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

AIM:

To 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 to avoid sink mark forming in asthetic class A surface. 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.
• Create 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.

Design Methodology

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

B surface is created by offsetting Class A surface to 2.5 mm as the wall thickness is given as 2.5 mm.

Now the offsetted class B surface having slot of pathes so we have to rectify those by using join command to extract those subelements and fill those gap by using multi-section surface command to get the complete surface of class B.

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.

Class C surface is created by using sweep command

There are methods of creating sweep

1. where the surface is parallel to the tooling axis then we use Draft direction with 3 degree angle
2. where the surface is perpendicular to the tooling axis then we use with reference to surface with 90 degree angle

Final trimed surface (Closed volume)

To get the final trim surface first we need to join class A with C surface and then trim them with the class B surface to get the closed volume body component.

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 do house degrees 5 degrees to die draw.

Procedure for creating the DOG HOUSE

• the First step is to create a side core axis.
• I have chosen 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 the multi-section surface 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

BLUE colour – Zero draft

RED colour – Negative Draft

Draft analysis of DOG HOUSE using the Side Core Axis and Main Tooling axis

Draft analysis of final Door trim component

Conclusion

Hence the Final component (closed volume) is successfully created along with required draft analysis and also created dog house as per design rules.