![]() This will make that mold half the B-side. In this case, because the clip increases the surface area of that side of the part, the "clip-side" part surface will adhere more strongly to its mold half. Take for example the case of a clip formed using a pass-through core (see clip hook illustration). In some cases, however, this may not be possible. In most cases, ejector pads (or the vestiges left by their removal) are on the non-cosmetic sides of parts. The post is typically removed from the finished part in a secondary operation. When the part has cooled, the ejector pin pushes against the resulting post and, in the process, clips off the runner. In cases in which an edge gate cannot be used, resin is injected through an extension of an ejector pin channel. You can work with Protolabs' applications engineers to discuss pin locations and pin type on critical areas to ensure molding and part design concerns are solved.Ī post gate produces an extreme example of a raised ejector pad (see post gate illustration). Additionally, a longest pin, which is fully indenting, makes the plastic area thin, so make sure it is not too thin so that you do not end up with a hole in the part because of a short shot or the pin punching through the surface entirely. Keep in mind, with a shortest pin, you will be making a thicker section of plastic, which, if too thick, could potentially lead to a risk of sink on the back side of the part. Protolabs does have two other options besides just center cut: shortest, which leaves standing pad under pin or longest, which fully indents the pin into the part. See the illustration that shows center cut and shortest and longest pins on the surface. The pin would hit with half indenting the part and half raised pad on the part. The default configuration is a center-cut pin, which on an angled or curved face means the pin hits the tangent of 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 at one edge 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 will have to be a pad provided that is in the same plane as the pin-end rather than that of the part surface. A customer can have Protolabs look to see if a contoured pin is a viable option. Protolabs' process, however, usually does not support the production of contoured pins unless a customer requests it. In a traditional steel production tool it may be possible to machine the end of the pin to match the contour of a part surface that is not perpendicular to the direction in which the pin moves, producing a contoured pin. And if the surface of the part is not parallel to the flat end of the ejector pin, the cosmetic impact 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" to push against, and the surface of the pad must be perpendicular to the direction of pin movement. ![]() In Protolabs' process, the ends of ejector pins are flat and perpendicular to the direction in which the pin moves. Softer resins may also require the use of more or wider pins to spread force and prevent puncturing or marring of the cooled plastic. ![]() Some resins are "stickier," requiring more force for release from the mold. Resin choice can also affect pin placement or size. Factors like draft and texture of sidewalls and depth of walls and ribs can increase the likelihood that areas of the part will cling to the mold. Obviously the shape of the part is one (see example in illustration). Protolabs uses round ejector pins, and their placement depends on a number of factors.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |