Week 9 - Attachment Feature Creation - Challenge 1

Aim: 

To make Ribs,considering the Design engineering principles on the B side of the Coin Holder.

Theory:

Ribs are reinforcements,ususally thin, wall-like features added to the part to add internal support to walls or other features like bosses. In a similar fashion, gussets are support features that reinforce areas such as walls or bosses to the floor. Ribs provide stiffness and strength in molded parts without disturbing the thickness. They also help in Locating & arresting components of an assembly, Providing alignment in mating parts, Acting as stops or guides for mechanisms.

A well-designed rib will overcome the disadvantages like Increasing part weight and cost,Production cycle time required and appearnce of sink marks.

Ribs are also used as Covers, cabinets and body components with long, wide surfaces. They are also used as Frames and supports.

Ribs design features 5 main criticalities:
1. Thickness.
2. Height.
3. Location.
4. Quantity.
5. Manufacturability.

1) Rib Thickness:
Ribs should be designed to be 50-60 percent of the nominal wall thickness. Thicker ribs are more prone to create sink marks on surfaces.Rib Thickness should be 0.5 * Wall Thickness and the Top part of the Rib should have a thickness of 0.75mm minimum.

2)Rib height:
Rib height is nominally supposed should be 5 times the wall thickness.Taller Ribs can cause problems during producton as unfill can happen.Rib Height= 5 * Wall Thickness.

3)Rib spacing:                                                                                                                                      Ribs should be placed at a distance atleast twice the wall thickness.Rib Height/Rib width ratio = 3:1 –steel.
Rib Height/Rib width ratio = 2:1 –preferred

4)Rib draft:
A minimum of 0.5-degrees draft is sugested to ensure proper ejecton of the part.Rib draft = 0.5 to 1 degree.

5)Rib fillet:
Fillets are used at feature intersections to increase rib strength.Typically,Rib fillet = 0.125 * Wall Thickness.

6)Rib Root Thickness:
It is the thickness at the intersection of the Rib and Wall of the plastic component.Typically,Rib Root Thickness = (0.3 to 0.5) * Wall Thickness

Designing Ribs:

Considering the above engineering rules, Ribs are designed on a Coin holder part as shown. 

Result:

Ribs are designed with all the engineering principles.