Door Arm Rest Week 8 Challenge

                                                                                                                               DESIGN OF DOOR ARM REST

OBJECTIVE: The main objective of this challenge is to performe draft analysis on  given class A surface and to develop a final solid of door arm rest part and perform the draft analysis on the solid part  by using CATIA v5 software. A report has to be prepared by explaining about what is draft analysis and tooling axis and add all the relevant images to the report.

                                                                                                                                       DRAFT ANALYSIS

Draft analysis is a analysis which is performed on the objects or bodies in order to check the draft angle of various faces in a particular direction which is tooling direction.

Every part like sheet metal parts which are generated from a Press Tool or some forming tools, may be the plastic parts which generally come out from the plastic moulds and maybe the casting parts, all such kind of parts required some drafted face on the surfaces which are parallel to the tooling direction. If we don't provide drafts on the surface then it will stick to the mould surface and whenever the mould is in motion they will destroy the surfaces or also reduced the finishing of surfaces.

The Tooling Direction is basically the direction that the mold pulls apart. The mold is built in two separate pieces, basically. 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.

And the axis which represents the tooling direction is called tooling axis and selection of this is axis is a crucial step while performing the draft analysis.

CLASS A SURFACE: 

In automotive sector, a class A surface is any of a set of freeform surfaces of high efficiency and quality. Although, strictly, it is nothing more than saying the surfaces have curvature and tangency alignment – to ideal aesthetical reflection quality, many people interpret class A surfaces to have G2 (or even G3) curvature continuity to one another.

Class A surfacing is done using CAD applications. Class A surface modellers are also called "digital sculptors" in the industry. Industrial designers develop their design styling through the A-Surface, the physical surface the end user can feel, touch, see etc.

In general CLASS A surfaces are crated using autodesk alias software.

CLASS B SURFACE: Class B surfaces are the secondary surfaces that you can see sometimes, but are less important, such as the inside of your glovebox, ash tray, etc.. These must be smooth and "error-free" as well, but are not held to the standards that class A surfaces are.

CLASS C SUFACE: The Class C finish allows more imperfections than Class A or B. Class C is often specified for interior surfaces not readily visible, surfaces that will be covered by another part when assembled, or surfaces which the Customer feels do not need to meet a high cosmetic finish.

                                                                                                                      CREATION OF TOOLING AXIS

The given surface cannot be manufactured by using single tooling axis. so that we have to create one major tooling axis and one side tooling axis.

1. First extract the base  surface of class A surface

2. Now create an untrim of the extract and create a point at the centre of the surface at 0 milli meters.

3. Create a line command and select the type as normal to surface and select the point that we have create and name the line as main tooling axis,

And the above mentioned line is the major tooling axis direction line, now we will discuss how we can create side tooling axis,

1. Extract the front wall of the class A surface

2. Untrim the surface and create a centre point on it.

3. Create a line command and select the type as normal to surface and select the point that we have create and name the line as main tooling axis,

                                                                                                                                                         DRAFT ANALYSIS ON CLASS A

In the below figure we can see the given class A surface along with two tooling axes which we have created earlier,

Since we have two tooling axes we have to perform draft analysis twice with both the axes,

The below image shows the expanded values and colour codes of draft analysis,

BY USING MAIN TOOLONG AXIS:

1. Select the draft analysis tool bar and click on the compass and align it with the main tooling axis properly. The views of class A surface with proper colour coding is as shown in below pictures,

ISOMETRIC VIEW

FRONT VIEW

SIDE VIEW

TOP VIEW

2. Repeat the same thing again but here instead of main tooling axis select the side tooling axis and observe the colours. we can say that the faces which haven't cleared when using main tooling axis will get cleared now. The views of the draft analysis are as shown in below figures,

ISOMETRIC VIEW

FRONT VIEW

SIDE VIEW

TOP VIEW

In the below image we can clealry notice that the ribs ans side walls have got cleared in draft analysis using side tool axis,

                                                                                                                                             CREATION OF CLASS B SURFACE

Here i have divided class B surface into four parts namely

• FIRST HALF
• SECOND HALF
• WALLS
• HOLE

CREATING FIRST HALF:

1. Extract the faces of class A surface

2. Untrim them exrapolate them until they intersect with each other

3. Offset the two surfaces and trim them to form the required shape

4. Apply edge fillet with proper radius and rename it as first half.

CREATION OF SECOND HALF:

1. Extract the two surfaces of class A surface 

2. Extrapolate and offset them to 2.5 mm in proper direction

3. Trim the two surfaces in order to form required surface which is similar to  given class A surface.

4. Apply edge fillet to the trimmed edge with proper radius considering the thickness of the solid body

5. create a point on class A surface as shown in below figure,

6. Create an axis system with reference to the the point which we have created earlier

7. By taking ZY plane as a reference create a line which is tangent to the filleted surface of class A as shown in below figure,

8. By using multiple extract option extract the edges of the class A surface and use smooth curve option in order to make the curve smooth.

9. Now sweep the line profile and by slecting extract as guide curve and offset it.

10. Now extract the flat surface on the top side of the class A surface

11. Untrim the surface and offset it to the required distance

12. Create a line and split the offseted surface as shown in below figure

13. Now using blend option create a surface between the two surfaces and join the three surfaces by using join command.

14. Extrapolate the first half surface and previously joined surfaces and trim them.

15. Now extrapolate the second half surface and trim it with first half surface and apply edge fillets to it,

CREATION OF WALLS:

1. Extract the wall of the class A surface.

2. Now untrim the surfaces and extrapolate them and offset them

3. Trim them to get the required shape

4. Apply edge fillets to the surface with proper radius.

CREATION OF HOLE

1. Extract the hole surface from given class A surface

2. Offset it to the required direction with proper distance.

3. Finally trim it with previous surface and we will get a hole in class B surface.

4. Apply edge fillet to the hole.

5. Extrapolate edges of the surface to make sure proper intersection of class B with CLASS A- CLASS C surface. The below image shows the final class B surface.

                                                                                                                                           CREATION OF CLASS C SURFACE

1. The class C surface cannot be created in a single sweep or single multi section commands.

2. For that reason first we have to create sweep on all the flat surfaces that we have by giving a minimum draft angle of 3 degrees.

3. For all the remaining surfaces which are not flat we have to create them by using multi section solid command.

4. Extrapolate and trim the edges which are not attached to each other and make sure all the class C surfaces are attached properly.

5. Finally join the trimmed class C surfaces  with all the remaining surfaces inorder to form a single surface. The final class c surface is as shown in below figure.

6. After creating a C surface to close the holes  Join class C surface and class A surface together and publish the surface if you want.

7. Now trim it with class B surface and create a closed surface of door arm rest.

8.By using close surface command in part design make the cosed surface into a solid part and the views of solid part are as shown below

ISOMETRIC VIEW

FRONT VIEW

SIDE VIEW

TOP VIEW

                                                                                                                           DRAFT ANALYSIS ON DOOR ARM REST

Similar to the class A surface here alos we have to perform draft analysis using two different tooling axes.

DRAFT ANALYSIS USING MAIN TOOLING AXIS:

The different views of draft analysis using main tooling axis are shown below

ISOMETRIC VIEW

FRONT VIEW

SIDE VIEW

TOP VIEW

DRAFT ANALYSIS USING SIDE TOOLING AXIS:

The different views of draft analysis using side tooling axis are shown below

ISOMETRIC VIEW

FRONT VIEW

SIDE VIEW

TOP VIEW

NOTE: In the draft analysis of both class A surface and final solid surface of door ar rest some of the faces are not clearing draft analysis due to improer class A surface. so that the class A designers have to modify the class A surface.

                                                                                                                                             PART NAVIGATOR

                                                                                                                                               CONCLUSSION

Hence, we are concluding that a solid body of door arm rest has been designed by using given class A surface and draft analysis is perforemed on both the class A surface and final solid output. A report has been prepared by explaining all the features by adding suitable images whenever and wherever required successfully.