Expandable Cavities

Expandable Cavities (EX-CAV) mold undercuts such as threads, dimples, and protrusions outside of molded parts.  The patented EX-CAV design eliminates the engineering, maintenance, and machining required for side action mechanisms which results in smaller molds or higher mold cavitation.

B-Side Expandable Cavities are anchored into the ejector plates and actuated during the machine knock-out sequence. Often times a 2nd ejector plate set is used for final part ejection with an ejector pin or sleeve. Runners may go across the top of the EX-CAV and the molded parts edge gated as long as this does not interfere with the EX-CAV expansion.

Expandable Cavities

A-Side Expandable Cavities are anchored between the mold “B” plate and support plate and actuated immediately during mold open/close at the main parting line by the cavity insert. The molded parts are then generally ejected with an ejector pin or sleeve. Because there is airspace around the A-Side EXCAV at the parting line, the molded parts must be top gated with a 3-plate cold runner or hot tip.

  • Eliminates engineering, maintenance, and machining required for side action which results in Smaller molds or higher mold cavitation.
  • Four standard sizes offered to satisfy a wide range of parts.  Custom EX-CAV are available for parts up to 350mm in diameter.
  • The EX-CAV expands along a conical shape, 10˚ per side.
  • Manufactured from A-2, 54-57 HRC material for repeatable expansion. For optimal performance, the EX-CAV should ride against a hardened striker insert which can be manufactured by Roehr or customer supplied.
  • Maximum temperature: 260˚C / 500˚ F
  • Expandable Cavities generally operate without lubrication.
  • EX-CAVs can be ordered with molding detail for a ‘mold ready’ component.
  • EX-CAVs Fixtures for machining details in house are also available.
  • Standard Expandable Cavities have a molding diameter size range from 0.25mm (.010”) to 40mm (1.575”) and offer complete 360⁰ thread or undercut geometry.
  • Custom Expandable Cavities can be manufactured with molding diameters up to 350mm (13.75”)
  • B-Side Expandable Cavities are actuated by the mold KO Plates which push the EXCAV out of a tapered pocket in the “B” Plate.
  • A-Side Expandable Cavities are actuated by a taper incorporated into the cavity insert and expand immediately with the mold main parting line opening.
  • Roehr Tool can supply Expandable Cavities as “Blanks” without the machined molding details or “Complete” with molding details included so the EXCAVs are ready for moldbase installation when received by the customer.
  • Expandable Cavities can be used with all types of materials including high temperature and corrosive variants such as PEEK and PVC.
  • Protective coatings can be applied to the Expandable Cavities for wear and corrosion resistance.

Roehr’s Expandable Cavities come in a variety of sizes and shapes to fit a wide range of undercut release and part size configurations. Roehr’s Engineering Team provides support throughout the Expandable Cavity design process to ensure a successful and profitable experience for our customer’s and yours. Custom cores with size requirements that fall outside of the standard Expandable Cavitiy ranges are available. In addition, finished cores with machined, EDM’d, or ground details can be supplied. Contact Roehr Tool at information@roehrtool.com for an application review and quotation.

ExCav Additional Components

Machining Fixture
Machining Fixture
Hollow and Pin Bolt
Hollow & Pin Bolt