The plastic parts of pipe fitting and elbow shape often need be demolded with arc core-pulling structure mold, also called with arc core-pulling mold. Generally mold consist of crank mechanism or gear system, actuated by angle pin of slider, hydraulic cylinder or motor, some times design the structure in mold with two-stage action sliders when pipe with snap-fit or internal dimples.

For standard pipe fitting and elbow parts(based on EN13480,ASME B31 or other standards ) that are easy purchased from marketing. But many industry products with non-standard pipe or elbow that cannot be replaced with the standards. If it needs big quantity, special material or unique mechanical property request, the best choice is to develop mold(injection or die-casting) for mass production.

In the respect of mold, what challenges tooling manufacturer often meet is arc core-pulling mechanism design that will be directly impact of mold cost, tooling strength, tooling making or project development schedule and subsequent tooling maintenance. Arc core-pulling mechanism normally incorporates critical structures below:
1. Crank mechanism.
2. Four-bar linkage.
3. Two-step action slider designed in mold if pipe or elbow with inner snap-fit,internal dimples or threads. (the 1st step driven by angle pin or hydraulic cylinder, the 2nd step actuated by motor.)
4. Dynamic seal of cooling and oil system design.