A day on the assembly line

Every machine is run, measured and signed off before it is boxed. Here is what a day on a power-tool assembly line generally involves, what gets checked along the way, and what happens to a machine that does not pass.

Building in steps

A power-tool assembly line is usually divided into stations. At each one, a few parts are added and a few things are checked: a bearing pressed in, a gearbox fitted, a cable routed and clamped, a housing closed and screwed together. Splitting the work this way means each step is done the same way every time, and a fault is more likely to be caught close to where it happened rather than at the very end.

Much of the checking happens during assembly rather than after it. A screw tightened to the wrong torque or a part fitted the wrong way round is far easier to put right while the housing is still open.

What gets checked

When a machine is complete, it is switched on and run. Checks at this stage typically cover the things a user would notice first, and a few they never would:

• Electrical safety. Insulation and earthing are tested, because a machine that runs well but is not safe is not finished.
• Running behaviour. Speed, noise and vibration are compared with what the machine should do. An unusual sound often points to a bearing or gear that is not seated correctly.
• Functions. Switches, speed control and any electronics are tried in turn, so the machine behaves as the manual describes.
• Fit and finish. Housings, guards and base plates are checked for gaps, loose parts and damage.

A machine that passes is signed off and packed.

When a machine fails

A machine that fails a check is taken off the line. It does not go into a box with a note to sort it out later. It goes to rework, where the cause is found, the part concerned is replaced or refitted, and the machine goes through the checks again. Only when it passes does it carry on to packing.

Failures are useful in another way too. If the same fault turns up more than once, it usually points to something earlier in the process, such as a batch of parts or a step at one station, and that is where it gets fixed.

Why it matters to you

For a tradesperson, the point of all this is simple. The machine you take out of the box or Systainer should work the first time, and work the same way as the next one off the line. That consistency is built in on ordinary days like this one.