BASE BRACKET DESIGN - CLASS-A,B&C

DESIGNING CLASS A, B & C SURFACE OF BASE BRACKET

OBJECTIVE

Create the Base Bracket Plastic component through the given Class-A surface, and create tooling axis, perform draft analysis and also create Class-B surface& Class-C surface.

INTRODUCTION

The Draft allows the part to easily eject from the mold. The draft angle is to reduce friction between the core, cavity and part and it also avoid the damages. The minimum draft angle is 0.5 degree and the most common draft angle used in the plastic design is 3 degrees.

 In CATIA the draft analysis is performed based on colour ranges identifying zones on the analysed element where the deviation from the draft direction at any point, corresponds to specified values.

Tooling direction is the main element that to be consider while designing a plastic component. In moulding machine the arrangement is given to open the mould along the direction. It is the direction in which the core and cavity opens.

CLASS A SURFACE

1.Visible surface and aesthetic look
2.Surface with textures
3.Surfaces provided by customer(OEM)
4.Don't have any features like(rib ,snap ,bosses etc.) on class A surface.
5.Class A surface is made from scanned data with different software like alias etc..
6.Surfaces which is having CURVATURE CONTINUITY IS CALLED class-A.

CLASS B SURFACE

1.Invisible Surfaces.
2.Surface mostly don't have textures
3.Surface need to be create according to class-A surface.
4.Having all features(Rib, boss, snap etc.) in B-side surface only.
5.Surfaces which is having TANGENT CONTINUITY IS CALLED class-B

CLASS C SURFACE

Which join both Class-A and Class-B Surface

METHODOLOGY

GIVEN CLASS – A SURFACE (BASE BRACKET)

PROCEDURE

• First the connectivity between the surfaces to be checked, by using the join option see how the surface is connected and ensure that there are no surface gaps in between the component.
• The other method to check connectivity is using the boundary option. By Extracting and disassemble the boundary of the class – A surface we can check visually gaps between the surface.
• Create a boundary for the hole in the Base bracket. Using Circle / Sphere / Ellipse centre option create a point w.r.t the boundary. Create a line using point – direction(z) option that line is dummy tooling axis.
• Create a plane w.r.t point created before and YZ plane
• An intersection sketch is made using the YX plane and the class a surface
• By using the point – point line option extend the line along the sketch. With the bisecting line option selecting the two line the TOOLING AXIS is created

DRAFT ANALYSIS

• For plastic parts the Nominal draft angle is 3deg, but even 7deg is allowed for the subassemblies like ribs and slots
• INSERT - ANALYSIS - FEATURE DRAFT ANALYSIS
• First the compass is moved to the part (the compass should be placed on the tooling axis) which used to define the new current draft direction, then lock the draft direction using the lock icon
• The colour chart indicates the various condition of the draft angle . the green colour indicates that the part passes and the and can be used for the further operations 
• By using the analysis under the running point icon we can check draft angle at the various surfaces of the component 
• There are two modes in the Draft analysis quick mode and fully detailed mode 

CREATING CLASS B SURFACE

• First work on the ribs. Extract the top surface of the first rib with No propagation and also extract both side surfaces of the ribs. Untrim the surfaces one by one and hide the extract
• Extrapolate the all the untrimmed surfaces one by one (Click on the boundary and the surface)
• Now, Trim the first and the second surface and Trim the Trim1 and the third surface
• Offset the surface for 2.5mm which is the thickness
• Repeat the steps for the Rib 2, connecting surface and the base surface
• Fillet the surface where ever required

CLASS-B SURFACE

CREATING CLASS C SURFACE

• The boundary is created for the Class-A surface, the boundary of the both holes in the surface also created.
• Sweep (Draft with direction) the boundaries one by one with tooling axis with 3Deg draft angle
• Use join option to combine all the swept surfaces
• Trim the joined surface with the Class-B Surface to form the Class-C surface

CLASS C SURFACE

PUBLICATIONS

• TOOLS - PUBLICATION
• Publication is done because It can be easily visible and can be easily accessible while performing further operations
• Select the Base bracket (Class A Surface) (Class-B&C) the tooling axis and select publish 

 PART BODY 

Convert the obtained Class-C surface into part body using Close surface option 

DRAFT ANALYSIS OF SOLID BODY

FEATURE TREE

CONCLUSION

From the given Class-A Surface, Class-B and Class-C Surface were created and tooling axis for manufacturing were created and draft analysis were carried out successfully.