What is Metal Punching: Process, Benefits and Best Practices
Sheet metal punching is a forming process in which sheet metal is pressed into a shape using a punch press. The process involves the use of a hand-held press or a punch press to remove material from the sheet metal using a die.
The sheet metal parts produced take the shape of the die through a cutting process known as shearing. The surrounding sheet metal is scrap and can be recycled to produce more sheet metal coils for the metal punching process.
By: Tuling Engineering Team 8-minute read
Tuling sheet metal punching facilities are capable of producing accurate, bulk-manufactured parts with custom dies and tooling facilities. This blog is a resource by Tuling Engineering Team.
Metal punching includes many processes including bending, embossing, flanging, and coining. Metal punching can produce sheet metal parts of various shapes, designs and sizes and is not limited by choice of material
Metal Punching Process
The sheet metal punching process falls under two categories.
Cutting
Cutting is a type of metal punching process that almost always produces sheet metal parts by cutting them out of the sheet metal blank.
In this sheet metal punching process, the large sheet metal coils are loaded and the following stages occur
- Shearing: The initial sheet metal rolls are sheared to a workable size and prepared for sheet metal punching. This involves shearing or cutting the sheet metal with large stamping blades.
- Blanking: This is the actual sheet metal punching process where sheet metal is cut around the perimeter of a shape to produce the workpiece or the final product.Depending on the complexity of sheet metal parts, subsequent metal punching operations may be required to produce the final product.
- Punching: Punching is another type of shearing operation that produces a hole in the sheet metal. The removed piece is called a slug.
Hole punching or die punching is where the workpiece takes the final shape. A die can be used with a punch press to cut an exact shape from the sheet metal.
You can also use custom tooling and dies to produce non-standard shapes. The punch applies a force through a die, building stresses on the edges and cutting the blank.
Forming
Forming is another type of metal punching where instead of cutting dies, forming dies are utilized. Forming dies press on the sheet metal and exerts a force impressing a form on the sheet metal.
Forming is mostly used for larger parts and works by forcing sheet metal into a die cavity using a punch. This process is called drawing and many formed features can be made with drawing.
Applications of Sheet Metal Punching
Sheet metal punching is used in various applications including the automotive industry, cookware, aerospace industry, and electronics.
- Car panels: Sheet metal punching is used to make car body panels such as fenders and hoods.
- Enclosures: Many electronic device enclosures are made by metal fabrication techniques involving sheet metal punching.
- Cladding: Cladding on buildings and structures utilizes metal punching aluminum into required sizes and shapes for perfect alignment and seamlessness.
- HVAC Systems: Almost all components of an HVAC system use sheet metal punching. Air ducts, ventilation components, and air conditioner units are made from metal punching.
Choosing the Right Punch Press
There are many types of machines capable of metal punching.
Mechanical Press
This uses force generated from weight and mechanical gearings to press or form the sheet metal. The sheet metal forms in the desired shape under the force of the punching tools.
Hydraulic Press
Hydraulic press is another kind of mechanical press that uses pressure generated from fluids or oil in a sealed environment to transfer force to the workpiece to shear it.
CNC Punching
CNC machines are modern punch press machines for custom tooling. They have NC controller and digitized control for fast and quicker punching operations.
You can program multiple punching tools and generate a punching sequence for your tooling. CNC punching also allows you to enter the machine setup for more control like choosing how much force to exert.
Which Metals Can be Punch Pressed
Punch press requires the metal specimen to have a combination of material properties. The most important is malleability. A metal should be shaped without cracking and its strength, which is its internal structural integrity under repeated force.
Considering this, sheet metal punching can work with numerous metals. The type of metal depends on your product and final environment. Tuling punch presses can work with steel, iron, aluminum, copper, mild steel and its alloys.
Other Considerations Regarding Your Punching Projects
Punch presses do not provide the best edge finish because the shear cutting the sheet metal for custom-shaped holes do not produce sharp edges. Usually, a finish is necessary on large formed parts to reach the desired shape. Blanking and punching, however, produce sharp edges by cutting the surrounding material. The punched-out piece is usually of high quality and results in clean punches.
For optimum punching, there are a few other considerations
- Production volume: High-volume production runs require metals that can withstand progressive stamping.
- Thickness: Choosing a metal for punching means drawing out the optimal thickness for quicker and optimum production cycles.
- Surface finish: softer metals like copper and aluminum produce better surface finish
Industries Where Metal Punching Mostly Used
If you plan to work with metal stamping and pressing, you should consider the industry where the part will be utilized.
Medical Industry
Medical applications require biocompatible and sterile-friendly metals. Perforated trays, catheter components and pins are examples of metal punch pressed products that are made from stainless steel or titanium.
Automotive Industry
The automotive industry uses metal-punched parts from small mounts and brackets to large fenders and body panels. These applications require a small weight-to-strength ratio and generally use aluminum and aluminized steel.
Aerospace Industry
The aerospace industry requires punched metal parts for skin panels, bulkheads, and doors. The most prominent use is to stamp holes for rivets in panels. These applications typically use aluminum alloys and titanium.
Best Practices for the Punching Process
Metal punching requires careful design and checks. Metal punching is done on sheets with an average material thickness between 0.001 inch to 0.625 inches and this requires the design to be optimized so that there are no unnecessary cuts and tears.
You can improve your metal punching design considerations using these tips
Bend Radius
In metal punching sheet metal is bent, so the internal bend radius must be greater than or equal to the sheet material thickness.
Round Hole and Slot
For punch operators like slots which use a cutting punch face, the diameter must be at least equal to the sheet thickness.
Tolerance
Because the material will be sheared or fractured, having an acceptable tolerance is crucial for the crack to not propagate into the material. This depends on the material you are using.
Metal
Your choice of metal for sheet metal punching will greatly affect your part’s strength, bending, and forming levels. This also influences the number of dies that will be used for example some metals require compound dies and others progressive dies depending on the design.
Sheet Metal Punching Alternatives
There are a few other metal-cutting processes that can be used instead of sheet metal punching. Laser cutting is a better alternative to metal punching and results in better and more accurate outer perimeter.
Laser cutting is expensive and mostly reserved for one off parts or in bulk manufacturing laser cutting is used for high-accuracy pieces. You can learn more about our laser-cutting techniques here.
Laser cutting has high speed when working with thin metal sheets but as the sheets get thicker, the speed decreases, whereas a punch applies much greater force than required and can produce the same amount of parts in lesser time while working with different metals.
Tuling Metal Punching Service
At Tuling we have a host of metal punching machines from CNC punch presses to hand-powered punching presses. We offer quick evaluation and design expertise for your metal punching order and partner with companies in the EU and North America.
