Week 8 - Challenge 5 - Door Trim Lower

AIM :

To create the Door Trim Plastic component through the given Class-A surface with the creation of the Tooling axis meeting the requirement of the Draft angle, and taking the thickness of the component as 2.5 mm.

REPORT :

This report demonstrates the design of an Automotive Plastic Component – Door Trim (Plastic) using industry principles such as 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 Door Trim Plastic 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 all the features are above the Nominal Drafting for the creation of the Solid Model.

THEORY :

The terms are briefly explained below:

1) 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.

2) 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.

Fig : Draft Analysis for Class A Surface

Fig : Multi-section view

3) 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. In this case, X-axis can be a possible Tooling Axis Direction.

4) 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.

5) 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 & grey colored surface is the Class B surface.

6) 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 Grey colored surface is the Class B surface & the Dark brown colored surface is the Class C surface

OPERATIONS :

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.
• Here are some patches which are not offset as required, these patches must be filled properly with their respective dimensions.
• The patches are on the 3 edges of the Door trim (shown in below figs.)
• The offset of these surfaces is shown below.

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 are 3 patches on the door trim (1 on the left side and the other 2 on the right side)

-------> Starting with the creation of Patch Region 01.

The Patch region 01 is visible properly in the fig. shown below

• Extract the required portions i.e. the whole door trim except the patch region 01 (edges) using "Multiple Extract" and keep the complementary mode on. The Complementary mode helps in the selection of the surface which should not be extracted very easily.
• Now Extract the horizontal surface, and the vertical surface one by one using "Multiple Extract" which is connected with each other through the fillets.
• After extraction give a boundary to the surface with limits.
• Extrapolate the surface on the boundary with the appropriate length.
• Where these horizontal and vertical surfaces of the door trim intersect with each other use the Trim command to trim as shown in below fig.

• Measure the edge fillet radius of any edge of the grill and give the edge fillet.
• Creating fillets.
  • Create Fillets while maintaining the part thickness between the Class A and Class B surfaces.
  • The Value of the Fillet is given by the equation (B surface fillet = A surface fillet +/- Thickness of the Part).
  • The sign + or – must be decided so as to maintain the part thickness which in this case is 2.5mm.
• Now join the Offset and the Patch region 01 Surfaces with each other.
• Patch region 01 is completed.

-------> Now the creation of Patch Region 02.

The Patch region 02 is visible properly in the fig. shown below

• Here steps for creating Patch region 02 will be same as the patch region 01, Multiple extraction with complementary mode on, Extraction of the 2 surfaces where fillet joins them, boundary, extrapolation, and Trim.

• Creating fillets.
  • Create Fillets while maintaining the part thickness between the Class A and Class B surfaces.
  • The Value of the Fillet is given by the equation (B surface fillet = A surface fillet +/- Thickness of the Part).
  • The sign + or – must be decided so as to maintain the part thickness which in this case is 2.5mm.
• The Patch region 02 is completed.

-------> Now the creation of Patch Region 03.

The Patch region 03 is visible properly in the fig. shown below

• Here the methodology is the same just the process is repeated and Long.
• Extract all the surfaces but in 3 parts as shown below in fig. This partition in 3 parts is because of the edge fillet which joins them together. Different patches are shown with different colors (green, maroon, yellow).

• Give boundary and extrapolate any 2 surfaces, here I used the green and maroon surface first.
• Trim the surface with each other. Now we have 2 surfaces the lower vertical surface (yellow), and the trimmed surface (light blue) as shown in fig below.

• Now repeat the methodology, give boundary to both the surface extrapolate, and then trim with each other.

• Here we got the whole surface except the edges are not filleted. Measure the edge fillet radius of both the edge of the door trim and give the edge fillet.
• Creating fillets.
  • Create Fillets while maintaining the part thickness between the Class A and Class B surfaces.
  • The Value of the Fillet is given by the equation (B surface fillet = A surface fillet +/- Thickness of the Part).
  • The sign + or – must be decided so as to maintain the part thickness which in this case is 2.5mm.
• Patch region 03 is completed.

Here the Class B surface is created.

2) Creation of C surface :

• Using the Boundary feature, the surface edges of Class A Surface and create boundaries on two surface edges, i.e. the inside hollow surface and the outer edge.
• The sweep option is carried on the boundary lines to create a draft length extension (5mm) and draft angle (87°). Here instead of taking 90°, we have to take 87° because of some inclination and for trimming with the Class B surface.
• After the Sweep Operation, the Class B surface and the sweep surface are trimmed with each other in order to create the Class C surface.
• Finally, Join the Class A Surface and the trimmed Surface to create the Final component.

Draft Analysis on the Closed Surface :

Screenshots of the Tree Structure :

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

CONCLUSION:

The Design of the Automotive Plastic Component – Door Trim from Class A is completed using concepts of Draft angle, Draft Analysis for Class A and Final enclosed surface, Tooling Axis creation, and implementation, and Class B and Class C creation.