Week 9 - Challenge 3 - Bumper

Aim: To create a Plastic part from a given class A surface of a bumper and perform draft analysis on the part.

Objectives:

1. To create a tooling axis for the component.
2. To create Class B & C surfaces form the parameters: Thickness (3mm), minimum draft angle(3°).
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.

Tool Used: CATIA V5.

Introduction: In this project, a Bumper is to be designed using a given class A surface, the parameters for the design are as follows:

• Part thickness: 3mm
• Draft angle: 3°

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

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.

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)

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 x axis.
• Now, we can create a dummy tooling axis in the x direction using a point on any curve on the class A surface.

(Main tooling axis created using tooling axis in x direction)

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.

(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 are many missing fillet and surface patches. These patches needs to be corrected for proper class B surface.
• Using Extract, extrapolate and trim tools, class B surface is created.

(Class B Surface creation using offset, untrim and extrapolation of class A)

(Class B sub-surface trimmed to obtain outline geometry)

(Fillets added to class B surface on the outside; Fillet radius = Fillet in class A- thk.)

5. Creation of class C surface:

• Class C surface is created by extracting the boundaries of class A surface and using the sweep command and the direction of draft, surfaces are created, these surface. This is done to the c surfaces parallel to the direction of pull
• For all the surfaces perpendicular to the direction of pull, simply extend the boundary in the perpendicular direction to the edges of class A surface.
• Trim and Join all the Class C Surfaces; Afterwards join class C curfaces with Class A surface.(Class C surface creation using boundary of class A Surface

• 

(Creation Of class 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.

(Final Draft analysis of the Part body)

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 all surfaces. This ensures that the surface finish of the plastic component will be smooth when manufactured with the mentioned draft angle and tooling axis.