Advanced Sheet Metal Design Using NX Cad_Casing Design

Objective :

The Main aim of this project is to design sheet metal casing using Siemens NX Sheet Metal Application.

Software Used :

Siemens NX 12

Introduction :

NX Sheet Metal provides a set of tools within the NX design environment that allows for simple and fast design of sheet metal parts, dependent on their material and manufacturing process. With NX Sheet Metal, formed and unformed representations of the parts are created closely following the industry workflows and best practices for bending calculations, tooling, and sheet metal features.

Sheet Metal is a metal with a small thickness ranging from 1-3 mm which is made thin and flat by rolling or hammering process. A number of mechanical components are made up of Sheet Metal. Sheet metal is widely used in the manufacturing industry due to its various advantages. In this project, sheet metal is designed in Siemens NX CAD software following the industrial approach. The use of a parametric modeling environment is the main use made in this project.

Design Methodology Flow chart :

The casing designed for this project consists of features like cut-outs, bends, flanges, holes, dimples, and beads. Every feature is designed in an order following the industrial procedure to keep the design intent. The design methodology used for this project can be summarized as depicted in the flowchart below:

Design Process :

1. Create the base tab first and cut out the areas using normal cut out tool .
2. Used bend tools for bending the part from the desired location .Add flanges and apply unbend and then using hole provide the hole as per the specification.
3. Add Dimple tool through which we add the dimple and add bead tool.
4. In the last rebend the part from the necessary area and model the 2D view to get clear idea.

Features Used :

• Sketch: The sketch is the fundamental base element for any feature in the design of any sheet metal component. Most of the features require a sketch. The very first step is to sketch which is then used to create a tab or the base feature. So, the first sketch can be called a base sketch. For other features which are the children features of the tab, the sketch may require again on a particular plane or a face.

• Tab: The tab is the very first feature in any sheet metal component design process. All the other features of the sheet metal in Siemens NX are based on the base feature or tab. A tab is created after a sketch is created in any of the planes or datum plane created. The tab is always the parent feature for other features following it. In this casing design, the tab is created after a simple sketch in the XY plane.

• Bend: Bend feature is added wherever a bend in the sheet metal component is required. It may be at any position or at any angle. A sketch is required to create a bend. It can be an open profile and it can be either a straight line or a curve. For this project of casing design, two straight lines symmetric with respect to X-axis are drawn for the bending curve.

• Flange: The flange is an additional face created automatically from any edge of the existing sheet metal component. It is additional material connected to any face or edge which is bent from the respective edge or face. It can be at any position or at any angle. For this casing design, four simple flanges are created with the material inside the edge of the existing component.

• Break Corner: This feature breaks the sharp edges in the corners and makes it round or adds chamfer. It is like the fillet feature in some other CAD software. It prevents the fracture breaking of the sharp corners.

• Unbend: This is a very powerful and very useful tool in Siemens NX. It allows all the bends made by the various features to the unbent state at once. In order to achieve a flat configuration of the sheet metal as per the design intent, it is necessary to choose the bends in order. It is also possible to box select all the bends at once. Once the unbend feature is used, further features can be carried out using the sketches created in the unbent state.

• Hole: Hole feature in sheet metal design workbench is just like in the model workbench. It can create either simple or counterbore or countersink or tapped holes. For this casing, first, the four points are sketched symmetric to the x-axis in position and the hole feature is applied.

• Dimple: Dimples in sheet metal components provide more strength and rigidity to the flat structure of the component. Dimple feature in Siemens NX is created using the sketch created in any face or any flange of the sheet metal component. For this casing design project, a dimple made up of a 16 points curve is used at the center of the component.

• Beads: Beads are the features added in sheet metal components in order to increase the stiffness of the component. Beads require a sketch in order to apply the feature. It can be either an open or closed profile. For this casing design project, four small beads are applied in the symmetric positions as shown in the image below.

• Rebend: All the features added after the unbend feature are added in the unbend state itself. After the addition of sketches and additional features are completed, the sheet metal component has to be rebent to the required position. This is done using the rebend feature and selecting all the bends in order or by box selection. This completes the design process of the casing adding the features.

• Flat Pattern: Flat pattern is the representation of the entire sheet metal component in the 2D form of the flat sheet metal with all the bends, cut-outs, holes, and additional features in the form of lines or edges. The flat pattern ensures the ability to cut the sheet metal out of the raw sheet metal plate. It removes the possible errors such as interference or collision within the same component.

• Drafting: After the design is complete, the execution or the manufacturing of the component requires a technical drawing of the component with the provided scale and with accuracy. The necessary details such as annotations, callouts, bend tables can be added as per the requirement. For this casing design project, a drawing is created out of the flat pattern in a 2:1 scale in A4 size, and the bend table is added.

Drawing Sheet

Different Views