Tool Making - CMM (Coordinate Measuring Machine) a intro...

   CMMs are comprised of four main components: the machine itself, the measuring probe, the control or computing system, and the measuring software.

                                      Machines are available in a wide range of sizes and designs with a variety of different probe technologies. Common applications for coordinate measuring machines include dimensional measurement, profile measurement, angularity or orientation, depth mapping, digitizing or imaging, and shaft measurement. Features common to CMMs include crash protection, offline programming, reverse engineering, shop floor suitability, SPC software and temperature compensation.

IT IS:-

             A coordinate measuring machine (CMM) is a device for measuring the physical geometrical characteristics of an object. This machine may be manually controlled by an operator or it may be computer controlled. Measurements are defined by a probe attached to the third moving axis of this machine. Probes may be mechanical, optical, laser, or white light, amongst others.

Uses                                                                 

They are often used for:

• Dimensional measurement
• Profile measurement
• Angularity or orientation measurement
• Depth mapping
• Digitizing or imaging
• Shaft measurement

Features

They are offered with features like:

• Crash protection
• Offline programming
• Reverse engineering
• Shop floor suitability
• SPC software and temperature compensation.
• CAD Model import capability
• Compliance with the DMIS standard
• I++ controller compatibility

The machines are available in a wide range of sizes and designs with a variety of different probe technologies. They can be operated manually or automatically through Direct Computer Control (DCC). They are offered in various configurations such as benchtop, free-standing, handheld and portable.

New Probing Systems

There are newer models that have probes that drag along the surface of the part taking points at specified intervals, known as scanning probes. This method of CMM inspection is often more accurate than the conventional touch-probe method and most times faster as well.
The next generation of scanning, known as non-contact scanning includes high speed laser single point triangulation, laser line scanning, and white light scanning, is advancing very quickly. This method uses either laser beams or white light that are projected against the surface of the part. Many thousands of points can then be taken and used to not only check size and position, but to create a 3D image of the part as well. This "point-cloud data" can then be transferred to CAD software to create a working 3D model of the part. These optical scanners often used on soft or delicate parts or to facilitate reverse engineering.

Portable Coordinate Measuring Machines

                                          Portable CMMs are different from "traditional CMMs" in that they most commonly take the form of an articulated arm. These arms have six or seven rotary axes with rotary encoders, instead of linear axes. Portable arms are lightweight (typically less than 20 pounds) and can be carried and used nearly anywhere. The inherent trade-offs of a portable CMM are manual operation (always requires a human to use it), and overall accuracy is somewhat to much less accurate than a bridge type CMM. Certain non-repetitive applications such as reverse engineering, rapid prototyping, and large-scale inspection of low-volume parts are ideally suited for portable CMMs.

Multi-Sensor Measuring Machines

Traditional CMM technology using touch probes is today often combined with other measurement technology. This includes laser, video or white light sensors to provide what is known as multi-sensor measurement..