Coordinate Measurement Technology: An Introduction To Dealing With Microns

Quality control is no longer just for finished products—measurement technologies now actively control the entire manufacturing process. Contributed by Faro

Quality is not monitored, it is produced. Suppliers to the automotive sector could tell you a tale or two about this. Not only do they need to deliver their parts to large car manufacturers “just in time”, the parts also need to be near fault-free. If product quality is not up to standard, these companies could lose their customers.

The importance of precision measurement is now a recognised reality in today’s manufacturing world. As technology improves, so have the tools available to manufacturers—both in their function and in their accuracy. A broad range of tactile and optical measurement technologies are now available to manufacturers.

The most common of these tactile or touch technologies is a group of devices collectively known as hand tools. This family includes classics such as micrometres and callipers. They are some of the most frequently used hand measuring instruments, but they are not without fault. As they rely on the user to take the measurements and correctly interpret the results, measurements can vary greatly depending on the operator. Furthermore, hand tools also do not easily provide the measurement documentation demanded by today’s customers.

Tactile Measurement In Manufacturing

Coordinate measuring machines collect detailed dimensional data by moving a ball tip sensing device called a probe along the surface of the part being measured.

Optical or non-contact measurement technology has been greatly improved in recent years. Though they often work reliably, offer the advantage of being contact-free, and are increasingly easy to use, many of these devices do not provide the high level of accuracy of tactile methods. Those optical devices that do yield relatively accurate results can only take measurements in two dimensions. Tactile methods continue to be the best option when three dimensional measurements in the micron range are required.

Though traditional in their use and common in manufacturing, lower-cost tactile technologies like hand tools are not enough by themselves to ensure long-term manufacturing quality. Traditional hand tools and improving optical methods can be used to support other measurement processes, but to achieve the measurement accuracies demanded today, they often cannot be viewed as standalone full solutions.

Complex Manufacturing Processes

It is not just about accuracy. Parts and components are becoming increasingly more complex as a result of faster and more accurate processing techniques. Measurement technologies need to keep pace with this reality. If users want to safeguard complex manufacturing processes, they should make use of improved coordinate measurement technologies.

In modern manufacturing, a wide variety of products are produced in a single process. This is an additional challenge for measurement engineers as control must be maintained over manufacturing processes at all times. Such control is currently only possible with flexible coordinate measurement technologies.

Design engineers also play an important part as their work is yet another area where companies use coordinate measurement technologies. When designing new or improved parts on their computers, they generally do not worry about how easy or difficult it will be to inspect the parts later on. Fabrication methods that take measurement technologies into consideration could help alleviate this problem.

Importance Of Traceability

A distinct advantage of coordinate measurement technologies is their traceability. Conformity to national and international standards is extremely relevant as it is the only way to validate measurement results. It enables users to verify that their parts are in tolerance with a high level of confidence. Companies integrated into the global value-added chains rely heavily on traceability.

Coordinate Measuring Machine Design

Portable CMMs take the accuracy and consistency of traditional machines right to the manufacturing floor where they can be moved around and used conveniently.

Coordinate measurement technology is often deemed as the definitive authority in the metrology sector and with good reason. Coordinate measuring machines (CMMs) have experienced an extremely rapid level of development since their introduction in the 1950s.

CMMs collect detailed dimensional data by moving a ball tip sensing device called a probe along the surface of the part being measured. In simple terms, all CMMs determine the coordinates of a point in space. Linear encoders built into each axis allow them to track their movement relative to the probe with very high precision. High accuracy devices used properly and under ideal conditions can give results that deviate from the true value by as little as 0.1 μm.

Some CMMs are manually operated while others are computer controlled for automated inspections. When they were first introduced, all CMMs required a specialised operator to manually move the probe from point to point to take measurements as they were not computerised and required the operator to record and calculate measurement data and results.

Today’s manufacturers increasingly rely on the precision provided by CMMs. This fact is due to the accuracy and traceability they provide to an ever demanding market.

Optimised Functionality

The parts to be measured by CMMs are usually digitised point-by-point. Touch probes trigger when contact is made with the surface, automatically recording the resulting position. To ensure the effectiveness of the process, encoders and sensors must be routinely calibrated.

The measurement values are processed using a host computer and the captured points are used to calculate basic geometry. These include deformities, curves, and freeform shapes. The computer is also responsible for controlling the measurement machine itself. Results can be easily graphed thus, optimising the reporting process.

Measurement Technology As A Service

Traceability is a distinct advantage of coordinate measurement technologies.

The use of CMMs is often decided by a company’s engineering or quality department. The measurement technology manufacturer must work with the prospect’s engineers in order to ensure the technology provided fulfils the customer’s requirements. CMM software must be flexible and adaptable to various needs to ensure that the quality of the parts and part components being manufactured is not compromised.

Often, measurement technology manufacturers offer various solutions for a company’s entire product portfolio and the unique problems each presents; giving those looking for improved measurement and manufacturing processes more control of their measurement strategy.

A Portable, Tailored Solution

Today’s CMMs are offered in different performance classes and can be customised to match individual requirements. Regardless of company size, CMMs are an integral part of the quality control process. Small, medium, and large sized companies all can have similar applications and even more similar goals: to manufacture the best possible product using the best possible process.

Though CMMs have been improved from their early days in the 1950s, they still operate using the same principles as when they were invented. Accuracy as well as functionality have been improved, but traditional or fixed CMMs still have flaws. The most obvious is their need to remain in a fixed position. To effectively monitor manufacturing processes, dimensions must be checked quickly and accurately right on the production line.

A suitable alternative to fixed CMMs is the portable CMM. They take the accuracy and consistency of traditional machines right to the manufacturing floor where they can be moved around and used conveniently. This minimises or even eliminates the downtime created by having to take parts to a CMM room.

Traditional CMMs still carry relative high price tags and complexity. Portables have not only broken the inspection room barrier, they are far less expensive and relatively easier to use than their traditional counterparts. Portable CMMs deliver faster returns on investment, improved functionality and a better user experience.

APMEN Metrology