Selecting a stroboscopic inspection light used to be a compromise. Traditionally selecting a Xenon strobe was based on matching web widths, selecting the one that was best suited for available mounting locations, and brightness or intensity from the mounting location. With the advent of LED strobes, plant managers now have many more options. Because the majority of inspection applications deal with the quality of print, coatings, or surface as a continuous process, plant managers should focus on the following 11 factors to select the right inspection strobe.
The process: Is the application a good candidate for stroboscopic inspection? Stroboscopic inspection is ideal for lines moving at very high speeds with either repetitive-pattern media or homogeneous media. A repetitive medium is any continuous material that is marked with an image that has a non-varying repeat length. A homogeneous medium is a continuous sheet material that has no pattern to lock onto. On these materials, strobes are used to detect either a repetitive mark or a single random defect.
The material being inspected: Is the material metallic, paper, plastic, film, metal, or cloth? Is it dull, semi-reflective, or highly reflective? For a dull matte surface, strobes can be mounted at almost any angle. For highly reflective surfaces the light needs to be mounted at a steeper angle. Inspecting a mixture of surfaces or finishes may require an inspection system with multiple intensities or projection adjustments.
Web or line width: How wide is the area being inspected? The ideal strobe configuration is based on the width as well as the distance from the strip and the required flash rate. See fixed mount coverage areas.
Process line speed: How fast is the process running? Each strobe system has a range of flash rates over which it operates. You need to be able to match the strobe’s flash range to the processing speed.
Repeat length: What is the size of the repeat? Smaller repeat lengths require shorter flash durations. Larger repeat patterns can tolerate longer flash durations.
Inspection location: Where do you need the inspection performed, at the end of the process or along the process line? The decision will determine whether a to select permanently mounted or portable strobes.
Amount of light: For proper inspection, strobe lighting should be four times brighter than ambient light. LED lights are brighter than Xenon strobes and more likely to provide this level of output. This is especially evident in security printing, where UV strobes are widely used. New LED UV strobes eliminate the need for a dark viewing area or a box around the inspection area to block out ambient light.
Distance from the web or line: Plant conditions can restrict how close the lights can be mounted to the surface being inspected.
Environmental conditions: Several environmental conditions can affect the ability to inspect, including solvents, excessive heat, excessive moisture, and any hazards to the operators. New LED lights significantly reduce safety concerns when using volatile chemicals. Still, the physical safety of an operator is always a primary concern.
Inspection cycle: Is the inspection cycle continuous or periodic? This will determine if a light-duty or heavy-duty light is needed.
Single or double-sided inspection: This will determine how many lights are needed and what sort of cables or synchronization functions are required.