Week 9 - Attachment Feature Creation - Challenge 1

Report:

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

Introduction:

A plastic part design is a very complex process and it requires the involvement of many factors like functional requirements, processs constraints, material selections and assembly and structural issues. The wall thickness, draft and textures, ribs and bosses, holes/depressions etc are some of the important elements to be considered in the design of the plastic parts. Adhering to the 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 the manufacturing cost.

Ribs:

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

To give a good strength to part we can increase thickness of a part but this inturn increases the weight of the part which is non-desirable. So rib are the best solution for increasing the strength of the part.

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

• They should be designed with a thickness i.e half the wall thickness to avoid a thick sections at the wall base.
• To minimise the sink marks, design ribs that are approximately 60% of the joining wall thickness for minimum risk.
• Best practices include spacing at a distance of atleast twise the wall thickness.
• Glossy material require a thinner rib (40% of wall thickness)

An advantage of using ribs is that they increase the strength of part without icreasing the thickness of wall. Walls that are too thick can sink, waro or results in other defects. This integration in parts results in less material usage; more cost effective.

Procedure:-

• Since we have the coin holder, ribs creation is started with extracting the plane over which the construction for the ribs can be performed.

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

• After that moving to the part workbench, this line is thickneed by 1mm since the rib thickness has to be 0.4*t

• This thickned rib is drafted bt 0.5 degree. Pulling direction is taken as upper face of the ribs.

• Then drafted rib is assembled into the coin holder part body.
• Another rib is created at spacing of 2*t of the design rules and assembled to the coin holder.

• Lstly, both ribs are provided with fillets of 0.25mm radius.

Checking the rib design:

In order to check the dimensions of the ribs, the coin holder is intersected along the XY plane to obtain the boundary lines.

Root analysis:

For the root analysis, a tritangent circle is reated from the outlines of ribs and base surface, and then circle dimension is measured.

Height:

Thickness:

Draft analysis:

Ribs need to be checked for draft analysis, to ensure all the features have passed the tooling direction

• Open the feature draft anlysis from insert menu.
• Move the component to align with tooling axis and then select the component.
• Here, change the minimum draft angle to 0.5 degree since the draft provided to ribs is 0.5

Results:

The ribs for the center console coin holder has been successfully created considering the design rules mentioned in the given data.