Week 9 - Attachment Feature Creation - Challenge 2

AIM: To create the attachment features such as the screw boss and Dog House for the Centre console coin holder with respect to the design rules.

INTRODUCTION:

SCREW BOSS

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.

Design rules:

Let's consider Nominal wall thickness is T

Height of rib H- 3:1 ratio

Draft Angle for inside and outside - 0.5 degree

Fillet radius- 0.25 mm

The inner diameter of the rib - depends on metric size screws. IF we take the M6 Screw is inner dia is 5 mm.

The thickness of boss W- 0.6*T

DOG HOUSE:

The dog house is an engineering feature used in the plastic trim design. Dog houses are used as supporting features. Sometimes other engineering features like snaps; locators etc. are mounded on them to increase their strength.

DESIGN RULES:

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.

Design attachment features Screw Boss and Dog House :

Draw circular sketch inside the circle of dia 5mm and for outer circle wall should be 0.6*T on one side so outside dia = 2*(0.6*2.5)+5(inside dia)=8mm and Pad it with main tooling direction considering height to dia ratio of 3:1

DRAFT :

Give draft of 0.5 degrees with tooling axis.

Now have to support the screw boss and draw sketch ribs with respect to the below rules

Pad the sketch using the thick option for a thickness value of 1 mm.

Draft to ribs of 0.5 degrees.

To do union trim with screw boss, assemble with coin holder body, and give fillets to the edges.

Translate the screw boss using paste special with the link and using translate point to point option

Designing Dog House:

Draw a sketch of a rectangle with respect to the axis system created in the point.

sweep the drawn sketch to create the dog house and extrude the upper to create upper surface and thicken it in for 2.5mm and draft the body 0.5 degree

Draw a sketch and sweet to trim split the front face properly

Now to create coaring cut section as shown in the design rules of the B and C sections,

Extract the inner surface of the Dog house and coin holder surface, and offset the base surface between 3 to 6 mm.

Trimmed all surfaces to create a coaring section.

Switch to the part workbench and split the C and B Sections with the solid part.

DRAFT ANALYSIS:

Analysing draft angle with respect to tooling axis.

isometric view of Coin holder design with attachment features.

CONCLUSION: Hence created the attachment features such as the Screw boss and Dog House for the Centre console coin holder with respect to the design rules.