Week 9 - Attachment Feature Creation (Ribs & Screw Boss) - Challenge 1

1st Step - Check the connectivity of the Class A Surface

(A surface made by the designer which is given as an input to the plastic modeler to work on. It is aesthetic surface
and the outer most surface.)

• Ensure that there is no gap between the component, using join command.
• We can visually check it or by clicking boundary command.
• Therefore first check completed.

2nd Step - Find the tooling axis of the component.

It is defined as the direction in which the mould/core and cavity open. Selection of the direction of the tooling axis depends on the ease at which components can be easily ejected.

By analysing the component the most easily ejectable direction is somewhere close to the Y direction,(might be inclined to it) so we have made a sketch on the YX plane of Axis System) to create a bisecting line considering the 2 faces which might be difficult to be tooled.

Then resultant tooling axis is created using the bisecting method.

3rd Step - Now creating Class B Surface

(A surface below a certain thickness from the class-A surface is class-B surface. This is the surface that contains
engineering aspects of a model.)

1. Intially extracting the reqired surface's part using Extract feature from Class A surface.
2. Then perform Untrim followed by Extrapolate inorder to increase the length
3. Now trim the surfaces to required surfaces
4. Then Offset the surface inorder to get the required thickness
5. And now trim inorder to get the required surface
6. Now fillet the surface to required amount

4th Step - Creating Class C Surface

(A surface that joins class-A and class-B surfaces is class-C surface.)

1. Create Boundry around Class A Surfaces
2. We will Get 1 for outer boundary
3. Use Sweep feature with subtype - "Reference Surface"
4. Provide 90 degree as angle

CREATING THE RIB

Ribs are thin wall protrusions that extend perpendicularly from a wall or plane. They are usually found in clusters offering support to a plane that would have otherwise been too thick, but can also be stand-alone support for a single wall. They are commonly used to provide additional support and strength to a part. Thickness and location are essential to rib design.

First, the base surface where the rib has to be created is extracted using the Extract command. A positioned sketch is created and the profile for the rib is drawn.

Then We have to design ribs as per industrial standards

Now, we have to check for the Rib root thickness.

To check for the Rib root thickness, We have to take an Intersection with the XY plane and the Coin holder component. Once we get to the intersection we have to create a tri-tangent circle at the rib area and measure it. The value must be within 30% greater of the wall thickness.

CREATING THE SCREW BOSS

Screw 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. Their primary use is to strengthen holes or slots in the surface present in the part model.

Design rules consider while creating a screw boss

DRAFT ANALYSIS

Draft analysis is a method used in design to check whether the component created in CAD is manufacturable based on the draft condition applied. The main reason behind the draft analysis is the part manufactured should be easily removed from the mold. It also gives an idea of the draft angle from the tooling direction. Here we are giving a tooling direction in order to eject the component easily from the tool. The ideal draft angle given in automotive industries for plastic components is 3 degrees.

Some of the components where draft analysis is done are hood, fenders, roof, side doors, etc.

The draft analysis is an important tool as it helps the user to analyze the draft on various surfaces, the draft analysis in CATIA uses the color codes for the identification of the draft. Each color has its own meaning for the minimum draft negative draft and under draft.

The draft analysis toolbar provides two modes for analysis of the draft, first is the quick analysis which basically has three colors for analyzing GREEN, RED, AND BLUE on the other hand other option is the full analysis mode which enables a few more details into the draft and is used in the complex components like the instrument panel, etc. In the above challenge, we have used the quick analysis made for analyzing the draft here. Now, bring the compass and align it with the tooling axis and click the lock button in the dialog box.

So, from the solid body draft analysis we can see that all surface including RIBS and SCREW BOSSES are clearing the 0.4 degree draft angle. So this plastic part is manufacturable with B side engineering features in injection process.