Minimum draft angle

Values of various curve and surface characteristics are measured at given points, between given points and along a curve or a surface to facilitate checking and evaluation of curves and surfaces to decide their appropriateness for downstream applications. Advanced methods compare measured values with tolerance specifications. Tolerances are specified for the maximum allowed gap on and between curves and surfaces, for deviation of tangent and curvature values, and on either side of the minimum draft angle. 

Minimum draft angles of 3 degrees inclusive are recommended so as to prevent problems with ejection. 

FIGURE 4.12 Test run on a mold extension area for identifying minimum draft angles... 

For further process optimization, the minimum-deformation forging was selected primarily because it was capable of producing a high-quality flash-free forging with no draft angles, thus eliminating subsequent maahining steps... 

Shell moulding allows intricate shapes to be produced with minimum taper or draft angle. An angle of to 1° is usually sufficient, compared with the 2° to 3° needed with green-sand casting. 

Referring again to Fig. 8.31, the minimum wall separation (X) should be no less than 5 times the wall thickness (W) (X > 5WO, except for extreme situations when 3 times the wall thickness can be used. However, tack-offs (P, Q, R) used to stiffen the part are feasible. The combined wall thickness (S) should be 1.75 times the wall thickness (S = 1.75W0. Inserts, such as the one at A can also be used in rotational molded parts. The recommended draft angles will vary according to the material as indicated in Table 8.15. 

Draft angle, inside ideal/minimum line of pull ... 

The minimum draft required to remove a part depends upon part configuration, depth of draw, part size, and type of GRTP used. Parts having 1-7/16 in. high walls with only 1.5 deg draft have been stripped For deeper parts, 3 deg draft is probably the minimum. Since the greater the draft the easier the part is formed and stripped, the largest permissible draft angle should be chosen. 

Incorporated channels 0-rings (round or rectangular) Minimum 1 ° draft angle is recommended... 

Draft angle usually zero, but 0.5-1 desirable on long extended surfaces, or if mold cavity is deep. Minimum section ranging from 1 mm for aluminum alloys and steels, 2 mm for copper alloys, but can be as low as 0.6 mm for some applications. 

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