How Should Manufacturers Approach Buying CMMs?

CMMs

The Coordinate Measuring Machine, otherwise referred to as the CMM is a familiar tool in manufacturing facilities. It stands out as one of the most effective and reliable tools used in quality control. Used for three dimensional measurement and verification, CMMs come in different designs and of course brands.  This makes it hard for a manufacturer with little or no knowledge on CMMs to buy one.  There are however, factors that can make the whole buying process easy. Such factors include:

Stick To 5 Axis CMMs

Most CMMs perform the movement needed to gather data from the surface of a part. 5 axis CMM machines use a different approach. That is because with a CMM that works on a part’s surface, acceleration prompts inertial deflections in the machine’s structure. This generates errors, which can be costly. 5 axis CMM machines get rid of this problem by using an articulating head designed to move in two rotary axes as it takes measurements. This makes it easy for the CMM to move at a constant speed in one direction. The infinite positioning of the head and the resulting synchronized motion mean a 5 axis CMM like the HB or LM can easily access different parts using one stylus.

Accuracy

Servo system stiffness common in conventional CMMs often limit higher speeds, making data inaccurate and unreliable. 5-axis technology solves this problem with ease. It articulates head and two rotary axes that overcome the speed barrier. Keep in mind that the 5-axis head is lighter and more dynamic compared to what conventional CMMs use. This translates to a better bandwidth, which makes it easy for the device to follow part geometry changes with precision all because of the tip’s sensing capabilities.

Output

Measuring some parts can be hard. Take a bladed disc for instance. It is an aerospace part that presents serious access challenges. The part will call for several head indexes to accurately measure its features. Only a 5 axis device can reduce cycle times by scanning blade sections continuously.

Automatic Vs. Manual

Consider why you need the CMM. What does your company produce? Do you have several types of parts manufactured on an infrequent basis? Do you have a high volume production of just a handful or parts? You will most likely need a manual device for the former, because you, the operator, must be present to take the measurements. The latter question presents a situation where one will be need an automatic device.

It is however important to note that the aforementioned rule does not always apply. The larger the parts, the better off you are with a manual device like laser trackers and articulated arms. In a nutshell, it is easy to bring a manual inspection device to a part as compared to moving the part to the machine.

Convenience

This has a lot to do with issues such as portability and ease of use. Portable CMMs are suitable for applications like part alignment and part mating. This is mostly because they bring together spate components of large assemblies like an aircraft. This in turn saves time and money. It gets better if the CMM is easy to use, with fewer complexities.

by George Chitos

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