Week 9 - Attachment Feature Creation - Challenge 1

Week 9 - Attachment Feature Creation - Challenge 1

Aim:

To design ribs for the coin holder following the design rules and carry out rib root thickness analysis.

Input Data:

The coin holder model created for one of the previous exercises is used as input.

Purpose of Ribs:

Ribs are added to plastic parts to increase the strength of the part without inceasing the part wall thickness. Ribs also prevent part warpage and can also facilitate locating and arresting the components of an assembly while providing alignment in mating parts. Ribs can also act as stops or guides for mechanisms.

Procedure:

1. Create an extract of the surface on which the rib should be made.
   
   
2. Make a positioned sketch with a line for extruding the Rib.
   
   
   
   
3. Extrude the line to the required height 12.5mm (5 x Wall thickness) and thicken it. The thickness shoulf be 0.4 x Wall Thickness, which is 1 mm in this case.
   
   
4. Add draft of 0.5 degrees to all the faces of the ribs.
   
   
5. Now the rib is added to the body and fillets of 0.25 mm are added to all the faces.
   
   
   
   
6. We need to check the rib root thickness to ensure that it is within limits to prevent sink marks in the part.
7. This is done by creating a tritangent circle at the intersection of plane to the solid body as shown in the below image.
   
   
8. We can add as many ribs as required. The distance between the ribs should be such that ratio between the height of the rib to distance between them is preferably 2:1 or atleast 3:1.
   
   

Draft Analysis