OBJECTIVE

The objective of the project is to design the Door Arm Rest from the Class-A surface to the final solid model and the draft analysis on the model is also performed for the created tooling direction.

INTRODUCTION

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.

TOOLING DIRECTION

The Tooling Direction is basically the direction that the mould pulls apart. The mould is built in two separate pieces, basically the Cavity and the Core. 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 the bisecting method is used to find out the tooling direction. We can use any method but the ultimate aim is to reduce the cost of manufacturing by reducing the complexity in manufacturing the component.

PROCEDURE

The procedure is divided into two parts first creating the tooling axis then performing the draft analysis.

Creation of Main tooling axis using the bisecting method:

• The first thing to do is to find the possible tooling direction by visually checking the part. Rotate the part in all directions and find out the most suitable direction for tooling. Here in this case viewing from Z direction we can clear the face in tooling.
• Then a point on the surface of the part was created, we can create the point anywhere on the surface but usually, we take CG point or take a point near to the centre. On this point, we put a new axis system.
• Then, finding the X direction tooling axis by using the intersect command the boundary in the X direction or XZ plane has been projected.
• Then the required draft line is extended using a point to point line command. Then by using the bisecting line command the tooling axis in the X direction was created.
• Since in the Y direction there is no wall to perform bisecting method, we finalize the tooling axis in the X direction as the main tooling axis.

Creation of sliding tool axis:

• Since the part has different flanges so the part can’t be manufactured with the main tooling axis so considering the side core uses the sliding axis for the part is also created.
• Now to create the Sliding Tool Axis for the Bin region, Check for the region where the Bin region is seen clearly. Here, it can be seen as Y-axis.
• Now, create a point on the base of the Y-axis. Create a Line on the Point and extend.
• Open the Draft Analysis tool and Set the Direction and Lock it and click the surface.
• Move the Axis of the axis to check the surface until the bin is shown green and then lock the current axis by right-clicking it.
• After locking the Surface, go to the line which was initially created and double click on it. Select the Direction as Compass direction and click ok.
• The axis is then shifted to the currently locked axis.

CREATION OF CLASS – B SURFACE

• To create a B surface, we need to offset the Class-A Surface but the Surface cannot be the same as for Class A as it would create errors while the model is manufactured.
• So the class-A surface was offset to the thickness of the model (that is 2.5mm). Then the required surface has been extracted and untrimmed.
• Then the required edges were extrapolated such that every surface intersects with the neighbouring surfaces by using multiple extracts and smooth curve command.
• After completing the extrapolation, trim the surface such that the extracted surface is similar to that of the class A surface (without fillets).
• then the hole in the pocket were also created using offset surface, split and trim surface.
• Then the required edges were filleted by reducing the fillet value for 2.5mm with the actual fillet value of the class-A surface.

CREATION OF CLASS – C SURFACE

• After creating the B surface, the C surface needs to be created. To create the C surface, the sweep option is used.
• To create a sweep, there should be a boundary created to it. The boundary should be created separately as creating the boundary completely doesn't create the sweep smoothly as the model contains many patches.
• So the smooth option is used to create the smooth surface and the Class A surface model is swept smoothly over the plane areas. For the draft angled areas, the boundary should be created separately to create the sweep over that area.
• Now join the Class C surfaces together to create the C-surface.

CREATION OF DOOR ARMREST

• Now, start with joining the Class A and Class C surfaces together. Next, trim the combined surface with the Class B Surface to create the final surface.
• Then the surface needs to be checked for any irregularities by using the join or boundary option.
• After creating the closed surface, the close surface option from the Part design is used to create the Solid part body.

PROCEDURE FOR DRAFT ANALYSIS

Mode:

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

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 move the pointer over the surface. This option enables us 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 we move the pointer over the surface, the display is dynamically updated. Furthermore, circles are displayed indicating the plane 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

Direction:

• The first check box is a locked direction icon 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.

By using the above features the draft analysis is carried out first for the class – A surface and next for the part body by using the Main tooling axis and sliding axis. A 3-degree draft angle was provided for easing the removal of the component from the cavity.

CONCLUSION

Finally the Class A, B & C surface is published along with the main tooling axis and sliding axis. The Draft Analysis was carried out successfully and the model is ready to be manufactured.