Core & Cavity Modeling in Pro-Engineer

By C. Hatch

Useful for Complex Molded Parts

  • Approaches part modeling from a tooling perspective.
  • Uses 3 basic parts to create a final product
    • Core – the male part of a mold
    • Cavity – the female part of a mold
    • Part Body – the solid that the core and cavity act upon
  • This approach simplifies modeling irregular and complex geometries
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Default Coordinate System Defines the Global Zero

  • This is necessary when using the “Design in Place” approach.
  • All major components have the same Zero
  • Assembly placement is within parts by the relationship between the geometry and the Zero
    • Global Zero is not used for:
    • Assemblies that rely on constraints
  • Components shared between multiple assemblies, for instance screws
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Part Coordinate System Defines the Local Zero

  • Create a Local Zero Coordinate System
    • Defined by the Global Zero
    • Defines the position of geometry to Global Zero
    • May be offset or rotated
    • Define axis directions based on project conventions
  • Create Local Datum Planes
    • Based on Local Zero Coordinate System
    • Base of all part geometry
    • Name them after the axis that define them
  • Alternate Approach
    • Use skeleton geometry to define and control the part coordinate system and planes from the parent assembly
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Use only the Local Datum Planes

  • HIDE THE GLOBAL DATUMS, FRONT, TOP, & RIGHT AND THE COORDINATE SYSTEM IN THE LAYERS AND SAVE THAT STATUS.
  • DO NOT CREATE ANY LINKS TO GLOBAL DATUMS OR COORDINATE SYSTEMS!

Define Reference Geometry for the Part

  • Points, Datum Planes, and Axis in Addition to the Local Zero features
    • Define major features of the part
      • Parting lines
      • Screw boss levels and locations
      • Interfaces to other parts
      • Screen center
  • Alternate Approach
    • Use skeleton geometry to define and control the part coordinate system and planes from the parent assembly
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Core Part Start

  • Extrude a block from the parting line
  • Make the block bigger than the final part will be
  • Add the basic internal shape of the part to the block on the parting line side
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Core Part Details

  • Add draft and rounds to features as you go
  • The earlier they are added, the better the chance of them working properly
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Create Complex Features as Separate Parts

Designing as a separate part has many advantages:

  • Drafts and rounds are performed on a simpler part and are more likely to work
  • Common features like bosses and snaps are easier to reuse in different parts
  • It is easier to swap out or remove a feature from the part model
  • Interactions between the feature and complex surfaces on the part are not part of the modeling process
  • The resulting part model tree is much cleaner and easier to understand
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Add Secondary Features to Core Part

  • Cut the secondary features from the core part
  • Add rounds and drafts to surfaces created by this operation
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Finish Adding Features to the Core

  • Cut features like ribs past the outside of the core
    • This will ensure that they conform with the contours of the housing without relying on complex surface operations or rib commands
  • When the core is complete, create a publish geometry feature of the solid surfaces
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Cut the Core from the Part

  • The part is a separate model
    • It starts out with a base block, just like the core did
    • Make the block slightly larger than the desired part in all directions
  • Use the cutout from other model feature
    • Select the publish geometry feature from the core as the cutter
  • Add any features that rely on surfaces resulting from the cutting operation
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Cut the Cavity from the Part

  • Create the Cavity Part with the same techniques as the core part
    • The cavity base block extrudes to the opposite side of the parting line from the core
  • Separate features between the core and cavity based on their draft direction
  • Add any finishing features
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Working with Multi-Part Models

  • In order to modify a subpart it must be in either the working directory or the path
  • To change a subpart such as the core, right click on it in the model tree and select open base
  • The main part must be regenerated before the changes to a subpart will appear
  • In order to create a copy of a part in another location, open the part and all subparts and use the backup command

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