There are several machining techniques that product manufacturers use to improve the functionality and overall appearance of metal parts. Sheet metal bending is a standard method for improving the quality and appearance of your sheet metal products.
In this article you will learn more about the principle of sheet metal bending, its purpose and how to make the most of it. You will also learn about the types of sheet metal bending and the advantages and disadvantages of the process.
What is sheet metal bending?
Sheet metal bending is a metal forming technology that involves rolling or bending the edges of sheet metal over each other. You will need to fold the edges of the sheet to create a two-layer area. The sheets have different thicknesses and are generally divided into thick and thin sheets.
The thick plate category includes thicker metals than the thin plate category, making them less suitable for hemming processes. It is important to always ensure the accuracy of the sheet metal bending process, as this affects the appearance and surface quality of the part.
Purpose of Sheet Metal Bending
The main objective of sheet metal bending is to improve the structural strength and durability of the sheet metal. This makes the sheet metal stronger and resistant to defects such as cracking, twisting and bending. Folding the edge of a sheet of metal over itself makes it stiffer and thicker, ensuring it doesn't deform under pressure.
Another purpose of sheet metal hemming is to create a neatly hemmed edge on end pieces. You can align the folded edge with the curves of the surrounding material for an ideal, polished look. The automotive industry uses this sheet metal processing technique in applications where a product's appearance is critical to its overall value.
The main objective of bending sheet metal is therefore the aesthetic and functional benefits.
How does sheet metal bending work?
The process of folding or folding the edges of a sheet of metal onto itself to form a clean, finished edge is done using specific tools and steps. However, these factors depend on the type of bending your parts require. The following are the typical steps of sheet metal bending.
1. Tools required
Here are some of the standard tools needed for hemming.
- sheet
- Tool for bending sheet metal or press brake
- Flattening tool (e.g. pliers, press or roller)
- Finishing tool (e.g. hammer or sandpaper)
- Quality inspection tools (e.g. micrometers)
2. Preparation
To carry out the sheet metal bending process successfully, make sure that the sheet is flat and free of impurities that could hinder the process. Then set the bending tool to the desired bending width and angle. Place the sheet metal into the bending tool and assemble the edge to be bent using the bending tool.
3. Hemming method
The folding tool or press brake bends the edge of the sheet metal at a 90° angle and folds the originally folded edge back into the sheet metal to form a seam. Then staple the hem to ensure a secure, comfortable fit. You can also use finishing tools to improve uneven or rough edges.
There are two standard processes for processing sheet metal. That includes:
Conventional folding
The traditional die bending method uses a punch and die to create a folded edge on the edge of metal parts. Typically, the die must be positioned under the sheet metal while the metal is bent over the die to form the punch-folded edge.
rolled hems
In this sheet metal bending process, the edge of the sheet metal is gently folded onto itself using a folding roller. This method is ideal for parts that require a softer, more moderate bend or for thin sheets.
4. Inspection
After completing the bending process, you should inspect the finished part for damage or deformation. There are several tools such as: Use a micrometer or caliper to confirm that the hem is the correct width and thickness. This allows you to make any necessary corrections to ensure the finished product meets any requirements or standards.
4 Types of Sheet Metal Bending
This section discusses typical types of sheet metal bends.
1. Open hems
Open hems often have soft, curved outer edges and an air bubble in the folds. They are best suited for handles and many other frequently touched applications and hand parts. Open hems provide best results with a material thickness of 0.040 to 0.125 inches and a minimum flat length of four times the material thickness.
Bend the sheets at a 30 to 45 degree angle to create open seams. Then, place a washer and smooth the material with the washer. Standard gap sizes are 0.060, 0.090, 0.125, 0.187, and 0.250 inches.
2. Closed hems
Closed hems or tight hems are standard because they are easy to do. A closed hem is a completely flush hem where the sheet metal is rolled or folded over itself. However, there may be some disadvantages to the materials. This type of sheet metal seam is very compatible with materials with a thickness of 0.040 to 0.125 inches.
Do not attempt to form sheets thicker than 2-3 mm (0.125 in) as they may break. Most importantly, make sure the flat length of the fold is at least four times the thickness of the material to prevent it from breaking.
You can also deform the sheet metal 90 degrees to form closed seams and then use a press brake to flatten the material onto itself. As a general rule, closed seams are not ideal for aluminum as it is very susceptible to breaking and cracking.
3. Teardrop Hems
Teardrop hemming involves bending the edge of a sheet of metal 90º and then rolling it into a teardrop shape using a hemming tool. You can use hanging stitching for materials that do not have the flexibility required for closed seams.
This sheath provides a strong and durable edge that guarantees excellent resistance to deformation. Teardrop sheaths are ideal for many brittle metals such as aluminum. However, teardrop hems are expensive because they require skilled labor and sophisticated tools to create.
4. Rolled hems
Manufacturers use rolled hems to eliminate raw sheet metal edges on metal parts. Product manufacturers and designers often use laminated hems for molded edges, cabinets, electronics, and doors. This sheath offers an attractive appearance and a safe product to handle.
First fold the edge of the metal piece 90º and then roll it over the sheet to create a smooth, rounded edge. You can use a folding or rolling machine to create a rolled hem. Laminated hemming provides a fine, flawless finish and improves the durability and physical properties of sheet metal products.
Different Bending Processes for Sheet Metal Parts
Product manufacturers typically use two standard methods for bending sheet metal back on itself in a variety of applications. Below are the processes used in sheet metal bending:
Die Bending Process
The die bending process is perfect for high volume molding operations. This process involves bending the flange along its length using a die and press. Generally, the sheathing itself is made by forming, in which the flange is formed with a hemming tool after the drawing and trimming operations are completed.
Bending the formed flange involves several steps, which are normally determined by the respective opening angles of the flange. This process is best suited for producing flat, non-complex panels. Additionally, setting up a production tool for hemming is somewhat expensive but offers low cycle times.
Roller hemming process
The roller hemming process is usually performed with a hemming roller. An industrial robot guides the folding roll while folding the edges, ensuring greater efficiency. This process was originally developed to improve the flexibility of bending operations. The roller moves along the edges of the sheet in several steps to bend it to the desired angles. The roller hemming process can be divided into several pre-hemming and final hemming processes.
However, you can change the orientation of the sheet metal to reduce bending roll travel while increasing cycle time. Roll hemming technology is flexible and suitable for small and large quantity production. Most importantly, the necessary tools cost significantly less than those required for the sheath molding process. However, cycle times are longer than in the die bending process.
Advantages of Sheet Metal Bending
Here are some of the general benefits of sheet metal sheathing technology:
Greater strength and rigidity
Metal bending strengthens the edge of the metal sheets used in parts, making them more resistant to deformations such as warping and bending. Folding the edge of the metal back on itself will make it stronger and thicker. This means it is not susceptible to deformation under pressure.
Improved appearance
This machining technique provides parts with clean, aesthetically pleasing edges. Additionally, you can adjust the folded edge to fit the curves of the surrounding material, creating a smooth, shiny appearance.
Better functionality
Manufacturers across industries often use hemming to create a secure, solid edge to improve the functionality of various metal products. Bending sheet metal improves the functionality of metal parts, especially in the automotive industry, where many components must withstand extreme stress and wear.
Greater resistance to damage
Sheet metal bending provides metal parts with excellent resistance to damage and wear caused by chemicals and other corrosive compounds, as well as adverse environmental or weather conditions.
Limitations when bending sheet metal
Although most manufacturers and product designers embrace sheet metal sheathing for its advantages, you should also be aware of the following disadvantages of this technique:
Late
The sheet metal bending technique is time-consuming, especially when processing large or complex metal parts. The drawing, tool setting, and bending steps may take longer.
Requires skilled workers
Sometimes it is necessary to hire qualified workers to carry out the bending process efficiently and with the best results. The folding tool operator must have sufficient training and experience to operate the equipment and fully understand variations in the bending technique.
May cause deformation or damage to sheet metal
Hemming is a critical process that, if not done correctly, can deform or damage the sheet metal. Complications such as insufficient or excessive bending can lead to deformation of the sheet metal and cause structural problems.
Considerations and tips for hemming sheet metal
Here are some tips and suggestions that can provide the most effective solutions for your hemming needs:
Material selection
The choice of sheet material should be based on your expectations for the final parts, including durability, strength and corrosion resistance. However, different materials such as magnesium and aluminum may require different bending methods.
The right alignment
Another important factor that must be taken into consideration in the hemming process is the correct orientation of the sheet in the hemming tool. This ensures that the bending tool edges the sheet in the desired direction. Make sure to position the sheet in the middle and line it up with the fold to create an even, even seam.
Selection of folding method
Make sure to perform the folding technique carefully and correctly to avoid bending or over-folding the sheet. Most importantly, always close the bending tool slowly to avoid damage or defects to the sheet metal.
Finishing option available
Consider how you can improve the functionality and appearance of the final pieces after hemming. With basic finishing tools like sandpaper and a hammer, you can easily smooth out rough, jagged edges.
Quality control
Perform quality checks at every step of the bending process to ensure the final part meets all requirements. For quality control, you can use testing equipment such as a gauge or micrometer to confirm that the hem is the correct width and thickness.
Concluding
This article explained in detail the sheet metal bending process and everything you need to know about the technique. Therefore, you must be able to identify the types of bends and the methods that manufacturers use to create a bend at the edge of a sheet metal and find the right method for your metal parts.
Common questions
What are the common application areas for sheet metal bending?
The sheet metal bending process is widely used to produce metal parts with complex shapes and structures in industries such as heating, automotive, metal furniture, aerospace and electronics.
What is the difference between sheet metal bending and hemming?
Although these processes involve rolling sheet metal edges onto themselves, there are differences. Bending involves rolling the edge of sheet metal so that it is flush with itself, while bending involves joining the edges of two materials together to form a solid connection.
Is sheet metal bending expensive?
The cost of sheet metal bending varies depending on the material used, project complexity, production volume and sheet thickness. However, this process is cheaper than other metal bending or forming processes such as casting, forging or stamping. It does not require expensive tools like the listed procedures.
