Week 10 - Challenge 1- Attachment Feature Creation (Ribs & Screw Boss)

TOOLING AXIS CREATION:

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 eject able direction is somewhere close to the Z direction, (might be inclined to it) so we have made a sketch on the YZ 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.

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 mould. 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 analyse the draft on various surfaces, the draft analysis in CATIA uses the colour codes for the identification of the draft. Each colour 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 colours for analysing 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 analysing the draft here. Now, bring the compass and align it with the tooling axis and click the lock button in the dialog box.

TOP VIEW

FRONT VIEW

RIGHT VIEW

LEFT VIEW

ISOMETRIC VIEW

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.

Next, the profile is extruded, to find the height (h)=Wall thickness * 5

=2.5*5

= 12.5 mm

Therefore, the height is 12.5 mm

The extruded surface is thickened,

Thickness (w)=0.4*t

=0.4 *2.5

=1mm

Therefore, the thickness of the rib is 1 mm

The draft is applied to the sides of the ribs. As per the design rule, the ideal draft angle is 0.5 degree

Then fillet is applied to the faces of the rib. As per the design rule, the fillet can be 0.25 mm.

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 moulding designs. They are used to aid in the assembly of moulded 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

• Thickness

• Draft

• optional radii

• Boss gussets

• Type of ejection

The construction process of creating the screw boss is explained below:

For thickness, the design rule is as follows,

Thickness (w)=0.6*T

=0.6*2.5

=1.5 mm

Therefore, the thickness of the boss can be 1.5 mm per side.

In this case, we have considered the size of the screw boss as M06.

Once the sketch is completed, then it is padded using the Pad ‘command. The height to diameter ratio can be 3:1

Next, the draft is given to the boss. As per the design rule, the draft given for screw boss is 0.5 deg.

Then fillet is applied to the faces of the rib. As per the design rule, the fillet can be 0.25 mm.

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Tree image

STEPS