Week 9 - Attachment Feature Creation - Challenge 2

AIM : Create Dog house for coin holder and door trim considering the design rules mentioned.

INTRODUCTION: Boss features are commonly found in injection moulding designs. They are used to aid in the assembly of moulded parts by providing a channel for a screw.

Dog house is a feature that helps you to avoid sink marks.

TREE STRUCTURE : 

CREATION OF TOOLING AXIS :

extract the class A base surface, and create a point with (0,0) co- ordinates

create an 3D intersection line with reference to yz plane

then create the line on the one side with reference to the drafted two points. and again the same procedure for another side.

using the line command, bisect the two lines to form a centre line and name it as the tooling axis.

the line which pass through the mid point of the two line segement is known as the bisecting lines.

CREATION OF DRAFT ANALYIS IN CLASS A SURFACE : 

• draft analysis is the major important role of design check which show the design can be manufacturable with the required tooling direction. 
• for an plastic product design, there must be a minimum draft angle of 3 degree.
• after the creation of tooling axis, open the draft analysis command using insert - analysis - draft analysis. 
• set the axis system in the line of tooling direction. 
• then draft angle for this product is analysized.

SCREW BOSS DESIGN :

Avoid bosses that merge into sidewalls because they can form thick sections that lead to sink. Instead, positon the bosses away from the side walls and in needed, use connecting ribs for support.

Consider using open boss design for bosses near a standing wall. Avoid bosses that merge into the side walls because they can form thick sections that lead to sink. Instead position the bosses away from the side wall and needed use connecting ribs for support. Consider using open boss design for bosses near a standing wall.

Normally, the boss hole should extend to the base wall level, even if the full depth is not needed for assembly. Shallow holes can leave thick sections, resulting in sink or voids. Deeper holes reduce the base wall thickness, leading to filling problems, knit lines or surface blemishes. The goal is to maintain uniform thickness in the attachment wall because of the required draft, tall bosses those greater than 5 times their outside diameter can create a filling problems at their top or a thick section at their base.

DOG HOUSE DESIGN :

 Dog house is an engineering feature used in plastic trim design. Dog houses are used as supporting feature. Dog house is a feature that helps you to avoid sink marks. and also used for solving the lenght issues for screwing and also for the aatachment of perpendicular screw boss. 

"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

• CREATION OF DRAFT ANALYSIS IN FINAL PLASTIC PRODUCT :

ISOMETRIC VIEW :

FRONT VIEW :

SIDE VIEW :

TOP VIEW :

DOOR TRIM DRAFT ANALYSIS : 

tooling axis is created using bisecting line method. But in the components where it has a bin, then the tooling axis is considered as a line normal to the base surface of bin. Same is done with this component. A line normal to base surface is created and considered as tooling axis.