected?

visual testing is particularly effective for detecting the following features:

• Surface damage, such as scratches, dents, or impact marks
• Cracks and imperfections, provided they are clearly visible on the surface
• Burrs and dimensional deviations, for example following forming or machining processes
• Contaminants or foreign substances that impair further processing or function

What are the advantages of visual testing?

visual testing is the fundamental method of non-destructive testing and offers the following advantages in particular:

• Widely applicable, regardless of material type and component geometry, provided sufficient accessibility and lighting are ensured
• Immediate availability of results, as evaluation is performed directly by visual testing
• Non-destructive execution, without impairing component function
• Cost-effective initial inspection step, particularly as part of a tiered inspection concept

In which applications is visual testing appropriate?

visual testing is used in nearly all areas of industrial quality assurance. Typical applications include incoming goods inspections, in-process checks, and final inspections prior to shipment.

It is particularly suitable as an initial inspection step to identify and remove obviously defective parts at an early stage and to target further inspections accordingly.

In which industries is visual testing typically used?

visual testing is used across all industries wherever component surfaces, visible features, or assembly conditions must be systematically assessed, including in:

• Automotive and supplier industry
• Aerospace
• Mechanical and plant engineering
• Energy and power plant industry
• Rail vehicle and railway technology
• Metal processing as well as forging and foundry operations

The specific design of the inspection depends on the component, accessibility, lighting conditions, and the respective quality requirements.

Which standards are relevant?

visual testings are conducted based on the agreed-upon customer specifications, drawings, and inspection plans. The organizational and documentation processes are integrated into our quality management system in accordance with DIN EN ISO 9001.