Week 11 - Project - A pillar Design with Master Section

A PILLAR DESIGN WITH MASTER SECTION

Aim: To create a Plastic part from a given class A surface and master section of an A-pillar plastic cover with dog house for assembling. Also perform the draft analysis on the created part.

Objectives:

1. To create a tooling axis for the component.
2. To create Class B & C surfaces form the parameters: Thickness (2.5mm), minimum draft angle(3°) for the part and (0.5°) for B side features(dog house surface).
3. To create a solid body from the closed surfaces formed by joining and trimming Class A, B & C surfaces.
4. To perform draft analysis of the final plastic component ensuring the minimum draft angle is met on all the surfaces of the part.
5. Create the B side features (dog house) on the proper position as per the design rules and performing draft analysis.
6. Using Boolean operation, merge part body with class B surface.

Tool Used: CATIA V5.

Introduction: In this project, an A-Pillar cover is to be designed using a given class A surface and master section for class B features, the parameters for the design are as follows:

• Part thickness: 2.5mm
• Draft angle: 3°
• Design Guidelines of A pillar cover is given as:

1. Draft - 0.5 degrees on the walls of boss
2. Thickness of base of dog house - Typically 40%* of the nominal wall.

• Radii - 0.25mm.

The part is developed keeping the aforementioned parameters in mind while creating class B & C surfaces and subsequently class B features.

Constraints:

• Changes if any in Class A surface shall be very minimal.
• Part thickness cannot deviate more than 30% of the nominal thickness in any direction.
• All design rules shall be followed strictly.
• All surfaces shall be completely closed before converting to solid. A maximum tolerance of 0.003mm is allowed.
• Minimum draft on B side feature walls is 0.5°.

Report:

1. Class A surface:

The following surface is given as the input for the creation of the part. This will be the main aesthetic surface for the switch bezel.

(Class A surface)

(Master Section)

2. Creation of tooling axis:

• Firstly we visually determine the ideal direction of pull for the simplest geometry of mould, for the given class A surface, the direction of pull should be along the y axis.
• Now, we can create a dummy tooling axis in the y direction using a point on any curve on the class A surface.

3. Draft analysis of class A surface:

• To continue with the design process first we need to find out the tooling axis for the surface and check for all the drafts using Draft Analysis tool of CATIA. Use the main tooling axis for the draft analysis. The analysis is done for 3° draft, all the surfaces that have more than 3° draft are highlighted in green.
• It is observed in Class A surface that the minimum draft angle is at least 3°, so we can accept the tooling axis as main tooling axis.

(Class A Draft analysis using main tooling axis)

4. Creation of class B surface:

• Class B surface is created by offsetting the main surfaces of the class A surface.
• After creating the offset, there is a missing fillet and. This patch needs to be corrected for proper class B surface.
• Using sweep command with the extracted edges of the missing patch, create a sweep, then join it with the offset to create the class B surface.

(Class B Surface creation using offset of class A, Missing Patches need to be corrected)

5. Creation of class C surface:

• Class C surface is created by extracting the boundaries of class A surface and using the sweep command perpendicular to the class A surface for the edges parallel to the tooling axis and sweeping with draft direction for edges perpendicular to tooling axis.

(Creation Of C Surface)

6. Creation of a close surface:

• Join the Class A and C surfaces; Make sure that there are no open boundaries.
• After getting a seamless join/ trim of class A & C surface, check the intersection of Class A+C surface with the Class B surface, extrapolate the Class B surface accordingly wherever needed to cut the A+C surface

(final closed surface using class A, B & C surface)

7. Creation of part using the surface:

Using the close surface feature, make the part out of the created surface.

(Part Body created using Close Surface feature)

8. Draft analysis of Part:

Using the tooling axis and similar method to previous, analyse the part for draft angles in all surfaces. Make small changes in angle of draft and angle of pull until all surfaces are shown to have proper minimum values of draft.

(Draft analysis iof main part body)

9. Creation of B-Side features: Dog House

• Using the master sections make plane where dog house is to be positioned and extract the inner edges of the dog house. Extrude the outline to make planes for creation of dog house.
• Thicken the dog house exterior. Similarly make surfaces to create dog house support and ribs.
• Using Boolean operation prepare the final trims of dog house into a single features.
• Draft the walls of the dog house and perform draft analysis using the tooling axis for the dog house.
• The back wall of dog house fails when draft analysis is performed with main tooling axis, therefore tooling axis parallel to dog hose wall is needed.
• Make a pocket as required on the top of the feature.
• Create a side core axis and study the draft analysis of the dog house.

(Creation of Dog House)

(Dog house Draft analysis with main tooling axis, failing in back side)

(Creation of tooling axis for dog house draft analysis)

(Final Draft analysis of the dog house inner)

Conclusion:

• The solid part is obtained using the close A, B & C surfaces. The draft analysis shows the part has proper minimum value of draft on surfaces that had proper class A surface and acceptable draft value where input had less than minimum draft angle. This ensures that the surface finish of the plastic component will be smooth when manufactured with the mentioned draft angle and tooling axis.
• B Side features are created ensuring proper assembly of part an enough stiffness.
• B Side features are created as per design guidelines and follow the design rules.