Week 9 - Attachment Feature Creation - Challenge 2

Aim - Create the boss and Dog House for the Centre console coin holder.

Introduction - Bosses find use in many parts of the design as points for attachment and assembly. The most common variety consists of cylindrical projection with holes designed to receive screws, threaded inserts, or other types of fasteners. As a rule of thumb, the outside diameter of bosses should remain within 2.0 to 2.4 times the outer diameter of the screw or insert. The dog house is an engineering feature used in the plastic trim design. Sometimes other engineering features like snaps; locators, etc. are mounded on them to increase their strength. Dog houses are subjected to draft analysis to prevent breakage of the component during ejection from the mold cavity.

Design rules for screw boss

1. Draft.

2. Thickness.

3. Height to diameter ratio.

4. Optimal radii.

5. Boss gussets.

6. Caring out the bottom.

7. Planning ahead for the type of ejection.

General Guidelines for bosses

Draft - 0.5 degree on the wall of the boss.

Thickness - Typically 40% of the nominal wall at the base.

Height of diameter ratio - 3:1

Radii - 0.25mm maximum radii

Boss gussets must meet rib guidelines.

Need to plan ahead for the type of ejection - If less than 25mm tall, the draft is not required when sleeve ejection is not used.

Over 25mm tall, the draft is required outside the wall only if sleeve ejection is used. If sleeve ejection is not used, the draft is required on all walls.

Doghouse

Doghouse guideline

1. Draft.

2. Doghouse wall.

3. Part surface.

4. Bottom of the doghouse.

5. Wall thickness.

6. Height and Width.

Doghouse width

The minimum doghouse width for doghouses is 12mm. 3:1ratio of steel width to Height 2:1 is preferred.

Firstly extract the bottom of the coin holder and taking a point at it.

After that draw a sketch on it and extrude it or Sweep with draft direction.

then offset the plane 20mm

then trim between offset plane and sweep after that extract, the plane of the doghouse is then extrapolated and then offset 22mmm ahead then trim it.

After that draw sketch on it then pad it

after that apply draft

after that draw, a sketch then pad it then untrim the main body

after that add screw boss and doghouse body to the main coin holder body.