Week 8 - Challenge 3 - Coin Holder Design

Aim: Draft analysis of a CATIA Component created using surface commands

Theory: -

Draft angle: A draft angle is a slant that is applied to each side of most features of an injection molded part. The angle, which is positioned to run toward the direction of a mold's pull and parting line, helps with releasing the part from the mold.



Draft analysis: The Draft Analysis allows the user to easily analyze a part for a proper draft angle. A Draft Angle describes the amount of taper for molded or cast parts perpendicular to the parting line. Find the Draft Analysis in the Tools tab. Draft Analysis is applicable for 3D part models.



Tool Axis Creation: -

In Molding, machine arrangement is given to open the mold along a direction which is known as Tooling Direction.

1. Likewise in our model, we first create a tooling axis from the side walls:-



Note: As the Side wall is at 90deg, hence at first one should talk to the Class A surface-generating team to provide a draft angle for easy extraction and in such cases, we will take the geometrical centre for the draft axis.


2. Now we move on to make the B Surface:-

As there are different components in the body, hence it is recommended that one should segregate and split the parts for easy surface generation and also cascade the components in orderly manner.



> For Surface Generation we first extract the surfaces from the Class A Surface and then we use the command “Untrim” to fill any holes and gaps.
> Now we Extrapolate the boundary in a manner that the walls gets intersected and hence completing the surface.



> Then we use the “Trim” Command to trim the excess parts following which to generate the thickness as mentioned (i.e 2.5mm) we Offset the walls outside.





Note: One should always remind that B Surface should not be generated above the Class A surface as the Class A surface holds the aesthetic value and comes in direct contact with the consumer, therefore no changes should be made to the class A surface.

Draft analysis:-

Standard Measurements:

Model Thickness: 2.5 mm
The minimum Draft angle provided: 3 deg angle


Class A surface Draft analysis:-



Final Body draft analysis:-





A different view of the draft analysis:-



Front View: -



Isometric View:-





Top view:-



Side View:



Note:

Green Surface: Denotes that the model satisfies the required draft angle
Blue Surface: Denotes that the model draft angle is below the required draft angle.

Different surfaces:-

Class A surface:



Class B surface:



Class C surface:



Note: To generate the Class C Surface, we have used “Sweep Command” along with the “Reference to surface” option at 90 degrees, as in this part the C surface is at a right angle with the Draft axis.


Conclusion: Draft analysis is a very essential tool for manufacturing a plastic product using Core and cavity manufacturing techniques, hence draft angle should always be provided appropriately.