Week 10 - Challenge 1- Attachment Feature Creation (Ribs & Screw Boss)

AIM

To create a Drill handle Plastic Component through a given Class A Surface, create the ribs and screw bosses and perform Draft Analysis on the final plastic component.

OBJECTIVE

• To make sure that the model meets the requirements of the draft angle.
• To create the Tooling axis using bisecting method.
• To perform Draft analysis on the given Class A Surface.
• To create the required Class B and Class C surfaces.
• To obtain a solid body from the surface using Close Surface feature.
• To create the Ribs & Screw bosses as design rules.
• To perform draft analysis on final plastic component.

CLASS A SURFACE

• Class ‘A’ surfaces are primarily used in the automotive environment and refer to those surfaces which are visible in a product. In other words: A - class surfaces are those aesthetic/free-form surfaces, which are visible to us (interior/exterior), and have an optimal aesthetic shape and high surface quality.
• The surfaces or regions which are visible nowadays are considered for Class-A modelling. It is one of the reasons why the importance of Class-A modelling is increasing day by day. Majority of the time this term is used in Plastic Part designs.

CLASS B SURFACE

• The Class B surface is created from the Class A surface, keeping the thickness of the component in check.
• The Class B surface resembles an offsetted surface from the Class A.

CLASS C SURFACE

• The Class C surface is used to bind the Class A and Class B surface together in order to form a closed surface.

PROCEDURE

Creating Tool Axis

• Initially the given Class-A surface was imported and checked for any discrepancies in the boundary and performed draft analysis on it at 3-degree draft.
• The ejection from the mould after manufacturing the interior trim must have the nominal 3-degree draft angle.
• The Y direction is suitable for creating the tooling axis because in the Y direction most of the surfaces are clearing while performing draft analysis.
• The base surface of the class-A was extracted to create a reference point on the surface using the point, create a line in the Y-direction.

• Generally tooling axis is created using bisecting line method but here A line normal to the surface is created in the y direction and considered the tooling axis.

Creating Class B surface

• First offsetting entire class A surface to 3mm in the inward direction as 3mm is thickness of component.
• Some of errors were created in the offsetted surface like incomplete surfaces, gaps, small patches.

• These errors were solved by extracting surfaces, join by sub-elements to remove, extrapolating, sweep, multi-section surfaces etc commands.
• Joining patched surface to main surface, Class B surface was created.

Creating Class C surface

• We first extract the edges from the Class A surface with the help of the multi extract command which we create the path for a sweep for class C.
• Create a sweep with reference to the curve and the reference surface with a 90-degree angle and give the inside direction Check for the continuity of the surfaces if there is any gap go for extrapolated and trim all together now, we will get the class C surface.

• Joining class-A surface and class-C surfaces together.

Creating Solid Body

• Later, Joined Class A & Class C surface is trimmed with Class B surface to form the drill handle surface.

• Using the surface created, the solid component was obtained using the Close surface feature present in the part workbench.

• The Tooling axis, Class A, B and C surfaces were published.

Attachment Feature Creation Ribs & Screw Boss

Ribs

Ribs are thin wall-like structures that add support and rigidity to injection moulded parts. They are thinner than primary walls and are used to support these walls, as well as bosses, by running perpendicular to these structures. Ribs are often used to replace thick wall sections to avoid sink marks, warp, and voids.

The function of rib in plastic component:

Ribs are used to strengthen the walls of the mould without increasing wall thickness which means that minimize the problems that come into play when the wall thicknesses have to be increased. In essence, if the wall is too thick, warping and sinking can result so that the entire design may need to be rejected.

Rib root thickness analysis

Screw Boss

Screw Boss features are commonly found in injection moulding designs. They are used to aid in the assembly of moulded parts by providing a channel for a screw.

Screw 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. Their primary use is to strengthen holes or slots in the surface present in the part model.

General Guidelines for Screw Bosses:

Draft - 0.5 degrees on the walls of boss

Thickness - Typically 40%* of the nominal wall at the base.

Height to Diameter Ratio - 3:1

Radii - 0.25mm maximum radii.

DRAFT ANALYSIS

• First, we should change model into material mode.
• Go to insert and in analysis select feature draft analysis.
• Align the compass along tooling axis and lock it.
• Next click on the surface and see that the surface is within the permissible limit of the values.
• The green colour area shows that it satisfies the 3-degree draft angle. If not satisfied then by using the Running point tool the area is measured and then altered to get a successful draft for the created tooling direction.

On given Class A surface

On obtained PART BODY

CONCLUSION

• The creation of Tooling axis and Draft analysis were performed.
• The solid component was created from the surface geometry.
• Attachment Feature like Ribs & Screw Bosses were created as per design rules.
• The necessary screenshots and files were attached.
• The Class A, B, & C surfaces and also the Tooling Direction have been Published.