INJECTION MOLD P3 3 Semipositive
The semipositive mold (FIGURE PP.2c and d) combines certain features of the open flash and fully positive molds and makes allowance for excess powder and flash. It is also possible to get both horizontal and vertical flash. Semipositive molds are more expensive to manufacture and maintain than the other types, but they are much better from an applications point of view. Satisfactory operation of semipositive molds is obtained by having clearance (0.025/25 mm of diameter) between the plunger (top force) and the cavity. Moreover, the mold is given a 2 taper on each side. This allows the flash to flow on and the entrapped gases to escape along with it, thereby producing a clean, blemish-free mold component.
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