Week 9 - Attachment Feature Creation - Challenge 1

Aim:

To create the rib for the Centre console coin holder considering the design rules.

Introduction:

Plastic parts design is a very complex process and it requires the involvement of many factors like functional requirements, process constraints, material selection and assembly or structural issues. Wall thickness, Draft, and Textures, Ribs & Bosses, Holes/Depressions, etc are some of the important elements to be considered in the design of plastic parts. Adhering to these basic design guidelines for injection molded parts can improve the moldability of the designs and the life of the mold, increase the operational life of the part and reduce manufacturing cost.

Ribs:

Ribs are a feature in plastic injection molded parts. They are thin extensions that run perpendicular to a wall or plane. They are commonly used to provide additional support and strength to a part.

Thickness and location are essential to rib design. Here are some helpful design guidelines:

• They should be designed with a thickness that is1/2 the wall thickness to avoid a thick section at the wall base.
• To minimize sink marks, design ribs that are approximately 60% of the joining wall thickness for minimum risk.
• Best practices include spacing at a distance of at least twice the wall thickness. Glossy materials require a thinner rib (40% of wall thickness)
• Design Rules for Rib creation.

An advantage of using ribs is that they increase the strength of the part without increasing wall thickness.walls that are too thick can sink,wrap or result in order defect.there integration into a part results in less material usage therefore a more cost effective solution.

Procedure

We have the coin holder,ribs creation is started with extracting the place over which the construction of the ribs can perform.

On this plane the line is drawn then will be then extruted along the direction of tooling axis to a height of 12.5 mm following the design rule of H=5*t

then we extrude it by 12.5 according to design rule.H=5t

after that we give a thickness of 1 mm according to design rule of ribs.Thickness of rib=0.4*t i.e 0.4*2.5=1mm

H=12.5

then we give draft to 4 faces of 0.5 degree according to design rule.

After that we gave the edge fillet of 0.25

now we intersect the XY plane with our body

we got this profile.

Root analysis

foe that a tritangent circle is created for the outline of ribs & base surface &then the circle dimension is measured as

shown in fig below

Now we have to create another same rib for that we follow the below criterion.

Draft analysis

Tree structure