Week 8 - Challenge 1 - Base Bracket Design

BASE BRACKET DESIGN REPORT

Aim : To create the Base Bracket Plastic component through the given Class-A surface.

To create the tooling axis for the given Class-A Surface meeting the requirements of the draft angle and at the end perform the Draft analysis on the model.

Tooling Axis

The tooling axis is the direction of drawing a sheet metal where the finished component is easily ejected on a particular direction and axis.

In Molding, machine arrangement is given to open the mould along a direction which is known as Tooling Direction. In other words. The mould is built from two separate halves (Core and Cavity) and tooling direction basically defines the direction of mould pulls apart.

There are 3 methods to create tooling axis, which are :

• With respect to 3 axis (X, Y, & Z)
• Normal to surface
• Bisecting method

In the given model tooling axis is found out using the axis method.

In the given model (base bracket), it will clear all the surfaces in Z-axis direction, so that Z-axis is chosen as tooling axis.

For creation of tooling axis, a point is inserted in the centre of a hole on class A surface through which tooling axis can be drawn in Z direction.

Figure of class A surface with point in the centre of hole:

Tooling Axis:

Material Used & Why?

The material used for this Base Bracket is Polypropylene. It is because this part lies under the hood of the vehicle which supports/covers the hydraulic lifts, so that it should posses high temparature withstanding capacity as well as good strength. Therefore, Polypropylene is selected.

Being a thermoplastic polymer, it can easily be formed into almost any shape. It has excellent chemical and heat resistance and is generally resistant to impact.

Class A,B & C Surface

Class A Surface:

It is the outermost aesthetic surface which is visible to customers (the outermost visible surface of a product).

Here, class A surface is given:

The class A surface is joined inorder to make it a single part and then checked the boundary to confirm that it is closed.

Class B Surface:

It is the offset of the class A surface at a particular distance. The offset distance depends on the thickness between Class A and Class B surface.

Here, the thickness given = 2.5mm.

Procedures to build class B surface:

• Extracted each and every flat surfaces from class A excluding fillets.
• Untrimmed all the extracted surfaces and offseted those surfaces 2.5mm downwards.
• Extrapolated the offseted surfaces inorder to make sure all the surfaces are in contact.
• Trimmed the offsets to get an output same as class A surface
• Fillets are given to the required edges based on the thickness and curvature of the class A fillets.
• For external fillets 5.5mm (3mm+2.5mm) is given and for internal fillets 0.5mm (3mm-2.5mm) is given.

Class B surface offseted 2.5mm downwards (-ve Z-direction) is given below:

Class C Surface:

This surface connects the Class A and Class B surfaces. (Surface in between Class A & B surfaces)

Procedure to build Class C surface:

• Boundary of class A surface is extracted and then smoothcurved the boundaries
• Then that boundary is swept along the tooling direction until it gets coincided with the offseted class B surface.

Joined and Closed Class A,B & C surface:

After creating class B & C surfaces joining operation is done between class A and class C surface. Then, Class B surface is trimmed with joined Class A & C surface to get a whole closed single surface. Then in part workbench using closed body command, a solid body is generated.

Figure is attached below:

Closed surface:

Solid body:

Draft Analysis

In the criteria of making a plastic material, the mold should release the material when finished. if the mold surfaces are 90 degrees the material won't release from the mold because of friction due to contraction of material when cooled.The ejection of the part from mold depends on the draft. A zero draft can result in difficult or no ejection. It is recommended to add a draft of 3 degree or above inorder to remove it from the mold without any damage.

Procedure:

• Change the view mode to customize view parameters and give material as view mode.
• In the draft analysis toolbar, set the draft values and color (3 degree and above - green, 0 to 3 degree - blue, less than 0 - red).
• Drag and drop the axis system on the tooling axis and lock it.
• Perform draft analysis.

Draft analysis of Class A surface:

Drfat analysis of final plastic component:

The both areas which showing blue color (represented in figure below) has an angle of about 2.8 degrees which is less than 3 degree and it is also manufacturable.

Screenshots of the solid model with the proper color code of the draft angle in various orientations:

Tree:

Conclusion

All the procedures are done properly and the result is obtained.