MANUFACTURING DIARY #04

Manufacturing Diary #04
The CNC Could Make It. So We Didn't Use It. Why?

We had a CNC machine that could make the part.
So we decided not to use it.

Sounds strange, right?

The drawing had deep ribs, sharp internal corners, and hardened steel.
Technically, our CNC could handle it.

But making it that way meant:
Long-reach tooling
Deflection and chatter risk
Multiple setups
Tool-breakage risk
More finishing
More inspection

At that point, we weren't really optimizing the part.
We were optimizing the process around proving that CNC could do it.

So we looked at the geometry again.
And sometimes, the smarter answer is sinker EDM.

Not because EDM is better.
Because the geometry is asking for a different process.

This is one of the traps in manufacturing.

We often think the most capable machine should be the best machine for the job.
But machine capability is only part of the equation.

What matters is the whole process:
Setup + tooling + machining + finishing + inspection + risk + lead time

A lower hourly rate can create a higher-cost part.
A more expensive process can sometimes produce a cheaper one.

Don't optimize the machine. Optimize the part.

That's why I stopped asking only:
“Can CNC do it?”

The better question is:
“Should CNC do it?”
Capability answers “can.”
Engineering answers “should.”

Shop Floor Note
The best manufacturing process isn't always the one using the most capable machine.
Sometimes, good engineering means knowing when not to use it.

Have you ever chosen not to use the most capable machine for a job?
I'd be interested to hear why.