Advanced Sheet Metal Design Using NX Cad Challenge_2_Box Assembly
OBJECTIVE:
Learn to design a sheet metal box assembly in industrial manner by using siemens NX.
INTRODUCTION:
Sheet metal parts are widely used in machinery, enclosure, brackets, and automobile due to its various advantages. The parts are normally manufactured with break press. Sheet metal is nothing but the thin sheets made from metal of size ranging from 0.5 to 6mm. in this project I used NX CAD tool for designing the sheet metal bracket. NX CAD is used as design tool in more than 85% of the sheet metal industries.
DESIGN METHODOLOGY:
Box assembly is design by keeping industrial procedure in mind to follow the design intent. The design methodology used for this project is summarized in below flowchart.
DESCRIPTION:
All the features used during designing the box assembly are described below. Some of the features were used repetitively at different instances.
Sketch:
For creating any sheet metal surface, we have to first make a sketch. So, I started with creating simple rectangular base sketch for crating the tab. Other then tab, various sketches are also made on different planes or faces for creating other different part during designing.
Tab:
Tab is the first parent feature in sheet metal designing using siemens NX tool. All the other features are usually based on tab. In this casing design, I created the tab by using the sketch on XY plane having dimensions of 150*200.
Flange:
Flange is used to add extra material to the existing edge at any angle and of any size. For this project of box assembly design, I added four flanges on different edges, firstly I added two flanges with 200mm length normal to the XY planer and then another two flanges with length 70mm were added normal to XY plane.
Closed corner:
Close corner features are used to close a corner where two adjacent flanges meet by extending the bending the bends and flanges. For this box assembly I used the closed corner feature twist to close the open corners at the bottom side of the flanges.
Flange for fastening:
For fasting or connecting the two flanges on side box assembly I first created a flange without length and then another flange having dimension of 6.5mm length within outside bend.
Hem flange:
Hem flange feature is used to modify the model by folding the edge of a flange. The main purpose of this feature is to increase the stiffness and for safe handing. For this box assembly I created the hem flanges with 0.5mm bend radios and length of 4 mm.
Mirror body:
As of now half part of the box assembly was designed remaining half part was designed by using mirror body feature, which saves lot of time. I used to mirror body feature to mirror half body about YZ plane.
Unite:
Unite feature is used to combine two different bodies which are in contact. I used unite feature to combine the body before the mirror and after the mirror feature.
Dimple:
Dimple is the feature that lift the area of model inside the sketch that simulates a stamping tool. Generally, it helps to strengthen the flat structure. For this box assembly I first created an appropriate sketch and then I used final dimple on one side of box assembly. same dimple was mirrored to the other side of box assembly for the purpose of perfect landing.
Bends:
Bends are similar feature like dimple the only difference is that by using dimple we lift an area while in bead we lift the contour of the sketch. It also added to strengthen the component. For this project, one small bend was created near the top left corner having diameter of 15mm. then it was created mirrored along the XY plane to obtain the four best on each corner.
Hem flange:
At this hem flange is used to create rounded edge at the top which help in easy handling.
Lid creation:
For creating the lid for box, a datum plane was created at a distance of 202mm from XY plane. The sketch was created by taking the reference of the edges from the top view of the design. Then the tab was created with the sketch to create the lid.
Flanges:
For closing box with proper alignment flanges having web length of 3mm were added to both sides.
Tab for hinge:
Rectangular tab was created on YZ plane.
Break corner:
Beak corner feature is used to smoothen or chamfer the sharp edges of the sheet metal part. This action helps to prevent the stress concentration and fracture breaking. For this assembly I used blend with 10mm.
Flanges:
For the obtaining the required result two flanges of 40- degree bend each of length 4mm were created adjacent to each other.
Hem flange:
For creating the hinge for the box lid an open bend outside type flange with radius 5mm and sweep angle 325 degree was added at the end of the previous flange.
Unbend:
Unbend feature is one the most powerful feature in NX. In industry we have to make all the making and sketch on flat sheet metal before it went to actual operations, so this unbends feature allow us to do that activity in siemens NX software. For this project of box assembly design, I used this feature 2 time to make the further operations/ sketches.
Normal cutout:
Normal cutout feature used to cut material by projecting a sketch onto the model and then removing material perpendicular to the faces intersected by the projection. For this box assembly I used normal cutout feature to remove two rectangular area which leads to forming the hinge barrels on both sides.
Rebend:
Rebend feature is used to restore the unbend feature to tis previous bent state along with any feature added after the unbend feature. this is done by using rebend feature and selecting all the bends carefully in order they unbended.
Mirror body:
After that the body of the hinge was mirrored about YZ plane and similar one formed in the other side.
Tab for creation upper hinge:
A single rectangular tab was created on top surface of the lead.
Flanges:
Similar to the bottom hinge, a flange was also added to the upper tab at 45 degrees with length of 13mm.
Hem flange:
Similar to the earlier process, an open hem flange of radius 5mm with angle of 325 degree was created.
Normal cutout:
As per requirement material is removed in the form of four rectangular by using m=normal cutout feature for creating the hinge barrel.
Rebend:
Part of upper tab which was unbended for creating the hinge barrel was rebended and the design for box for design for box assembly completes.
Flat pattern:
Flat pattern feature allows us to create 3D sheet metal component into 2D form in siemens NX software. By using this pattern feature we can easily avoid error like interference or collision.
Drafting:
After designing 3d model for further process of manufacturing we have to convert the entire sheet metal component into 2D for easy interpretation. For this project of box assembly, a drawing is created out of the flat pattern in 5:1 scale in A4 size sheet with additional drawing of 3:1 scale.
Different view of box assembly:
Isometric view:
Front view:
Top view:
Side view:
Conclusion:
Successfully learn to design a sheet metal box assembly in industrial manner by using siemens NX.