Inspecting while manufacturing – When time really is money

A subway railway cars manufacturer needed to conduct a dimensional inspection/verification. The objective was to validate the position of some fiber glass finishing part holders.

The inspection was to be carried out with a Faro arm type portable CMM, in an indoor finishing bay. Because the inspection results generated by this type of device are directly impacted by the set-up’s rigidity, the whole set-up had to be stable. Accordingly, production needed to be stopped to ensure the set-up’s global stability.

ISSUE:
The Production department refused to grant access to the railway car – even for the 2 ½ hours that we would need to do our measuring job accurately – because that would leave 8 men doing nothing, and it would delay the assembly line…

Within such companies, this kind of conflict between the Production and the Quality departments is pretty common. Most of the time, it is the Quality department – and the quality of the product – that loses to production.

So much for arm measuring then…

Luckily, there is an interesting alternative: Optical CMM that allows dynamic measurements.

WHAT’S THAT? HOW DOES IT WORK?

Well, it’s pretty simple. The system used tracks both the part to be measured and the probing device in real time. Because the part is continuously tracked while it’s moving, the components are measured just as if the part was still.

Here’s how it goes:

1. Install reflectors on the part to track;

2. Create a “Reflectors referential” from the reflectors installed on the part (at that particular point in time, the production guys must still leave the railway car so to stabilize the whole thing, but this takes only a few minutes);

3. Activate the “Dynamic mode” on the optical CMM;

4. At that point people can resume work. No more “production time” lost due to measuring!

This method allows you to measure as usual, without having to worry about vibrations or the part moving!