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The Positioning Device Of Checking Fixture

Jul 27, 2017

        The gage is a general term for a dedicated measuring tool for product inspection. It can not only detect the dimensions of individual parts, but also detect the matching between parts and the relative position of the holes. The determination of gage structure design and the guarantee of measurement accuracy are largely dependent on the choice of reference plane and reference pin. Positioning device, is to make the measured parts of the reference plane, the hole and the measuring device to maintain a certain relative position, so as to ensure the measurement of reasonable and stable.

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  Commonly used positioning elements are support nails, positioning blocks, positioning pins, V-shaped blocks, mandrels and so on. The positioning elements should have high accuracy, wear resistance, strength, and stiffness. The material of positioning element is generally T9A, T10A and other tool steel. If the diameter is larger (> 12mm), 20 # or 20Cr (carburizing hardened to HRC55 ~ 65), 45 or 40Cr (hardened to HRC45 ~ 50) should be used. If the material of the product is a soft material (such as PVC, etc.), the material and hardness of positioning block can be appropriately reduced. The hardness of positioning element can be determined according to the accuracy level of measured parameters (GB / T1800-1998): Precision IT9 ~ IT11 level, hardness HRC45 ~ 50; accuracy of IT7 ~ IT9 level, hardness HRC55 ~ 60; accuracy of IT5 ~ IT7 level, hardness HRC60 ~ 65.

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  Usually the positioning of main reference point, is called positioning surface, and the support surface is to support the auxiliary reference point. The positioning surface and support surface need to be arranged according to the reference point, accurately reflecting the corresponding reference point position. The positioning criteria of gage must meet the principle of six-point positioning, which is generally distinguished by the main datum (datum), sub-datum (line datum), sub datum (datum). The main reference is generally three positioning points, respectively marked with A1, A2, A3; sub-benchmark is generally two positioning points, respectively marked with B1, B2; sub-benchmark is generally a fixed point, marked with C (as shown below).



  Common positioning methods:

        1. Face (edge) positioning;


  2. hole positioning;


  3. Outer positioning;

  4. Internal and external thread surface positioning;

  The outer positioning is similar to the external thread positioning, as shown in the following figure. The position of internal thread is similar to that of the bore, to calculate the diameter of locating pin should be according to the thread diameter.


  In the process of locating the pins, the parts must be precisely positioned on the gage before the parts are clamped and tested, and then to determine the position of positioning holes according to the part drawing reference. In the positioning hole, in order to ensure the positioning accuracy of pin positioning, guide sleeve must be installed. The center of guide sleeve, relative to the body coordinate system, need attain the positioning accuracy within ± 0.05mm.

  5. Combination benchmarking;

  Simulated sheet metal surface A, B and glass surface to constitute a combination of benchmarks.


  Checking fixture, as an indispensable tool for automobile lean manufacturing, has the advantages of simple, fast, accurate and intuitive feature, which can bring good benefits to OEMs and auto parts suppliers. Beijing Kingco has a full set comprehensive strength of gage design, manufacture, assembly, commissioning, measuring, with developed various types of auto parts and assembly seized. Beijing Kingco professional first-class design team, cooperate with FAW-Volkswagen, Beijing Benz, Beijing Hyundai, Great Wall Motor, Wuling Automobile and other domestic and foreign automobile OEMs in long term, to provide excellent product quality and caring after-sales service in the industry brand.