“Make a go/no-go, Tom!”—you may have heard this shouted on the factory floor when a batch of parts comes in out of spec. But is relying on a go/no-go gauge really a good idea?
On the surface, it seems simple: separate the good parts with a jig, keep production running, and send the bad ones back to the supplier. Problem solved, right? Not quite.
Imagine this: a supplier delivers 10,000 parts. After using the jig, only 2,000 pass. Meanwhile, your marketing colleague Jerry has already promised the customer 9,000 finished products by the end of the month. The supplier scrambles, works overtime, produces another 35,000 parts—but again, only 7,000 are good. They then increase the price fivefold to cover their yield loss.
Now you’re frustrated, blaming the supplier. But from their side, the logic is clear: quality control by rejection is costly for everyone.
The Core Issue
A go/no-go gauge is an inspection tool, not a solution. Inspection is a post-process filter. Modern manufacturing quality, however, comes from process stability and control—not from sorting out defects after production. This is the foundation of Six Sigma and lean manufacturing: prevent defects rather than detect them.
How Engineers Should Secure Quality in Mass Production
-
Design for Manufacturability (DFM): Consider risks from the start—machine limitations, operator handling, environment, etc. If a feature is prone to high variation, find an alternative rather than assuming a jig will fix it later.
-
Simplify processes: The fewer steps and reworks, the lower the variation. Cooling fixtures, secondary machining, or manual adjustments should be minimised wherever possible.
-
Stay close to the process: Don’t just sit in the office waiting for reports. Go to the factory, observe how parts come out of machines, watch operators, review CPK/PPK, and collaborate with suppliers to reduce variation.
-
Monitor in production: During mass production, demand regular IQC and OQC reports to ensure the process remains in control.
Another Challenge: Geometric Complexity
As parts become more geometrically intricate, designing an accurate go/no-go gauge becomes harder. Picking a single reference point or pass/fail criterion on a 3D surface often leads to ambiguity and unreliable measurement.
So, Is Go/No-Go Still Useful?
- For simple geometries and low-volume production: maybe yes.
- For high-volume, complex manufacturing: definitely no. The focus must shift to building stable processes that produce in-spec parts consistently.
Bottom line: Go/no-go is not a quality strategy. It’s a short-term filter. True quality comes from designing robust processes, engaging directly with manufacturing, and preventing defects before they happen.