Week 10 - Challenge 2- Attachment Feature Creation (Dog House)

Attachment Feature Creation

Create the Dog House for the Door Trim considering the design rules

INTRODUCTION

DOG HOUSE

Dog house is an engineering feature used in plastic design. Dog houses are used as support feature. Sometimes other engineering features like snaps, locators, and screw bosses are mounted on them to increase their strength.

Dog houses are subjected to draft analysis to prevent breakage of the component during ejection from the mould cavity. Dog house and other engineering components are built on the B-surface.

OBJECTIVE

• Create a Tooling axis for the given CLASS -A surface.
• Create the CLASS B and C surfaces of door trim using the given CLASS-A surface.
• Create a final surface model and convert it into a solid body using the close surface command in the part design workbench.
• Crea ate side core axis for the dog house
• Create Dog house on the B surface by considering the design rules.
• Perform draft analysis for both Class-A surface and Final part body.

• Tooling axis Creation

  In injection molding, the Class A surface is first analyzed to determine the axis or tooling direction that separates the molds. Tooling direction is critical for plastic product design because it determines mold direction

  What is Draft Analysis?

  Draft Analysis

  For molded or cast parts, the draft angle is the amount of taper perpendicular to the parting line. It is measurable in degrees. Because plastic shrinks and sticks on molding surfaces as it cools, we draft the walls of the plastic part so that it ejects or breaks free from the molding surfaces more easily and without dragging. To reduce the risk of damage to the parts and ensure ejection, a functional injection molding part must have drafts on both the cavity and core sides.

  Nominal values for Draft angles

  1. 3 Degrees is a nominal draft angle
  2. 5 Degrees can also be manufactured. Increasing the manufacturing cost
  3. 7 Degrees is considered for Textured surface parts

  Importance of Draft in injection molding

  • Reduces the possibility of part damage due to friction during the release
  • Reduces mold wear and tear
  • Ensures a uniform, smooth, unscratched finish
  • Ensures the integrity and uniformity of other surface finishes and textures
  • Reduces overall cooling time by reducing or eliminating the need for unusual ejection setups

  Steps followed for Draft Analysis

  • The created part must be changed to the material mode in the display frame
  • Compass is enabled and placed in the direction of the Tooling Axis
  • The lock command is then used to fix the compass along the tooling axis
  • Color codes are classified and a Draft angle is applied
  • Running point analysis is used to display permissible draft angle

  • Draft analysis of CLASS-A surface

    CLASS-B surface creation

    Class-B surface means the thickness of a part it is not visible and is inside part. In other words, the Class-B surface is a surface below a certain thickness from the class-A surface. This is the surface that contains engineering aspects of a model.

  • Crean ate offset surface of Cin LASS-A about 2.5mm inward direction.
  • Check for discontinuity and rework on the offset surface using extract, multi-extract, multi sections surfaces.
  • Join the surfaces and ensure the final CLASS-B surface created has no gaps.

  • CLASS-C surface creation

    The surface that joins class-A and class-B surfaarethe s is class-C surface. Class C is often specified for interior surfaces not readily visible, surfaces that will be covered by another part when assembled

    • Create the sweep concerningerence to the surface and tooling axismulti-extractingting the CLASS-A boundary
    • Join the sweep surfaces by using commands like extrapolate, trmulti-sectiontion surface.
    • Finally join all the sweep surfaces and ensure the continuity of the CLASS-C surface.

  • Class (A+B+C)

    Here we combine all the surfaces into one closed surface using the Trim tool Command

    Conversion of Closed surface into Solid Part

    Using Solid Command, we convert the closed surface to a solid surface in the Part model

  • DOG HOUSE DESIGN:

    Dog house: Dog house is an engineering feature used in the plastic trim design. Dog houses are used as supporting features. Sometimes other engineering features like snaps; locators, etc. are mounded on them to increase their strength. Dog house and other engineering Features are built on B-surface.

    Design rules for Dog house creation

    "C" is where the doghouse contacts the backside of the surface

    Doghouse wall thickness at the intersection of the part wall ( C ) should be 40% or less than the main wall stock ( T ).

    The height of ( B ) should be between 3.0 – 6.0 mm

    Dog house design procedure by considering the design rules:

    Extract the surface on which we want to create the dog house and create a sketch on a plane

    Dog house Sketch

  • ISOMETRIC VIEW

    SIDE VIEW

    FRONT VIEW

    TOP VIEW

    ->) For a detail dive into the model, the catia part file of the same part has been attached below.

  • Conclusion

    Creating the Attachment Feature Creation (Dog House) Plastic component through the given Class-A surface, Draft Analysis, Dog House is successfully completed.