Week 9 - Attachment Feature Creation - Challenge 2

Attachment Feature Creation - Challenge 2

AIM

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, 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 oher engineering components are built on the B-surface.

OBJECTIVE

• Create 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 final surface model and convert it into solid body using 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 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 clearing 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 with respect to the lines created.

• Follow the same procedure for the second intersection and create a bisecting line 2.

• Using the bisecting line 1 and bisecting line 2, create a new bisecting line and if it clears the draft analysis test, rename it as tooling axis.

Draft analysis of CLASS-A surface

CLASS-B surface creation

Class-B surface means thickness of a part it is not visible and is inside part. In other words, 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 CLASS-A about 2.5mm inward direction.
• Check for the discontinuity and rework on the offset surface using extract, multi-extract, multi sections surface.

• Join the surfaces and ensure the final CLASS-B surface created has no gaps.

CLASS-C surface creation

Surface that joins class-A and class-B surfaces 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 surfaces with reference to surface and tooling axis by multi extracting the CLASS-A boundary
• Join the sweep surfaces by using commands like extrapolate, trim, multi section 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 surface together.
• Then Extrapolate the B surface little bit outward direction to make sure that there would not be any gap when trimming with joined surface.
• Then trim the extrapolated CLASS-B surface with 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 do house is 1.5 degree to die draw.

Procedure for creating the DOG HOUSE

• First step is to create a side core axis.
• I have chosen normal to the point method for creating the side core tooling axis.

• Create the dog house by creating 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)

The expanded Tree Structure for the geometrical set and the Part Body

DRAFT ANALYSIS

The Draft Analysis is a command 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 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 DOG HOUSE using the Side Core Axis

Draft analysis of final Door trim component

Conclusion

i have successfully created CLASS B and C surfaces using the given CLASS A surface of door trim and craeted main tooling axis and side core tooling axis. Performed draft analysis for both final component and the dog house.