Week 8 - Challenge 5 - Core & Cavity Design

Aim: To create the Core and cavity blocks for the switch bezel.

Steps followed

1> Tooling Axis creation.

2> Checking Draft analysis for created tooling axis.

3> Creating parting surface.

4> Creating parting line.

5> Creating core side.

6> creating cavity side.

Tooling Axis 

Tooling axis is the axis in which core and cavity open during completion of injection molding.To create the tooling axis, we need the proper orientation or view that gives the correct features and draft available in the component. So here the

component view from the Z direction gives the proper view for the tool to see the features present in the geometry. To create the tooling axis from the Z direction we need the tooling axis from the other X direction since it gives the draft

available at the slanted part.

The tooling axis created from the X direction by following steps.

1. The class A surface is extracted.

2. Then the center point is created using the point > on the base surface at 0mm.

3. At the point created the axis system is created

4. After that switching the view of the model to the X direction and creating the tooling axis.

Using the intersect in ZY plane to get the boundary lines.

Then the lines are created along the slant surfaces.

Then these two lines are bisected to get the tooling axis for the X or the final

1. Next, switching in the Y direction and intersecting the switch bezel part in ZX direction to get the intersecting lines.

2. Using the axis center point, a line is drawn in sketch mode and it is constrained at the angle of 6 degrees. (this angle value is an arbitrary

value and can be changed to get the final tooling axis that provides a positive draft )

3. At last, both the lines are bisected to get the final tooling axis.

4ellow line represent the Tooling Axis for surface.

Draft Analysis.

Draft analysis help to interpret the draft angle provided on the surface along the tooling axis, Minimum 3 degree draft angle to to be acheived over one side infers that the manufactured part will be easyily removable from core and cavity after injection mold. Green colour infer that all surface meets minimum draft angle along tooling axis.

Creating Parting Surface.

Parting surface is the middle surface which is common to the both half of core and cavity. Extrpolated B Surface usually considered as parting surface for any part. Blue Surface represent as parting surface here.

The parting surface of a mould are those surfaces of both mould plates adjacent to the impressions which butt together to form a seal and prevent the loss of plastic material from the impression. The parting surfaces of a mould are those portion of both mould plates, adjacent to the impressions, which butt together to form a seal and prevent the loss of plastic material from the impression.

Creating Parting Line

The boundary created along the profile of part on the B surface is present as parting line, the actual molded part lies inside this parting line during the injection molding. It is represented by dotted line in above pic.

Core and cavity design:
The Mould Core & Cavity are the shaped sections in either half of the mould tool which give the plastic product its final shape. The hot molten material is injected into the core & cavity and then sets hard into shape. The design of the core & cavity is essential in the correct formation of the product. The sequence of events during the injection mould of a plastic part is called the injection molding cycle. The cycle begins when the mould closes, followed by the injection of the polymer into the mould cavity. A core is usually made of the best quality sand and is placed into the desired position in the mould cavity. Core prints are added to both sides of the pattern to create impressions that allow the core to be supported and held at both ends.

Core :
The core design is started with extracting the parting surface that becomes the datum for the core and cavity.

Extract the A surface and C surface and trim with extrpolated B surface.

The acheived surface is converted to enclosed rectangular box by extruding rectangular profile at a distance from the parting line along tooling direction. Hence it is closed and joined together to form closed surface  which is converted to solid body in part model.

Cavity :
The cavity is the part where the injector and filling of the molten plastic happens. The cavity block is prepared by triming extrapolated B surface and same profile used in core for rectangular block to extrude along the tooling direction.

The acheived surface is filled and joined to create closed suface as shown in the picture.

Checking the created surface for core and cavity partition in 2D sketch.

Parting line and Parting surface :
A parting line, in the industrial casting of molds, is the borderline in which draft angles change direction. That is, it is the dividing
line that splits the core and cavity halves of a molded part. It is sometimes a starting point for the mold parting surface.
Here intersecting the parting surface, core, and cavity across the ZX plane gives the intersecting line that tells the parting line

Converting Core and cavity surface to solid and translating along tooling axis to view the created soilds .

Feature Tree:

Conclusion: Thus Core and cavity is created as per the part profile along tooling direction.