Challenge

Week 8 - Challenge 6 - Core & Cavity Design

VVidhan Shah17 Dec 2022

Challenge 6 - Core & Cavity Design

AIM :

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

THEORY :

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 :

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

Parting surface design principles :

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

Principles to follow to design Parting surface :

Design the injection mold simply as possible. Avoid or reduce side parting as much as possible to reduce the complexity of mold making.
Ease of de-molding as far as possible, for instance, the plastic parts should stay in a fixed half of the injection mold and should be ejected by the ejection system avoid, side de-molding action,
Ensure the dimension accuracy of the molded parts, Try to make the parts similar to dimensions and accuracy requirements in the same mold to reduce manufacturing and assembly errors.
Ensure appearance requirements of molded parts, finish or mismatch usually occurs on the parting surface, so the parting surface should not be designed on high-quality requirement surfaces.
Ensure adequate venting. If possible parting surface should be placed at the end of the mold flow. This is going to be an 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 the edges of the part. When designing a part, always keep in mind its part lines.

DESIGN RULES FOR CREATING CORE AND CAVITY :

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

Design rules:-

The proper draft should be given to the part so that the part can be ejected from the core and cavity.
A minimum 3-degree draft should be given to the Class C surface. If the part has a 0-degree 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 :

When you look at the part we have designed the color-highlighted region side is the core side since it has the projections .here we are extrapolating the class A so that we can use it for trimming purposes while creating core and cavity blocks

if we can observe from the draft analysis we have done on this component in the previous challenge the A surface and C surface had tooled along the A side i.e., "main tooling axis" direction.

the parting line is the area in which the parting surface and component meet or the core half and cavity half meet/junction between the painting surface and the component

here we will intersect the a and c surfaces joined together with the b surface so that we will get a parting line which is the clear splitting line between core and cavity .it is the very exact junction where core and cavity closes at the parting surface and intersection of the component with the parting surface is the parting line

so we are considering it as a part of the core .for creating the core we need untrimmed class C and class B surface which we created before .here we are trimming class B with extrapolated class B.

We have a splitting surface between the core and cavity i.e., a parting surface that defines where the core and cavity are going to split and the features which come after it.

now we are creating a rectangular shape sketch so that can cut off the surface

while creating we also make sure that the boundaries of the sketch are inside the parting surface.

After iso constraining the sketch we named it parting surface. then we will extrude it along the tooling axis in a separate geometrical set named "core design".

later we trim the core along with the parting surface and extruded surface. the image below shows what a core looks like.

and we will extract the boundary and fill the top to make it a closed surface so that we will get the core solid block out of it .

Use the Close Surface feature to make a solid body from the surface.

here we will use the intersection between the x-plane with the parting surface and core. the pink color shows the core, yellow is the core where its walls are extruded along, and the blue shows the parting surface which split the core and cavity, always ensure to have a parting surface on the B side

now let's design the cavity, we follow the same process as above first we will extrude the surfaces/walls along tooling axis direction, we ignore the component area and rim the body with b surface and then fill the bottom portion to make it closed body for solid block/cavity block

here after making cavity block we made the intersection with the X axis again. the image below shows the cavity block which is in green and the blue dotted highlighted is the 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 and form a sealed hollow to avoid melt flow leakage and maintain certain holding pressure, the pressed surface is called parting surface, usually parting surface is the biggest projection outline of the part.