Week 8 - Challenge 5 - Core & Cavity Design

Design Report:

1. Class A: The Class-A Surface which is obtined as a input from stedio is checked for curvature continuity by boundary and dissambly method to obtain the domine based curves. As per the feature given, it must have only one domine based curve. As per the feature there is no holes or slots inbetween them. The obtained results by curvature check shows that the Class A is perfect.

Curvature Continuity Check

2. Tooling Axis: The tooling axis is made partially bisectional. The tooling along YZ-plane is made bisectional but the tooling along XZ-plane is made by angular method by connecting axis and surface at a certain angle of more then three degree to the parallel reference surface. The main tooling axis is cleared by bisecting XZ and YZ plane tooling axises. In the bellow image the orange is the main tooling axis and the subordinate tooling axises are considered to be yellow.

Main and Sub-Ordinate Tooling Axises

3. Surface Draft Analysis: The surface draft analysis is done to get an idea on manufacturability of the model even before starting the trim works. Based on the colour code, the positive, negative and nutral drats can be observed easily. The positive drafft of above 3 degrees is mandetory to make an injuction molded plastic component. If proper draft is not observed then the design is to be reconsidered. In the below image we can observe that all the surfaces are uniformly green with positive draft which shows the draft parameters are satisfied over here on Class A surface.

Surface Draft Analysis

4. Closed Loop Surface and part model: Once the A surface inspection is done successfully, the Class-B and Class-C surfaces are created, with required draft angle(3 degree or 3 degree and above), radius(12.5mm) and offset distance(2.5mm). The trimed closed loop surface model is converted into part model and part draft analysis is conducted to check the design for manufacturing. The result obtained in draft analysis shows that the part model surface satisfys the design requirement.

Part Draft Analysis

5. Core and Cavity: In actual an injection molded part is made by filling the space between the core and the cavity. The core and cavity plates are designed with the help of part model. Where part model serves as an input for completing the mold set up design. If the projections on core and cavity plates are small then multiple parts are made in a single mold setup, which is guided by gating systems. For larger sized projections single complete mold set up is needed. Simple and Easy to manufacture mold systems are usually prefered in industries.

Core and Cavity

The cavity is considered to be the fixed part since it is engaged with the extrusion machine and the core is considered to be the moveable part. once the molding processes is completed, the core opens and the molded part is ejected with the help of ejector pin from the core plate. Usually the B surfaces are held to the core, as it is hard to strip of the B- side feature from the mold set up. But this theory is not constant for all parts. For example Coin holder mold set up is little different from this theory. The parting surface is kept at the end of the mold set up. The flash occurs on the parting surface, since Class-A serves as the vissible area of the automobile the parting line is usually prefered in Class-B surface. In the above image sky blue coloured part is cavity and dark blue coloured part is core. The parting surface is exactly at the intersection of the core and cavity plate, but while considering the part the parting surface merges with the B-surface. Inorder to visualize the core and the cavity setup clearly, the entire setup is provided with multiple views below.

Front, Top, Side and Isometric view of Core and Cavity set up

6. Publication: After completing the entire design works, the necessary results ar published, inorder to visualize the results easily, instead of getting into search into the arranged sequencial geometrical sets. The publication helps to make the user interface comfortable.

Publication