Week 9 - Project - A pillar Design with Master Section

AIM :

To create the A Pillar component through the given Class-A surface and the given mastersection. To begin with, the tooling axis for the given Class-A Surface should be created meeting the requirements of the draft angle and at the end perform the Draft analysis on the model.

Create the Dog House considering the design rules.

REPORT :

This report demonstrates the design of an Automotive Plastic Component – A Pillar with Engineering feature Dog House using industry principles i.e. Draft angles, Draft Analysis, Determining and implementing of Tooling Axis, Class A, Class B, and Class C surfaces. The component is designed using Surface Design and Solid Design techniques in CATIA V5.

OBJECTIVE :

• Conduct a Draft Analysis on the Class A surface for the A Pillar for determining the appropriate Tooling Axis.
• Creation of other surfaces i.e. B & C Surface for creating a solid component
• Performing the final Draft analysis for the inspection and checking if the feature are above the Nominal Drafting for the creation of the Solid Model.

THEORY :

The terms are briefly explained below:

1) MASTERSECTION :

Master sections are the guides for design requirements that decide the component packaging after technical (Styling, Concept or Class-A) surfaces. Here in this challenge, created the solid part body from the class A surface and B-side features (Dog house) for the class A surface. The master section measurements are considered to make the solid part body and Dog house. Created a tooling axis by using the bisecting line method and created a side core axis for clearing the B-side feature of the dog house. The draft angle is provided to the dog house outer faces concerning the Tooling axis, and the draft angle to inside faces are provided concerning the side core axis. The draft angle for a solid part body is 3deg, the draft angle for the dog house's outer surface is 0.5deg, and the draft angle for the internal surface of the dog house is 0.5deg.

2) DRAFT :

The draft is an angular tapering given at the design stage to every Plastic Component that has to be manufactured. It is given in the direction of the Mold Movement. The Draft allows the parts to release easily from the mold without creating friction between the surface of the component and the core and cavity plates.

When a Plastic component cools down inside the mold, its natural tendency of it is to shrink and attach to the core or cavity half. The movement of the mold opening causes friction on the walls of the component as well as the core/cavity blocks. This reduces the life of the mold as well as the component itself. The component may also have a rough surface finish as well as a weak structure due to this. This problem can be solved by giving a draft to the component.

Most applications require minimum draft angles of around 0.5º to 1º however, 3º draft angles are widely accepted for cost-saving purposes. 7º Draft angles are given to textured surfaces like Instrument Panels. Minimum possible draft angles are given to screw bosses, ribs, and stiffeners due to their critical nature.

3) DRAFT ANALYSIS :

Draft Analysis is a tool in CATIA that identifies the zones which deviate from the specified values of angles along a defined draft direction using color codes. Draft analysis is the first step performed after receiving the Class A of the component. Draft analysis should be passed in order to make the plastic component manufacturable. Acceptable draft angles are used as a range for draft analysis.

For Analyzing the Draft of the Class A Surface:-

1. Change View Mode Customization to Material mode
2. Go to INSERT ----> ANALYSIS ----> FEATURE DRAFT ANALYSIS.
3. Select the compass from the dialog box, and move the compass to the Tooling Axis.
4. Click on the surface to apply the color region on the component.
5. Change the range to 0º to 2.9º. Apply the settings as shown in Figure.
6. As shown the target area has a 0º draft angle which was the concerned face since it's a flat surface.
7. Thus, it passes the criteria of having a suitable draft and the Class A can be further designed into a solid plastic component and manufactured.

4) TOOLING AXIS :

The tooling Axis is the direction in which the Mold opens and closes. Part Drafts are given along this axis. Identify faces that can potentially create problems while manufacturing. Surfaces at angles along a desired Tooling Axis. Extract a plain surface and create a point on its center for Axis system creation.

Here we have 2 tooling axis (Horizontal for whole A pillar, Vertical for Dog House)

5) CLASS A SURFACE :

In automotive design, a class A surface is any of a set of freeform surfaces of high efficiency and quality. It is the visible aesthetic surface of any automotive component. Class A surface refers to those surfaces which are visible and abide by the physical meaning of a product. This classification is primarily used in the automotive and increasingly in the consumer goods industry. It is a requirement where aesthetics has a significant contribution. For this reason, the exterior of automobiles is deemed Class-A.

6) CLASS B SURFACE :

Class B surfaces are Engineering Surfaces that are invisible to the eyes or often on the back side of the Class A surfaces. It is mainly the thickness of the component or Class A. These surfaces need to be designed as per the Class A surface i.e., the continuity, thickness of the component, functionality, etc should be maintained. These surfaces include the main engineering features such as Screw bosses, Ribs, Snaps, Stiffeners, and fixations. B surfaces also do not contain any aesthetic styling content and textures since it is not visible to the eyes.

Below fig shows both Class A & Class B surfaces.

The light blue colored surface is the Class A surface & dark blue colored surface is the Class B surface.

7) CLASS C SURFACE :

Class C surfaces are connectors between Class A and B surfaces. This surface connects both A and B surfaces along the Tooling Axis. It contains the draft as per the design. It is basically the thickened surface between both A and B surfaces.

The light blue colored surface is the Class A surface, the dark blue colored surface is the Class B surface & the yellow colored surface is the Class C surface

8) DOG HOUSE :

The dog house is an engineering feature used in the plastic trim design. Dog houses are used as supporting features. Sometimes other engineering features like snaps, locators, Screw bosses, etc. are mounded on them to increase their strength. Dog houses are subjected to draft analysis to prevent breakage of the component during ejection from mould cavity. Dog house and other engineering components are built on B-surface.

OPERATIONS :

A. Creation of Final Component without Engineering Feature :

1) Creation of B surface :

• Offset the relevant surfaces from Class-A surface, the offset length is 2.5 mm since the thickness is 2.5 mm (as per master-section).
• Here 1 patch which is not offset as required, this patch must be filled properly with the respective dimensions.
• The patch is on the edge of the A Pillar (shown below in figs.)

The light blue colored surface is the Class A surface & orange colored surface is the offset surface.

As you can see in the above fig. there is a patch on the A Pillar.

-------> Creation of Patch Region.

• Give two Boundaries to the surface with limits only on the Patch region. One boundary on the horizontal patch region and one on the vertical patch region.
• Smooth curve the given boundary on the patch (as shown in fig. below).

• Sweep the created smooth curve for filling the patch region as per the following selections,

1. Subtype : With reference surface.

2. Profile : Vertical patch region.

3. Guide curve : Horizontal patch region.

4. Surface : Default.

• Now join the Offset and the Patch region Surface with each other.
• Here the Class B surface is created.

Creation of C surface :

• Using the Boundary feature, create boundaries on small regions of the Class A Surface in order to get the perfect curve and proper sweep surface.
• Smooth the boundaries with the smooth curve command.
• Sweep the smooth curves at 87 degrees.
• Now Fill the surface with a line and fill command where there is some non-joined curved surface, Extrapolate the smooth curve ends to intersect, and Trim the swept surfaces with each other.
• Join all the Trimmed surfaces in order to create the Class C Surface.
• Here the Class C surface is created.

• Now Extrapolate the Class B surfaces where the Class C and Class B surfaces are not intersecting with each other and trim it for creating the final component.
• Join the trimmed and Class A Surface, Here the final component is created.

Draft Analysis on the Closed Surface :

Screenshots of the solid model with the proper color code of the draft angle in various orientations (Isometric, Front, Side, and Top View)

B. Creation of Engineering Feature on the created A Pillar :

1) Creation of Dog House :

• Here the Dog house is created in 4 Steps i.e. Walls, Ribs, Core, and Push Pin. These 4 steps are to understand and create the Dog House.

-----------> Step 01 : Walls

• Create three Lines on the given master section (inner walls of the dog house) and a plane on that lines.
• Extrude the lines with the appropriate length with respect to the created plane. (as shown in fig.)

• Now Trim the extruded surfaces with each other.
• The inner Side walls are created.
• Now for the inner back wall create a Line on the mastersection, and extrude it with the horizontal plane and appropriate length.
• Trim the Side walls and Inner wall with each other. Here the inner walls are created.

• Now create a closed body of the inner walls, give thickness to the walls as per the Master section in the Part design.
• Give Draft to the thickened inner walls and the outer walls with 0.5 deg, with the neutral element as the back wall and pulling direction as the side core axis (for inner walls), and main tooling axis (for outer walls).
• Split the created inner walls of Dog walls with the A Pillar Closed surface in the upward direction.

-----------> Step 02 : Ribs

• In the Beginning, create a line on the base of the ribs with the appropriate length and extrude it.
• Create a closed body of the base of the Rib, give thickness to the base as per the Master section in the Part design.
• Split both sides of the Rib base with the thickened walls of the Dog house.
• Give Draft to the thickened Rib base with similar options as the inner walls draft.

• Now create a line on any one side of the rib with the appropriate length and extrude it.
• Offset the extruded line which is created on the side of the rib till the other side of the rib.
• Create a line on the top of the ribs and extrude it.

• Create a closed body of both the ribs, give thickness to the walls as per the Master section in the Part design.
• Give Draft to the thickened Ribs with similar options as the inner walls draft.

-----------> Step 03 : Core

• Offset the inner walls with 1.6 mm and outward direction.
• Extract the surface of the Final component where the Dog House is resting (as shown in below fig).

Light blue colored surface is the extracted surface

• Offset the extracted surface between 3 to 6 mm as per the instructed rules. Here 4.5 mm is taken.
• Trim the offsetted base surface with the inner walls.

• Now Split the Trimmed surface with the Thickened walls of the Dog house in the outward direction for cutting the core from the dog house surface .

• Give a Draft to the core with similar options as the inner walls draft.

-----------> Step 04 : Push Pins

• Extract the top surface of the Dog House, create a point at the center of the extracted surface, and create a plane with Plane type : offset from plane and offset : 00 mm.
• Draw a sketch for push pins on the extracted surface of the dog house and pocket it with 03 mm.

• Give Edge Fillets on the top and back edges with 1.5 mm, Ribs edge with 0.25 mm, Core edges with 0.25, and Dog house face as well as push pin face with 0.25 mm.
• Union trim all these operations which are created in a separate body with the A Pillar closed body. Hence Dog House is created.

Draft Analysis on the Closed Surface :

Screenshots of the solid model in various orientations (Isometric, Front, Side, and Top View)

TREE STRUCTURE FOR A PILLAR WITH DOG HOUSE.

CONCLUSION:

The Design of the Automotive Plastic Component – A Pillar with engineering feature from Class A is completed using concepts of Draft angle, Draft Analysis for Class A & Final enclosed surface, Tooling Axis creation & Implementation, Class B & Class C creation, and Dog house.