Corporate Buyers Guide

The heart of a coordinate measuring machine is the measuring probe. It is a very small, round tipped, needle that gently touches the object being measured. A gentle deflection tells the device that is holding the needle that it has found a point on the object. A signal is sent to the controller which records the point based on the position signals from all the axes that moved the probe. The amount of deflection of the needle is considered in determining the location of the point on the object.

Four mechanical structures of coordinate measuring machines are available for holding the measuring probe. The bridge system holds the CMM probe vertically downward on a horizontal beam which is supported on both ends by posts in a bridge fashion and is located on a granite table. This is the most common design for metrology labs and manufacturing. Gantry systems are very big bridge shapes where the horizontal beam holding the CMM probe moves in a gantry form on top of the uprights. The horizontal or cantilevered probe is held by an arm on a single fixed vertical support. The probe can move in the X direction and up and down in the Z direction. The gantry and the horizontal measuring methods are used for very large products. The fourth method is the articulated arm. Here the CMM probe is held by a 4 or 5 axis arm and all measurement are in reference to the base of the arm.

Today’s software and inexpensive computing power permit measuring systems such as a coordinate measuring machine to obtain temperature signals and other data to correct the measurements for errors due to thermal expansion or flexing parts

A vision inspection system is a tremendous tool when properly specified. Unlike many measuring and inspection tools, vision inspection requires very precise configuration of the lighting. Further, the optics of the system in terms of magnification, field of view, depth of field and resolution narrow the usage to the inspecting of a particular object.

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The “eye” of the vision inspection system is the CCD camera. In recent years the CMOS camera has made progress for certain applications. The CCD pixels send an analog signal to the frame grabber, which then converts it to a digital format. This requires complex electronics. The CMOS pixels have part of the electronics in each pixel and it sends a digital signal to the frame grabber. This simplifies the electronics of the vision system.

The CCD camera is still preferred for its higher resolution and speed. Either camera can be black & white or color. For high precision and resolution, the B&W camera is preferred.

The vision inspection system has a stage or platform on which the object is placed. The stage can move in the X and Y direction. It can be moved by hand, servo motors or be programmed by a CNC control. Height or Z axis measurements are possible by a laser probe coming through the camera lens.

 All vision inspection systems can with a dedicated computer and the required software plus a screen for visual observation