Week 9 - Attachment Feature Creation - Challenge 2

COIN HOLDER CENTRAL CONSOLE SCREW BOSS AND DOGEHOUSE DESIGN

AIM:

Create boss and doghouse on coin holder component following the design rule. Perform draft analysis of final output.

The coin holder central console data provided to us, we need to create screw boss, doghouse and tooling axis in two direction.

After that we performed draft analysis, whether the component is manufacturable or not.

TOOLING AXIS CREATION:

Analyze all surfaces for the possibility of tooling clearing all surfaces. For this component the main tooling axis should be perpendicular to the base surface.

SCREW BOSS DESIGN:

Boss features are commonly found in injection molding designs. They are used to aid in the assembly of molded parts by providing a channel for a screw. Designing plastic screw bosses is fairly straightforward but there are a few considerations to ensure a strong connection between parts and mitigate cosmetic defects.

Consideration for making screw boss

Cosmetic

If cosmetic are common, avoid thick sections that will be susceptible to sink. One common problem area is bosses located on or near exterior walls, we recommended moving these inwards. In addition, as a rule of thumb, we advise no more than 60-70 percent of the adjacent wall thickness for bosses.

The design cube demonstrates several boss designs, both good and bad, including how to use ribs and gussets to reinforce connection points.

Strength

Screw bosses can be reinforced with ribs or gussets for added strength and durability. As we mentioned above, a boss should not be next to walls, but you can coring ribs to keep it connected to the parts exterior wall without risking sink.

Material

Softer, less brittle materials work best for molded parts that need to accept screws. If your part will need to be threaded multiple times. Plastic bosses are typically only good for single use, since the threads are cut by the screw as it’s placed into the part.

Create a two circle where the screw boss is required. The circle dia should be calculated with the thickness of the component. In case we are using M6 screw the inner side of the hole should be 5 or 5.2 mm

For the outer screw boss, the thickness of the component is 0.6 times the thickness

In our design w is 2.5 X 0.6 = 1.5 (thickness per side)

And outer diameter of the boss will be 5.2 + 3 = 8.2 mm (Ideal boss dimension)

The height to diameter ratio is 3:1. The height is 15.6 mm. The dia is 5.2 mm, So the height is 15mm. Science the height is larger the boss becomes weak.

So in order to strengthen it we provide ribs.

The draft angle is 0.5 deg.

DOG HOUSE DESIGN:-

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

Design considerations for doghouse design are

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

• Doghouse wall thickness at the intersection of the part wall (C) should be 40% or less then the main wall stock (T).
• Height of (B) should be between 3.0 to 6.0 mm

Here C is 1mm which is 40% of the component thickness.

B is 4.19 mm which is between 3 to 6 mm

DRAFT ANALYSIS:-