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How To Choose A New Coordinate Measuring Machine

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Quality control is a major concern in the contemporary manufacturing sector, and coordinate measuring machines (CMMs) are the current industry standard for ensuring that newly produced parts are accurate to blueprint specifications. 

But while all CMMs share the same based components (the machine body, the probing system, the computer components and the software itself) CMMs are also highly specialized, and designed to meet specific metrological needs. In order to select the right CMM for your production line, you will need to understand how a CMM’s particular shape, size, and technology make it suited to one type of measurement or another. 

Those who follow the latest news about CMM equipment will know that CMMs are typically divided into two classes, those that use manual probes, and those that use light to scan parts and products. These two classes can be subdivided even further into gantry, bridge, cantilever, and horizontal arm (in the case of manual probe CMMs), and white light and laser scanners (in the case of non-manual CMMs).

Most production lines rely on manual probe CMMs, but even here the different between a bridge CMM and a horizontal arm can be very significant, which is why it is important to know the comparative strengths and weaknesses of each CMM. 

Here is a general breakdown of the different types of manual probe CMM and what tasks they are best suited for:

  • Bridge: The most popular style of CMM, a bridge CMM moves the probe along the X, Y, and Z-axis, and sensors along each axis monitor the probe’s movement to gather extremely precise information about the part’s measurements. Bridge CMMs are simple to build, and easy to use and maintain, which has made them a popular metrological solution for small-to-medium size parts. 
  • Gantry: These are typically the largest CMMs, and are often mounted directly onto the shop floor via a series of pillars. Gantry CMMs are used to measure large or very heavy parts that nonetheless need to be built to a high degree of accuracy. Due to their size and weight, gantry CMMs are usually not seen outside of factory floors producing large items for the automotive and aerospace industries. 
  • Cantilever: Like gantry CMMs, cantilevers are much more specialized, but where the gantry specializes in large parts, the cantilever focuses on smaller ones. The beam that measures the X-axis attaches to the side of the structure that houses the Y-axis. This imposes strict size limitations, but makes the cantilever CMM more suitable for automatic loading and unloading. 
  • Horizontal Arm: This is one of the most innovative types of CMM. Using a probe attached to protruding arm, horizontal arm CMMs are often used in tandem to measure both sides of a part simultaneously. For this reason, they are commonly found in the automotive industry, although they are also used to measure smaller parts.

In most cases, these types of CMM all come in different sizes, but generally one will be favoured over the others in a particular sector. While there are other considerations that need to be taken into account when selecting a particular CMM (the materials from which it is made, for example), choosing which of these styles works for you production line will be the first step toward finding the right machine for you.

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Milos Radakovic