Attachment Feature Creation (Dog House) using CATIA V5

AIM:

Creating the dog house for door trim considering the design rules.

INTRODUCTION:

DOG HOUSE:

Dog house is a 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:

• Creating the tooling axis for the given Class A Surface.
• creating the class B & C surface of the door trim using the the given Class A surface.
• Creating the final Surface model and convert into the solid body using the close surface command in the part design workbench.
• Create dog house on the B Surface by considering the design rule.
• perform draft analysis for both class A and the final body.

DESIGN METHOLOGY:

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.

Given CLASS-A surface

Check for continuity of the given surface using Join or Boundary commands.

If there are no gaps on the A surface, create tooling axis.

Procedure for Tooling axis creation:

• Check the best possible tooling direction by manually adjusting the compass.
• By analysing it is found that the 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.

Draft analysis of CLASS-A surface:

CLASS-B surface creation:

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 offset surface of in CLASS-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 surfaces. Class C is often specified for interior surfaces not readily visible, surfaces that will be covered by another part when assembled.

Join the sweep surfaces by using commands like extrapolate, multi-sectiontion surface.

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 wthe ith Join 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
• Minimum width of the dog house is 12 mm.
• Height of B should be 3-6 mm
• Minimum draft for the dog house degrees 5 degrees to die draw.

Procedure for creating the DOG HOUSE:

• Create the dog house by creating a positioned sketch on the z-x plane. Using extrude or sweep method create dog house outer walls.
• Now close the top wall using the offset command.
• 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.
• Using Boolean operation, union trim the dog house body part with the door trim component.

3D Part model in various orientations (Isometric, Front, Side, and Top View)

DRAFT ANALYSIS:

The Draft Analysis is a command that enables you to detect if the part you drafted will be easily removed. This type of analysis is performed based on colour ranges identifying zones on the analysed element where the deviation from the draft direction at any point, corresponds to specified values.

Draft analysis is done after determining the tooling axis, draft analysis is used to check whether the minimum draft (3 degrees) is maintained or not.

• Procedure for performing the draft analysis are as follows
• Change the view mode of the component to be in customized parameter mode and then select the shading mode as materials.
• Then open the featured draft analysis tool from the insert menu.
• Then click on the use the compass to define the current drafting direction and then drag and align the compass on the Tooling axis.
• Then lock the draft direction and perform draft analysis by clicking on the component.

Colour Range representation

GREEN colour - Positive Draft

RED colour – Zero draft

BLUE colour – Negative Draft

Draft analysis of final Door trim component:

Conclusion:

I have successfully created CLASS B and C surfaces using the given CLASS A surface of the door trim created main tooling axis. Performed draft analysis of the final component with the dog house.