RT Collapsible Core

Roehr’s RT Series Collapsible Cores (RT) are available in sizes to fit most inside detail applications. Whether molding threads or complex details, these cores can simplify design and production. Collapsible Cores allow for smaller molds to run faster cycles with less moving parts.

Both styles of the Collapsible Cores (Standard and MiniCores) are three-part assemblies, designed for simplicity of installation, reliability in operation, and long life. The three parts include a Collapsible Core, a Positive Collapse Sleeve, and a Center Pin.

RT Collapsible Core

Roehr’s MiniCore broadens the applications of collapsible core molds to parts as small as 0.425 inches. Due to the smaller diameters involved, the MiniCores employ three larger collapsing segments combined with three narrow, non-collapsing blades which are part of the center pin. As a result, the internal undercut geometry is not 360 degrees around but instead interrupted in three places. The 3-blade design allows for more collapse which means a deeper undercut feature can be released.

In addition to threads, other configurations such as dimples, cut-outs or protrusions beyond the capabilities of unscrewing molds can be successfully molded. Three standard sizes of MiniCores are available with diameters from 0.425 to 0.965 inches.

  • Simplicity of installation
  • Reliability in operation
  • Long life
  • Faster cycle times
  • Improved part quality
  • Faster cycle times.
  • Easier to maintain.
  • Three part assemblies

Material A-2 | Hardness 54 – 57 HRC

  • Designed to collapse independently when the center pin is withdrawn.
  • The fit between segments is controlled to permit flash-free molding.

Positive Collapse Sleeve

Material 52100 | Hardness 54 – 57 HRC

  • Designed to function if the Collapsible Core should fail to collapse independently. In normal operation, the PC Sleeve is not functioning. It is essential to have such a unit for maximum safety and reliability in automatic and semi-automatic operation.

Center Pin

Material D-2 | Hardness 60 – 62 HRC

  • Serves to expand the segments of the Collapsible Core to their molding position.
  • The pin must protrude beyond the face of the collapsing core segments, and it must have a radius around its top edge to operate properly.

Standard Collapsible Cores have a Max. OD (“A”) of thread or configuration ranging from .720”(18.29mm) – 4.225” (107.31mm) and offer complete 360˚ thread or undercut geometry.

MiniCores have a Max. OD of thread or configuration ranging from .645”(16.38mm) – .965”(24.51mm) and offer up to 70% full thread or under­cut geometry. (Internal geometry is interrupted in three places to allow core segments to collapse.)

Molded parts do not need to be closed at one end. They can be partially or completely open. Also, undercuts do not need to be continuous.

Cores are capable of operating without benefit of lubrication, however, treat­ing the Collapsible Core with an additional treatment for wear reduction or corrosion resistance is beneficial.

Roehr’s collapsible cores 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 collapsible core 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 Collapsible Core and MiniCore 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.

RT Additional Components

Grinding Rings
Grinding Fixture