Advanced Sheet Metal Design Using NX Cad_Box Assembly

Objective:

To design the Sheet Metal Box Assembly Using Siemens NX Metal Application.

Introduction

Sheet metal is metal formed by an industrial process into thin, flat pieces. Sheet metal is one of the fundamental forms used in metal working, and it can be cut and bent into a variety of shapes. Countless everyday objects are fabricated from sheet metal. Thicknesses can vary significantly; extremely thin sheets are considered foil or leaf, and pieces thicker than 6 mm (0.25 in) are considered plate steel or "structural steel".

Sheet metal is available in flat pieces or coiled strips. The coils are formed by running a continuous sheet of metal through a roll sitter.

NX Sheet Metal Creating fast, accurate flat patterns is the goal of any organization that manufactures products which contain sheet metal parts. 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, the most common of which is straight brake sheet metal forming.

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. The value lies in improving quality and reducing cost of sheet metal parts by producing an accurate sheet metal pattern as the correct input for part manufacture, whether internally or to a supplier.

Design Methodology Flow Chart

Feature 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.

• Closed Corner:is a command to modify two flanges in one operation and to close the corner where two flanges meet. During flattening the corner and the relief geometry are made appropriate for flat pattern.

• Hem Flange:is a command to modify an edge of a sheet metal part by folding it onto itself for the purpose of safe handling or to increase edge stiffness.

• Mirror Body: Mirror body feature allows the solid body to get copied and mirrored with respect to a plane. Here, the design made till this stage is a half part of the box which is then mirrored with respect to YZ plane. A black edge appears on the face of the side flange representing the separation between two bodies.

• Unite: It combines the volume of two or more bodies into a single body. Two box and lid parts are combined using this feature to create a single body.

• Datum plane: It creates a datum plane used to construct other features. It is created to form the lid.

• Datum coordinate system: It creates a datum coordinate system used to construct other features. It is created as a reference to mirror the bodies and the features.

Different Views