Additionally, a longest pin (which is fully indenting) makes the plastic area thin, so designers should make sure it is not so thin that you end up with a hole in the part on account of a short shot or the pin punching through the surface entirely. Keep in mind that with the shortest pin, you will be making a thicker section of plastic-which, if too thick, could lead to sinking on the back side of the part. There are two other options besides just center cut: Shortest leaves the standing pad under pin, while longest fully indents the pin into the part. The default configuration is a center-cut pin, which on an angled or curved face means the pin hits tangent to the surface. Configuring a pad that is slightly recessed into the part surface is the default configuration for pins on contoured surfaces. Because it is in a different plane than the part surface, the pad may be raised slightly above the part surface or recessed slightly below the part surface at one edge. If a pin needs to act on a part surface that is not parallel to the pin-end, there should be a pad, provided it is in the same plane as the pin-end rather than that of the part surface. From top to bottom, these include a center cut pin, which is indented on a curved part surface shortest cut pin, which adds a pad, shown in yellow, above the curved part surface and longest cut pin, which fully indents the pin into the part. The above illustration shows three basic types of pins on a non-flat surface. Many molders usually do not support production of contoured pins unless customers request it. In traditional steel production tools, it may be possible to machine the end of a pin to match the contour of a part’s surface that is not perpendicular to the direction in which the pin moves. And if the surface of the part is not parallel to the flat end of the pin, the cosmetic marring will be even more obvious. If the part surface at that location is textured, the smooth surface of the pad will be apparent. To be effective, the pins need a flat “pad” on the part to push against, and the pad’s surface must be perpendicular to the direction of pin movement. Some molders use round ejector pins with flattened ends perpendicular to the direction in which the pin moves. Softer resins may also require more or wider pins to spread the removal force, as well as to prevent puncturing or marring of the cooled plastic. Some resins are “stickier,” requiring more force for release from the mold. Resin choice also affects pin placement or size. Other factors, such as draft and texture of sidewalls, and depth of walls and ribs, increase the likelihood that areas of parts will cling to the mold. The number of ejector pins and their placement depends on several factors. Once the mold is opened, the pins extend into the mold cavity, push the part out, and then retract, letting the mold close and be refilled. Pins are in the B-side half of the mold, the side in which the part remains when the mold is opened. This is an example of the illustration some molders provide early in the process of designing the mold so that the location and size of both the gate(s) and ejector pins can be approved. In some cases, manufacturers provide contour pins, which are ejector pins manually ground at an angle to closely match the part’s contoured surface. The goal for engineers and molders is to design and position pins to minimize their effect on parts although molders typically determines pin placement, customers get to sign off on pin locations before an order is finalized. They let technicians apply a force to eject a part from the mold, and, in some cases, can leave marks. Ejector pins are the “bouncers” of the injection molding world.
0 kommentar(er)
