The applications of a flash-free collapsible core are nothing short of incredible. Undercuts, O ring grooves, tabs, ribs, bosses, locking tabs, and threads are easily produced. Straight or even back-tapered bores are no problem.

Actually, all of the features listed could be combined on one core! Since the core contracts before the part is removed almost any feature can be molded into the side of a bore. No rotation is necessary.

Core Development
During the development of the core, the emphasis was on the sealing ability of the fingers as well as the simplification of the finishing process. Several prototypes were produced using three different manufacturing procedures.

A customer provided actual in mold testing at its facility and recorded the results. The first core flashed badly. A design flaw was discovered. Major design changes were made after this first attempt and a great deal of attention was put on the bending procedure. It seemed to be the key to a successful seal.

Two more prototypes and numerous changes to the bending fixture produced a working core. It was good, but it could be better. The best features of each of the prototypes were combined into a new design and three different processes were tried on three more prototypes.

To speed things up all three designs were run at the same time. A new and highly accurate bending fixture was created and used on all three. Initial testing in molding produced perfect results. More innovations and design changes made the core more robust and reliable.
The customer was very happy.

Yet another larger core was produced using the latest design and submitted for testing. It performed flawlessly. As an afterthought it was asked if the core could be sampled using nylon instead of the intended polypropylene. The customer agreed and once again the core succeeded. The nylon was molded at 1800 psi with no flash. The core was produced using the standard procedure. It was not tweaked to run nylon; it just seals that well.

The current design had some interesting advantages. The entire core assembly is much shorter than previous designs. This allows it to be used in smaller presses, presses that could not support a rotating setup. It simplified the mold construction—no racks, no gears, no drive components that a rotating setup uses.

All of the motions needed are performed by the normal open and close motion of the press. The finishing of the molding area has been greatly simplified. No special fixtures, no long instructions, just grind it! This presents a potential cost-effective alternative to a rotating core setup.