Week 9 - Project - Master Section Development

AIM

To create a B-Pillar, Dog House, Locator and Rib with the given Class-A surface and the Master Section which follows OEM Standard Design Rules.

OBJETIVE

• Picture of the sketches with Sketch solving status’s geometry tab
• Picture of the Detailed tree structure.
• Picture of the 3D CAD
• Create closed body
• Create tooling axis and follow design rules.
• Follow the Master section to create flange
• Follow the master section for thickness and to create the Closed volume.
• Follow master section to create Attachment features

INTRODUCTION

B-Pillar:

• Pillars are the vertical or nearly vertical supports of a car's window area or greenhouse—designated respectively as the A, B, C or D-pillar, moving from front to rear, in profile view
• In the case of the B (or center) pillar on four-door sedans, the pillar is typically a closed steel structure welded at the bottom to the car's rocker panel and floorpan, as well as on the top to the roof rail or panel
• Furthermore, B Pillar is the most complex component/structure of the vehicle body This is because the front door closes on the B pillar while the rear door hinges onto it.This pillar provides structural support to the vehicle’s roof.

Master Section:

• Master Sections are the guides for design requirements which shapes the component after technical styling of Class A Surfaces.
• Master Sections are parameterized model of the vehicle body that outlines the guide for NPD Team.

PROCEDURE

Step-1

Class A Surface:

• First import the given Class A surface model of the B Pillar in CATIA V5.
• Class A Surface is the outer skin of the product which is purely an aesthetic model with no engineering properties involved
• The CLASS A Surface has lot of irregular patches and complexity which are improved using Multi Section Surfaces and Surface Trims which forms the Improved Class A Input
• A Tangential Error Propogation method is used to validate the Surfaces using Boundary option.

[Fig1]

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Step-2

TOOLING AXIS

Main Tooling Axis:

• A tooling axis needs to be created in a direction from which it can capture most parts/features of the component. Generally a tooling axis will be created perpendicular to the base surface of the component.
• In this case we need to create the tooling axis in Z - direction. So in order to create the tooling axis in Z - direction, we first need to create a reference point.
• A reference point can be created using the master section 1 given as an input. Create a point using the point in between option and select the two end points of the master section DOG HOUSE which will give us a point at the center. Once we get the center point change the point in ‘between’ option to ‘coordinates’.

[Fig3]

• Now for the direction of the tooling axis use compass direction method where we need to drag the compass and place it on the Class A improved surface. Then rotate the compass to certain direction which satisfy optimal for the draft analysis.
• Then use lock direction to lock the orientation of the compass and use it as reference in the line defination when creating the Main Tooling Axis

[Fig4]

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[Fig7]

[Fig8:(Draft Analysis of Class A improved surface]

Side Core Tooling Axis:

• Side Core Tooling Axis used to eject the parts during injection modling
• This Axis is used because the Attachment feature is bounded by close walls
• This is create Point direction method in the Line option where the reference point is from main tooling axis and for the direction a plane is created as ashown in the Fig-9.

[Fig9]

Step-3

Flange Creation:

The Class A has Flanges which are obtained through Master Sections and developed and compared.

[Fig10]

[Fig11]

Step-4

Class B Surface:

• 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 B Pillar Design the B surface is offset 2mm 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
• The Offset Surface leads to Surface Degenerations if

1. Rapid change in curvature or surface continuity
2. Low Radius of CLASS A
3. Conic or Styling Fillets

The Remedy is to untrim , extrapolate and trim or create surfaces using Multi Surface Option and Join

[Fig12]

[Fig13]

• In this way the Patches are coorected along the B Surfaces and the part is Extraploated with offset of 2mm from A Surface.
• Same way as Class-A Surface we have to create flanges for the B surface also with offset of 2mm from A surface as shown in the master section.

[Fig14]

[Fig15:(Fillet for the Flanges)]

[Fig16]

Step-5

Class C Surface:

• 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 Surfaces must be drafted outwards from the A Side to avoid the parting Line along the A Surface
• 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 in Fig18.

[Fig17]

[Fig18]

Step-6

Closed Surface:

• 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 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

[Fig19]

[Fig20]

[Fig21]

[Fig22]

Step-7

ATTACHMENT FEATURES:

The Attachment features are the Fixation and Location features that Fixes the components The Common Attachment features used in B Pillar Are

1. Doghouse with 4 Way Locator
2. Ribs

Dog House

• Using the Master Section the Doghouse is created and then part modelled using Thickness option.
• The 4 Way Locator is Formed above the Dog House which locates the B pillar towards the Mating Surfaces

The Dog House Design Rules are-:

• The Thickness of the Connecting surface towards B Side should be 40% off the main thickness
• The Walls are drafted with Min 0.5 Degrees along the Main Tooling Direction
• The Attachement feature created needs a seperate tooling axis to clear the part Hence a Lifter Axis is used
• The Surfaces that are cleared along the Lifter axis are also given a Minumal Draft
• The Height of the attahcment walls should be a minimum of 3 mm
• This avoids the plastic defects on the B Side and maintains the texture of A Side

[Fig23]

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[Fig28]

[Fig29]

[Fig30:Draft angle]

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[Fig38]

[Fig39]

[Fig40:Under cut so that it will not form Sink Mark or Flow Lines]

[Fig41]

[Fig42]

[Fig43]

[Fig44]

[Fig45]

4 Way Locator

• To create 4 way locator we have to follow master section but in this case one othe master has different parameter which differ from 4 way locator so only one of the master section can be followed as shown in the Fig45.

[Fig45]

[Fig46:Sketch for 4 Way Locator]

• Four Way Locators are Tapered along the Edges to create an entry point for locators and the Locator Walls are drafted along the Main Tooling Direction.
• The Walls are minimum of above 0.4 times of the total Thickness to avoid shot incapacity during plastic product creations and the apex walls are ensured to enough for creation of parts.

[Fig47]

[Fig48]

[Fig49]

[Fig50:Fillet]

[Fig51:Rotational Movement along X,Y,Z Axis ( Clockwise and Anticlockwise)]

RIBS

Ribs provide stifness to the parts and can be improve thougness whithout increasing the part thickenss and locators and provide allignment to the mating parts

The Design Rules for two way and four way fixtures are

• Rib Wall Thickness should be 0.4 times of Thickness of the part
• The Drafted walls of rib should be within 0.5 degrees
• The top height of rib should be at least 0.70 mm thick to allow the molten plastic to reach the top to avoid Short Shot
• The Thickness of the Rib, Fillet Radius, Draft and rib root thickness are measured and are withing the design specifications

In B Pillar The Ribs are 50mm apart on both Sides

[Fig52]

[Fig53]

[Fig54]

[Fig55]

[Fig56]

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[Fig59]

• Thus B Pillar Cover is Surface Development is completed and attachment features are added.
• It should be noted that the fixation of bolt locators always follow 3-2-1 Taylor Principle.
• Translational Movements along X,Y,Z Axis ( Positive and Negative) also can be done but I have done through sketchs.
• Rotational Movement along X,Y,Z Axis ( Clockwise and Anticlockwise) for the Dog House.
• The Improvement in Given B Pillar could be an addition of another Dog House at an extreme end to satisy the Taylor's principle and Thermal Stakes are provide that arrests all degrees of freedom and completly fits the B Pillar Part

NEW MASTER SECTION DEVELOPMENT

As one of the Master Section has some error here I have created another Master Section with Intersection method on the B pillar as shown below figures.

[Fig60]

[Fig61]

[Fig62]

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 B Pillar DRAFT ANALYSIS

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 is provided below

DRAFT REPORT

The Draft Report for B Pillar Model is shown Below

[Fig63]

[Fig64]

[Fig65]

[Fig65]

[Fig66]

[Fig67]

• 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 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
• These surface are corrected using Surface Operations and generaly in OEM Class A Improvement requires prior approval from Styling team and the draft report and analysis is used to get approval

VIEWS(ISOMETRIC, SIDE, FRONT, TOP)

TREE STRUCTURE

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. The Design is then validated with Master Section and understood the use of Master Section Development in Product Design through development of B Pillar Cover used in the Car Interiors.