Week 9 - Attachment Feature Creation (Ribs & Screw Boss) - Challenge 1

Drill handle with Attachment Feature Creation (Ribs & Screw Boss)

Objective:

• Create the rib for the Drill Handle considering the design rules.

• Create the Screw boss for the Drill Handle considering the design rules

Take the Thickness of the component to be 2.5 mm

To design the Bumper first you need Class A Surface, if you have Class A Surface means you can create the tooling axis and do further design.

Given Class A Surface:

Class A surface is the outer most surface of the component, it is an aesthetic surface. It is also called as Strak. As a designer we don't have rights to modify the class A surface without permission.

Then we have check the class A surface whether it is joined or not by using boundry command if the boundry command shows only the the outer edges means we can work on class B otherwise we have to correct class A then only we can work on Class B.

The above image is the Class A Surface.

Tooling Axis:

Tooling axis is very important to design a product. It is nothing but the direction of the molds open close and whether it is moves in the x, y or z direction. First we have to decide which direction is probabily suitable for the particular product. Once we get the Cass A Surface, we can check the surface and able to create the tooling direction.

Procedure to Create the Tooling Axis:

• First we have to create a point on the flate face or circle midpoint to create a line here i chose the falt face.
• Once we created the point means we can create a line (Dummy axis) on the point in the suitable direction. We can find the suitable direction by simply see the object from x,y and z directions. If the object is fully visible from one of the direction means that is the line direction.
• After finding the direction just create a dummy axis and axis system.
• Then intersect the part with yz plane and create an bisecting line using the side angular lines which might create a problem.Do the same step in the xy plane to create an another line.
• After creating the two line which might create a problem, then draw a biseting line using the two bisecting line that we drawn from the yz and xy plane but here both lines are not bisecting so we can take any one of the line from xy or yz
• Here, I took xy plane bisecting line as a tooling axis becasue it might create a problem.

Draft Analysis:

Draft: Draft is used to remove the component fom the core and cavity. It will reduce the wear in component and molds so the the life of core and cavity will increase.

Draft Analysis: The Draft Analysis allows the user to easily analyze a part for proper draft angle. A Draft Angle describes the amount of taper for molded or cast parts perpendicular to the parting line.

The minimum draft angle ranges between 0.5 o 3 degree. Mostly 3 degree angle is widly used to make many components.

Class A Draft Analysis:

Procedure to do Draft Analysis:

• Once we created the tooling axis means we can do draft analysis. First we have to switch the view mode to shading with material.
• After switching to shading with material mode we can now click draft analysis tool. Then we have to place the compass on the tooling axis by clicking and draging the compass red dot.
• After placing the compass lock the direction and click the surface to do draft analysis.

• From the above image we can see that the green area has the draft angle above 3 degree. Here there is no red color in the surface.
• The blue color surface indicates that the draft angle ranges between 0 to 3 degree (Exactly 1.5 degree).
• If the color is red means negative or below 0 degree. We can change the color and angle value by clicking the color and values. But green,blue,red are standard colors.

Final Plastic Component Draft Analysis:

Here also we are using the same methods that we followed in class A draft analysis but instead of class surface we are choosing Final Plastic Component with additional features like ribs and screw bosses(Closed Part).

• From the above image we can see that the plastic component is clearing the darft analysis so that it is possible to manufacture this part.
• The green area has more than 3 degree angle so it is posible to eject the component from the mold without sticking to mold.
• The blue color on the ribs and screw bosses means the draft angle ranges between 0 to 3 degree but the actual degree is 0.5 degree we can check the individual spot degree by using analyses under the running point tool in the display of the draft tool.

Class B Surface Creation:

Class B Surface is the inner surface it can be created by using the class A surface by using several surface features.

Basic Features used in Class B Creation:

• Offset
• Exract
• Trim
• Radius
• Sweep
• Join
• Multisection
• Extrude etc.,

First, we can directly offset the class A surface then we can correct the errors occured in the offset.

The above images show the process of creating the class B surface.

Class C Surface Creation:

The surface which is used to close the class A and clas B surface is called class C surface. Simply it gives thickness to the component. We can create the surface using the features mentioned in the below image or other features.

Here I used reference with surface sweep command to create the class C surface.

Class A+B+C Surface:

After the creation of all three surfaces we can join them together with join or trim commands.

Solid Plastic Component With Rib and Screw Boss Features:

We created only surfaces but we need solid part, so after the creation of all surfaces we should do close surface from part workbench. Finally the Drill handle Design with additional features are ready for manufacturing.

Publications:

It is used to easily find out the main parts like tooling axis, class A,B and C surfaces.

Attachment Feature Creation (Ribs & Screw Boss):

Ribs:

Ribs are a feature in plastic injection molded parts. They are thin extensions that run perpendicular from a wall or plane. They are commonly used to provide additional support and strength to a part. Thickness and location are essential to rib design.

Ribs Design Rules:

For Part Thickness 2.5mm

• Minimum Drfat: 0.5degree
• Maximum Radius: 0.25mm (or) Radius = 0.125*T = 0.125*2.5 = 0.3mm
• Rib Thickness : w = 0.4*T = 0.4*2.5 = 1mm
• Minimum Top Thickness of the Rib: 0.75mm
• Rib Depth = 5*T = 5*2.5 = 12.5mm
• Distance Betwwen two Ribs: 2T (But here we are not considering this)

Sketch of Rib:

Rib In Final Part:

Screw Boss:

In plastic parts, bosses are typically used to assist in assembly, as a receptacle for a screw or threaded insert or as the locator for a mating pin on another part. Because of its function, a boss must have sufficient strength to do its job. This dictates a minimum size for the feature.

Screw Boss Design Rules:

For Part Thickness 2.5mm

• Minimum Drfat: 0.5degree
• Maximum Radius: 0.25mm (or) Radius = 0.125*T = 0.125*2.5 = 0.3mm
• Inside Dia : d = For standard screws(M6) = 5.2mm
• Thickness = 0.6*T = 0.6*2.5 = 1.5mm (So Outer dia id 8.2mm)
• Screw Boss Height to Diameter Ratio 3:1 = 15.6:5.2, Therefore Height = 15.6mm
• Depth of the Hole = 0.3*T = 0.3*2.5 = 0.75mm

Sketch of Rib:

Screw Boss In Final Part:

The completed design in various orientations (Isometric, Front, Side, and Top View):

The below images are the different views of the solid plasitc component with draft analysis color code.

With Draft Analysis Color Code: