Week 9 - Challenge 1 - Base Bracket Design

Base Bracket design

Objectives

• Create a plastic component of certain thickness (2.5mm) using the given Class A surface
• Create a proper tooling axis for the component
• Perform Draft analysis for both the Class A and the final component

Tooling Axis

Tooling axis is the direction in which the mould and the cavity opens. There are two methods in creating the tooling axis

• Bisecting method
• Point-direction method

For this component bisecting method is used to create the tooling axis

Bisecting method of creating tooling axis

• First a reference point is created on the Class A surface and then the direction is considered
• For this component Z-axis ensures the proper direction to eject component hence the tooling axis is created along the Z-Axis
• The x- and y-axes along with class A were used to develop the tooling axis using the Intersection curve
• Using similar sides of the components two lines are created which then bisected by another line with the reference point as the centre and along Z- axis
• To differentiate the appearance of the tooling axis its display properties are customized and then published

Draft analysis

A draft of minimum 3 degree must be provided on both core and cavity sides in a component for smooth ejection and for good surface quality. As the plastic shrinks and sticks onto the molding surfaces as it cools, walls of the plastic part should have a minimum draft so that it ejects or breaks free from the molding surfaces easily and without any drag.

Advantages of draft in injection molding

• Reduces the possibilities of part damage caused by friction during ejection process
• Reduces wear and tear in mold
• Helps to obtain uniform,smooth and unscratched surface
• Decreases overall cooling time by eliminating the need for unusual ejection setups

Nominal Values of Draft angles

• 3 Degree is a nominal draft angle
• 5 degree is possible but increases the manufacturing cost
• 7 degree considered for textured surfaces of parts

Performing Draft analysis

• Draft analysis is performed for both the given Class A surface and the component created out of it
• First the component is view mode is changed to material mode
• Selecting the “Feature Draft Analysis” command in the “Analysis” toolbar enables various parameters for performing draft analysis
• The compass is enabled and placed in the tooling axis and its direction is inverted along the tooling direction of the component
• The component is selected for draft analysis, the color code is customized according to the requirements using the Color Scale option.
• To view the angle at various points “analyses under the running point command is used”

Creating the component

Input Class A is given

• As the first step the draft analysis is performed and the surface is checked for any open boundaries

Class B

• All individual surfaces are extracted, untrimmed, and offset to a certain distance (2.5mm)
• The excess portions are trimmed and joined using Trim tool
• Then the fillets are applied respectively

Class C

• The Boundaries of the Class A surface are extracted
• Using the boundaries, surfaces are swept along a certain degree with respect to the tooling axis
• Using trim tool the edges are trimmed and the surface is joined together

Final trim

• Using Join command the class A and the Class C surfaces are joined together
• Then the Class B surface is trimmed and merged with the joined surface using trim tool

Creating Solid Component

• With the help of Closed Surface command in the part workbench a solid component is created

Performing Draft analysis for final component