In determining best practise and defining the proper test process, one generally considers the trade-off between cost and quality. The initial purchase price, (often the ongoing support costs are neglected), of test equipment is one of the primary factors considered in determining the cost of a test system, but what is often neglected is an understanding of the real costs of an inadequate test solution.
Defects introduced in the manufacturing process always cost in time and money. The size of that cost depends largely on when in the process the defects are discovered. The cost of a defect rises exponentially, the later in the process it is discovered. Defects found immediately after they are caused are easy to fix while defects found by the end user of a product can be very costly to the company.
The costs associated with finding and fixing a defect at various stages of the manufacturing process needs to be understood. Consider the example of an operator swapping two pins in a connector on a moderately complex harness assembly. For each stage we’ll break down what steps must be taken to fix the defect if it was not detected until that stage.
Assembly
If the operator knows immediately that a pin has been placed into the wrong cavity the fix only takes a few seconds to move it to the correct cavity. Automated test equipment can be used at individual build stations to check for errors as the harness is built and ensure operators catch these manufacturing defects. Errors reported by the test system are easy to diagnose because the last action the operator took must have been the cause of the error. A fix at this stage costs very little.
Final Electrical Test
Errors in final test take more time to diagnose because any of the finished connections could be the source of the error. If using good automated test equipment a quick identification of the defect that caused a test error will be made. If not, it often takes more effort to understand the real problem. Typically, once a defect is identified the harness must be transported from the test area back to a production operator. The defect has to be described to the operator in order to fix it. If the harness was fully complete then the operator may have to cut through braiding or tubing and scrap material to get to the connector to fix the problem. Then after fixing the problem the operator will have to redo the work that was done previously to put the harness back together, transport it back to the test area, and have the test operator perform the final test again. All of those steps can add up to significant time and material costs that are not included in the production schedule or bill of materials.
Functional Test
If the harness defect is not caught until installed into the end product the diagnostic times further increase. Usually the harness is one of many items in a system that could be causing problems. Determining the source of a functional test failure can be an extensive and expensive process. Once the harness is identified as the cause of the problem it will have to be removed from the product and then the specific defect may have to be diagnosed separately. All of the work from the Final Test stage explained above will have to be performed to fix the defect and then the harness will have to be reinstalled into the product and the functional test performed again. The time spent in these efforts adds significant costs, but often the worst case scenario at this stage is if the nature of the defect damages the product.
One example is of a company that makes high end gyroscopic cameras for search and rescue. While performing a functional test on their product, two swapped wires caused the camera to burn up, costing thousands of pounds.
End User
The most costly scenario is having defects found by the end user! Depending on the product, there will be costs for the product to be returned, or costs to send someone out to inspect the product. One company that makes a product for the trucking industry frequently spends over £1,000 simply to get a technician out to diagnose a problem in the truck. A much larger cost, however, could occur if the defect causes you to lose credibility in the eyes of your customer, or even in the industry. One extreme example is a cable shop that was involved in an automotive recall due to a faulty cable they produced. This cost them over £750,000 in immediate costs and an unknown amount of lost future revenue due to decreased reputation.
What is the real cost of inadequate testing?
The real cost of a defect depends on a number of factors and taking the time to figure out this information is very valuable. Once understood, the defect cost, found at each varying stage of the process, enables clear decisions on how to implement a test process. As an example, one company building a complex product determined that a certain type of defect discovered in the functional test stage cost them £15,000. This type of defect occurred, on average, once a month. So the cost of missing this defect earlier in the process was £15,000 / defect x 12 defects / year = £180,000 / year. Thus any investment less than £180,000 in equipment or process improvements that could detect this error earlier would be saving money in the long run. The numbers will be different for each situation, but the principle is the same – knowing the numbers provides a realistic investment value to improving the process. Often simple process changes, like performing an extra test a step earlier in the assembly process, yield significant savings with relatively little cost outlay.
For full confidence in the right test process, time taken to determine potential costs is key. For electrical testing, Cirris offers a free tool to help determine the cost of defects. Take a look. This information enables consideration not just of the costs of setting up a test system, but also the costs of failing to do so.
From simple tests to complex assemblies, Cirris Solutions has a cable tester to meet your needs.
