Week 8 - Challenge 5 - Core & Cavity Design

CORE AND CAVITY DESIGN

JEEVA R

AIM:

To create the Core and cavity blocks for the switch bezel which we have designed in the earlier challenge.

DRAFT ANALYSIS:

The Draft Analysis command enables you to detect if the part you drafted will be easily removed. This type of analysis is performed based on color ranges identifying zones on the analyzed element where the deviation from the draft direction at any point, corresponds to specified values.

PARTING SURFACE:

Generally, injection mold has two major components: the movable halves and the fixed halve, during the injection molding process, these two halves are pressed tightly from a sealed hollow to avoid the melt flow leakage and maintain certain holding pressure, the pressed surface are called parting surface, usually parting surface are the biggest projection outline of the part.

Parting surface design principles: Parting surface design directly affects the product quality, ease of construction and operation of the injection mold, the mold design is one of the key factors to success.

Principles to follow to design Parting surface:

1. Design the injection mold simple as possible. Avoid or reduce side parting as much as possible to reduce complexity of the mold making.
2. Ease of de-molding as far as possible, for instance the plastic parts should stay in fixed halve of injection mold and should ejected by ejection system avoid, side de-molding action,
3. Ensure the dimension accuracy of the molded parts. Try to make the parts similar dimension accuracy requirements in same mold to reduce manufacturing and assembly errors.
4. Ensure appearance requirement of molded parts, finish or mismatch usually occurs on parting surface, so the parting surface should not be designed on high quality requirement surfaces.
5. Ensure adequate venting. If possible, parting surface should be place at the end of the mold flow. This is going to be advantage of filling and venting.

PARTING LINE:

Part lines are where the two halves of the mold meet. This generally creates a physical line on a part that is both visible and noticeable to the touch. These lines, however, can be hidden or minimized when placed along edges of the part. When designing a part, always keep in mind its part lines.

To create a plastic part there are two major components core and cavity. The core has the impression and the cavity have the depression.

CORE AND CAVITY:

A core is the one part of the mold and responsible for half of the molded part. Actually, core is the projection of the body and Cavity is the depression of the body. These core and cavity combine to form a mold, then the plastic material is injected into these molds to get a plastic part.

DESIGN RULES:

• The proper draft should be given to the part so that the part can be ejected from the core and cavity.
• Minimum 3˚ draft should be given to the Class C surface. If the part has 0˚ draft, then there will be friction occurs in the core and cavity.
• The side core should be avoided because the manufacturing cost of the component increases.
• The parting line is the line that split the mold into two halves the core and the cavity. So, the parting line should be always in the Class B surface so that we can not see the parting line.
• Avoid sharp corners as the cost to manufacture the sharp corner is very high.
• The thickness of the part should always have uniform thickness throughout the part.

PROCEDURE:

CORE DESIGN:

1. Extrapolate the class A surface.

2. Trim class A and class C together, then class B with class A and C trims to get the projections on the core.

3. Draw a rectangular sketch extrude and fill the upper surface. Join the extrude and filled surfaces, then trim it with the projection surface to get a closed profile. Use closed surface command to get a solid core part.

CAVITY DESIGN:

1. Take the B surface and create a sketch of rectangle and extrude. Filled the bottom and join the extrude and fill, then trim the join with b surface to get a closed cavity block. Use closed surface command to get a solid cavity block.

PARTING LINE:

Take intersection of solid switch bezel and B surface, we get the parting line.

PARTING SURFACE:

Take the B surface and split it with the parting line, we get the parting surface

SECTIONAL VIEW:

DETAILED VIEWS:

TREE STRUCTURE: