Tips of Sheet Metal Fabrication
According to the difference of sheet metal structure, the fabrication process is different. But the total processes are below ways: The ways of blanking are a lot and the main ways are as below.
- Shear: Using shear to cut simple raw material. It is mainly giving preparation for mold blanking. The cost is low and precision is under 0.2, but it can only manufacture strip material or square material without hole and corner cut.
- Punch: Using punch to cut the flat piece which is unfolded on the sheet metal into different sizes of material with one or more steps. The advantage is time short, high efficiency, high precision, low cost, and be suitable for mass production, but need mold design.
- NC blanking. When NC blanking, first, it needs to write the NC process program. Using programming software, writing the drawing into the program that the NC process machine tool can recognize, and making the tool cut different flat pieces in all kinds of sizes on sheet metal by one step and one blade according to this program. But its structure is limited to the blade structure with low cost and the precision is under 0.15.
- Laser blanking. It is used the way of laser cutting. It can cut the sheet metal structure on the large sheet metal and the same as NC blanking, it needs to write a laser program. It can cut all kinds of flat pieces with a complex structure with a high cost and the precision is under 0.1.
- Sawing machine: mainly using aluminum, square tube, figure tube, round bar stock, and so on. Cost and precision are low.
- bench:sink hole,tapping,enlarge hole,drilling
The main process for Sheet Metal Fabrication Machining.
Usually, the angle of the sinkhole is 120 degrees. It is used for rivets. And 90 degree is for countersunk head screw and tapping the bottom hole in the English system.
- Flanging: always named extrude or burring. It extrudes a bigger hole on a smaller basic hole, then taps. It is mainly used for thin sheet metal, increasing its hardness and thread laps to avoid sliding teeth. The shallow flanging around the hole is normal and the thickness is no change,.When the thickness becoming 30%-40% thin, it can get the height of 40-60% higher than the normal flanging height. When squeezing 50% thinner, it can get the largest flanging height. When the sheet metal is very thick, such as above 2.0,2.5, it can tap directly.
- Press: It is a process of mold forming. Usually, the press processes are piercing, cutting corners,blanking, bump, tearing, extruding, forming, and so on. These processes need a relevant mold to operate, such as piercing blanking die, bump die, tearing die, extruding die, forming die, etc, It mainly needs to pay attention to position and direction during operation.
- Self-clinching: It is mainly self-clinching nut, screw, spring screw, etc. It completes operation through a hydraulic self-clinching machine or punches to join on the sheet metal. Also, there is way of flate-in, and pay attention to the position.
- Bending: It is bending 2D flat sheet metal to the 3D products. Its operation needs a bending bed and relevant mold. It has a bending sequence and the principle is bending first which doesn’t affect the next blade and then bending which will affect the next blade.
- The bending number is 6 times sheet thickness under T=3.0 mm to calculate slot width,for example: T=1.0,V=6.0,F=1.8,T=1.2、V=8、F=2.2、T=1.5、V=10、F=2.7、T=2.0、V=12、F=4.0
- Bending bed die includes straight blade, bent blade(80 degrees,30 degrees)
- When bending aluminum with crack, it can increase the width of the upper mold cavity and low mold R(annealing can avoid cracking)
Attentions when bending for Sheet Metal Fabrication
- drawing, required sheet metal thickness.
- quantity, bending direction.
- bending angel.
- bending dimension.
- appearance, chromium plating without crease.
- Relationship between bending and self-clinching process: Usually self-clinching first and then bending, but some material will be interference after self-clinching, so it should bend first and then press. And some process needs bending – self-clinching-bending again.
1. Welding: definition of welding: Welding is a process for joining similar sheet metals. Welding joins sheet metals by melting and fusing firstly, the base metals being joined and secondly, the filler metal applied.
- fusion welding: argon arc welding, CO2 welding, gas welding, manual welding.
- Pressure welding: spot welding, butt welding, bump welding.
- brazing: chromium electric welding, copper wire.
2. Welding method:
- CO2 gas shielding.
- argon arc welding.
- spot welding etc.
The welding method is according to actual requirements and material. Usually, CO2 gas shielding is used for welding sheet metal; argon arc welding is for stainless steel, aluminum plate, etc, Robot welding can save working hours, improve work efficiency and welding quality, and reduce working intensity.
3. Arrow lines and joint
4. Welding missing and preventive measures
Spot welding: If the hardness is not enough, it can hit bumps and increase the welding area.
CO2 welding: high producing efficiency, less energy consumption, low cost and strong ability to resist rust
Argon arc welding: penetration shallow, low welding speed, high production cost, tungsten inclusion defects, but with strong points of better welding quality, welding non-ferrous metal, such as aluminum, copper, magnesium and so on.
5. Reasons of welding deformation:
increasing jig while preparation is not enough before welding Improving process while welding jig is not good Welding sequence not good.
6. Welding deformation correction method:
- Flame correction method
- Vibration method
- Hammering method
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