Testing Methods for Product Validation versus Manufacturing Test
The main goal of product validation is to determine that the design of the product will meet its specification/requirements. It’s the earlier-stage ringing out of the design, sweeping and cycling through various stimulus (e.g., input voltage limits, load limits) & environmental dimensions (e.g., temperature, humidity, vibe) to help determine how the design will perform once it’s out in the world. These units under test (UUTs) are often exercised to the point of failure and are not intended to be sold.
On the other hand, the main goal of manufacturing test is to verify that the unit passes a subset of key specifications before it leaves the factory and heads to a customer. It’s often the final step before the unit is packed up and shipped out.
As such, these two categories of test often have different testing methods associated with them.
Product validation testing may have several different monikers attached to it, depending on the details of the goals of the test, but you’ll likely hear terms like HALT (Highly Accelerated Life Testing), environmental, endurance, durability, and reliability. The term regression testing may also come up. Regression testing is simply the subset of testing required to be performed to make sure the design still works after a design change was made.
Generally speaking, validation testing is going to involve one or more of these:
- Product stimulus sweeps –
In this case you’re trying to exercise the product’s inputs in order to see how the product performs. This could include things like:
- varying input power supply voltages
- hammering on a communication interface to determine any overflow/error conditions
- varying motor speed against various profiles
- pushing buttons with robotics at varying pressures and locations
- varying the load of an actuator to stress it mechanically
The product may be cycled through its paces many times (hundreds, thousands, millions) to test the durability or provide statistical significance for failure rates.
The product may be tested up to, or beyond its theoretical design limits.
- Environmental sweeps –
In this case you’re trying to stress the product’s environment in order to see how it performs. This could include things like:
- Running shock and/or vibe profiles
- Varying temperature
- Varying humidity
- Validating ingress protection from dust, water, or salt
- EMI (Electromagnetic Interference) chamber testing
When we talk about manufacturing test in this context, we’re generally referring to non-destructive final functional testing or end-of-line testing (we won’t get into HASS (Highly Accelerated Stress Screening) or board-level testing here).
With the main goal being a final check before the product leaves the factory, or the subassembly becomes part of a larger assembly, we generally want to perform things like:
- Verify that the behavior of the unit under test (UUT) is within a range of expected values
- Save the measurements and analyses captured during this assessment, for use by quality groups to assess designs and suppliers, and for use during possible rework and redesign of the UUT
- Alert the test operator of any issues or shutdown the procedure if imminent damage is suspected.
- Prepare a new or amend an existing record that will become part of the UUT’s history
This testing would usually be done at room temperature (but not always), verifying a subset of what was checked out during the product validation phase.