What is Sheet Metal Bending Process
The sheet metal bending process is a cold bending method to bend/shape the sheets of metal to manufacture a product of certain geometry. It is also a basic operation to make the metal stamping parts.
How can Sheet Bending Process Do?
Force is applied to a workpiece with the help of sheet metal bending machine to transform its geometry to attain a product with the desired shape. The process is not as simple as it appears, yet there are certain dimensions, and rules to be fulfilled to carry out a sheet metal bending procedure, for example, checking the material of the product, calculating the k-factor, and the shape of the metal, and many more. The malleability property of the metal makes it very special in bending operations.
6 types of sheet metal bending
All sheet metal parts have the same goal which is to bend a sheet of metal to attain a certain product shape. But these methods differ in their performing operations. These various types of bending in sheet metal are fulfilled with the help of machines. Different bend sheet metal is different in the bend angle and bends radius with the same goal along with the standard techniques which not only ensure precision in work output but also a better aesthetic workpiece product.
There are six types of bending processes used to form metal that any sheet metal engineer or press brake operator must be familiar with.
V-bending
V-bending is the most common sheet metal bending process. It involves the use of machinery tools called to die and punch. The die used in this bending process is a V-shaped die, while the punch is also designed in a V-angled shape. The punch presses on the sheets of metal into a V-die and this is how the V-bending of sheet metal is obtained.
Roll Bending
Roll bending is a method used to bend sheet metals into rolls or curved shapes. The process employs a hydraulic press, a press brake, and three sets of rollers to make different bends or a big round bend. It is useful in forming cones, tubes, and hollow shapes as it takes advantage of the distance between its rollers to make bends and curves.
U-bending
In terms of principle, U-bending is akin to V-bending. It uses the same instrument (except a U-die) and process, although the only difference is that the shape formed is U-shaped. U-bending is very popular. However, other methods produce the shape flexibly.
Rotary bending
The rotary bending method is deployed wherever a bending of greater than a 90-degree angle is required. It can also be considered similar to that of V-bending, but the output in this process is more uniform and aesthetic as the metal sheet bending machine used in this method doesn’t scratch the surface of the sheet.
Edge bending
This technique of edge bending sheet metal helps the manufacturer to bend the edges without damaging them. The sheet metal edge bending method is most commonly utilized in those sections of sheet metals that are shorter than the remaining metal part. It helps eliminate the sharpness of the corners and increases the aesthetic appearance of the outcome.
Wipe bending
Wipe bending is another method used in bending sheets of metal edges. The process depends on the wipe die. For example, the sheet metal must be properly pushed onto the wipe die. The wipe is also responsible for the determination of the sheet metal’s bend inner radius.
What Materials Are Good For Sheet Metal Bending Processes?
These are some of the best materials used in various types of bending in sheet metal. Carbon steel is the most commonly used material among the above-mentioned materials.
Carbon steel
Carbon steel is one of the most flexible and strong materials to be used in a sheet metal operation. As this material is recyclable, hence it will help to reduce the carbon footprints as well.
Aluminum
Aluminum is largely used in lightweight applications. Special care must be taken in bending the aluminum material to avoid collapsing or cracking in the corners of the material.
Stainless steel
Stainless steel comes to one’s mind first when the resulting product needs to have the properties of robustness and better metal strength. Stainless steel also requires the use of a high-power sheet metal bending machine to shape the product.
Titanium
Titanium is corrosion-resistant material and high strength material – much suitable for sheet metal bending techniques. If your product is medical or sports equipment, then the most preferred material from your list should be titanium.
Copper
Cost is the strongest anti-corrosive material yet the cheapest. High precision sheet metal bending is obtained from copper. Copper is a tested material being used widely by many metal bending industries throughout various applications.
3 tips For Bending Sheet Metal
While manufacturing a metal product, the sheet metal bending rules must be kept in mind and be proficient in multiple processes to avoid failure. It can become difficult if the proper measures are not taken.
To ensure that your metal bending goes perfectly, these are some tips to be considered in bending sheet metal. Making sure to check each of the 3 tips will help you achieve a product with greater efficiency.
Make use of bend allowance
Bend allowance is a property of the metal to the extent it can be bent. We recommend you make bend allowance calculations that determine the length of the sheet required to make a bend of a specific angle and radius. Keeping the bend allowance and bending force into consideration during a manufacturing process will help you to obtain a neater product outcome. It will also help you achieve an accurately flattened manufacturing model.
Use Heat for thick/heavy Bends
Some metals are likely to break or crack when bending is made from the force. Such metals require the use of heat instead of force to make the desired bend in sheet metal. Hot forming and Annealing are two technical terms when it comes to bending with heat. Annealing helps to soften a metal – more malleability. While hot bending is simply the use of heat till the metal gets red and then using force to bend it. These tricks majorly reduce the risk of metal braking and cracking.
Don’t bend to a Sharp Internal Corner
Sharp internal corner bending means greater internal stress. Even if the metal is ductile and malleable, it may end up cracking. This issue can be majorly avoided if you consider the radius of the bending tool. You should slowly work back and forth between your bend lines until the sheet metal is bent to the desired angle. An eye should be kept on the inside bending radius, which must be equal to the forming sheet metal thickness. An example can be the way, if you are bending a sheet thickness that is 3 mm thick, then the inside bend radius should also be 3 mm. The same is the case with bending angle, which means that it must not be greater than the overall thickness of the metal sheet.
7 Things to Consider About Sheet Metal Bending in the Design Process
Bending is one of the most popular metal fabrication processes. This involves the manipulation of flat sheets of steel, aluminum, brass, and other metals by pressing and bending to obtain new usable shapes.
Engineers can turn sheet metals into highly functional pieces through the bending process. Bending is a crucial design process in metal fabrication. A metal sheet is made to take shape of the final product and that’s why this is a vital process. Below are the things to consider about sheet metal bending;
Bending Direction
When bending sheet metal, you should ensure that it’s perpendicular to the metal fiber direction. Bending sheet metal parallel to the fiber metal direction results in cracks at the bend. Also, the bending strength reduces and the sheet metal may break easily.
Minimum Flange Width
In your drawings, the flange width should not go under four times the thickness of the metal. This is to avoid the occurrence of marks during the metal fabrication process.
Bending Clearance
When bending sheet metal, a particular gap should be secured to avoid bending failure that is often caused by interference. When there is no gap between two bend edges, interference ought to happen. A clearance of at least 0.2mm can effectively avoid this bending interference.
Bending Height
Sheet metal bending height must be at least two times the metal thickness plus radius. When the bending height is too low, sheet metal might be deformed and twisted. This makes it challenging to obtain ideal dimensional accuracy and the preferred shape.
Also, bending beveled edges leads to bend distortion. This occurs when the bending height is too small.
Minimum Sheet Metal Bending Radius
The minimum radius of bend sheet metal depends on the tools used and the bending process. More ductile metal sheet tends to have a smaller inner bed radius. To maintain maximum strength, the bending radius should exceed the minimum bending radius of the sheet metal. Each metal has its standard minimum bending radius.
A big metal radius might not translate to better results. Having a too large bend radius might translate to a larger bending spring back. Also, it might prove challenging to achieve a perfect bending height and angle. It’s ideal if the bend radius is reasonable.
While most metal fabricators emphasize on a zero bending radius, it’s not always the best idea. Zero radius causes external breaking or cracking or metal. Also, it reduces bending strength, especially in hard sheet metal materials.
Minimum Hole Size for Sheet Metal
The thumb rule for sheet metal design is that the hole’s diameter should be equal or larger than the thickness of the metal. When drawing holes, it’s vital to remember that too small holes that might break the tool. Small-size punches are used for small sheet metal holes. The lesser the size of the punch, the higher the chances of breaking.
Choice of Material
Different materials can withstand specific bending processes. Generally, metal sheets of a regular thickness of 1.3 mm can withstand almost anything. They are easy to bend and maintain their maximum strength. However, not all materials behave the same. Thicker steel sheet metal might behave utterly differently from a similar-sized aluminum sheet metal. Your results depend on the metal fabrication experts you choose for the task.
The Neutral Axis and Considerations for Sheet Metal Rolling Process
When a metal steel plate is a cold bent, the inside surface of the bend is compressed and the outside surface of the bend is stretched. Somewhere in between lies the neutral axis which is a line in the steel that is neither compressed nor stretched. The tighter the radius the bigger the opposing forces become – bringing up the concept of minimal radius.
The location of this line is key to determining the blank or developed length for bent pieces. Blank or developed length is the amount of material required to make the desired bend. Usually, the neutral axis is slightly closer to the inside of the bend. For practical purposes, it is located at half of the thickness for thickness values less than 0.08 inches with a minimal error.
Based on experience, the general equation to find the distance from the inside face to the neutral axis is as follows:
To calculate the blank length of a bent piece, we first have to determine the position of the neutral axis. The developed length of the piece will be the developed length of its neutral axis – in the equation below, we are referring to AB.
Another way to determine this blank length is using the following equation and tables.
We can find K1 in the following table :
And we can find K2 from the following table:
