Certain part designs will remain a challenge to be produced, and it evokes a lot of effort from the designer's point of view. One such case is considered here, wherein the simulation results helped in persuading the customer to accept the alternate designs in order to make the parts much easier to produce, and to improve the yield.
The part discussed in this case is of a luminary application and has high aesthetic requirements. The part is flat on all sides, has very little to no radius, and has a 0.5 mm step with sharp edges, to be preserved throughout the production process.
Adding to the challenge, the feeding points are restricted to one surface only, and no gating points are allowed for venting or overflow pads.
Simulations were done with and without vent and over flow pads. The results indicated a significant improvement in terms of reduction flow defects in the case of shot with vent and overflow pads (Figure 5a).
Figure 5a - Simulation results without (left) and with (right) the v ent and ove1:flow pads.
Initially the customer was hesitant to accept the modifications as they were concerned about the removal of the gate marks during finishing operations. CRP developed and demonstrated an effective method to finish the part by use of a sanding operation with a fixture, resulting in the customer accepting the proposed design. CRP can substantially reduce the reject levels from the existing level of more than 40%, if not eliminating it.
