When a part cools, it shrinks to the core. The draft angle helps the parts to avoid being affected by the core. Even if you have the idea of canceling the draft angle, you must not cancel the draft angle. If the draft angle decreases, the locking force of the part will increase, so the force required to separate the part from the mold will also increase.
The molding time must be extended, because only in this way can the parts be fully cooled and taken out of the mold. Because the parts must be cooled to enough hardness to be ejected without deformation.
This cooling time can account for 50% ~ 80% of the whole molding time. On the contrary, the larger the draft angle, the smaller the force required to take out the parts from the mold and the shorter the time required to take out the parts from the mold.
Considering the contradictory factors mentioned above, for most filling materials, a compromise method is to reduce the draft angle to 1. However, it is easy for people to take 1 as the customary value in any case, thus ignoring the possible cost savings brought by a reasonable draft angle.
Extended data
In mold design, the draft angle of the core or boss can be the largest in a certain height range, and the draft angle of the cavity can be the smallest in a certain height range. The draft angle of the core is the largest, and the draft angle of the moving die cavity is the smallest, so that the die can be repaired according to the actual situation of the workpiece after the die test.
The ejection mechanism of the hydroforming machine tool is in the moving die part. Only by ensuring that the workpiece stays in the moving die after opening the die can the ejection of the workpiece be effectively completed. When designing a mold, when it is not completely sure which mold half the part will stay in after opening the mold, properly adjusting the draft angle within the tolerance range of the part size can make the part stay in the expected mold half after opening the mold.
When there are concentricity requirements for d 1, d2, d3 and d4 in parts, the parting surface must be designed on the same core from A to A, d 1 and d2 to ensure the requirements of the mold, but it is difficult to determine which half of the mold the part stays in after opening the mold. When designing the die, as long as the draft angle of the moving die is as small as possible and the draft angle of the static die is as large as possible (within the dimensional tolerance range of the part), the part can remain in the moving die after the die is opened.
In the design of plastic products, it is usually necessary to set an inclination angle on the inside and outside of the edge as the draft angle, so as to facilitate the separation of the product from the mold. If the product is attached to the vertical outer wall and is in the same direction as the mold opening, the mold after plastic molding needs a lot of mold opening force to open, and it is very difficult to believe the process of product ejection after mold opening.
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