When to Automate – When do you choose automated testing over manual testing?
At the core, this is driven by the “why” you want to automate in the first place. The most common reasons to automate testing in low/medium volume manufacturing include:
- Decrease test time
- Human error reduction
- Product quality
- Labor utilization improvement
- Safety of both personnel and product
Decreasing Test Time
Whether for production throughput or getting through design validation, time savings is a major driver for automation. Determine how long each aspect of your test sequence takes. This includes:
- part load
- assembly steps
- fixture, harness, or probe motion time
- measurement/switching settling time
- measurement time
- calculation/analysis time
- part unload
Lining these up in rank order will give you a good idea if which components dominate your total test time. You’ll need to make sure the aspects that dominate can actually be improved with automation that’s reasonable for your setup. For example, if your test time is dominated by part placement or assembly steps, robotics may help. But, if a robot can increase your production rate by only a small number of parts per shift, then the extra profit your company makes on those extra parts should be balanced against the cost of the robot. On the other hand, if your test time is dominated by a test tech probing various points and setting up various instruments, basic test automation may help significantly.
Human error reduction
Not that machines never make mistakes (they do), but humans are generally more error prone. Humans get distracted. They get bored. They get pre-occupied. A good example is reading a value off of a multi-meter incorrectly and recording that wrong value on a test results sheet. If the wrong value is within the specified limits, but the actual value was outside the limits, then you may have a false pass on your hands, and you don’t want that part leaving the factory! Or, if the opposite occurs, you could end up scrapping or wasting time troubleshooting a good product, which is obviously bad for your company’s bottom line.
Automated testers help improve product quality mainly in two ways. First, the quality perceived by the end-customer increases when a tester detects a functional problem before the troublesome unit is sent to the end-customer. This usage of a tester doesn’t directly increase product quality, rather it identifies the good units and culls the rest.
The second way that product quality increases with a tester is through better design. By reviewing the test results of all units, the product design team can begin to understand where the product design needs improvement. The ultimate goal of design is that no units ever fail during assembly, making the tester superfluous. In reality, that objective can never be achieved, and testers will always be useful for at least a final pass/fail assessment.
Labor utilization improvement
People are good at performing tasks where creativity and judgment are important. Machines and computers are good at algorithmic repetitive tasks. By giving a test engineer and test operator an automated test system, the best attributes of both machine and human are used.
We’ve seen some of our manufacturing clients boost production by up to 3X while driving down cost or production per part by 30% through the use of sensible automation. Simple automation can often have dramatic effects. For example, enabling the test operator to retrieve a trace from a scope automatically by activating a foot pedal while holding two probes on test points, rather than having to clip the probes and then press buttons on the scope, can speed up a test step by 5X.
Full automation enables a single test operator to do the job of many by having an N-Up tester that allows an operator to load one part while the other(s) are being tested.
Personnel safety and harm is especially important when the test requires an operator to probe in areas of dangerous high voltage, high current, or moving parts. By using hands-off automatic connections of measurement sensors to test points, such as by proper fixturing or part handling equipment, the human can maintain safety and reduce risk while benefiting from the use of automation. Furthermore, if part failure may be catastrophic and cause harm to the operator, then automation keeps the human away from the part during testing.
Product safety should also be considered when the part is expensive and inadvertent destruction during testing is possible. By adding automatic shutdown capability to the test system in the event of certain limits being exceeded, part damage and possible human harm can be averted. For example, if a part has excessive current drawn on the power rail, the test system can detect excessive power being drawn by the part and shutdown rapidly enough to prevent a bursting power supply due to overheating.