Sheet metal punching is a versatile and efficient process that can be used to create a wide variety of products. Whether you are a beginner or an experienced manufacturer, this article will help you to understand the basics of sheet metal punching and to produce high-quality parts safely and efficiently.
This guide will explain the different types of punching operations, the advantages and disadvantages, the equipment used, and the safety guidelines that should be followed. Let’s get started by defining the process.
What is sheet metal punching?
Sheet metal punching is a manufacturing process that uses a punch and dies to create holes and other features in sheet metal. The punch is a tool pressed into the sheet metal, while the die supports the sheet metal during the punching process. The hole or feature is created by the punch pressing into the sheet metal and cutting through it.
Sheet metal punching is a very versatile process that can be used to create a wide variety of holes and features in sheet metal. It is a fast and efficient process, and it can be used to create high-quality holes and features.
Sheet metal punching is used in a wide variety of industries, including automotive, aerospace, electronics, and appliances. It is a critical process in the manufacturing of many products, such as car bodies, aircraft components, and electronic devices.
Key features of sheet metal punching operations
Punch and die: The punch tool presses into the sheet metal that is resting on the die cavity below. This shears the material, creating the desired hole or shape.
Press machine: Applying high force is required for the punching operation, so hydraulic or mechanical presses providing tons of pressure are used.
Fast turnout: The punch strokes up and down quickly, allowing fast production. Modern punch presses operate at 100+ strokes per minute.
Tool and die sets: A range of standardized punches and dies are used to produce different hole sizes, louvers, slots, notches, and custom shapes.
Burr creation: The shearing action creates a raised burr edge along the top side of the hole which is removed via deburring processes.
Accuracy and precision: Modern CNC (COMPUTER NUMERICAL CONTROL) turret punch presses index sheet location and tool position for precision, repetitive hole patterns.
High tonnage capacity: Punching thick material like steel plate requires presses rated for maximum tonnage to cut and form without failing.
What is sheet metal punching used for?
Sheet metal punching is a fast and efficient process that can be used to create high-quality holes and features. It is also an inexpensive process, making it a cost-effective option for many manufacturing applications.
Here are some of the things that sheet metal punching is used for:
- Holes: Punching round, square, slotted, and other shaped holes for fasteners, wiring, tubing, mounting, etc.
- Louvers: Punching patterns of slots or holes for ventilation, screens, and aesthetic effects
- Cutouts: Forming larger openings for handles, windows, access panels, or removing scrap skeletons
- Blank separation: Punching out internal cutouts leaves the desired blank profile needed for further forming
- Shapes: Punches produce ovals, rectangles, stars, letters, and custom profiles
- Embossing: Forming raised or recessed detailed shapes and lettering for labels, logos, buttons, and decorations
- Piercing: Cleanly piercing holes for plumbing, trucks, trailers, electronic chassis, enclosures, and panels
- Ductwork: Punching mounting holes and inlet/outlet openings in HVAC duct components
- Audio equipment: Creating speaker openings, control panels, equipment racks, and component chassis
- Drainage holes: Punching patterns of drain holes in motor housings, machinery guards, electronic enclosures, etc.
- Welding: Mating surfaces for welding and other joining processes
Industries that use sheet metal punching
Sheet metal punching is an essential process in the manufacturing of many products. It is a versatile process that can be used in a wide variety of industries, including automotive, aerospace, electronics, and appliances.
Here are some examples of products that are made using sheet metal punching:
- Car bodies
- Aircraft components
- Electronic devices
- Appliances
- Furniture
- Medical devices
- Construction materials
Advantages and disadvantages of sheet metal punching
Sheet metal punching is a very versatile and efficient manufacturing process. It has several advantages, such as speed, accuracy, repeatability, and cost. However, it is important to be aware of the disadvantages of sheet metal punching, such as its noise, dust, and safety concerns. Let’s look into it.
Advantages of sheet metal punching
Speed and efficiency: It is a fast and efficient process. It can be used to create a large number of parts in a short amount of time.
Versatility: A wide range of available punches and dies accommodate many shapes and sizes.
Accuracy: CNC punch presses with automatic tool changers provide great accuracy. It can be used to create holes and features with very tight tolerances.
Repeatability: It is a very repeatable process. It can be either completely or semi-automated. It can be used to create identical parts repeatedly.
Cost: Punch and die tooling are inexpensive compared to other processes. It is a cost-effective way to create high-quality products.
Minimal secondary processing: Sheared edges typically do not need additional finishing work.
Low waste: Precision punching maximizes material utilization with little wasted scrap.
Wide material range: Can punch up to 1” thick mild steel as well as aluminum, stainless, and other metals.
Low operating labor: Automated punch press operation requires minimal direct labor.
Disadvantages of sheet metal punching
Noise: Punching creates repetitive, loud striking noise. This can be a problem if the punching is being done in a noisy environment.
Dust and metal shavings: Can create a lot of dust and metal shavings. This can be a problem if the punching is not done in a well-ventilated area.
Safety: Can be a dangerous process if not done properly. It is important to follow safety guidelines when operating sheet metal punching equipment.
Burr creation: Requires deburring of top-hole edges, adding a secondary step, in some cases.
Upfront costs: Significant investment required to get punch press equipment.
Skill required: Experienced programmers are needed to optimize punch sequences.
Occasional jamming: Material misfeeds or tool breakage can jam up the process. It is not common, but it may happen, mostly due to human error.
Different types of sheet metal punching
The type of sheet metal punching operation that is used depends on the desired outcome. Modern CNC punch presses with automatic tool changers can easily and rapidly switch between these processes for high mix production. The main types of sheet metal punching are:
Piercing: This is the process of creating a hole in sheet metal without removing any material. The punch is pressed into the sheet metal and cuts through it, but the material is not removed. Piercing is typically used to create holes for rivets, screws, and other fasteners.
Blanking: This is the process of creating a hole in sheet metal and removing the material. The punch is pressed into the sheet metal and cuts through it, and the material is removed from the sheet metal. Blanking is typically used to create individual parts, such as washers and spacers or to cut-out shapes to create new blank profiles for further bending and forming.
Notching: This is the process of removing a small piece of material from the edge of sheet metal. Notching is typically used to create notches for tabs and other features.
Slotting: This is the process of cutting a long, narrow slot in sheet metal. Slotting is typically used to create slots for electrical wiring, plumbing pipes, and other components.
Perforating: This is the process of creating a pattern of holes in sheet metal. Punching multiple mini holes in patterns for decorative effects and drainage. Perforating is typically used to create decorative features, such as louvres and perforations.
Embossing: Forming raised and/or recessed detailed shapes and lettering into the metal surface.
Lancing: Making a partial inward cut that still leaves material connected to the sheet. Used to create tabs, standoffs, etc.
Slitting: Cutting straight slit lines into sheet metal to facilitate bending.
Stamping: Using punch dies with the desired imprint shape to stamp information like part numbers.
Nibbling: Using a punch and die set to progressively “nibble” away material to cut irregular shapes.
The process for sheet metal punching
The process for sheet metal punching can vary depending on the type of punching operation being performed and the tool or machine being used. However, the general process is as follows:
- Design: The locations and dimensions of all required holes, cutouts, and forms are specified in the engineering drawings
- Program: CNC punch press programming defines the sequence of tools and operations. Modern CAD/CAM software aids programming
- Set up: The required punch and die sets are installed in the punch press turret in the programmed sequence. Proper clamping, lubrication, and clearance is ensured
- Load: The flat sheet metal stock is loaded onto the punch bed and aligned using back gauges and stops. Clamping secures the material
- Adjust: Punch speed, stroke depth, and other parameters are set and adjusted for the material thickness and tooling
- Run: The automated punch press cycles, using the programmed sequence of tools to punch all features in the sheets per the design
- Inspect: Punched parts are checked for accuracy of hole size, location, and any defects
- Deburr: The rough top edge burrs created by punching are removed by deburring processes. Clean parts are produced
- Unload: Finished punched parts are unloaded and the skeleton scrap stripped out.
Sheet metal punching is a relatively simple process, but it is important to follow safety guidelines and use the correct techniques to ensure a safe and successful operation. Proper tooling prep, precise part fixturing, and process monitoring helps achieve consistently accurate punched components.
In the following video you will be able to watch a sheet punching machine in action.
Equipment used for sheet metal punching
Properly equipping a punching station with the right machinery, tooling, controls, and material handling flow is essential for cost-effective hole punching production. The essential equipment is the punch press. Besides that, other equipment is needed as well.
The punch press
The most common type of equipment used for sheet metal punching is the punch press. A punch press is a machine that uses a punch and die to create holes and other features in sheet metal.
A punch is a tool pressed into the sheet metal, while the die supports the sheet metal during the punching process. The hole or feature is created by the punch pressing into the sheet metal and cutting through it.
There are two main types of punch presses: mechanical and hydraulic. Mechanical punch presses use a flywheel to store energy, which is then used to power the punch. Hydraulic punch presses use hydraulic fluid to power the punch. They both include programmable controls and high tonnage capacity.
The rest of the equipment
The key pieces of equipment used for punching sheet metal include:
Punch and die sets: The male punch and female die provide the shaped cutting profile for holes, louvers, forms, etc.
Tool holders: Standardized tool holders securely grip punches and dies in the press turrets and beds.
Sheet supports: Steel tables or support arms position sheet metal blanks for accurate punch alignment.
Back gauges: Adjustable fences precisely locate and guide sheet metal placement for repetitive accuracy.
Clamps: Hold down clamps like vises or toggle clamps fix sheet metal in position during punching.
Tool lubrication: Either oil or grease is automatically applied to punch and die sets to reduce wear.
Scrap removal: Skeleton cutouts are stripped out of the punched sheet via hands or scrap conveyors.
Deburring system: Sheared hole edges are smoothed by chambering, rolling, or abrasive deburring machines.
Programmable controls: CNC allows programming punch patterns and integrates with CAD/CAM software.
Safety equipment: Guards, awareness barriers, E-stops ensure operator safety around the high-force presses.
Safety guidelines for sheet metal punching
Strict adherence to punch press safety protocols, training, and procedures prevents serious crush and amputation injuries. Here are some recommended safety guidelines for sheet metal punching operations:
Machine guarding: All accessible areas of the punch press must have guards and barriers to prevent accidental contact with moving parts. Guards should be interlocked with power supply.
E-stop buttons: Emergency stop buttons must be clearly identified, easily accessible, and immediately halt operation when activated.
Lockout/Tagout: Lockout and tagout procedures must be followed before any maintenance, service, tool changes, or inspections.
Part ejection: Parts should eject safely into a container and away from the operator. Kickers and knockouts aid safe part clearing. Be careful when removing the sheet metal from the punching machine. The sharp edges of the hole can cause cuts.
Gloves banned: Workers should never wear gloves due to risks of them becoming caught in the press.
Press feeding aids: Using support arms, step ladders, or ergonomic lift assists protects workers from overstretching or back injury when loading sheets.
Noise abatement: Require hearing protection as punching generates very high noise levels exceeding 85db.
Punch and die maintenance: Tooling must be properly secured, aligned, and replaced when excessively worn.
Cleanliness: Keep the punching area clean and free of debris.
Operator training: All workers must receive extensive training in safe press operation, setup, and maintenance.
Operator readiness: Never operate a punching machine while under the influence of alcohol or drugs.
Safety inspections: Conduct regular safety inspections of punching machines and work areas. Have a written safety plan in place for sheet metal punching operations.
OSHA compliance: Adhere to all applicable OSHA regulations 1910.217 and 1910.212.
Sheet metal punching: Last thoughts
Sheet metal punching is a versatile and efficient manufacturing process that can be used to create a wide variety of products. Nowadays, there is equipment available that makes this process quite simple and safe.
For decades we have been helping companies to set up sheet metal punching operations. Feel free to reach out to us at your earliest convenience to get started.
