Regarding the undercut of injection molding how to release from the tooling, and which way is the most reasonable, are always common consideration in injection molding industry. Generally, injection molding undercut release from the tooling includes slider, lifter, movable insert overmoulding, gear, Shutting-off between the cavity and core sides, and parts releasing from the tooling by force, etc.. This article will make specific analysis from following aspects.
If the undercut is on the surface of the part, it is recommended to use the slider releasing from the tooling without affecting the part appearance. The undercut is determined by the part structure, and it needs to make slider based on the direction of undercut to ensure releasing from the tooling smoothly.
If the undercuts are holes with assembling and locating function, and has concentricity requirement, especially the holes are in the same line, but can not connect, it is also recommended to use the slider releasing from the tooling.
If the undercut is too large, it is recommended to use the inner slider releasing from the core side. This way is stable and reliable, but the cost is higher than the lifter’s.
If the undercut is small and inside of the part without appearance requirement, it is recommended to use the lifter releasing from the tooling. The angle of the lifter is better not exceed 12 degrees, if it is more than 12 degrees, the lifter is easy to break and deform, which will lead to press the tooling.
Movable Insert Overmolding
When the undercut can not release from the core side, can only use the movable insert. That is to say, when operating, put insert into the cavity for injection; after shaping, eject the part together with the insert; then separate from the insert by hand or machine outside.
If the inside of the part is thread, the part can only be released from the tooling by means of gear.
Shutting-Off between the Cavity and Core Sides
If the undercut does not affect the appearance and function, it can release from the tooling by shutting-off between the cavity and core sides, which is simple, affordable and stable.
Releasing from the Tooling by Force
If the undercut is small with R Angle for transition at its root, and there is enough space for deformation, it can be released from the tooling by force when one side is open. Different plastic material with different hardness, so their depth of undercut are also different. For PC and ABS materials, the undercut to be released by force can only be around 0.3 mm, and PP can be around 1.0 mm.
The undercut can help product to achieve functional requirements by assembly, meet product surface technology requirements and make the product diversification and marketization! So, it is very important to understand the rationality of undercut releasing from the tooling.