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

AIM : Create the rib and Screw boss for the Drill Handle considering the design rules.

Class-A Surface

Class-A surfaces refer to those surfaces which are visible in a product. In other words, class-A surfaces are those aesthetic/free-form surfaces, which are visible to us (interior/exterior), and have an optimal aesthetic shape and high surface quality. It is created by the styling team and gives to the part design engineer to create the part with all engineering aspects.

Class-A Surface:

The given class-A surface is checked whether there is any patches or not using bondary command.

Tooling axis

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

In Molding, machine arrangement is given to open the mould along a direction which is known as Tooling Direction. In other words. The mould is built from two separate halves (Core and Cavity) and tooling direction basically defines the direction of mould pulls apart.

There are 3 methods to create tooling axis, which are :

• With respect to 3 axis (X, Y, & Z)
• Normal to surface
• Bisecting method

In the given model tooling axis is found out using Normal to Surface method.

In the given model, it will clear all the surfaces in its Y-axis direction, so that the surface approximately perpendicular to Y-axis is chosen and is extracted from the class A surface. Tooling axis is created normal to that extracted surface.

Draft Analysis Class A Surface

In the criteria of making a plastic material, the mold should release the material when finished. If the mold surfaces are 90 degrees the material won't release from the mold because of friction due to contraction of material when cooled.The ejection of the part from mold depends on the draft. A zero draft can result in difficult or no ejection. It is recommended to add a draft of 3 degree or above inorder to remove it from the mold without any damage.

Procedure:

• Change the view mode of the component to be in customized parameter mode and then select the shading mode as materials.
• In the draft analysis toolbar, set the draft values and color (3 degree and above as green, 0 to 3 degree as blue, less than 0 as red).
• Drag and drop the axis system on the tooling axis and lock it.
• Perform draft analysis.

Draft Analysis of Class A surface:

Creation of Class B & C Surfaces:

Class-B Surface

It is the offset of the class-A surface at a particular distance. The offset distance depends on the thickness between Class A and Class B surface.

Here, the thickness given = 2.5mm.

Procedures to build class B surface:

• Offset the joined class-A surface to 2.5mm inward direction.
• Rework on the patches and discontinuity of the offset surfaces using the features like extract, multi-extract, sweep, multi-section surfaces, extrapolate.
• To ensure the continuity of the Class-B surfaces check the boundary command to find out the boundary.
• Hence class-B surface creation is done.

Class B surface offseted 2.5mm is given below:

Class-C Surface

This surface connects the Class A and Class B surfaces. (Surface in between Class A & B surfaces)

Procedure to build Class C surface:

Since it is a complex class-A surface, we cannot simply create the class-A boundary curve and sweep it at one shot. Hence, we need to create smaller boundaries using boundary command and then create sweep of 90 degrees with reference to the surface option if the class C should come in perpendicular to tooling axis. Sweeps at the areas were class C should come parallel to tooling axis should have a 3 degree draft vaue with repect to tooling axis to pass the draft analysis. Also, at the fillet/curve areas, use multi section surface inorder to sweep and complete the class C surface.

Join every induvidual sweeps using join command and for the edges which hasn't joined, extrapolate and trim off the sweep surface corners at the required edges.

The Class-C Surface:

Final Surface Creation

Joining and Closing of Class A,B & C surface:

After creating class B & C surfaces joining operation is done between class A and class C surface. Then, Class B surface is trimmed with joined Class A & C surface to get a whole closed single surface. Then in part workbench using closed body command, a solid body is generated.

Closed surface:

Solid Body:

Attachment Feature Creation (Ribs & Screw Boss)

Rib Creation

Ribs are usually designed to Improve Strength of Plastic Part without increasing the thickness of the component.

• Design Principle for Rib Creation

• Ribs are thin wall protrusions that extend perpendicularly from a wall or plane. They are usually found in clusters offering support to a plane that would have otherwise been too thick, but can also be stand-alone support for a single wall. They are commonly used to provide additional support and strength to a part. Thickness and location are essential to rib design.

  First, the base surface where the rib has to be created is extracted using the Extract command. A positioned sketch is created and the profile for the rib is drawn.

• Next, the profile is extruded, to find the height,h=Wall thickness * 5

  =2.5*5

  = 12.5 mm

  Therefore, the height is 12.5 mm

• The extruded surface is thickened,

  Thickness,w=0.4*t

  =0.4 2.5

  =1mm

  Therefore, the thickness of the rib is 1 mm.

  

Rib Root Thickness:

Screw Boss Creation

It helps to screw component together. Screws are secondary features which is on B surface. Bosses are used to attached & assembly features of many components.

• Design Principle for Screw Boss Creation

DRAFT ANALYSIS:

After creating a solid body from the closed surface, performed a draft analysis on it, to check the draft angle (0.48 deg) of the solid body.

Tree:

CONCLUSION:

• The Tooling axis and the part with B Side Features is created from the given Class A Surface and Draft Analysis is Performed.