In-process quality control

Why looking is not enough

The capacity of a thin-walled section comes from the effective cross-section: the part of the plate elements that actually carries load. If the flange or lip width drifts by a few tenths of a millimetre, stability behaviour gets worse — while nothing is visible to the eye.

In-process control is therefore measurement, not inspection by eye.

What is measured

The typical check points:

• profile length — the accuracy of cutting,
• the position of the operations: the height and offset of screw point markings, the position of holes,
• flange and lip width,
• straightness,
• squareness — the angle of the bends.

Tolerance values for these come from the machine’s documentation.

When it is measured

At the start of a run

Always the first parts after a new profile, new coil or new setting. Profile changeover is part of the operating procedures.

During the run

By sampling. In cold forming the characteristics do not jump, they drift slowly — tool wear is gradual, so the error grows gradually too.

At the end of the run

As a closing check, so the statement covers the whole run.

Where the result goes

Measurement is only worth something if it is kept. With a digital quality control form it attaches to the project’s production job, so it stays traceable: which member was made with which program and what setting.

That traceability is what can be used in a later dispute — worth far more than a general declaration. Nexa and Factory2.

The designer’s side

If a produced member does not match what the design assumed, that is a structural question, not an erection one. Then:

• the size of the deviation has to be established,
• its effect on capacity assessed,
• and a decision made whether it can be installed.

That is a designer’s decision, not a manufacturer’s.

The point

In-process measurement is the link between the structural model and reality. Without it the calculation stays an assumption rather than a verified statement.