Week 9 - Attachment Feature Creation - Challenge 2

Aim: Create the screw boss and dog house fro the centre console coin holder cosidering the design rules mentioned in the vedio

 SCREW BOSS

• Bosses find use in many parts of the designs as points for attachment and assembly. The most common variety consists of cylindrical projections with holes designed to receive screws, thread inserts or other type of fastening software
• To reduce stress concentration and potential breakage, bosses should have a blended radius,rather than a sharp edge,at their base
• Avoid bosses that merge into some walls because they can form a thick sections that lead to sink instead use connected ribs for support 

General Guidelines for Bosses:

•   Draft  - 0.5 degrees on walls of boss
•   Thickness -  Typically 40%* of the nominal wall at the base.
•   Height to Diameter Ratio -  3:1
•   Radii - 0.25mm maximum radii.  
  

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

• Draft
• Thickness
• Height to diameter ratio
• Optional radii
• Boss gussets
• Coring out bottom
• Planning ahead for type of ejection 

SCREW BOSS DESIGN

1. Screw boss can be on B-surface or it can be on dog house in this we are mounting it on dog house
   draw a circular sketch inside circle of dia 5mm and for outer circle wall should be 0.6*T on one side ,out side dia=2*(0.6*2.5)+5(inside dia)=8mm

2.pad it ith main tooling direction considering height to dia ratio of 3:1

H=B*3=5*3=15mm give draft of 0.5 deg with tooling axis

3.now to support the screw boss we need to give ribs for it

4.draw a sketch for the ribs

5.pad the sketch by clicking on thicken option

6.give draft of 0.5 deg 

7.do union trim with screw boss and give necessary fillets 

assemble to coin holder main body

DOG HOUSE : Dog house is a feature helps you to avoid sink marks

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

• Height of  ( B ) should be between 3.0 – 6.0 mm

• C is where dog house contacts back side of surface

Design rules for screw boss

• Draft
• Dog house walls
• Part surface
• Bottom of Dog house
• Wall thickness
• Height and width 

DOG HOUSE DESIGN
1.extract the base of the class A surface and offset it to 2.5mm because of thickness and draw a sketch of rectangle and should be open from one side for dog house

2.using sweep with tooling direction and draft it at an angle 1.5deg for the outer surface

3.close the upper surface by offset the below extracted surface and then trim it

4.go to part design and thicken the surface by applying part thickness to 2mm and now for inside faces of dog house we need side core tooling axis created in it z-direction
give draft to the inside surface of 0.5deg

5.now create c and b sections as shown in the design rules,offset the base surface in between 3 to 6 mm
Extrapolate the surface to acheive desired length and go to part work bench and split the c and b section with thicken part 

6.provide draft to inside surface

7.give the radius of the fillet as 0.4*T=0.4*2.5=1mm and for outer edge give fillet as inside radius +part thickness and assemble with the cion holder

draft analysis for dog house

draft analysis

side view

top view

PART BODY

COIN HOLDER PART BODY