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

Q: Create the Dog House for the Door Trim considering the design rules mentioned in the video. Consider the thickness of the part to be 2.5 mm.

"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 

ANS: Class-A surface means visible surface. It gives the aesthetic of the component which is created by the styling team and gives to the part design engineer to create the part with all engineering aspects.

Before starting the creation of the class B surface we must ensure that the given class A surface is properly closed and the surface continuity is proper. This can be done either with the help of the join operation or by using the boundary feature.

Creation of main tooling axis

• Check the best possible tooling direction by manually adjusting the compass.
• By analysing it is found thathe t y axis as tooling direction would clear most of the faces without any difficulties.
• Now extract any surface and create a mid-point on it.
• Then create a dummy axis creating a line on the point and direction along the y-axis.
• Perform draft analysis to find whether the given axis clears the draft analysis. If not create a new tooling axis.

• Intersection method

  • Create a new tooling axis by intersection method.
  • Create intersection along z and x directions.
  • Take the first intersection and Create lines which are coinciding the curves having a draft angle. Then create bisecting line 1 concerning the lines created.and do the same to another side also,
  • Using the bisecting line 1 and line 2, create a new bisecting line and if it clears the draft analysis test,it will be the main tooling axis.

  • 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.

    • Create an  offset of class A surface to distance of 2.5mm inward direction.
    • Check for discontinuity and rework on the offset surface using extract, multi-extract, multi sections surfaces.
    • use boundary tool to check whether the class B surface has any open areas

    • CLASS-C surface creation

      The surface that joins class-A and class-B surface 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,it gives thickness to the part.

      • Create the sweep from the class A surface edges by creating boundary and sweep direction should be same as tooling direction,
      • Create multiple sweeps where single sweeps are not possible,
      • Finally join all the sweep surfaces and ensure the continuity of the CLASS-C surface.

      • Creating the Final surface

        • For creating the Finals door trim surface, join the CLASS-A and CLASS-C surfaces together.
        • Then Extrapolate the B surfacea  little bit outward direction to make sure that there would not be any gap when trimming with the joined surface.
        • Then trim the extrapolated CLASS-B surface with Joined surface CLASS-A and CLASS C
        • Make a solid part body using the close surface command in the part design workbench

        • DOG HOUSE Creation

          • Dog houses are designed to avoid SINK MARK created on the CLASS-A surface by screw bosses and to solve the length issues when giving screw bosses which need to be assembled to other components.
          • It is also useful when perpendicular screw bosses are required on the part to the tooling direction.
          • C thickness should be 40% of the main wall thickness T
          • Height of B should be 3-6 mm

          Procedure for creating the DOG HOUSE

          • Create a side core axis.
          • Chose the normal to-the-point method for creating the side core tooling axis.
          • Create the dog house by creating a positioned sketch on the z-x plane. Using extrude or sweep method create dog hose outer walls.
          • Now close the top wall using offset surface and trim it
          • Using thicken command in the part workbench, create a solid part of the dog house.
          • Give proper draft angles and fillets by considering the design rules.
          • create dog house by offseting side walls at a distance of 40% of wall thickness,
          • Trim the dog house with the main door trim panel.
          • Create side core tooling axis in X direction
          • Give drafts to the inside portions of dog house of 0.5 deg.
        • All the images are given below,
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      • CONCLUSION

        Dog House for the Door Trim considering the design rules has been created in Catia V5.