Week 10 - Challenge 1- Attachment Feature Creation (Ribs & Screw Boss)

Object :- Design of Ribs and Screw Boss for Drill Handle following the design rules in given class A surface. And perform Rib root thickness analysis and draft analysis on the final component.

Introduction :- Drill handle is made from the plastic and this component is made by plastic molding process. And this is designed with the help of CATIA V5 software. Because it comes under surface design and CATIA is best to perform surface design and draft analysis. It has more accuracy than other.

Consider the thickness of the component 2.5 mm.

Draft Analysis of Class A Surface In CATIA :- It provides colour based identification. With the help of this we can easily find that which surface is in clear and which is in stuck by colour changing. Here I give the draft angle 3 degree. The result in colour based that the surface which green (means draft angle > 3 degree) is right. And where the colour is blue mean draft angle is 3 degree to 0 degree if this surface area is low then you can go. If you find red colour zone then it means draft angle is less than 0 degree. Then you will have to create tooling axis by another way if possible, otherwise you can say your design engineer to correct for designing.

Here I give a 3 degree draft angle. But some area is looking blue which is not good. We can not change the design because it is Class A Surface which is designed by other team. We can only say to them for modification. When I give 0.5 degree draft angle then everything is fine. So it may be acceptable.

Rib Design :- Ribs provide a means to economical stiffness and strength in molded parts without increasing overall thickness. They also facilitate

• Locating and arresting components of an assembly,
• Providing alignment in mating parts,
• Acting as stops or guides for mechanisms.

Proper Rib design involves many issues which is consider carefully when designing-

1. Thickness
2. Height
3. Location
4. Quantity
5. Manufacturability

Guidelines for Ribs on Show Surfaces

• Draft - 0.5 degree per side minimum
• Thickness - Typically 40% wall thickness
• Height ≤ 5 x wall thickness
• Spacing - 3:1-steel hieght / width ratio maximum
• Thickness at the top ≥ 0.75mm
• Optional Radius - 0.25mm maximum
• Rib root thickness should be under deviation of +-30% from the wall thickness
• Design Suggestions

Ribs should be spaced so that the steel between the ribs is at a

• Height / width ratio
  • 3:1 steel
  • 2:1 is preferred