Lifters or Sliders for Undercuts on Four Sides?

As mold designers, we are all aware that, in normal circumstances, lifters are created for inner undercuts and sliders are created for outer undercuts. However, when we have undercuts on all 4 sides of a product, which makes it impossible to release the product by force, how should the mold be designed? See the following figure for the product. Shall we create lifters or sliders? Now, let me explain the mold design solutions for such products to all of you.

undercut around the parts

Design analysis

When coming across such products, we will firstly consider whether it is possible to create lifters. However, analysis shows that the undercuts in the 4 corners will not be able to be released with the help of lifters (lifters in the arrow direction).


Since lifters are not able to ensure complete release of the undercuts, we have to think about the design scheme that combines lifters and inner sliders. As shown in the figure below, green parts are inner sliders, and pink parts are lifters.

How it works

Mold core and cavity open a bit, then the slope of the wedge drives the sliders to move towards the center, so as to release the undercuts from the 4 corners of the product. At the same time, the lifters eject the product out while the undercuts are released completely. Finally, you can take the product out and close the mold for the next production run.

4 sliders for undercuts

undercut be released

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