Door Arm Rest Week 8 Challenge

DOOR ARM REST DESIGN

Objective: To design Door Arm Rest and perform draft analysis on both the Class A Surface and the final model along the tooling axis meeting the requirements of the draft angle.

Introduction:

Class A Surface:

In automotive design, 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 computer-aided industrial design applications. Class A surface modellers are also called ‘digital sculptures’ in the industry. Industrial designers develop their design styling through the A surface, the physical surface the end user can feel, touch, see etc.

Class B Surface:

Class B Surface is a surface below a certain thickness from a Class A Surface. We can also say that it is an engineering surface because it contains all the engineering aspects of the model which is required.

Class C Surface:

Class C Surface is a surface that joins the Class A Surface with Class B Surface.

Tooling Axis:

Tooling axis is the direction in which the mold or core and cavity opens.

Draft:

Draft is the angle in which the part is tapered to allow it to release. As the part cools, it tends to shrink to the core side of the mold. Draft is required on all parts in the direction of mold movement in order to allow parts to release or eject from the mold properly.

Most parts or applications require a minimum of 0.5 to 1 degree, however 3 degree is widely accepted as normal.

Draft Analysis:

Draft analysis is done in order to detect if the part that has been drafted will be easily removed or not. This type of analysis is performed based on the colour ranges identifying zones on the analyzed elements where the deviation from the draft direction at any point corresponds to the specified values. When the draft analysis passes, it means our part is easily toolable or can be easily ejected.

Methodology/Approach:

Procedure:

1. Importing Class A Surface:

First of all, we have to import the class A Surface into the Catia V5 Software.

2. Continuity Check:

After getting the Class A Surface from the styling team, we have to ensure that the Class a Surface is properly joined and has no discontinuity on it. To check that we have to use the Boundary command or Join command.

3. Creation of Tooling Axis:

First of all, we have to analyse manually or visually to see which direction is the most appropriate for tooling axis. After analysing we found that Z-direction is very easy to be tooled. So, we create the tooling axis through the hole by creating points and then extracting the flat surface which is to be normal to tooling axis. This is our main tooling axis.

4. Draft Analysis of Class A Surface:

First of all, we should change the view to the Customize View parameters and then select the material mode and then Ok. After that we will open draft analysis command and then click on the compass icon and then align the compass of the window with the tooling axis earlier created and then lock the draft direction. After that click on the surface and see that the surface is within permissible limit of the draft value. The surface should be green and in the column 3 degree should be inserted.

For the red color at corner we have to consult with styling team for the improvement in curvature.

But we found that the side wall and the ribs are not clearing the draft in z direction as they are turned into blue and red. So, we have to introduce a new tooling axis for the side core. For that, we have to extract the rib walls and untrim it then we create a point on that untrimmed surface and on that surface normal to it we create a line which would be our side tooling axis.

Again, we perform draft analysis for the side core and the result is below.

5. Creation of Class B Surface:

First of all, we divide the door arm rest into first half, second half, and the pocket area.

For first half;

• Extract the upper surface one by one

• Untrim them

• Offset them downward by 2.5 mm and trim them together

• After that extract the flat side portion

• Extrapolate it in upward

• Offset it inside by 2.5 mm

• Trim the upper and the side surface and do fillet

For second half;

• Extract the upper surface and the lower flange

• Extrapolate them

• Offset the surfaces in inward direction by 2.5 mm

• After that trim them and do fillet

Join of first and second half;

• First of all, we have to create a point on the class a surface and on that point we have to create a line tangent to the fillets and constrain them.

• After that we have to do multiple extract of the edge of class a surface and then do smooth curve and then sweep them and offset the seep by 2.5 mm downward.

• After that the slanted flat surface is extracted, untrimmed and then offset below by 2.5 mm.

• Now we join the two surface by blending them and then join them.

• After that we extrapolate the first half and the join and then trim them.

• Again, we extrapolate the second half and trim with the first half and do the edge fillets.

For Pocket area;

• Extract the surface

• Untrim them

• Extrapolate them

• Offset the surface by 2.5 mm in outward direction

• After that trim them

• Do the same for the hole and then trim with the last trim.

• After that trim the pocket with the join of first half and second half.

• Then provide them fillets.

• At last, extrapolate the surface so that it will easily trim and this is our final b surface.

6. Creation of Class C Surface:

• First of all, we extract the boundary of the flat surface or the surface which is easily swept and then sweep the boundary one by one.

• Now we apply multi-sections surface for complicated area to connect them.

• Here most of the portion are not connected with one another so we extrapolate them and then trim them one by one.

• At last, these surfaces are joined which is our final c surface.

7. Solid Body Formation:

• Join the class C surface with class A surface.

• Trim the B surface with the join created earlier.

• Now we see that lower portion of the hole is not joined. So we extract the surface, untrim it and offset upward by 1.5 mm since we don’t know the actual value and at last trim it with the join created earlier.

• Now go to the part workbench and close the part using close surface option.

8. Draft Analysis of Solid Model:

First of all, change the view to Customize View Parameters and then check material mode selected and perform the same operation as done for Class A Surface while we did in doing draft analysis.

Main Tooling Draft;

For this draft (i.e. red color at corner) we have to consult the styling team for curvature improvement.

Side Tooling Draft;

Tree Structure:

Conclusion:

From the given Class A Surface of Door Arm Rest, Class B Surface and Class C Surface were created to form a solid model and Draft analysis was done for both Class A Surface and the 3d model along with the tooling axis meeting the requirement of draft angle.