What Is a Coordinate Measuring Machine? How Does Leasing One Save You Time & Money?

There are various bridge-type CMMS available, however, all bridge CMMs consist of a moving staging table (bridge) configuration that includes a measuring head used to determine values on the Z-axis by moving up and down the bridge of the machine.

The bridge covers the distance of the machine’s base. The same measuring head also determines the values on the X-axis, which is accomplished by moving the head back and forth across the bridge. Y-axis values are measured by moving the entire bridge over the granite base.

Fixed-bridge CMMs, also known as stationary CMMs since they do not move, measure the Y-axis by moving the staging table instead. Consequently, a stationary CMM can determine Y-axis value with a higher degree of certainty, but is unable to support larger amounts of weight.

A cantilever CMM is used for smaller measuring ranges. It differs from a bridge-style CMM in that the moving measuring head is attached to one specific side of the machine’s base, making this type of measuring machine less flexible.

The machine’s large support base combined with it’s low weight allows for efficient and accurate measurements with very little measurement uncertainty.

This type of coordinate measuring machine is not as accurate as others. However, horizontal arm CMMs are very useful when measuring larger parts and workpieces that don’t require highly accurate measurements. Their flexible design makes measuring difficult-to-reach features easier, and their size can accommodate larger pieces.

Horizontal arms on either side of the machine are paired, working simultaneously to produce measurements that are collected via one single coordinate system.

A gantry configuration is similar to a bridge CMM, but is typically much larger. The machine’s measuring volume, which determines the maximum size of an object the machine can measure, is increased by raising the bridge on mounted pillars.

Being structurally similar to a bridge CMM, but capable of measuring much larger parts with a high degree of accuracy, make the gantry CMM highly relevant in the aerospace industry.

There are many varieties of portable and handheld CMM devices that include both contact and noncontact options, such as articulating arms and laser tracker systems. Portable CMMs are used to determine highly accurate measurements and can provide more information than a caliper or micrometer.

The computer-aided design means inspection of manufactured parts is precise and accurate, and their mobility in comparison to large, stationary CMMs can be a huge advantage in shops where space is a limiting factor.

Coordinate measuring machines use different types of probes and probing systems to generate an electrical signal each time the probe contacts a point on the manufactured part. The position and angle of one of three probes on its axis is determined by a sensor monitoring its position, allowing for more complex surfaces to be measured.

When the probe contacts or detects a particular location on the surface of an object, the machine samples the location of all three position sensors and measures the location of that one specific point on the object’s surface that’s come in contact with the specific location on the object’s surface.

This process is then repeated across the object, creating a point cloud that describes the areas of interest on the object’s surface. The point cloud is then used to generate a three-dimensional digital image, or map, of the object.

There is an extensive selection of CMM probes available, which can either be contact or non-contact. Probes, depending on their design, can operate manually or automatically. When they are controlled automatically, they maneuver using Computer Numerical Control (CNC) or Direct Computer Control (DCC) software.

However, when used manually, they can be triggered by touch. These types of probes are referred to as touch trigger probes, and are quite common today. Multi-sensor probes that combine optical and touch scanning are also available.

The standard CMM programming language is called dimensional measurement interface standard (DMIS), however, it is not used by every CMM manufacturer. CAD/CAM programs are also used by some CMM machines.

Software compatibility should be taken into consideration when deciding what CMM system is right for you. Many machinists are trading in their master parts for master CAD models as software integration continues to make advances in measurement testing and inspection processes.