Core & Cavity Modeling in Pro-Engineer

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

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

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

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

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

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

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

ADD SECONDARY FEATURES TO CORE PART

  • Cut the secondary features from the core part

  • Add rounds and drafts to surfaces created by this operation

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

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

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

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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