Week 9 - Attachment Feature Creation (Ribs & Screw Boss) - Challenge 1

Door Handle Design

Given Surface

Tooling axis Creation

In injection molding, the Class A surface is first analyzed to determine the axis or tooling direction that separates the molds. Tooling direction is critical for plastic product design because it determines mold direction

Steps followed

On the extracted surface, a reference point is first created.

To plot clearance lines, a new axis system is used.

The x- and y-axes along with class A were used to develop the tooling axis using the Intersection curve

To form the Tooling axis, two clearing lines were bisected as shown below

The tooling axis's graphic properties are changed to identify the Tooling axis

On XY Plane

On YZ Plane

Bisecting with the two lines from the XY and YZ Plane we get an Ideal Tooling Axis

Creation of Class A surface

the given Surface is Joined together, using the Join command

the Above Class A surface is later undergone draft analysis using the Draft analysis Comand.

What is Draft Analysis?

Draft Analysis

For molded or cast parts, the draft angle is the amount of taper perpendicular to the parting line. It is measurable in degrees. Because plastic shrinks and sticks on molding surfaces as it cools, we draft the walls of the plastic part so that it ejects or breaks free from the molding surfaces more easily and without dragging. To reduce the risk of damage to the parts and ensure ejection, a functional injection molding part must have drafts on both the cavity and core sides.

Nominal values for Draft angles

1. 3 Degrees is a nominal draft angle
2. 5 Degrees can also be manufactured. Increasing the manufacturing cost
3. 7 Degrees is considered for Textured surface parts

Importance of Draft in injection molding

• Reduces the possibility of part damage due to friction during the release
• Reduces mold wear and tear
• Ensures a uniform, smooth, unscratched finish
• Ensures the integrity and uniformity of other surface finishes and textures
• Reduces overall cooling time by reducing or eliminating the need for unusual ejection setups

Steps followed for Draft Analysis

• The created part must be changed to the material mode in the display frame
• Compass is enabled and placed in the direction of the Tooling Axis
• The lock command is then used to fix the compass along the tooling axis
• Colour codes are classified and Draft angle is applied
• Running point analysis is used to display permissible draft angle.

Required features as mentioned in the Challenge

1. Rib Design

Ribs are a feature in plastic injection molded parts. They are thin extensions that run perpendicular to a wall or plane. They are commonly used to provide additional support and strength to a part. Thickness and location are essential to rib design.

Design Rules and Calculations

Calculations considered in Designing a Rib

• Thickness(t) = 3mm
• Rib Thickness: 0.4 X 3 = 1.2mm
• Rib Depth : 5 X 3 = 15mm
• Rib Thickness at the tip is 0.943mm
• The rib Draft angle is 0.5deg
• Rib Fillet radius considered : 0.25mm
• Rib Root Thickness is
  • Rib 1: D3.2mm
  • Rib 2: D3.2mm

Rib Design Images and Master sections.

Screw Boss

Screw bosses are typically used to assist in assembly, as a receptacle for a screw or threaded insert or as the locator for a mating pin on another part

Design Rules and Calculations

Calculations

Thickness (t) = 3mm

dia (d)= 1.6mm (M1.6 thread Dia)

W= 0.6X3 = 1.8mm

H/d Should be less than or equal to 3

H= 5.2*3 = 15.6, Considering 15mm as the Heigh

Draft angle is 0.5deg inside and outside

The radius is 0.25mm

Screw Boss design and Master section