Week 8 - Challenge 4 - Coin Holder Design

Aim

• To create the center console Coin Holder, a automotive Plastic component from the given Class-A surface.
• To create the tooling axis for the given Class-A Surface and check the requirements of the draft angle and perform the Draft analysis on the model.

Draft

Draft is the amount of taper for molded or cast parts perpendicular to the parting line. It also a slant that is applied to each side of most features of an injection molded part By applying appropriate draft angle the mold will be easier to remove and it also accounts for thermoplastic shrinkage in Injection molding. The draft may also alter the form and fit of the part during assembly.

A draft of minimum of 0.5 degree draft per side is recommended. For textured sidewalls use an additional 0.4 degree draft per 0.1mm depth of texture. But maintaning the minimum draft could be costly during manufacturing hence an optimum draft angle of 3 degree could be maintained.

Types of surfaces involved

Class A surface

This is the input surface for the design engineers for designing the inner panels or features of the parts. It is the styling surface of the component which shows the outer appearance of the parts.

Class B surface

The thickened surface is called as B surface. It is also called as engineering surface. This surface contains all the necessary part feature like fillet, ribs, bosses etc.

Class C surface

The surface joining the class A surface and class B surface is called as C surface.

Tools used

• Multiple Extract
• Trim
• Un-trim
• Offset
• Extrapolate
• Boundary
• Sweep
• Join
• Smooth curve
• Close surface
• Intersect
• Publication

Steps involved in creating the Coin Holder

Tree structure

Step :1 Check the class A surface

• The input class A surface is checked for any gaps or disjoints using the join or boundary commands.
• If there is any Minor error the it can be rectified or else send back to the Class A surface designer to make the necessary modifications properly.

In this case we can see that the Class A surface does not have any gaps or disjoints and has smooth and continuous boundary.

Step :2 Create the Tooling axis

The tooling axis is the direction in which the core and cavity opens and closes. In this case we can see that the bin area surface can be used as tooling axis center point. The intersecting lines can be drawn to identify the surfaces which could not be cleared in tooling axis.

Bisecting line tooling axis

The bisecting line is used to create a line bisecting the two reference lines created in normal direction. The bisecting lines helps us to achieve the average draft angle between the two reference lines.

Step :4 Publish

In the next step publish the tooling axis and Class A,B,C surfaces so that we can access it easily and use it for further creation of surfaces or thick body.

Step :5 Draft Analysis

Once the tooling axis is created the draft analysis can be done. For viewing the draft analysis results we need to change the view parameters into customise mode enabling only the material.

Go to insert-analysis-feature draft analysis.

The compass option is used to choose the tooling axis. The color coding shows the result of the draft analysis done. The limits of the draft angle can be changes according to the needs.

Types of the modes in the analysis

A single limt can be chosen to show the positive or negative draft

Multiple limits can also be set based on the requirements

The draft angle value can be found at any given point of the surface. For this case 3 degree is chosen as the optimum angle and we can see that the some parts of the model has positive draft angle highlighted in green color and some parts with zero draft highlighted in blue color. The negative draft is shown in red color.

Class A Surface Draft Analysis

Since the part has faces which do not clear the tooling axis and the faces having zero degree draft from the Class A surface, the part is infeasible to manufacture.

Step 6 Creating the Class B surface

• The class B surface can be created by offsetting the Class A surface, for ease of design we can divide the surface into smaller portions and then work on them.
• The surfaces are extracted and then they are untrimmed and extrapolated to get the required intersections and the surfaces are trimmed off and offsetted according to the required thickness.

• Fillet value

  In order to maintain constant wall thickness Fillet value= Fillet value + wall thickness

Side walls

Base Surface creation

Top wall creation

Side wall and flange creation

Trim and get the Class B surface

Create the Class C surface with help of the sweep option

Join the Class B and Class C surface

Finally trim the join with the class B surface and get the required model.

Draft analysis of the coin holder

We can see that the side walls have no draft angle from the class A surface hence the part is infeasible to manufacture. Hence the class A surface needs to be modified.

Conclusion

Thus the tooling axis is created considering the part ejectability and the coin holder is designed using catia v5 and the draft analysis is done. we can see that the part does not satisy the draft analysis hence the draft angle must be provided on the class A surface by the Class A surface deign team.