Base Bracket Design and Draft Analysis using CATIA V5.

AIM: To create the base bracket plastic component through the given Class-A surface and at the end perform the draft analysis on the model.

OBJECTIVES:

• To ensure proper tree structure is followed.
• Geometrical sets should have a proper name based on the sketches present inside of them.
• All the sketches should be created under the geometrical set.
• Use of the close surface feature to make a solid body from the surface.
• To publish the tooling axis Class A, B and C surface.

THEORY:

• Draft Analysis:

Draft analysis helps to detect if your drafted part is easily removable from the mould (in case of plastic component) or die (in case of sheet metal). All plastic components will have a minimum draft of 0.5 to 3deg. And for automotive sheet metal parts, the draft will be 7deg or more. If a mould wall is perpendicular to the part ejection, there is ample friction or interference between the mould and the part which will not allow one to release from the other. This is why design engineers give a minimum draft to the part.

In CATIA V5 the feature draft analysis dialogue box looks like this:

1. Mode:

• The mode option let you choose between quick analysis and full analysis mode.
• In quick mode, there are 3 ranges blue, red and green colours. In the case of the plastic component, we will set the draft angle as 3°.

2. Display:

• The first box is to open and close the colour scale dialogue box.
• The second box is the analysis under the running point when activating the checkbOx and moving the pointer over the surface. This option enables you to perform local analysis. Arrows are displayed under the pointer, identifying the normal to the surface at the pointer location (green arrow), the draft direction (red arrow), and the tangent (blue arrow). As you move the pointer over the surface, the display is dynamically updated. Furthermore, circles are displayed indicating the plane is tangent to the surface at this point. The displayed value indicates the angle between the draft direction and the tangent to the surface at the current point.
• Click the No Highlight Representations button to set the display option of highlight effect sources as 'on/off. When checked 'On" the surfaces are selected but they will not be seen in the specification tree.
• Click the Light Effect button and the colours of the analyzed elements react to the light source.

3. Direction:

• The first check box is the locked direction icon which is used to lock the direction of the compass after selecting the specified direction.
• Click on the compass icon to specify the new pulling direction to remove the part.
• Click the Inverse button to automatically reverse the draft direction. When several elements are selected for analysis, the draft direction is inverted for each element when the button is clicked.

• Tooling Direction:

The Tooling Direction is the direction that the mould pulls apart. The mould is built into two separate pieces. 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. There are different methods to find out the tooling direction. Here we are using bisecting method to find out the tooling direction. We can use any method the ultimate aim is to reduce the cost of manufacturing by reducing the complicity in manufacturing the component.

PROCEDURE:

• Step 1: Importing the Base Bracket File and Check Class A Surface design file:

After receiving the Class A of the Base Bracket 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 Z-axis as a dummy as it doesn't interfere with any slots or holes.

Figure3: Dummy Tooling Axis around Z-Axis

• Create a new plane along YZ Plane and Intersect the plane and the Class A surface as shown in Figure 4.

Figure4: Intersection of Class A of Base Bracket with the new plane created along YZ Plane.

• 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 5.

Figure5: Extended Lines for faces.

• Create a Bisecting Line for the extended lines long the centre point and name it as Tooling Axis as shown in Figure 6.

Figure6: Tooling Axis.

• Now that the Tooling Axis is created let's Publish the Tooling Axis and the Class A Surface using Insert > Publication.

Figure7: Tooling Axis and Class A Surface Publication.

• Step 3: Draft Analysis:

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

Figure8: 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 9.

Figure9: Draft Analysis tools for Base Bracket.

• Figure 10 shows the tool which uses the compass to define the new current draft direction.

Figure10: Uses the compass to define the new current draft direction.

• Figure 11 shows the use of the Tool Analyses under the running point feature.

Figure11: Using the Analyses under the running point feature.

• Figure12 shows the screenshot of the Draft Analysis of the Base Bracket.

Figure12: Screenshot of Draft Analysis of Base Bracket.

• Step4: Class B Surface:

Consider the thickness of the component as 2.5mm. Now we need to create a B surface which will be similar to the A surface at an offset value of 2.5mm.

• First, we are creating the ribs in this operation. To create the ribs, first, extract the surfaces of it from Class-A Surface.

Figure13: Screenshot of Extracted parts.

• Once the surfaces are extracted, un trim them and then extrapolate them by 10mm by using point propagation. Now trim these surfaces and offset them to 2.5mm.

Figure14: Rib 1 at an offset value of 2.5mm.

• A similar process will be done on the other side of the Rib 2.

Figure15: Rib 1 and Rib 2 at an offset value of 2.5mm.

• Now let's create the base of the brackets with the same steps which we used for creating the ribs and trim the base and the ribs to make a Final trim off the part.

Figure16: Trimming the Rib 1 and Rib 2 with the base part at an offset value of 2.5mm.

• Towards the last part of creating the Class B Surface, we will join the Final trim part with the other base part to obtain the below Surface B.

Figure16: The Final Trim output of the Class B Surface at an offset value of 2.5mm.

• Once all the surfaces are created trim these surfaces to form a Class B surface and give the appropriate fillets to form a Class B surface.

Figure17: The Final Trim output of the Class B Surface with an overall fillet of 3mm.

• Step5: Class C Surface:

• To create a Class C surface, first, extract the boundaries of the Class A Surface.

Figure18: The outside boundary of the Class A Surface.

• Now using the Sweep option create the surface. To perform this operation, Go to the Toolbar > Sweep > Profile type > Line > Subtype: With draft direction > Guide curve 1- (select the extracted boundaries) the in Draft direction (select the tooling axis) angle and length as 3° and 20mm respectively and click ok.

Figure19: Sweep operation output on the boundary surface of Class A Surface.

• The same process will be done for the holes, extracting the boundaries and using the sweep operation to form a surface.

Figure20: Sweep operation output on the holes of the boundary surface of Class A Surface.

• Now we will use the Join command to join all the 3 Sweep operations that we have created. This will give us the Class C Surface.

Figure21: The final output of the join operation, the Class C Surface.

• Step5: Trimming the Surfaces:

• After the creation of Class A, Class B and Class C surfaces, we need to join Class A and Class C surface to form a new surface. Then trim the joined surface with Class B surface to form the final required surface.

Figure22: The final output after timing the output of Class B and Class C surface.

• Now that we have the required surface we can make a solid body out of it. To make a solid body we will go to the Part Design section over there we will use the Close Surface tool to make a Solid Body.

Figure23: The Solid Body made with the Close Surface Tool.

• Tree Structure:

Figure24: 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):

Figure25: Model in Various Views.

RESULT:

• The Base Bracket has passed the Draft analysis test as the draft values of the Base Bracket are less than 3° and the Bracket is safe for production.

Figure26: Result of Draft Analysis.

• We have also achieved the Close Surface Body with a thickness of 2.5mm, with the various steps which were used in creating the Class B and Class C Surfaces.

Figure27: Result of Close Surface Body with 2.5mm thickness.

CONCLUSION:

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