Information Rich Metrology – Changing the Manufacturing Game

To support the manufacture of next-generation high-value products, increased reliance will be placed on metrology. In an article published by the Manufacturing Metrology Team at the UK’s University of Nottingham discusses an approach to metrology that, in the authors opinion, has the potential to significantly enhance the metrology capability in advanced manufacturing.

Review of need for metrology in manufacturing

Lord Kelvin said: “If you cannot measure it, you cannot improve it”, and this simple statement captures a great deal
about why measurement is an essential part of manufacturing. The following are some of the primary reasons why we put so much effort into measuring what we manufacture:

• To know whether a part is fit-for-purpose; for example, will a shaft fit within a hole, but
still give enough clearance to allow the flow of lubricating fluids?
• To allow assembly of complex components; without understanding the dimensions of
parts and their associated tolerances, it becomes almost impossible to fit one part to
another – this is an especially relevant point when assembling parts that have been
manufactured in different companies or different parts of a company.
• To allow control of a manufacturing process; there is little control without measurement,
for example, we may want to change the speed of a cutting tool depending on the surface
texture that it is producing – we, therefore, need to measure the texture (or something
from which we can infer texture) during the machining process.
• To avoid unnecessary scrap material and redundant processing time; metrology is
essential for quality control which allows us to attempt things such as net-shape
manufacturing – getting it right first time.
• To improve energy-efficiency; the less repeat manufacturing processes that are required,
the lower the energy required to produce a product.
• To give customers confidence in a product; “customers” in this context could be another
manufacturing concern that needs to use your components – without tolerances and
quality control, there will be a lack of confidence in the assembly processes down the line.
• To comply with quality standards, such as ISO 9001, and with established quality control
techniques, including six sigma and process capability indices.

For the above, and many more reasons, metrology is essential for manufacturing. While
traditionally metrology has been applied to the inspection of the final part, after the
manufacturing process is completed, nowadays the trend is to bring metrology into the
production line. This may just mean performing part inspection right after each step of the
manufacturing process (for example, between a roughing and a finishing operation in a
machine tool), or we can push integration even further by carrying out the measurement tasks
during the execution of each individual manufacturing operation, where the nature of the
operation allows it (for example, within an additive manufacturing process, measuring the
properties of a layer while it is being fabricated). Also, when considering, integration between
metrology and manufacturing, consideration about the measurement data are important. One
integration scenario may see a measurement triggering an alarm if something goes wrong
during a manufacturing operation (i.e. detection of an out-of-control condition); more
complex integration scenarios may see some form of implementation of feedback
mechanisms, for example, the triggering of a corrective action, or the real-time modification
of some manufacturing process control parameter to bring the process back to an in-control
state.
Such integrated metrology needs to the compatible with the manufacturing cycle time (we do
not want metrology to slow down the process, or at least not prohibitively), and measurement
systems need to be spatially located to be compatible with the type of integration: i.e. on the
production machine, or close enough if measurement is to be performed between
manufacturing stations.

The full article can be read here.