Fast, easy and convenient LDDM system

Fast, easy and convenient LDDM system

Bao Jianping, Anhui Metrology and Testing Institute

In August 2002, our firm purchased an MCV-4000 laser Doppler measuring instrument (LDDM) from Optodyne, Inc. Over the past two years, we have tested more than 150 coordinate measuring machines, 7 length measuring machines with a measuring range of more than two meters, more than 100 mechanical machining centers and optical coordinate boring machines and other large-scale machining equipment. Obtain considerable economic benefits.

The LDDM system is built using the principle of Doppler frequency difference effect, and is widely used in the testing and calibration of machine tools, coordinate measuring machines, XY platforms and various precision instruments. It has a compact structure, light weight, about 14 kg; easy to install and operate, fast to light; its Windows software automatically collects data and adopts RS-232 interface, which can automatically compensate for environmental conditions. In addition, we calibrate once a year and send it to the superior technical institution for tracing three times in a row. The frequency of the laser light source is stable and the length measurement accuracy is high. All of them meet the requirements of the JJG739-1991 dual-frequency laser interferometer working standard verification regulations. After more than two years of use, we feel that the biggest advantages of the system are high accuracy, stable and complete performance, easy operation, easy portability, affordable price, and high cost performance. It is a good choice for provincial and municipal technical institutions.

The LDDM system is easy to operate, and with a little training, it can be used. In particular, it is simple to debug the light. When detecting the six-meter coordinate machine, the light can be aligned properly by going back and forth twice. The system only needs 60% of the reflected light intensity to work. Even if the mirror is deflected by 20 degrees, it can still read normally.

This system has no beam splitter, no traditional bulky tripod, no need for heat engine and temperature balance, which greatly shortens the measurement setup debugging time, basically can work after starting. It takes only 45 minutes to detect the six single-axis indication errors of a six-meter double cantilever coordinate measuring machine. At the same time, due to the few components of the system, the structure is small and compact, and it is easy to carry, no abnormalities have occurred during the long-term journey bumps that have been field-tested for more than a year.

2003 was one of the hottest years. In August 2003, when we went to the workshop of a car manufacturer to inspect the CMM, the outdoor temperature was 39 ° C and the indoor temperature was as high as 34 ° C. There were dozens of processing equipment running around. Despite the harsh environment, the LDDM system works normally and stably, showing good anti-jamming functions and strong automatic environmental compensation capabilities (such as air temperature, air pressure, and temperature of the inspected instrument).

In early 2003, an enterprise had three newly purchased coordinate measuring machines to be tested. We consciously turned on the LDDM system continuously for nearly eight hours, and checked three coordinate measuring machines in one go. After inspection, the laser light source of this system has stable frequency and normal accuracy display, which has withstood severe tests.

In July this year, we participated in the installation and commissioning of the CMM. When detecting the straightness of the coordinate machine, the flight measurement function was used to collect data and draw a curve, which completed the commissioning work faster and better with the coordinate machine manufacturer. At the same time, the LDDM system worked continuously for seven hours without any abnormalities, and once again withstood the test.