Week 9 - Attachment Feature Creation - Challenge 1

AIM:  To Create the rib for the Centre console coin holder considering the design rules

INTRODUCTION

The Draft Analysis command enables you to detect if the part you drafted will be easily removed. This type of analysis is performed based on colour ranges identifying zones on the analyzed element where the deviation from the draft direction at any point, corresponds to specified values.

Tooling direction is the main consideration for plastic part and mould parts because it defines the movement of the mould part and the possibility of the plastic part coming out from the mould part (Core and Cavity).

TOOLING DIRECTION

The Tooling Direction is basically the direction that the mold pulls apart. The mold is built in two separate pieces, basically. You have a Cavity side and you have the Core side. The Core pulls apart from the Cavity and that's the Dyeline or the Tooling Direction.

PROCEDURE FOR CREATING TOOLING AXIS

Firstly import the given class A surface to the catia.

• Check For any defects in the surface such as boundries and estimate the possible tooling direction

Here, the input given was not a single surface. so, join the surfaces to create Class A surface

In the given surface the side walls are vertical without any draft to it. So, tooling axis is created in vertical direction along the base

CREATION OF RIBS

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.

There are some rules which we have to keep in mind while designing the ribs and those rules are:

1) Rib thickness - Ribs should be designed to be 40 percent of the nominal wall thickness. Thinner does not provide much structure and may be hard to fill. Thicker ribs are tempting, but they can begin to introduce sinks on the cosmetic surface.

2) Rib height - The Rib height should be greater than or equal to 5 times the wall thickness.

3) Rib spacing - Increase the number of ribs rather than their height in order to increase stiffness. Ribs should be spaced a minimum of two times the nominal wall thickness apart from one another. or it can be done in the ratio as well. The ratio will be of a height to width ratio. 

4) Minimum thickness at the tip - We have to ensure that the minimum thickness at the rib tip must be 0.75 mm

5) Draft - A minimum 0.5-degree draft will ensure that they release from the tool during molding.

6) Rib coring - Core thick ribs from the back or below to create a blank area and thinner rib walls.  This will help mitigate cosmetic sinks.

7) Radii - The fillets provided in the ribs should be in the range of 0.25mm to 0.5mm. Generally, it is recommended to give 0.25mm fillets.

First, I will extract the back surface and create a sketch on that side. The extract and sketch are shown below:

Sketches are extruded to a height of 12.5 mm From the base

Extruded sketches are converted into solid using thick surface

Draft angle of 0.5 is given to the ribs

Fillets of 0.25mm is provided 

 completed design in various orientations