Week 9 - Project - Master Section Development
B PILLAR DESIGN WITH HELP OF MASTER SECTION
AIM -
The Aim of this project to developed a closed surface model by using of the master section and also developed B side feature for locked the degree of freedom of the component .Here We can use B Pillar master section providing by the OEM Standards.
Software used- Catia V5
ABSTRACT-
The report details about the Design Life Cycle in Automotive Industry with an practical working model of B PILLAR COVER
on the B PILLAR of Car Interior. The report explains the steps followed in creating the tooling axis followed by detail methods in creating B-Surface, Class C Surface and to closed body.The Attachment features creation is also reported by following the design guidelines and finally analysis of Draft to prevent the failure and improve the feasibility of manufacturing the part in plastic injection molding.
DESCRIPTION
MASTER SECTION-
Master Sections are the guides for design requirements which shapes the component after technical styling of Class A Surfaces The body frame is mainly composed of floor longitudinal beams, upper side beams, door side beams, and front cover, the rear beam, A-pillar, B-pillar, C-pillar and other load-bearing beam structures are composed.
Master Sections are parameterized model of the vehicle body that outlines the guide for NPD Team
In this Report B Pillar Cover Creation with detailed procedures of Surface Development and Attachement features are covered.
OVERVIEW DESIGN LIFE CYCLE AUTOMOTIVE INDUSTRY
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 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
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 by bringing up a rough clay model and then it is 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
The procedure followed in creation of the plastic New Product Design are
1.Tooling Axis
2.B Surface Creation
3.C Surface Creation
4.Closed Body Creation
5.B Side feature Creation
6. Side core Axis creation
7.Draft Analysis
8.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 which is 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 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 which provide the Master section 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 and Draft provide in tooling axis 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.
In B Pillar Model there are Two Tooling Directions one on Main tooling and other on Lifter Side that is used to eject the parts during injection modling.
Lifter Axis is used because the Attachment feature is bounded by close walls.
Finally getting the Main Tooling Axis by using of the biescting line .
InPut -
Class A with the master Section.
CLASS A IMPROVEMENT-
A Tangential Error Propogation method is used to validate the Surfaces using Boundary option or join command help to check the quality of the
A surface.
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, Untrim,blend and other Surface commands. Trims which forms the Improved Class A Input.
Finally the Class A Improved is used as input Model and is Publihsed.
Flange Creation-
The Class A has Flanges which are obtained through Master Sections and developed and compared.
B side feature observed in master section and dimension of the B side Feature.
- Observed the Master section we find that requirement of flange in A surface.
Extrapolate the boundary of the A surface according to our master section and find the flange.
Class A with Flange
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. Here we offset 2mm.
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,
a. Rapid change in curvature or surface continuity
b. Low Radius of CLASS A
c. Conic or Styling Fillets
The Remedy is to untrim , extrapolate and trim or create surfaces using Multi Surface Option and Join.
In this way the Patches are coorected along the B Surfaces and the part is Extraploated with offset of 2mm 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. Draft direction is the tooling axis 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
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 ,untrim and surface trim etc.
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. And Closed surfacesolidify.
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
DOGHOUSE
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.
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.
The attachement feature needs a saparates tooling axis to clear the parth hence lifter axis is used.
RIBS-
Ribs provide stifness to the parts and can be to impart throughness whithout increasing the part thickenss and are 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.
Thus B Pillar Cover is Surface Development is completed and attachment features are added.
3-2-1 Taylor Principle-
A fundamental concern in metalworking is locating the part to be machined, punched, bent, or stamped relative to the work platform (fixture). For example, a CNC machine tool starts its process at a specific point relative to the fixture and proceeds from there. Hence, the accuracy with which a part is machined is quite dependent on the accuracy with which it is positioned in the fixture.
Accurate locating of not just one part, but each and every part that is loaded into the fixture is crucial. Any variation in part location on the fixture adds to the dimensional tolerance that must be assigned to the finished parts.
Additionally, the method of supporting and securing the part in the fixture affects not only dimensional tolerances, but surface finishes as well. This is true because improper supporting or clamping can temporarily or permanently deform the part. Hence, techniques for supporting and clamping must be considered together with the method of locating in order to assure repeatability from part-to-part.
The Locating Process: Degrees of Freedom
In order to completely specify the position in space of a three-dimensional
object (such as the cube that’s shown), we refer to six coordinates:
- Translational position along the X-axis
- Translational position along the Y-axis
- Translational position along the Z-axis
- Rotational position about the X-axis
- Rotational position about the Y-axis
- Rotational position about the Z-axis
These six coordinates are known as the six degrees of freedom of a three-dimensional object. As the double-headed arrows indicate, the translational and rotational positions can vary in either direction with respect to each of the three axes.
To completely prevent movement, all six degrees of freedom must be restricted.
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)
Rotational Movement along X,Y,Z Axis ( Clockwise and Anticlockwise)
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.
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
1.Show/hide Color scale
2.Running point Analysis
3.Highlight Representations
4.Light Effect
5.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
The Minumum Draft for All A Side Surfaces are 3 Degrees
The Surfaces that are below 3 Degree are shown Below
Invert Draft Analysis:
which is used to invert the axis system and used to analyze the negative tooling direction.
Draft Analysis Procedure-
1.The part created has to be changed to material mode in display frame.
2.Then by enabling compass definition the axis system is pan along the direction of the part and aligned in line with the
tooling direction.
3.Lock Direction is applied that fixes the compass and then the mode dialog box is formed by snapping at any point on the
part.
4.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
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 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.
The Tree Structure are Classified and the important features are published and the operations are renamed and classified
into geometric subset shown below.
The Draft Report for B Pillar Model is shown Below
when start the draft analysis
here change the angle of tooling axis in xy plane the find -2.75 drg draft at corner .
Finaly Chnage the 3 deg of Tooling axis angle and find all green surafce and save this axis as a tooling axis and publish it.
Some time the draft angle is 3 deg in C surface but show the blue color because of some where C surface draft angel is less than 3deg or equal
but catia v5 show it blue by default.
A surface and rib are cleared with main tooling axis.
For Dog house and 4 Way locator we can use lifter axis to cleared the draft analysis.
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.