As we know, During mold designing, If the product has inner undercut, we usually make lifter, If has outside undercut, we will make slider, But If it has undercut around the 4 corner, and couldn't be forced demoulding, what should we do? As below picture, should we make lifter or slider?

1.  Design Analysis
If so, first we will think about to make lifter, but after analyze, If make lifter the 4 corner of undercut couldn't demould(Lifter in arrowhead direction)

2.Plan of designing
If the undercut couldn't demould, We can only consider whether we can design with the lifter + inner slider. As below picture, the green part is inner slider, pink part is lifter.

3.Operation principle
When the back die core lift out the front die core, the lifter will move the inner slider, first of all to demould 4 corner of undercut, , the 4 lifter will eject product while demoulding undercut,  remove product, then close the mould for next production.