Week 8 - Challenge 5 - Core & Cavity Design

AIM

To Create the Core and cavity blocks for the switch bezel designed in the earlier challenge.

Creation of tooling axis for the given Class-A surface

• 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 molding process. This ensures proper clearance of the part after the process.

The below are the steps for creating the tooling axis.

• Create a point at the bottom surface of the switch bezel class A surface, and insert an axis system at that point.

• For tooling clearing axis in the Y direction, a positioned sketch is created by intersecting the class A surface with the ZY plane.
• lines are drawn to represent the faces parallel to the assumed tooling direction.
• Then the two lines are bisected, resulting in the tooling clearance axis in the Y direction.

• Similarly for X direction, a positioned sketch is created by intersecting the class A surface with the ZX plane.

• lines are drawn to represent the faces parallel to the assumed tooling direction.
• Since we do not have an opposite face we cannot bisect the lines to create a tooling axis. we create a line based on the required draft angle with the parallel face.
• That line represents the tooling clearance in X direction.

• Now, bisect both the tooling clearance y and tooling clearance Z to create a tooling axis.

• Publish the tooling axis and the Class A surface 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.

FRONT VIEW

BACK VIEW

TOP VIEW

DRAFT ANALYSIS OF THE SOLID PART

ISOMETRIC VIEW

Back view

TOP VIEW

CORE AND CAVITY DESIGN

Cavity hollow half of the mold; typically referenced as the A-side

Core half of the mold that fills the hollow side; typically referenced as the B-side

Parting Line line formed in the molded part where two halves of the mold meet

Creation of the Core and Cavity

Extrapolate the Class A surface.

Trim the extrapolated Class A surface with the Class C surface.

The above surface is trimmed with the class B surface.

A rectangular Sketch is drawn on the XY plane

Extrude the sketch along the Tooling Axis.

The core surface is trimmed with the parting surface.

The open core surface at rhe top is Filled along the boundary.

For the cavity design us the same rectangular sketch and extrude along the tooling axis.

The cavity srface is trimmed with the B surface.

Similar to the core surface, the open end is filled and then made into solid body.

The above image shows the core , Cavity and the Plastic component.

The green part is the cavity, the yellow part is the component and the pink part is the Core.

Front view

Back View.

right side view

The parting line is the junction where the Core and the cavity closes at the parting surface.

The parting line is created using by intersecting the joined class A and c surface with the B surface.