Advanced Sheet Metal Design Using NX Cad Challenge_1_Casing Design

SHEET METAL DESIGN OF CASING

OBJECTIVES

1. To design casing in NX sheet metal.
2. To draft the casing.

INTRODUCTION

In this design the casing is designed with the help of basic sheet metal features. It is designed using Siemens NX12.

DEFINING SHEET METAL

Metallic sheets ranging in thickness value from 0.15mm to 6.35mm were undoubtedly considered as sheet metal. If thickness is lower than the value 0.15mm then it is called foil. If thickness value higher than 6mm than it is called plates. It is measured using the guage, the greater the guage number thinner the sheet metal.

SHEET METAL OPERATIONS

1. SHEARING

2. BLANKING

3.PUNCHING

4.BENDING

5. TRIMMING

6. PARTING

7. SLITTING

8. LANCING

9. NOTCHING

10. PERFORATING

11. NIBBLING

12. EMBOSSING

13. SHAVING

14. DINKING

15. COINING

16. DEEP DRAWING

17. STRETCH FORMING

18. ROLL FORMING

In this casing design mostly bending, cutout and drawing operations are performed.

BENDING

In this process force is applied on the sheet metal and causes them to bend at adesired angle. This operation is performed by the press brake machine. The amount of bend angle depends on depth of bend and punch force given.

Three main types of bending are

1. U-type
2. V-type
3. Edge bending

U-type bending

The punch and die both are u shaped and commonly result in u bending.

V-type bending

The punch and die are v- shaped. It has three sub groups they were air bending, bottoming and coining.

Method/thickness(mm)	0.5-2.6	2.7-8.0	8.1-10.0	Above 10
Bottoming(v width)	6t	8t	10t	12t

Air bending (v width) 12.5t

Coining (v width) 5t

wipe bending

sheet held with wipe die against pressure pad.

Bending force chart

This chart is suitable for construction steel. If wanted to look for aluminium just divide those values by 2. Then for stainless steel multiply the value by 2.

DIMENSION GUIDE

Minimum bend radius - It is recommended that minimum inner bend radius should be at least 1 times material thickness.

Minimum flange length – I can be conveniently note from the bending force chart before tooling. Generally flange lenght must be atleast 4 times the thickness.

Minimum Bend height - H=2t + r

Bend relief – reactangular relief, tear relief and notch relief.

Bend relief prevent the material from tearing.

Bend angle – It has +/- 1 degree tolerence alomg all bends.

Bend allowance – The length of the neutral axis between the bend lines or the arc length of the bend. The bend allowance added to the flange lengths is equal to the total flat length.

K factor

The K-factor is used to calculate flat patterns because it is related to how much material is stretched during bending.

PROCESS FLOW

Sketch – origin centered rectangle-length=60mm, width=50mm

preferences-sheet metal-global parameters=1mm

Tab=1mm thickness

Normal cutout-sketch-left edge coincident rectangle-5mm wide, 40mm long

Bend -sketch-two symmetrical horizontal line 10mm from the upper left corner-bend angle=90 degree

Flange-selecting inner edges in top, outer egdes in bottom

Break corner-method-blend,radius=1mm

unbend-selecting main face as stationary face and one of its adjecent face as bend face

Feature-Hole-select points created in the flanges at midpoint, type-screw clearence,

screw size=M2,fit=H13

Dimple-sketch 5mm length each half side centered at (0,0,0)

Studio spline-select all the 16 corners

Move curve-select spline,Motion -angle,Angle=45 degree

Dimple-1mm depth,side walls- materials inside,rounding field=1mm

sketch-xy plane-5mm dia,8mm each from corners

Bead-select sketch,depth=1mm,radius=1mm

Rebend-select faces in reverse order

Flat pattern-select central sheet face and validate,visible in model views

Drafting- A4 size sheet,view-select flat pattern,sca

TOOLS AND FEATURES USED ON SHEETMETAL TO DESIGN CASING

1. Sketch
2. Tab
3. Cutout
4. Bend
5. Flange
6. Break corner
7. Unbend
8. Hole
9. Studio spline
10. Move curve
11. Dimple
12. Bead
13. Re bend
14. Drafting
15. Base view

TOOL AND FEATURE DESCRIPTION

1. SKETCH

It is a 2d representation of a 3d part. It includes entities like line, rectangle, spline, circle, etc. It is a predetermined drawing with dimensions and relations.

2. TAB

It is the base part for any sheet metal design. Flanges can be made only from the tab edges.

3. CUTOUT

This command is to remove the desired shape of material. Removal sketch can be drawn on the sheet metal face, wherever required.

4. BEND

It is to bend the tab/flange by creating the line sketch. The bend can be like U, v or channel shape.

5. FLANGE

It is created with one or more edges at specified location. The minimum flange length must be atleast four times the thickness of the sheet metal. Bend radius is equal to the sheet metal thickness.

6. BREAK CORNER

This command gives a smooth finish over the corners of the sheet metal part.

7. UNBEND

It makes the part unbend, that is all the features done are made flat. This is useful while sketching on the corners and bend areas.

8. HOLE

This feature is to put a hole on the part. There were screw type hole with specified scre size and fit.

9. STUDIO SPLINE

It results in a set of splines after selecting the points for its path. It is used for making splines along the sketch.

10. MOVE CURVE

It moves or rotates your curve.

11. DIMPLE

It rises a drawn sketch from the base plate. This command doesn’t save material instead it maintains the rigidity.

12. BEAD

It lifts material along contour sketch.

13. REBEND

This command puts back all the bends already created also along with new features included while in unbent state.

14. FLAT PATTERN

It is done before drafting. It gives a flattened version of the sheet metal part.

15. DRAFTING

This command is to have 2D drawing of the sheet metal part created.

16. BASE VIEW

It specifies the location, orientation, view and scale of the part for drafting.

CASING IMAGES

FRONT VIEW

SIDE VIEW

TOP VIEW

ISOMETRIC VIEW

DRAFTING

Creating a new draft on A4 size sheet of flat pattern#1.

CONCLUSION

The casing sheet metal part is created using NX12 software.