SURFACE DESIGN AND DRAFT ANALYSIS OF DOOR ARM REST BEZEL

DOOR ARM REST BEZEL

AIM

The objective of this project to develop Class A Surface input to a Product Design using OEM Design standards and procedures in CATIA SURFACE WORKBENCH

ABSTRACT

The report details about the Design Life Cycle in Automotive Industry with an practical working model of DOOR ARM REST CONSOLE on the Door Panel of Car Interior. The report explains the steps followed in creating the tooling axis followed by detail methods in creating B-Surface and developing the Aesthetic Class A Surface Input to closed Class C Surface and analysis of Draft to prevent the failure and improve the feasibility of manufacturing the part in plastic injection molding.

DESCRIPTION

DESIGN LIFE CYCLE

OVERVIEW OF DESIGN LIFE CYCLE IN AUTOMOTIVE [1]

The Stages of Design Life Cycle are

Concept Sketches:

Concept sketches are rough idea of free hand sketch obtained through styling team and will be used to prepare the Model. It is usually done through pen and paper and through some of the painting software. This is will be used to generate the concept for preparing the model by incorporating various styles and information obtained through the stakeholders

CLASS A Creation:

After finalizing the concept the sketches are usually worked in software’s such as Autodesk Alias to create Class A Surface

Class A Surface is the outer skin of the product which is purely an aesthetic model with no engineering properties involved

The input Class A Surface of along with the Door Panel is shown below

Clay Modeling :

The Class A Surface is concurrently worked by clay modelers to brainstorm and benchmark the styling of the product and later the Concept is validated and passed on to the Design team for the preparation of New Product Design (NPD) CAD.

NPD CAD

This where the development of surfaces to parts in CAD kick off and Design engineers involvement is vital in this stage.

The Designers will work on the Input Class A surfaces which are validated from the Feasibility team and vital process in creating NPD CAD begins at this stage

The procedure followed in creation of the plastic New Product Design are

• Tooling Axis
• B Surface Creation
• C Surface Creation
• Closed Body Creation
• Draft Analysis

TOOLING AXIS

The given Class A input is analyzed to envision the part to manufacture and Tooling axis or Tooling Direction or Die line is the direction that molds pull apart in injection molding. There are two mold pieces names core and cavity. Thus tooling direction determines Mold seperation and also becomes vital in developing the plastic product drafted to desired nominal angle for feasible clearance and ejection of final part from the mold.

The Steps Followed in creating Tooling Axis

1. A Reference Point is created along the Surface zero and new Axis system is created
2. The X Direction along the Class A and Y direction along the Class A were used to create Tooling direction
3. Finally the Tooling axis is created by bisecting the two lines and it is published. Class A Surface as input using surface operation commands Class B is developed
4. The tooling Axis determines the direction of Class C boundary swept with draft direction.
5. When viewing from tooling direction normal all the parts that are drafted should be visible so it gives an rough idea to determine product manufacturing in Injection molding

View from Normal at Tooling Direction all edges are visible

B Surface Creation

• The next step is to design B surface for the input which is usually the surface where all engineering aspects and support creations are done.
• The B surface Creation is performed using surface operations in CATIA which is an offset from Class A with dimension proportional to the thickness of the part
• In Switch bezel the B surface is offset 2.5mm from the input which is the thickness of the part
• The B surface is an extrapolated surface compared to A surface and forms the bottom skin of the part

Extraploated B Surface with offset of 2.5mm from A Surface

C Surface Creation

• The Next step is to from the C surface which is an intermediate surface between A and B and is used to give the closed surface appearance to the design
• The C Surface is swept using the profile as boundary line of Class A which is the Guide curve with a subtype along draft direction.
• The Direction of the sweep is the tooling direction formed earlier
• The draft angle for the sweep operation is provided which is 3 Degree and surface is swept for length above the thickness of the specified part
• The C surface is refined using smooth Curve options to remove the complexity and patches along the swept surface
• Finally the Class A and Class C surfaces are joined together and connexity of surfaces should be less than 0.003mm and the surfaces are merged.

C Surface merged with Class A

Closed Body Creation

• The merged surface is then trimmed with B surface to form the closed surface.
• The Closed surface is then validated to find the irregularities along the edges and imperfections along the edges were then corrected using operation like extrapolate and surface trim
• This Closed surface is the outer skin of the switch bezel and finally the part is formed by Closed Surface in part design workbench
• The final part is measured to validate the uniform thickness of the part especially along the filleted edges.
• The Uniform Thickness ensures that the part Created doesnt form Sink Mark and Flow Lines along Class A

DRAFT ANALYSIS

The finished part is then analyzed to detect if the drafted part will be easily removed from the injection molding

Draft Analysis option in CATIA is enabled through Insert> Analysis> Feature Draft Analysis

The Draft Analysis Icon has

1. Mode
2. Display
3. Direction

Mode:

This is the color code that specifies the color to part based on the draft angles and is two types

• Quick Analysis
• Full Analysis

The Color code specifications for Switch Bezel trim are displayed below

Display:

The various display modes are

• Show/hide Color scale
• Running point Analysis
• Highlight Representations
• Light Effect

The display options is used to refine the analysis and results

DIRECTION:

This is one of the important tool which

• Compass Definition: This is used to pan the compass to the die line or tool direction.
• Lock Direction: This option locks the compass at the specified position
• Invert Draft Analysis: which is used to invert the axis system and used to analyze the negative tooling direction

Draft Analysis Procedure

• The part created has to be changed to material mode in display frame
• Then by enabling compass definition the axis system is pan along the direction of the part and aligned in line with the tooling direction
• Lock Direction is applied that fixes the compass and then the mode dialog box is formed by snapping at any point on the part
• The Color Codes are classified and Draft Angle are applied
• Then the Running point analysis is used to hover around the part to analyze the permissible draft angles and the analysis is saved

The Analysis of the Door Arm is provided below

RESULT

• The Green color is drafted walls above 3 degree
• The Blue color is drafted walls from 0-3 degree
• The red surfaces are negative degree

• The analysis shows the drafted walls of the switch bezel are above the par of 3 degree which is permissible to manufacture in the injection modeling.
• The Running point analysis hovered along the drafted walls show parts are above 3 and will be easily cleared from ejection.
• The Areas in Negative Tooling that falls short to the permisble design Rules are shown below

The Class A Surface Input needs to resurfaced which needs apporval from the Styling Team This Negative Tooling may cause Core and Cavity Mold Removal

• The Tree Structure are Classified and the important features are published and the operations are renamed and classified into geometric subset shown below.
• The 2D Sketch created for this operation are positioned sketches projected through a point and all geometries are fully constrained

CONCLUSION

Thus a Tooling Axis is created and a open aesthetic Class A Surface is developed into a closed surface with all plastic design rules and a final part body is created out of it in CATIA Surface Work Bench

REFERENCES

[1] Automotive Plastic Design (Accessed 2020 September 07) Skill Lync | https://skill-lync.com/courses/all/automotive-plastic-design-using-catia-v5