Sheet punching. Image Credit: Anping Guangsenyuan Wire Mesh Co., Ltd.
Punching services provide a process that creates a hole through a workpiece. Punching is a very economical method of making holes in sheet or strip of metal. Holes of various sizes and shapes can be made quickly and simultaneously. In punching, the removed material is scap while in blanking, the removed material is a useful workpiece.
Punch Press. Video Credit: prattzc Punching process. Image Credit: Custompartnet.com
The machinery consists of a mechanical punch press. The press consists of the frame, motor, ram, die posts, bolster, and bed. A punch is mounted to the ram and the die is mounted to the bolster plate. The punch is advanced through the die and into the workpiece to create a hole via shearing. This process can be set and controlled via computer, also known as a Computer Numerical Control (CNC), which uses coordinates to place the hole in the correct location. The die is manufactured by die makers according to the design specifications for the workpiece being created. The work speed is controlled by the operator and the machine does not function on a fixed rhythm. The extra material drops through the die into a container and a conveyor system can be installed to the machine to remove the waste from the punch press.
Punch press components. Image Credit:Busch
There are two processes available for punching services: Sheet punching and coil punching.
Sheet punching is used for rectangular pieces as well as highly complex shapes. A sheet-fed punching press can be used to create unique pieces obtained from the same sheet but it produces 10%- 20% waste since the full sheet can't be used. Blanks can be sheared to size to minimize waste, but the cut blanks cost more money. It is used for small production lines (from 1 to 50 pieces). Sheet-fed punching machines require constant operator presence for loading and unloading the workpieces or the system can have robotized loading and unloading, although that requires a greater investment.
Coil punching is used for high volume production with two sides corresponding to the sides of the coil. Mass production can be used for pieces that are different from each other but are part of the same family, such as door frames which are produced as single pieces with a similar punch but different sizes. The machine works metal strips from coils that come from service centers with the right width which reduces the waste to 1% at most. Coil punching machines produce the workpieces automatically and an operator is only needed to load the coils and unload pallets. They have a 20%-30% lower hourly cost than a sheet-fed punching machine. The production time is also less because the material does not need to be loaded or unloaded.
Coil punching machine. Image Credit: Dalcos.
The material is usually a sheet but it may also be in rolls.
Sheet Metal- Metal components can be formed using a punch. The punch is usually the upper member of the complete die assembly and is mounted on the slide or in a die set for alignment (except in the inverted die).
Plastic- Plastic pieces are usually scrap materials, such as tails, molding flash and slugs from bottles, which need to be removed from the workpiece.
Paper, board, PP- or PE- foil- Paper and related products such as those used for labels can be self-adhesive or plastic laminated.
The punch can come in a variety of sizes and shapes. Three common shapes include a circle, oval, and square but shapes can be customized based on design.
Punch shapes. Image Credit: Manufacturing Process Reference
Punching presses can also create patterns and cuts in the sheet metal as well as designs along the edges. These processes are known as perforating and notching respectively.
Perforating and notching. Image Credit: custompartsnet.com
Punching is used for a wide variety of industries including manufacturing, food and beverage, and healthcare. The process allows for the final piece to have a contoured shape which includes cut and rounded corners. Due to the high flexibility of punching, the process is used to create labels for food and drinks, cosmetics, medicine and detergent. Punching can also be used to create novelties such as credit cards, playing cards, passports, and glued notepads.
Todd, Robert H., Dell K. Allen, and Leo Alting. Manufacturing Processes Reference Guide. New York: Industrial, 1994. Print.