Advanced Sheet Metal Design Using Siemens NX - Designing a sheet metal casing.

OBJECTIVE

 Recently I attended an online course called Mechanical Engineering Design; Sheetmetal Design - Udemy. Course covered the essential theoretical and practical knowledge required for designing sheet metal. By attending the course I got some ideas about the common processes, materials and the properties which matter the design, comparison between hardness,toughness and strength, what happens to the material when it is formed or bent, the theory behind forming and bending, form-ability and bend-ability of metal sheets and what factors affect them, forming limit diagrams and how they are created, bending parameters in design, K factor, neutral axis, bend allowance, the concept of spring back and ways to reduce it, deep drawing process, joining processes and their comparison, design guidelines to create cost-effective designs which are suitable for manufacturing etc. Then I decided to learn more about designing sheetmetal components using Siemens NX sheetmetal workbench.

The main objective of this project is to design a sheet metal Casing and to create a drafting for the same using Siemens NX sheetmetal workbench.

INTRODUCTION

 The applications of sheet metal casings are nearly infinite. It have applications in various sections of engineering such as Mechanical, Automotive, Aerospace etc. In this project I created a sheet metal casing using Siemens NX sheetmetal workbench.Mechanical Engineeers use Such sheetmetal  casings widely for protecting various components of machines such as various moving parts, electrical or electronic circuit boards etc. Such casings are usually simple, but they are durable and tough. Comparing other materials, sheet metal enclosures have many advantages such as better resistance to temperature variations, various corrosive chemicals, impacts from physical objects etc. So, Sheetmetal casings ensures durability and better performance.

DESIGN METHODOLGY

DESCRIPTION

The sheetmetal casing project was done according to the flow chart shown above. Initially I made preferences of the sheet metal while designing such as thickness, relief depth, relief width, bend radius etc. All these values were set into 1 mm.

Then after setting the preferences, sketch was drawn in the XY plane with required dimensions. Then 'Tab' command was used to create the base of the part. It is used to create a base for the part by applying thickness value to the sketch along a vector.

After applying the tab to above shown sketch, a 'Normal cutout' feature was used to cut the sheet metal part as shown below. Cutout was performed after sketching the portion to be removed with required dimensions on the tab.

Next step was 'Bending'. As the name implies this feature is used to bend the sheetmetal. We can bend the sheetmetal after selecting a sketch - in this case the two lines shown in the picture below- and the face. We also have to specify the bend angle.

After bending the sheetmetal part, flat ' flanges ' were added as shown in the picture below. Bend radii for all the four flanges were 1mm. Also necessary width and angle for flanges were applied in the dialogue box.

Next command I used is ' break corner '. It is used to round or chamfer sharp corners of the part.

Next step is to unfold the sheet metal part using ' unbend ' command. Here, the unbending operation is used to perform the punching operations. The sheetmetal part after complete unbending is shown below.

After unfolding the sheetmetal casing, four holes are made on the part after locating the position of holes using required sketches. Here in the dialogue box,  under type of hole option I selected '  screw clearence hole'.

Next step is to create a ' dimple ' on the sheet metal casing surface. In order to make the dimple I created a sketch first with required dimensions. Punch, die, corner radii were set to 1mm with 1 mm depth and minimum tool clearence to 5mm.The result is shown below.

After applying the dimple, next I made a bead on the part surface. Beads are used to improve the stiffness in metal sheets or plates. Depending on the workpiece size and material thickness, the ratio of length, width and imprint depth must be adjusted to obtain the maximum strengthening effect. After creating one bead the remaining three were made using mirror feature.

After all these operations, sheet metal part was folded back using ' rebend ' option. DFM (Design For Manufacturing) process is usually done at this stage. Process involves procedures to check whether the design is suitable for manufaturing or not. ' Flat pattern ' is the last feature in the part model tree. It ensures the manufacturability of sheet metal component. If sheet metal component is not flattening, it means the sheet metal part is not manufacturable.

CAD DRAWING

STANDARD VIEWS

Several standard views of the Sheet metal Casing such as front, Side, Top, Bottom and isometric views are shown below.

1. FRONT VIEW

2. SIDE VIEW

3. TOP VIEW

4. BOTTOM VIEW

5. ISOMETRIC VIEW

CONCLUSION

The Sheet metal Casing part was successfully designed and drafted using Siemens NX sheet metal workbench.