Today, we learned a hard but valuable lesson in quality control. During the FQC (Final Quality Control) for a batch of 500 stainless steel valve plungers, we caught a critical deviation.

The drawing strictly required a surface roughness of Ra 0.8 on a specific flat surface. Visually, the parts looked fine. But numbers don't lie—our surface roughness tester showed Ra 1.361. Upon closer microscopic inspection, slight chatter marks were visible

We immediately initiated a 5-Whys Root Cause Analysis:

🔹 Why Ra 1.361?

Chatter marks occurred during the turning process.

🔹 Why the chatter marks?

The depth of cut/feed rate was set too aggressive.

🔹 Why change the feed rate?

The operator wanted to speed up the production cycle.

🔹 Why wasn't this caught during FAI (First Article Inspection)?

The technician relied on visual judgment instead of using the measurement instrument.

🔹 Why rely on visual check?

It rarely causes chatter here. Can we accept it as a concession?"

My answer was a hard NO.

The root cause wasn't just a wrong parameter; it was a lapse in our quality mindset and strict FAI execution.

We scrapped all 500 pieces. Yes, it hurts our margin, but accepting "good enough" stops growth and kills customer trust.

We completely remade the entire batch, verified the Ra 0.8 requirement with instruments on every First Article, and only then prepared them for delivery.

When you make excuses for poor quality, you stop growing,rigorous QA is our only standard.

#PrecisionMachining #StainlessSteelMachining #QualityControl #CNCmachining #5Whys #ContinuousImprovement #ValvePlunger #MechanicalEngineering

No excuses in precision machining. If it fails the spec, it gets scrapped.