Challenge

Week 9 - Attachment Feature Creation - Challenge 1

GGokul Shyam1 Jul 2021

Design of Ribs

A class - A surface has been provided to me for designing a full solid body out of a surface and Validate it.

In this given surface first I need to check any open boundaries that may create errors while designing.

After checking I need to create a Tooling Axis for the Class - 'A' surface.

Tooling axis creation

The tooling axis is the direction of drawing a sheet metal where the finished component is easily ejected on a particular direction and axis. The tooling axis is important for removing the material when finished.

First, I will create An Axis system, from that axis system I will get two cross-sections. by using that cross-section lines I will create the tooling axis for the surface.

Taken Cross-section along ZY plane

Clearing toling Axis along Y direction

Now creating a Cross-section along the ZX plane

Clearing the tooling axis along the X direction

then using both tooling axis I can now create the main tooling axis for the class - A surface by the bisecting method.

After the creation of tooling Axis, I will now perform the draft analysis for the provided class - A surface.

From the created tooling axis, There is no negative draft, if viewed from the top.

but if I examine the model briefly it has some negative draft.

after the errors now I may create a secondary tooling axis ( side core tooling Axis), but for that also there should be a minimum of 3-degree draft angle on all the negative sides of this model.

So when I briefly examined the model I observed that the sides have 0 or negative degrees from the tooling axis.

As we can see, these blue surfaces are almost or equal to 0 degrees.

Now, this is an issue because it will not compete with the recommended classifications of a plastic part manufacturer.
If the surfaces are at 0 degrees the plastic part won't eject at the end due to contraction after the cooling process.

To tackle this problem there are mainly two reasons which I have come to know.

one way is to create a secondary and tertiary side core tooling axis to overcome this problem, but the overall point is to manufacture the product with fewer expenses.
So what I would recommend to the Class - A surface creator to give some draft angles on these sides for 3 to 7 degrees draft to negative sides.

Final model. After designing the Class - B and Class - C surface I will now continue to the designing of Ribs

Design Ribs

(image taken from Skill- lync design classes)

I will design the ribs from the bottom of the Coin holder

Wall Thickness is denoted as - ' t ' for the calculation.

First I will create the sketch required for the rib.

I will create a single rib and then do others if the rib is satisfied fro every calculation.

the formula for Rib height should be smaller than or = Wall thickness (t) x 5

= 2.5 x 5

t = smaller than or equal to 12.5 mm

Then the Thickness for the rib can be calculated as

Rib Thickness (w)= 0.4 x wall thickness (t)

= 0.4 x 2.5

(w) = 1 mm

Then the Draft angle for the rib can be calculated as

Rib draft should be greater than or = 0.5 degrees

Rib thickness at the tip after draft should be greater than or = 0.75mm

Then at last the rib Fillet is calculated

Rib fillet radius (r) = 0.125 x wall thickness (t)

= 0.125 x 2.5

r = 0.3125 mm

After fully designing the rib, let me find the Rib Root Thickness Value for the rib and Body.

here we can see the wall thickness is 2.5 and Rib root thickness is 2.71 which is greater than wall thickness. So at the junction of rib and wall thickness, it may create a little amount of sink mark.