Week 9 - Project - Master Section Development

Aim: To create B-pillar Design with Engineering Features such as locaters, doghouse, ribs etc. using the given master section reference surface and class-A surface of the B-pillar.

Given input:

• Class-A surface of the door applique
• Master section

Some important definitions

Engineering features:

• The extensions on the plastic components on the Class-B side of the surface are called engineering features or B-side features.
• These features play an important role during the assembly of the sub components to the main component for example: map pocket, arm rest are assembled to the main door.
• Locaters, snap fits, dog house, screw boss, ribs, heat stakes etc. are some of the B-side features in automotive industry.

Ribs

• Ribs increase the bending stiffness of a part.
• Without ribs, the thickness has to be increased to increase the bending stiffness.
• Adding ribs increases the moment of inertia, which increases the bending stiffness.
• Bending stiffness = E (Young's Modulus) x I (Moment of Inertia).

Dog house

• Dog house is an engineering feature used in plastic trim design.
• Dog houses are used as supporting feature.
• Sometimes other engineering features like snaps; locators etc. are mounded on them to increase their strength.
• Dog houses are subjected to draft analysis to prevent breakage of the component during ejection from mould cavity.

Draft

• The degree of taper of a side wall or rib needed to allow the molded plastic part to be removed from the metal mold.

Master sections

• Master sections are the guides for design requirements which decide the component packaging after technical (Styling, Concept or Class-A) surfaces.
  
  

B-Pillar creation:

1. Basic checks

• Check the connectivity of the class-A surface i.e. ensuring there are no surface gaps between the surfaces.
• This can be done either visually or manually by creating boundary of the component.
• The best way to know the connectivity and quality of the component is by checking how many domain boundaries have been generated using disassemble command.

2. The next step is to perform the draft analysis and for that we need the tooling axis

TOOLING AXIS:
Method.1

• Tooling axis is a line in which the core and cavity opens and the component is ejected.
• Visually check which would be the best direction for the tooling axis.
• create line normal to the surface by creating a center point or an axis system on the base surface at the center.
• Perform the draft analysis of the given class-A surface to ensure the tooling direction is clearing the past and is easily removable from the mold with the help of color scale.
• Adjust the compass in small radius if the normal to the surface line is not clearing the part fully.
• After adjusting the compass to appropriate direction sop that the part is clearing everywhere lock the compass and change the normal to the surface line to the compass direction and consider it as the main tooling direction.

Method.2: Bisection method

• Extract the four lines which is provided in the master section indicating 4-way locaters, this is because the engineering features will be ejected using main tooling direction.
• In the first case will take a bisecting line between the two yellow lines as shown in the image with a red arrows and get bisecting line.1
• Similarly, will repeat the step to find bisecting line between the two green lines to get bisecting line one and two
• Now create a bisection between the two bisecting line one and two and that will be considered as our main tooling direction.

1. DRAFT ANALYSIS: enables you to detect if the part you drafted will be easily removed.

• The visualization mode should be set to Shading with Edges in the View > Render Style command before performing draft analysis.
• Go to insert<analysis<feature draft analysis
• The Draft Analysis dialog box is displayed. It gives information on the display (color scale), the draft direction and the direction values and identifying the maximum and minimum values for the analysis is displayed too.
• We will be using the default mode i.e. the quick mode as it simplifies the analysis in that .it displays only three color ranges.
• The maximum and minimum values for the analysis should be adjusted to 0 and 3 respectively as per the automotive industry as displayed below in the color range box.
• However, the maximum and minimum values will vary in cases of B-side features alone. Drag the compass by holding left mouse button on the red dot of the compass and place it on the main tooling axis randomly.
• Click the Compass icon to define the new current draft direction by aligning the compass exactly along the main tooling axis.
• Click the Locked direction icon , for locking the direction of the tooling axis.
• After locking the direction single click on any random area on the component or surface.
• The part will be shown colored either or mixture of the three colors (green, red, blue) on it.
• Three bands of color on the part in the below example will indicate
• Green: the area has draft angle more than 3 degrees
• Blue: the area has the draft angle between 0 to 3 degrees.
• Red: the area has draft angle below 0 degrees (negative draft angle)
• In the above door arm rest example, the green area indicates that the part has draft angle more than 3 degrees and easily clearing the mold, while blue area has the draft angle between 0 to 3 degrees
• Similarly repeat the draft analysis on the close surface (solid model).

3. CLASS-B SURFACE

• Since the surface is fully styling hence we can take the whole surface as a single patch of surface.
• The offset value for creating Class-B surfaces is provided i.e. 2mm which can be incorporated from master section.
• On offsetting the class-A surface directly some patches will not be off-setted due to sub elements error.
• In that case we will filling that part of minor patches using multi section or sweep commands.
• Use the various surface commands such as boundary, trim, split etc. available in the generative shape design and create the Class-B surface accordingly.

4. FLANGES

• If we observe the master section carefully we can see that there are flanges extruded which has to be present on the final solid body.
• Therefore, we will create the flanges on Class-A as well as on final Class-B surface for an approximate length using master section.
• Below are some images showing the flanges in the master section and the class-A and Class-B surface with flanges.

5. CLASS-C SURFACE

• Create an exterior boundary for class-A surface.
• Using the available commands like sweep create the Class-C surface at an angle 3 degree to the tooling axis.
• Join the class-A surface and Class-C surface later by ensuring no gaps between them.
• Trim the Class-B surface after performing the above step and create a close surface.
• Cross check the final closed surface is completely closed ort not by using boundary command.

6. CLOSE SURFACE

• Go to part workbench and create a solid body out of the close surface.
• And perform the draft analysis again.

7. CEATION OF B-SIDE FEATURES

DOG HOUSE: engineering features used during assembly of sub components to main component

• Draft: 0.5 degree along main tooling direction inside and outside walls
• Inside Radius:1mm, outside radius:3mm, optional radius:0.3mm
• Height maintained: 20-25 mm
• Thickness maintained: 2 mm
• Location: as per master section
• Dog house and 4-waylocater should be extruded in the tooling direction always.

Four way locaters:

• Draft: 0.5 degree along main tooling direction
• Chamfer Radius:1mm, optional radius:0.3mm
• Chamfer:5mm x 45 degree
• Height maintained: 16-17mm referring the master section
• Thickness maintained: 1.5mm
• Location: as per master section or on the dog house
• Dog house and 4-waylocater should be extruded in the tooling direction always.

C-section cutout in doghouse

• C –value (2x0.4) =0.8mm
• B value (3-6) mm = 5mm maintained
• Radius: (1+1.2) =2.2mm, other radius=0.2mm
• Draft: 0.5 deg

FINAL DOG HOUSE ASSY: Mirror the dog house on the other side by creating mid plane using master section or you can also use translation command.

8. RIBS: Ribs increase the bending stiffness of a part

• Draft: 0.5 degree along main tooling direction
• Height maintained: 5T= 5x2= 10mm from class-A surface
• Thickness maintained: 40% of thickness = 0.4x2=0.8mm
• Radius:0.5 base radii
• Spacing = 50mm
• Location: as per requirement
• Ribs should be extruded in the tooling direction always.

9. FINAL B-PILLAR WITH ATTACHMENTS:
   
   
   
   
   
   
   
   
   
10. DRAFT ANALYSIS:

DRAFT ANALYSIS ON FINAL SOLID COMPONENT

DRAFT ANALYSIS ON DOG HOUSE

DRAFT ANALYSIS ON RIBS AND FINAL COMPONENTS

11. All areas are with min draft of 2.9 degree expect the area shown in the below images

• Minimum value at this area is 2.75 degree
  
  
  
  
• Area with negative draft
  
  
  

12. TREE STRUCTURE: