Week 10 - Challenge 2- Attachment Feature Creation (Dog House)

AIM

Create the Dog House for the Door Trim.

DOG HOUSE

Dog house is an engineering feature used in plastic design. Dog houses are used as support feature. Sometimes other engineering features like snaps, locators, and screw bosses are mounted on them to increase their strength.

Dog houses are subjected to draft analysis to prevent breakage of the component during ejection from the mould cavity. Dog house and other engineering components are built on the B-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.

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
• Color codes are classified and a Draft angle is applied
• Running point analysis is used to display permissible draft angle

"C" is where the doghouse contacts the backside of the surface

Doghouse wall thickness at the intersection of the part wall (C) should be 40% or less than the main wall stock (T).

The height of (B) should be between 3.0 – 6.0 mm

C 40 % of T or ≤ T

B 3 - 6 mm

Width ≥12 mm

Width to Height Ratio 3:1

Draft 1.5

SIDE CORE AXIS :

Axis which I have created using dog house back ( Tangent to the suface ). Toward the direction of X.

A SURFACE :

Given A surface. Do the mutliple extact and the ofsset into 2.5mm.

B SURFACE :

Offset the surface 2.5mm using A surface. And repair the surface if profile was not proper. Tools which I have used Multiple Exact, Single Exact, untrim, boundary, Extrapolate, trim, split, Edge fillet.

C SURFACE :

JOINING A & C :

FINAL TRIM:

PRE DRAFT ANALYSIS :

FINAL DRAFT ANALYSIS:

ISOMETRIC VIEW:

CONCLUSION:

As per given instruction we made the door trim design using close surface, tooling axis, dog house and draft analysis.