Week 9 - Attachment Feature Creation - Challenge 2
Aim: To design the screw boss and dog house for the coin holder
1. Screw boss design rules
(image is taken from the skill-lync design classes)
- First I sketch the lines required for the screw boss
I have taken the M6 standard for designing the screw boss
- The wall thickness for the screw boss should be calculated as
Thickness (w) =0.6 x t (wall thickness of the part)
= 0.6 x 2.5
w = 1.5 mm (for single side)
= 3 mm for both sides
So, the overall wall thickness is
= 5.2+3
= 8.2 mm
After that, I was given a draft for the screw boss. the next step is to create the ribs for the screw boss.
The height of the screw boss should be a 3:1 ratio to the wall thickness and the hole size.
After extruding the min of 0.5 draft angle is given to all faces of the screw boss.
The thickness can be given the same as the rib thickness given for the other ribs which are 1mm and given fillet value of 0.25 to all edges.
- The next step is to create a dog house for the plastic part.
The function of the dog house is to elevate the screw boss or any other part to touch the datum surfaces. In some cases, the fixing part is not touched by the plastic part to tighten, so a dog house is used to resolve this problem.
The design rules for creating the dog house is :
The intersection where the main part and dog house meets should have the 40% of the thickness to the main part and the thickness should be 3 to 6 mm.
The thickness value at the intersection is 40% of 2.5 mm.
Which is 1mm, and after applying the draft value the thickness at one side is 1mm and on another side is 0.77 mm.
The dog house design satisfies the design rules,
And above the dog house, the other screw boss is designed to touch the datum face of the opposite component.
Now creating a tooling axis for the dog house.
90 degrees to the main tooling axis is the side core tooling axis.
After finishing the product, apply the draft analysis to see if there are any negative errors.
- First for the screw boss.
- Second for the dog house inner part.
