Knowledge Base > Case Studies

Custom Imaging System for Critical Weld Exams

Purpose

A heavy transport equipment manufacturer is required to conduct a visual examination of an interior post weld for a critical component. A cross section of the product is shown in the figure above. Each interior weld location (see diagram) could only be accessed through a 9.5mm wide x 50+ mm deep trough and through a 1.8mm wide x 41mm long channel.
 

Challenge

The limited access point created a number of inspection hurdles. Initially their Quality Control department utilized a flexible borescope system. A miniature borescope was manually  inserted down into the channel and rotated 360 degrees along the target surface area. Although small enough to physically fit into the channel, the borescope’s lack of control caused significant image errors as the probe face could not be properly aligned.

The manufacturer approached Jamko’s Adjunct Engineering team to discuss alternative ways to conduct this inspection as well as other technologies that might be more suitable for this application. After an assessment review, the team decided that an off-the-shelf solution would not be adequate and a custom solution could be achieved. The following is a list of criterias or concerns that the team focused to address  while designing the custom solution.

1. Will there be enough light to see the surface without oversaturating the final image with too much light?
2. What camera system can fit into the channel to get the proper field of view (FOV) while maintaining good image focus?
3. Can we accurately and consistently position the inspection system to cover all areas of the internal inspection?

Solution

In order to meet all three basic criterias mentioned earlier, Jamko’s team of engineers decided to:

1. Mount the inspection device directly onto the part for stability
2. Utilize oblique lighting to counter specular surface reflections
3. Collect all images from a single insertion point and avoid inserting any physical components into the actual cavity of inspection

The flat upper rim was used as a locating feature for the inspection device. This allowed the user to easily apply a go-no-go approach to operating the inspection device. Once the device was located, the design allowed the user to rotate the optics and illumination vertically as well as independently with consistent results.

The system utilized oblique lighting to focus light waves adjacent to the surface profile. Unlike direct lighting where light is focused coaxially or along the same axis as the optical axis, a specular surface will reflect light waves directly back along the same axis causing image blurriness or loss of contrast and detail. Instead, by shining the light adjacent to the surface profile, an area of contrast can be seen from the shadow stemming from the surface feature.

The last design feature consisted of placing the objective lens in the 9.5mm trough. Unlike the flexible borescope where it was installed inside the 1.8mm channel, this approach eliminated the risk of damage to the inspecting device by keeping everything self contained in the larger member. The final image was collected and archived using a USB camera.

The final system specs:

• Operating Wavelength: 550 um
• Depth of Field: 2mm
• Field of View: 1.2mm x 1.7mm
• Resolve feature sizes to: 50micron
• System magnification: 2.1x
• Camera Interface: Windows USB 2.0 image capture

The final product was delivered to the customer and accepted within 2 months from start to finish. In practice, the Jamko solution improved the inspection process from 4 hours per part down to 20 minutes, a 12x reduction. In the end, the capital investment into the custom solution was a fraction of the miniature borescope solution that the manufacturer implemented prior to consulting with Jamko.

This paper as well as others found in our knowledge base at www.jamkocorp.com is one of a series of informational pieces made available to existing and potential customers.

Related

• Engineering Overview
• Magnification
• Unique Applications
• Video Probe