CUSTOM EXPANDABLE CAVITY SYSTEMS Expandable Cavity System – Features and Benefits
CUSTOM EXPANDABLE CAVITY SYSTEMS Components
Lowers development and processing costs The Expandable Cavity saves money at every step – from initial tooling to processing to maintenance. Intelligent engineering reduces or eliminates many costly factors such as complex design details, core slides and required mechanical components, added maintenance and replacement of high-wear items often found in traditional slide action molds.
Expandable Cavity The Expandable Cavity is typically made of A-2 tool steel, hardened to 54-58 Rockwell “C”. The typical tool has four segments which expand radially away, under their own spring force, from the center axis of the tool. In the closed molding position, the precision fit between each segment permits flash-free molding. Striker insert The striker insert is made from different types of tool steel. It is typically hardened to 32-45 Rockwell “C” scale, depending on the application. The striker insert has a lower hardness than the Expandable Cavity to ensure the eventual wear will occur on the striker insert and not the detailed Expandable Cavity. Depending on the part configuration, the striker insert can be used in the “A” or “B” side of the mold (see Figs. 1 and 2 for details). The striker insert must be closely fit to the Expandable Cavity to ensure that in the mold closed position the segments are completely sealed against one another. The tolerance on this fit must be held to ±0.0005 inch to ensure flash-free molding. Interchangeable center pin The solid center mandrel is the most common type of center pin. It may have an inner cooling channel depending on its size. The center pin provides an internal shut-off with the Expandable Cavity. Ejector sleeve An ejector sleeve is commonly used to ensure part ejection from the cavity. The sleeve rides forward over the center pin, once the mold is opened and the cavity expanded. Many times the expansion needed is dependent on leaving clearance for the ejector sleeve. Expansion limiter sleeve If part design is such that it could tend to stick in the “A” side of the mold when the Expandable Cavity opens, an expansion limiter sleeve can be used. This sleeve will restrict expansion and retain the part until activation of a stripper plate allows additional expansion prior to part ejection (see Fig. 3) .
Typical Expandable Cavity for “A” Side Striker Insert
Broad range of benefits Simple design
The revolutionary design and engineering of the Expandable Cavity saves steps and solves problems that have complicated plastics molding for years. In addition to simplifying new tooling design, it can be retrofit to existing molds. More reliable Complete reliability of the Expandable Cavity is assured, not only by the simplicity of the design, but also by the use of superior materials and proven proprietary processing techniques. You can count on minimal downtime and higher productivity. The Expandable Cavity has been field tested over several million cycles. More compact Using the DME Expandable Cavity allows you to design more cavities in each mold. Speeds molding process The Expandable Cavity concept eliminates the need for slide-action mechanisms and the additional machining steps they require. Various part ejection methods can be employed. Speeds development The Expandable Cavity concept simplifies the engineering required to design and manufacture a new cavity. This means that your new products go into production in less time than was previously possible.
Typical Expandable Cavity for “B” Side Striker Insert
General maintenance After 100-200 initial shots, the Expandable Cavity should be rechecked to ensure proper mechanical function. A routine maintenance program of your Expandable Cavity System is recommended after 50,000 to 100,000 cycles. Thoroughly degrease and demagnetize system components. Observe for signs of abnormal wear. A light lubricant such as a P.T.F.E. should then be applied to the Striker Insert, Center Pin and the Expandable Cavity. This will increase the life of the system components. Never use a heavy grease. Re-install Expandable Cavity System. If this maintenance procedure is performed as described above, several million cycles are easily obtainable.
The Expandable Cavity is maintained under compression during molding.
As the mold opens, segments are released automatically to the expanded position, and the part is released.
U.S. Patent Numbers 5,387,389 D 356,320
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U.S. 800-626-6653 ■ Canada 800-387-6600 ■ dme@milacron.com ■ www.dme.net ■ store.dme.net
U.S. 800-626-6653 ■ Canada 800-387-6600 ■ www.dme.net ■ store.dme.net
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