Week 8 - Challenge 4 - Coin Holder Design

DESIGNING CLASS A, B & C SURFACE OF COIN HOLDER

OBJECTIVE

Create the coin holder 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 (COIN HOLDER)

PROCEDURE

Continuity check

Input the class A surface

After receiving the class A surface check the continuity of the given class a surface to ensure that there is no discontinuity in the class A surface . This can be checked using join or boundary option

Tooling axis creation

Extract the bottom surface of the given class a surface (coin holder).

Create a point using on surface command.

Create a line along the Y direction using that point. the line created is the required tooling axis.

Class B creation

Base surface:

• Extract the base surface from the class A surface
• Untrim the extracted surface and the extrapolate the surface with point continuity such that it intersects with each other
• Trim the surface and offset the surface 2.5mm (thickness of the component) outwards

Side walls:

• Extract the side surface from the class A surface
• Untrim the extracted surface and the extrapolate the surface with point continuity such that it intersects with each other.
• Trim the surface and offset the surface 2.5mm (thickness of the component) outwards.
• Extract the inner projection from class A surface.
• Untrim the extracted surface and the extrapolate the surface with point continuity such that it intersects with each other.
• Trim the surface and offset it with 2.5mm
• Apply edge appropriate edge fillet to the edges

Top surface:

• Use multiple extract to extract all the surface from the top surface
• Extrapolate the surface both the sides with point continuity
• Offset the extrapolated surface outwards 2.5
• Outer surface:
• Use multiple extract option to extract all the surface of the outer surface
• Extrapolate the surface, offset the surface 2.5 and trim the surface

Trims:

• Trim the base surface and side walls together
• Apply edge fillet
• Trim the filleted surface with top surface
• Trim the final outer flange with previously trimmed surface
• Apply edge fillet wherever required

Class C creation

• Using the multiple extract option extract the boundary the class A surface (Guide curve)
• Using the multiple extract surface option extract the outer surface (reference surface)
• Use the sweep option to create the class C surface with the two multiple extracts as the input
• Extract the Class A surface near the hole
• Create a boundary of the inner hole in the class A surface
• Sweep the boundary and trim the surface to get the final class C surface
• Trim the class C surface with Class B and A
• Form the solid body using the final surface

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 
• If the surface satisfies the 3Deg then it shows in green in colour if not appears in red colour

Feature tree

CONCLUSION

Thus the Class B and  C and solid part were created for the given class A surface (coin holder) and draft analysis were carried out for both A surface and Solid part