Week 8 - Challenge 2 - Base Bracket Design

Objective:

Create the Base Bracket Plastic component through the given Class-A surface. 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.

Detailed Report:

Terms used:

Class A surface: It is outermost surface of automobile which gives aesthetic look to vehicle. It is physically touchable. It is obtained from clay modeling by reverse engineering. This surface is given input to plastic product designer to work.

Class B surface: This surface is created by taking offset from class A surface. It is surface on which all engineering feature like screw bosses, dog house, ribs & mounting are created.

Class ‘C’ surface: This is surface which joins class A & class B together.

Tooling axis: It is the direction in which core & cavity opens & closes.

Method followed:

1. Checking continuity of class A surface.
2. Deciding feasible tooling direction & creating tooling axis.
3. Performing draft analysis.
4. Creating class B surface from given class A surface.
5. Creating class C surface to join A & B class surface.
6. Creating solid feature by using closed surface.

1. Checking continuity of given class A surface:

• First of all we have to check continuity of given class A surface to ensure class A surface is properly joined or no discontinuity present. This can be done by using join or boundary command in CATIA . By looking visually in below image we see that surface has continuous connected boundary as highlighted by green line.

• Extracting the boundary of given class A surface we also check that continuity visually. Below figure shows base bracket model has continuity in class A surface.

2. Tooling axis direction:

• Next step is to decide tooling axis direction. Analyzing model visually to see which direction is most suitable for tooling axis. From below image it is clearly seen that surface has two holes at its top.

• From X & Y direction as tooling axis as shown below image we cannot clears two holes at top. As rule suggest that hole should be cleared in tooling direction

• For X axis as tooling direction cannot clear one hole & flat surface as shown in below figure.

• Similarly Y axis as tooling direction we cannot clear two holes also flat surface

• So Z direction as tooling axis clear top holes in tooling direction as well as flat surface & this is dummy tooling axis as shown in below image. To create dummy tooling axis, insert point at the top hole centre & draw line along Z.

• Now we will use bisecting method to find real tooling axis. In order to create tooling axis in Z- direction, create plane parallel to YZ plane & passing through reference point. Take intersection of YZ plane with class A surface. We will get the two curves.

• Now we have to see which surface will create problem or will be difficult for tooling. Because the surface which 90° to tooling axis will be cleared. So make two lines & bisect them to make tooling axis.

3. Draft analysis:

1. To perform draft analysis. Go to insert < Analysis< Feature draft analysis.
2. Switch customize view parameter mode to
3. Click on compass icon & align it with the tooling axis & click on the surface, we will get our results.
4. From the below image it is seen that surface in green color has more than 3° draft which is most required for tooling feasibility. Also see color variant display box.

• By inversing draft direction we get below image.

• Below image shows running point draft analysis.

• Below image shows full draft analysis.

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

Front view:

Right side view:

Left side view:

Top view:

4. Creating class B surface from given class A surface.

We divide class A surface & we work on each surface separately to create class B surface.

1. Rib 1
2. Rib 2
3. Slant surface
4. Flat surface

Rib 1 & 2:

• Extract the flat surface.
• Un-trim the surface.
• Extrapolate it.
• Offset it by 2.5 mm distance
• For both rib follow same procedure

Slant surface:

• Extract the flat surface.
• Offset it by 2.5 mm distance.
• Un-trim the surface.
• Extrapolate it by 10 mm.

Flat surface:

• Extract the flat surface.
• Un-trim the surface.
• Extrapolate it by 10 mm.
• Offset it by 2.5 mm distance.

• After offsetting all the surfaces, we have to trim these surfaces together to get our final class B surface. While trimming follow exact shape of class A surface. That is our final trim surface.

• This final trim is our inner surface so fillet edges of this surface as per formula,

Fillet radius = Class A surface fillet value + Part thickness

5. Creating class C surface to join A & B class surface.

• Extract the boundary of the class A surface & edges of the holes.

• Sweeping the boundary of class A surface & edges of the hole with the use of draft direction as tooling axis.

• Joining the class A & class C surface together.

• Trimming the class-B surface with joined surface created earlier.

• After trimming we get final base bracket close surface.

6. Creating solid feature by using closed surface.

• Solid model is created from closed surface in the part workbench. This is our design output. Below image shows the base bracket part in various orientations.

ISO view:

Front view:

Right side view:

Top view:

• Image of the expanded tree structure for the geometrical sets & part body, publications.