Sheet Metal Fabrication Technology And The Basic Processes For Sheet Metal Fabrication (1)
- Jun 05, 2018 -

Sheet Metal Fabrication Technology And The Basic Processes For Sheet Metal Fabrication (1)


1. Brief Introduction On Sheet Metal Fabrication


1.1 Brief Introduction On Sheet Metal Fabrication

This specification states the technological requirements to be noted in every basic processing method,like blanking,bending,stretching, forming and welding.


1.2 Key Word

Sheet metal, blanking, bending, stretching, forming, layout, minimum bending radius, burrs, resilience, return fold and welding.


2. Blanking

According to the different processing methods, cutting can be divided into punching, blanking, shearing, laser cutting and wind cutting.Because of the different metal fabrication methods, the processing technology of blanking is also different.Main sheet metal blanking methods are NCT punching and laser cutting.


2.1 The punching is processed by CNC punching machine. The range of sheet thickness for processing is as following:

cold roller steel, hot roller steel is less than or equal to 3.0mm; aluminum sheet is less than or equal to 4.0mm; stainless steel is less than or equal to 2.0mm.


2.2 The minimum size of punching is related to the shape of the hole, the mechanical properties of the material and the thickness of the material.


Figure 2.2.1Example of punching hole shape

Sheet Metal Fabrication


Table 1 Minimum size list for punching holes

MaterialCircular Hole Diameter bShort Side Width Of Rectangular Hole b
High carbon steel1.3t1.0t
Low carbon steel and brass1.0t
0.7t
Aluminum0.8t
0.5t


● T is material thickness, and the minimum size of punching is not less than 1mm.


2.3 Hole spacing and hole margin of punching process

The minimum distance between the outer punching edge and the edge of punched hole is restricted by the shape of the part and hole, as shown in Figure 2.3.1. When the punching edge of hole is not parallel to the outer edge of the part, the minimum distance shall be not less than t of the material thickness; when parallel, it should be not less than 1.5T.


Figure 2.3.1 sketch map of the hole margin and hole spacing of punching parts

Sheet Metal Fabrication

2.4 when the bending parts and drawing parts are punched, the distance between the hole wall and the straight wall of the part should be kept at a certain distance.

When punch bending parts or deep drawing parts, the hole wall should be kept at a certain distance from the straight wall of the work piece. (Fig. 2.4.1).


Fig. 2.4.1 the distance between the hole wall of bending parts, drawing parts and the vertical wall (straight wall) of the workpiece.

Sheet Metal Fabrication


2.5 Screw, bolt hole and countersunk seat

The size of screws, through holes for bolts and countersunk seats shall be selected according to the table. For the countersunk seat of countersunk head screws, if the plate is too thin to ensure the hole D2 and the countersunk hole D at the same time, priority shall be given to ensuring D2.


Table 2 Through holes for screws and bolts

Sheet Metal Fabrication


Table 3 the countersunk head and through hole for chamfer head screw

Sheet Metal Fabrication

"h" - height of screw head for reference

Required sheet thickness t≥h


Table 4 the countersunk head and through hole for countersunk rivet

Sheet Metal Fabrication

"h" - height of rivet head for reference

Required sheet thickness t≥h


2.6 Laser cutting is done by laser cutting machine. The max cutting thickness of steel is  less than or equal to 20.0mm and the max cut thickness of stainless steel is less than 10.0mm. It can cut thick material with high speed. And its defect is that it can not do forming process. The mesh parts should not be processed by this way because the cost is high.