Week 9 - Attachment Feature Creation - Challenge 1
Designing ribs on Coin holder:
Ribs:
Ribs are the thin line like structures placed in the inner portion of any body (i.e, Class-B or other supporting surfaces), helping in fixing the object in its assembly and providing stiffness, strength. These are not intended to be visible to the user, so they are placed on the B-surface. During the manufacture of Ribs in a plastic component, defects like sink marks are common. To prevent such things there are some guidelines to be followed in rib design.
Consider the present case of coin holder.
The thickness is 2.5mm. The parameters related to ribs are as follows:
Rib Thickness: 0.4*t = 0.4*2.5 = 1mm
Rib Depth: The max value is 5*t = 5*2.5 = 12.5mm
Draft: Minimum of 0.5 deg.
Fillet radius: Max of 2.5mm
Extract the lower part of Coin holder in the closed surface as shown.
With this as reference draw a line of 80mm and extrude it to height of 12.5mm (rib depth). Create a plane with perpendicular to extract as shown.
Convert extrude into solid by adding proper thickness (1mm). The distance between two ribs is determined by the following rule.
(Height of each rib)/(Distance between consecutive ribs) <3
Distance between ribs > (Height/3) = 4.33mm
Take the distance to be 5mm. Translate the rib created to a distance of 5mm as shown.
Add a draft of 0.5 degrees to all faces of ribs. These are then trimmed to the coin holder body.
Now intersect the plane with coin holder body to form a profile below.
Using tritangent circle option create a circle at the root of each rib. Measure the radius of each circle.
Rib Root thickness:
Draft analysis:
The draft analysis is done in following manner:
a) Select materials option in view mode customization toolbar.
b) Select "Feature draft analysis" under analysis option.
c) In draft box select the compass icon and orient it in tooling axis direction.
d) Lock the compass and click at any point on surface or body to get complete draft analysis.
Draft analysis of A-surface:
Draft analysis of Coin holder:
