Draft Analysis on a Fan Cover using CATIA V5.

AIM: To create a tooling axis for a fan cover model which satisfies all the rules of draft angle and perform the draft analysis on the model.

OBJECTIVE:

• Ensure proper tree structure.
• Proper names for every geometrical set according to sketches they represent.
• Every sketch should be under a geometrical set only.
• Publication of the tooling axis and the class-A surface.

THEORY:

• Draft:

The draft is an angular tapering given at the design stage to every Plastic Component that has to be manufactured. It is given in the direction of the Mold Movement. The Draft allows the parts to release easily from the mould without creating friction between the surface of the component and the core and cavity plates.

When a Plastic component cools down inside the mould, the natural tendency of it is to shrink and attach to the core or cavity half. The movement of mould opening causes friction on the walls of the component as well as the core/cavity blocks. This reduces the life of the mould as well as the component itself. The component may also have a rough surface finish as well as a weak structure due to this. This problem can be solved by giving a draft to the component.

Most applications require minimum draft angles of around 0.5° to 1°, however, 3° draft angles are widely accepted for cost-saving purposes. 7° Draft angles are given to textured surfaces like Instrument Panels. Minimum possible draft angles are given to screw bosses, ribs and stiffeners due to their critical nature.

• Tooling Axis:

The definition tab on the tool as dialogue controls how you want the tool to orient itself whilst cutting a multi-axis toolpath total as select to define the tool orientation. The default value is vertical which is used for standard 3-Axis machining and is fund larger continuously changing orientation.

• Draft Analysis:

Draft Analysis is a tool in CATIA which identifies the zones which deviate from the specified values of angles along a defined draft direction using colour codes. It highlights the regions of the draft using colours. Draft analysis is the first step performed after receiving the Class A of the component.

• Class-A Surface:

In automotive design, a class A surface is any of a set of freeform surfaces of high efficiency and quality. It is the visible aesthetic surface of any automotive component.

• Pulling Direction:

The direction part is partly ejected from the mould is called pulling direction. This direction also corresponds to the reference from which the draft faces are defined.

• Neutral Element:

It is the neutral curve on which the drafted angle will file, it will remain unchanged during the draft. Neutral and parting elements may be the same in some cases.

PROCEDURE:

• Step 1: Check the Class A surface design file:

After receiving the Class-A of the fan cover check for the connectivity of all surfaces on it. Use Join operation, boundary operation and disassemble. The check is over if any discontinuities do not arise. Delete the operations after the check.

Figure1: Join Operation for checking connectivity.

Figure2: Boundary Operation for checking connectivity.

• Step 2: Determine Tooling Axis:

• Create a Dummy Tooling axis along the best possible direction as per the Class A as shown in Figure 3. In this case, we have chosen the Z-axis as a dummy as it doesn't interfere with any slots or holes.

Figure3: Boundary Operation for checking connectivity.

• Create an Axis System on this line and a suitable point as shown in Figure 4.

Figure4: Axis System on Class A of Fan Cover.

• Create an Intersect between the two planes and the Class A surface i.e., the XZ and YZ plane intersection with the fan cover as shown in Figure 5 and Figure 6.

Figure5: Intersection of XZ plane with Class A of Fan Cover.

Figure6: Intersection of YZ plane with Class A of Fan Cover.

• Create extended Lines for the faces which may create problems in terms of Draft angles. In this case, the lines are created for each intersection as shown in Figure 7 and Figure 8.

Figure7: Extended Lines for faces on XY plane.

Figure8: Extended Lines for faces on YZ plane.

• Create a Bisecting Line for the extended lines along with the centre point on both the planes and name it Tool Clearing X and Tool Clearing Y as shown in Figure 9 and Figure 10.

Figure9: Tool Clearing for X.

Figure10: Tool Clearing for Y.

• Create a Bisecting Lines between Tool Clearing for x and Tool Clearing for Y along with the centre point. This is the main Tooling Axis required. Name it as Tooling Axis and publish it using Insert => Publication.

Figure11: Tooling Axis and its Publication.

• Step 4: Draft Analysis:

• Change View Mode Customization to Material mode as shown in Figure 12.

Figure12: Material Mode.

• Go to INSERT=> ANALYSIS=> FEATURE DRAFT ANALYSIS and move the compass to the Tooling Axis. Change the range to 3°. Apply the settings as shown in Figure 13.

Figure13: Draft Analysis tools for Fan Cover.

• Figure 14 shows the tool which uses the compass to define the new current draft direction.

Figure14: Uses the compass to define the new current draft direction.

• Figure 15 shows the use of the Tool Analyses under the running point feature.

Figure15: Using the Analyses under the running point feature.

• Figure16 shows the screenshot of the Draft Analysis of Fan Cover.

Figure16: Screenshot of Draft Analysis of Fan Cover.

• Tree Structure:

Figure17: Screenshot of Tree Structure of Fan Cover.

• Screenshots of the model with the proper colour code of the draft angle in various orientations (Isometric, Front, Side, and Top View):

Figure18: Model in Various Views.

RESULT:

The Fan Cover has passed the Draft analysis test as the draft values of the fan cover are less than 3° and the cover is safe for production.

Figure19: Result of Draft Analysis.

CONCLUSION:

Green Colour indicated the draft angles are all having permissible values and the draft analysis status for the Fan cover is Passed.