Week 9 - Attachment Feature Creation - Challenge 1

ATTACHMENT FEATURE CREATION - RIBS CHALLENGE

For the given Coin holder part we will create the B side feature to strengthen the entire part.

Use of Ribs :

1) Ribs provide a way to improve economical strength and stiffness in molded parts without increasing the overall nominal wall thickness.

2) They help in locating and arresting components of a assembly.

3) They also act as stops/guides for mechanisms.

General guidelines for design of ribs :

1) Thickness

2) Height

3) Location

4) Quantity

5) Manufacturability

The above factors should be considered majorly when designing ribs.

TOOLING AXIS :

We use the same main tooling axis created for the Coin holder component.

- Initially make a sketch as of the required length for the ribs. Then extrude the line considering the optimum height of the ribs design.

HEIGHT OF THE RIBS should not be greater than (5 x nominal wall thickness)

- Inorder to facilitate easy removal from mold we should give a minimum draft of 0.5 degree on all the walls. Use MAIN TOOLING AXIS as the Pulling direction and the base of the Coin holde part to be the neutral element.

- Now assemble the Ribs with the main body and then give a edge fillet of minimum 0.25mm on all the walls.

- It is important to analyze the rib design so that it satisies the design guidelines.

RIB ROOT THICKNESS should not be more than 30% of the nominal wall thickness.

Take intersection along the middle plane with the ribs to get the required cross section. Now draw a circle at the bottom part of the rib where the rib and main part joins.

The measured diameter of the circle should not be greater than 3.25mm ( 0.3 x 2.5 + 2.5) , higher the thickness at the root more the chances for Sink issues.

Various views of the Ribs design:

Draft anaysis for the Ribs :

As we have given a draft of 0.5 degrees to the walls of ribs the draft analysis results in a green region for the ribs and hence it is toolable.