Week 8 - Challenge 5 - Core & Cavity Design

CORE AND CAVITY DESIGN OF A SWITCH BEZEL

AIM:

To Create the Switch Bezel 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 also Create the Class B Surface & Class C Surface. At the end perform to give thickness of the model and also to create the Core and cavity blocks for the switch bezel designed in the earlier.

Tooling axis:

• It is defined as the direction in which the mold opens or core and cavity, with the help of tooling axis created along X and Y axes are used for creating the main tooling axis by using bisecting method.

DRAFT ANALYSIS

• Draft analysis is performed based on colour ranges identifying zones on the analysed element where the deviation from the draft direction at any point, corresponds to specified values. Draft is required on all parts in the direction of mold movement in order to allow parts to release or eject from the properly.
• Draft is the angle in which the parts is tapered to allow it to release. As the part cools, it tends to want to shrink to the core side of the mold. The draft allows the parts to release easily from the mold without creating friction between the surface of component and the core and cavity plates.
• Most applications require minimum draft angle of around 5^o to 1^o, however 3^o draft angles are widely accepted for cost saving purpose. 7^o draft angles are given to textured surface like instrument panels. Minimum possible draft angles are given to screw bosses, ribs and stiffeners due to their critical nature.

PROCEDURE:

CLASS A SURFACE:

CLASS B SURFACE:

CLASS C SURFACE:

FINAL TRIM:

TOOLING AXIS:

Tooling Axis is the tool travel direction. here the core gets along the axis of the tool travel. Hence creating a tooling axis is most important and first process for making a plastic part.

To Create a Tooling Axis, we have to first verify which direction is best suitable for the tool to produce the part in an efficient way. This can be usually done by just assuming the direction by examining the given surface.

PART:

DRAFT ANALYSIS:

Draft Analysis is a process to check the eligibility of the designed product to be manufactured without getting damaged. To get successful draft analysis, the part should have a draft of minimum 0.5 to 3 Degree. This draft should be in reference with the tooling direction of the core and cavity during molding process.

CORE AND CAVITY DESIGN:

• The mold core & cavity are the shaped sections in either half of the mold tool which give the plastic product its final shape.
• The hot molten material is injection 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 mold of a plastic part is called the injection molding cycle.
• The cycle begins when the mold closes, followed by the injection of the polymer into the mold cavity.
• A core is usually made of the best quality sand and is placed into the desired position in the mold 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.

PARTING SURFACE:

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

• Trim the Class B surface and previous trim command, to get parting surface of core and cavity design.
• The below figure is known as Parting Surface of the core and cavity design.

Core Design:

• The core design is started extracting the parting surface that becomes the datum for the core and cavity. The parting surface in most of the cases is kept at the b Class surface to avoid close and tight contact between the core and cavity.
• Draw Rectangular profile on Axis system XY plane.
• Extrude the profile along Z direction.
• Trim the surface of parting surface with component area and Extrude.
• Fill the top of the surface area.
• To join the Fill surface and Trim Surface to get Core Design surface model.

• To intersect the Axis System of ZX plane and select the core surface model, to get sketch profile.

Cavity Design:

• The cavity is the part where the injector and filling of the molten plastic happens. The cavity block is prepared by first extruding the outer boundary along the tooling direction.
• Draw Rectangular profile on Axis system XY plane.
• Extrude the profile along Z direction.
• Trim the surface of Class B surface and extrude.
• Fill the top of the surface area.
• To join the Fill surface and Trim Surface to get Cavity Design surface model.

• To intersect the Axis System of ZX plane and select the cavity surface model, to get sketch profile.

Parting Line:

• A parting line, in 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.
• To intersect Class B surface and Join.7 under Class A & C geometrical sets.
• The below figure consider the YELLOW Dotted line is known as Parting line.

RESULTS OF CORE AND CAVITY DESIGN: