Test & Inspection: Custom Noncontact Solutions Meet Unique Inspection Challenges
May 1, 2011
Today there is no lack of noncontact inspection tools. There are high-resolution video cameras, optics, multiple illumination sources, laser scanners, white light sensors, high-resolution displays, precision motion platforms, linear stages, along with computers and software packages that are used to control the inspection systems, capture the data, analyze it and store it in appropriately accessible formats.
Noncontact and multisensor measurement system manufacturers have made good use of these components to design standard products for measuring and inspecting parts that, due to the small size, fragility, deformability, inaccessibility or multiplicity of their features cannot be measured efficiently by conventional tactile equipment. For most parts that benefit from noncontact or multisensor inspection, there is typically a selection of measurement systems that will do the job well.
However, as designers push manufacturers to make parts that are smaller, more intricate or incorporate unique materials, the specialists who need to measure these components will inevitably encounter new challenges that standard noncontact measurement systems cannot easily handle. It is not that the pieces needed to meet the challenge are unavailable. More often than not they are. They have just not been assembled and integrated into an off-the-shelf product that will meet the particular need.
Most manufacturers do not have experts who have mastered the multiple disciplines needed to design and assemble an elegant custom noncontact measurement solution. There are, however, organizations within the manufacturing industry that do have the expertise or the project management experience necessary to offer such services at a favorable cost or benefit ratio.
DIFFICULT-TO-IMAGE PARTSBlack is wonderful for purposes of camouflage, but not ideal if one needs to image the surface of black parts to detect flaws or measure features. A manufacturer of high-stress internal combustion engine components had some critical parts that had to be 100% inspected for surface defects that were a potential source of failure.
Unfortunately, these metal parts are coated with a black wear-resisting compound that make them very difficult to image with standard equipment. The consultant devised a system that incorporated custom optics, part handling, lighting and camera combinations, and customized software that made a qualitative analysis and documentation of these parts faster and more reliable.
On a high-resolution screen, the inspector views the part as it is manipulated into various positions and with lighting combinations to make surface flaws readily detectable. If questionable areas are found, the operator can adjust camera software settings, lighting and magnification to optimize their visibility.
If a flaw is detected, the operator can capture the image, differentiate with color, measure the area occupied by the defect and mark it up with drawing and annotation tools so that engineers can quickly understand and review any problems. When the operator is finished, an electronic archive is created to preserve a complete record of the inspection process.
This solution reduces eyestrain, neck fatigue and other discomforts so that operators can perform at a high level for longer periods. It also creates a highly accurate and meticulously documented inspection process.
SMALL FEATURE FLAW DETECTION AND MEASUREMENTCustom noncontact inspection solutions may be qualitative, quantitative or a combination of both.
A medical manufacturer needed to inspect a small plate with hundreds of precisely machined perforations. Multiple quality issues needed to be addressed during a relatively high-speed 100% inspection process matching the pace of production: Were all the holes in the part model present? Were all the holes clear of dust or debris created during the manufacturing process? Did each of the holes conform to precise size and tolerances? Finally, were all of the orifices in the plate in proper relation to each other?
In this case, the recommended solution is a standard measurement platform, adapted so that both qualitative and quantitative evaluations can be performed rapidly and automatically with one setup on the same equipment.
At a low magnification level, the camera takes a picture of the plate so that the software can confirm the presence of all the holes and that there are no partial blockages in them. Additional pictures are taken at a high magnification level, allowing software to verify the size and location of the holes. By exception, the system also is capable of performing high-precision measurements of individual holes at this level.
FLEXIBLE AND DEFORMABLE COMPONENTSA company that manufactures illuminated display panels for aircraft was frustrated by the unwieldiness of trying to measure them on their coordinate measuring machine (CMM). The parts were large, flat, soft and flexible-attributes that tactile measurement systems are not well equipped to deal with.
Vision would be the ideal solution, but purchasing a system with a large table to measure these particular parts would be very expensive. The dilemma was handled quickly and at minimal cost by adding an optical probe to the Z-Ram of the CMM giving noncontact optical-video measurement capabilities whenever required.
In this case, the consultant installed the optical video head, integrated the video with appropriate measurement software and provided the operator with some initial measurement programs for some of the most common applications along with training. The CMM was more fully utilized and the cost of adding a new vision system was avoided.
INSPECTING THE INSPECTION SYSTEMSNot all measurement applications that can benefit from some expert consultation are complicated. One customer simply wanted to know if his existing vision inspection equipment was adequate for his company’s immediate and short-term needs. The consultant did a walk through of the company’s lab and examined the equipment. Then they had a detailed conversation about the types of evaluations that were being performed using vision.
In this case, the mechanical platform of the primary vision system was reaching the end of its useful life, but the optics were of high quality and had almost no wear. Therefore, the customer was able to mount existing optics on a new X-Y-Z motion platform to improve the performance of his system and save money.
EVERYTHING TO GAINIf there is a measurement or inspection problem, noncontact or otherwise, that seems to defy a standard system or existing tool solution, do not hesitate to call in an expert with custom systems capabilities. Everything is to gain by finding out how to perform a critical inspection better, faster and at the lowest cost.
There are independent consultants who can perform this service. A small number of companies also are willing to serve customers in this manner. They can provide the operator with a standard solution if possible, but branch into a custom solution if necessary. Q
QUALITY ONLINEFor more information on noncontact inspection, visit www.qualitymag.com to read the following:
“Extending the Frontiers of Noncontact Surface Inspection”
“Noncontact Inspection: From Shadowgraph to Multisensor”
“Noncontact Inspection Keeps Pace with Production”