VISIONx has launched a patent pending technology that it says is a better way to verify that manufactured parts match up with their CAD data. The company explains the merits in this special product spotlight.
Optical comparators, also referred to as profile or contour projectors, were first introduced in the 1940s and are still used in a range of industries to verify that manufactured parts are within tolerance. These instruments are well suited for use on the shop floor as well as in the metrology and quality control labs because they are versatile, easy to use and robust. They also deal well with complex geometries (i.e. shapes not easily described by simple elements like lines and circles) and, up until now, they have been the easiest way to quickly compare a part to its drawing to allow the operator to make an overall Pass/Fail determination.
And while optical comparators are considered to be a cost effective measuring tool, it is also widely recognized that they rely on old technology and suffer from a number of shortcomings. The most important is the need to use an overlay, also called a template or a Mylar. With traditional optical comparators, the part’s drawing is scaled to match the comparator’s optical magnification and printed on a transparent overlay. This overlay is then placed on top of the comparator’s screen and aligned with the image of the part. The operator can then ascertain if the part is within tolerance. There are many problems related to the use of these overlays, including the following:
• The cost of the overlays;
• The cost and maintenance of the equipment required to print the overlays;
• The cost and maintenance of the equipment required to calibrate the overlays;
• The time required to print the overlays;
• The time required to calibrate the overlays(and verify this calibration);
• Using overlays necessarily introduces an error when printing the part’s drawing onto the overlay (no printer is perfect);
• Overlays can tear, get damaged, stained and worn;
• Overlays need to be physically stored and retrieved, taking time and storage space;
• There is a risk that the operator may select the wrong overlay;
• Overlays can be used by only one person at a time;
• If you want your suppliers to verify with an overlay the parts that they are sending you, you need to physically send it to him, which results in costs and delays;
• Setting up overlays on a comparator is a slow and operator-intensive process;
• It’s impossible to “recall settings” for an overlay (i.e. position and orientation). The operator needs to realign every time that he sets up a part.
