Advanced Sheet Metal Design Using NX Cad Challenge_2_Box Assembly

                                                          Advanced Sheet Metal Designing of Box Assembly Using Siemens NX-CAD

                                                                                            Design of Box Assembly 

  

OBJECTIVE: 

                   To learn the Sheet Metal design process and to design a Sheet Metal Box Assembly in parametric CAD software Siemens NX following industrial workflow.

 

INTRODUCTION:

                   Sheet Metal is a metal with a small thickness ranging from 0.5-6mm 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, a box assembly of sheet metal is designed in Siemens NX CAD software following the industrial approach. The use of a parametric modelling environment is the main use made in this project.

                 This sheet metal box assembly consists of the main box, cover, and the hinge made out of sheet metal itself. All the parts are designed using the sheet metal features as presented here.

 

                           

DESIGN METHODOLOGY:

                                                                 

 

DESCRIPTION:

                     In the design process of this box assembly, various features have been repeated and are used in different parts. All of them are described below in the order followed in the design process.

 

Sketch for Base Tab:

                 For this box, a sketch for the tab is created in the XY plane first.

            

Tab Feature:

                   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.

                   The Constant Thickness of sheet metal base has been adjusted inthe Preferences Settings already to 1mm.

             

 

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 box design, firstly two flanges are made normal to the XY plane and then two other flanges are created normal to the XZ plane.

            

            

 

Closed Corner:

                 This tool closes the opening between two flanges or between the tab and flange which are perpendicular or at any angle. It should be adjacent to be able to apply the feature. It results in a closed part following the shape of the other part. For this box, a closed corer is used on both sides of the bottom of the flanges normal to the XZ plane.

             

 

Flange for fastening:

For the fastening purpose by the bending of edges, a flange without length is first made and another bend flange is used to bend it outwards to obtain the following result.

            

             

 

 

Hem Flange:

                   Hem Flange is the feature in sheet metal parts which bends the open edges at the end and prevent the sharpness of the sheet metal from any possible accidents. Also, it increases the strength and stiffness of the sheet metal part. A hem flange is applied at the end of both the flanges created earlier to get the following result.

        

 

 

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:

               After the mirror of the body is completed, it results in two separate bodies which is not the intended one. Unite allows us to combine the bodies and make one single body. After applying the Unite feature, the black edge on the face disappears.

                                                     

 

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 box assembly design project, a dimple is made on the face of one of the side flange. This dimple is then mirrored along the XZ plane to get the same feature on the other flange of the opposite side.

Sketch:-                                                                                                                                        Dimple Feature:-

     

 

 

Mirror Feature:

                Now the dimple feature is going to mirror according to the XZ Plane. For that take the mirror feature option and select the feature we are going to mirror and select respective plane.

                                                     

 

Dimple:

                Dimples in sheet metal components provide more strength and rigidity to the flat structure 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 box assembly design project, a circular bead is applied at the bottom face of the box. The first one is applied near one top left corner and it is mirrored along the XZ plane and YZ plane to get four beads on each side of the corner.

                                                

 

Hem Flange:

                      At this stage, the hem flange is applied at the top edge of the side flanges, and the flanges normal to the YZ plane.

                                            

 

Datum Plane:

                      Datum planes are used as a reference on a part where a reference does not already exist. For example, you can sketch or place features on a datum plane when there is no other appropriate planar surface. You can also use a datum plane as a reference to place set datum tag annotations.

                      Here the datum plane are creating with the reference XY Plane . From plane it's located with 203mm distance.

                                         

 

 

Lid Creation:

                      To create the lid for the box, a datum plane is created at a distance of 202 mm from the XY plane. The sketch is created taking the reference of the edges from the top view of the box design at this stage. Then the base tab is created with the sketch to create the lid. It will be a separate body in the box assembly design.

                                        

 

Flange:

                  A flange of 3 mm web length is added on both sides of the lid which allows it to close the box with proper alignment.

                                      

 

Tab for hinge:

                 A datum plane is created on the face of the flange perpendicular to the YZ plane and a rectangle is sketched to create a base tab.

                                   

 

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. Here, a radius of 10 mm is used at one corner.

                                 

 

 

Flanges:

                      Now, two flanges of 40 degrees bend each of length 4 mm is created adjacent to each other to get the following result.

                               

 

Hem Flange:

                   An open hem flange of radius 5 mm and angle of 325 degrees is added at the end of the flange to create the hinge for the box lid.

                             

 

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.

                           

 

 

Normal Cut-out:

               The unbend feature is used and the sketch is created on the face of the hem flange in the flat stage. Two rectangles are created as per the requirement for the hinge barrels of both sides. Then the operation normal cut out is carried out.

                         

 

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 rebend to the required position. This is done using the rebend feature and selecting all the bends in order or by box selection. For this part of the hinge, the rebend results in the following output.

                       

 

Mirror body:

              Again, the body of this hinge is mirrored to the YZ plane to form the same half on the other side.

                     

 

Tab creation for upper Hinge:

                A datum plane is created on the top face of the lid and the sketch for the tab is created. Now, a base tab is added. This tab will be the base for the upper part of the same hinge. Here, the tab is a single part extended over the length.

                     

 

Flanges:

            Similar to the earlier part of the hinge, two adjacent flanges are created at an angle of 37 degrees so that the hem flange following this step can be concentric to the earlier one.

                       

 

Hem Flange:

            Similar to the earlier process, an open hem flange of radius 5 mm extended over a 325-degree angle is created.

                    

 

Normal Cut-out:

            Again, the unbend feature is used and the sketch is created on the face of the hem flange in the flat stage. Four rectangles are created as per the requirement for the hinge barrels of both sides. Then the operation normal cut out is carried out.

                   

 

Rebend:

           Following the normal cut-out feature, rebend is used to get the expected output as shown in the image below. At this stage, our design for box assembly completes.

                   

 

                                                                              DESIGN OF BOX ASSEMBLY 

         The completion of the box assembly design with the features in NX is shown here.

                   

 

                                                                                           Appearances

                  

 

 

                                                                                              DRAFTING SHEET(Drawing)

       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 box assembly design project, a drawing is created  in the A3 sheet with an additional drawing of a 1:3 scale.

                                                    

                                                    

 

 

                                                             BOX ASSEMBLY DESIGN OF SHEET METAL 

                                                                                (MODEL VIEWS)

 

Front View:

                                                    

 

Side View:

                                                   

 

Top View:

                                                  

 

Bottom View:

                                                 

 

Isometric View:

                                                

 

Wireframe View:

                                                

 

 

 

CONCLUSION:

                        In this project, a Sheet Metal box assembly is successfully designed in the sheet metal workbench of Siemens NX. The advantage of a parametric modelling environment is used to maintain our desired design intent and all the necessary features are applied in order following the industrial workflow.