Week 8 - Challenge 2 - Base Bracket Design

AIM

To 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.

Creation of tooling axis for the given Base Bracket

• Firstly, the connectivity of the given Class-A surface must be checked, and ensure that there are no gaps between the surfaces.

• It is clear from the above image that all the surfaces are continuous without any gaps in between them.
• We can further disassemble the boundary so that the continuity is clearly visible.

• Tooling Axis direction is the direction in which the core and cavity open.
• The selection of tooling direction depends upon the product and the features of the product.
• The tooling direction is selected by visually checking the part and in such a way that there are no additional side cores required for the moulding process. This ensures proper clearance of the part after the process.
• The Base bracket has a hole on top, so taking that into considerations we need to specify the tooling direction.
• After visually checking the part, the Z-axis is considered the appropriate tooling axis.

The below are the steps for creating the tooling axis.

• Create a point at the center of the base bracket to create a dummy tooling axis and create an axis system at that point.

• A dummy tooling axis is created along the Z-axis to check for the tooling feasibility of each face of the BASE BRACKET. The faces perpendicular to the tooling axis will clear the tooling, but, it is important to check with the faces which are parallel to the tooling axis.

• In the case of the base bracket, the faces which are parallel to the tooling axis are only in the ZY plane. So, we take an intersection between the Class A surface and the ZY plane.

• Create lines representing the parallel faces to the tooling axis.

• Bisect the two lines to get the tooling clearing line in the Y direction. This line is the Main Tooling Axis.

Publish the tooling axis and the base bracket for easy access when working with them in the future.

Draft Analysis

When developing parts for plastic injection molding, applying a draft (or a taper) to the faces of the part is critical to improving the moldability of your part. Without it, parts run the risk of poor cosmetic finishes and may bend, break, or warp due to molding stresses caused by the plastic cooling. Equally important, an absence of a draft may prevent parts from ejecting from the mold, damaging not only the parts but possibly the mold itself—a costly and time-consuming detour.

In CATIA the draft analysis can be found by Insert > Analysis> Feature Draft Analysis.

Generally, the nominal draft angle will be 3 degrees.

In the above image, the tooling direction is fixed by placing the compass on the tooling axis of the component. Once the tooling direction is locked, the component is selected and draft analysis is done.

• The value of the minimum draft angle is changed to 3 degrees.
• The above image with all the faces in green color shows that all the faces have a minimum draft angle for the tooling. Hence, the design of the component can be finalized.

Back view

Left side view

Top view

Class B surface

It is a surface that is below a certain thickness from the class A surface. The engineering features of the product are on the class B surface while the class A surface is the styling surface.

The different surfaces are represented in different colors.

The three faces of the ribs are extracted from the class A surface.

Untrim the Extracted Surfaces.

Extrapolate the surface by 10mm trim them as per the class A surface

offset the surface based on the required thickness of the component.

Repeat the same for the second rib.

The process is repeated on the remaining base surface of class A.

The extra surfaces are trimmed in order to form a proper Class B surface as per the given class-A surface.

The above image shows the Final B surface with fillets of 5.5mm

Class C Surface

The Class C surface is the surface used to join class A and the Class B surface.

The boundary of the class A surface is selected and a Surface sweep is done along the tooling axis to get a C surface.

Join all the class c surfaces with the class A surface and trim the resultant surface with the Class B surface to get the above output.

The surface is then converted to a solid body by Closed surface command.

Front View

Top view

Side view