Analysis on planning management of vacuum pump structure fixture

Fixture design According to the above process scheme, we designed two sets of special fixtures. Both sets of clamps are mounted on the lathe spindle flange with a206H7 stop. The clamp 1 is an eccentric clamp, and the a206H7 stop is eccentric with the a184h7 boss to ensure the eccentricity of the workpiece hole. The clamp 2 is a concentric clamp for ensuring the coaxiality requirement of the workpiece hole. In order to ensure that the eccentricity of the workpiece meets the requirements of the drawings, the eccentricity e of the clamp 1 must be limited to a certain tolerance. Set the tolerance of the eccentricity e of the clamp 1 to $e, the fit of the clamp to the positioning surface of the lathe spindle flange is a206H7/h6, the maximum clearance is $1max= 0.075, and the maximum clearance of the work piece to the clamp 1 a184H9/h7 is $2. Max = 0.118, the maximum error of the eccentricity of the workpiece is: $max=$e12($1max $2max)=$e 12(0.075 0.118)=$e 0.0965. So, $e=$max-0.0965. $max=0.1@2=0.2, substituted into the above formula: $e=0.2-0.0965=0.1035. Therefore, the eccentricity of the clamp 1 should be controlled within the range of 12.5-0.05. Similarly, if the coaxiality error of the workpiece hole is $d, the coaxiality error of the two positioning cylindrical faces a206H7 and a180h7 on the clamp 2 is $f, then: $dmax=$f 12($1max $2max) =$f 12(0.075 0.103)=$f 0.089. Therefore, $f=$dmax-0.089=0.1-0.089=0.011. From the above calculation, it can be seen that $fU0, that is, the fixture 2 actually does not allow the coaxiality error to exist. Therefore, we have adopted the method of mounting the fixture 2 on the lathe and then machining the a180h7 positioning surface to eliminate the coaxiality error of the fixture 2 itself, thereby ensuring the coaxiality tolerance requirement of the workpiece. The machining process plan and fixture design we selected have been verified by practice, which not only ensures the machining accuracy of the workpiece, but also takes into account the production efficiency, and makes full use of the existing equipment potential and reduces the processing cost. This process is a convenient, economical and reliable process for processing such workpieces.