Flat Blank 



Material = grade G Plexiglas, unshrunk, 



nominal 0.5-in. plate 

 Flat blank diameter = 9-7/8 in. 



Circumference of flat part = 31 .0 in. 

 Actual thickness = uniform, 0.494 in. 

 Area of flat blank = 76.3 in. 2 



Formed Spherical Sector 



Circumference of 8-31/32-in. chord = 28.17 in. 

 Circumference of 9-17/32-in. chord = 29.95 in. 

 Length of the 7-in.-R arc = 9.7 in. 

 Length of the 7.5-in.-R arc = 10.25 in. 

 Area of concave side = 71 .5 in. 2 

 Area of convex side = 77.8 in. 2 



Cross Section at Centerline 



Variation in Thickness of the Formed Part 



Point No. Thickness (in.) 



1 



0.481 



2 



0.478 



3 



0.485 



4 



0.477 



5 



0.480 



6 



0.480 



7 



0.473 



8 



0.473 



9 



0.477 



Location of Points 

 on Flat Blank 



Figure 25. Typical sphericity and thickness of spherical sectors after die pressing 

 to 7.5-inch nominal radius of curvature. 



In addition to thickness, the curvature of the spherical sector was 

 also measured prior to annealing. In general, the curvature of the spherical 

 sector was uniform and closely matched that of the female die. The external 

 radius of the sector was within 0.000 to 0.005 inch of the mold curvature. 

 The largest deviations occurred at the center and at the edge of the sector, 

 while midway between the center and the edge there was the least deviation 



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