Blanking is a manufacturing process where a punch and die are used to remove blanks in preparation for processing and finishing. This cutting process is done by applying a shearing force to a material sheet. In blanking, the removed piece is the desired workpiece and is referred to as a blank. The process can be used to cut out almost any 2D shape and is commonly used for simple workpieces with simple geometry. Due to the shearing force, the pieces often need a finishing to smooth out burrs.
Blanking process. Blanking workpiece.
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The machinery consists of a blanking press, sheet metal, blanking punch, and blanking die. The dies used can be a generic shape or customized for a specific design but instead of having a cavity, it has a cutout in the shape of the desired workpiece. The sheet metal is placed over the die and below the punch tool (typically 10-20% of the material thickness clearance), which is also in the desired shape of the workpiece. The tools are made from a steel or carbide and pare hydraulically powered. The hydraulic press drives the punch downwards at a high speed into the sheet, the metal quickly bends and then fractures. The created blank falls into the gap of the die.
Types of Blanking
Fine or Precision blanking- Produces metal pieces with tight tolerances of +/- 0.0003. The blank is sheared from the sheet using three separate forces. The first is a downward holding force applied to the top of the sheet, the second force is applied under the sheet, opposite the punch. The two forces act together to reduce the bending of the sheet for flatter blanks. The third force is the blanking punch impacting the sheet and shearing the blank into the die opening. This technique produces a part with a flatter part with smoother edges so higher quality parts that do not require finishing can be produced. The clearance is around 0.001 inches and the blanking is performed at slower speeds. The additional equipment and tooling makes this process more expensive so it is better suited for high volume productions.
Fine or precision blanking. Image Credit: custompartsnet.com
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.
When selecting a blanking service provider there are several specifications to consider.
Who will the material? The customer or the service company?
Does the service company custom-produce dies?
Do they offer discounts for large volume orders? Much of the cost associated with blanking is setting up and calibrating the equipment.
Does the service company provide additional finishing services such as removing burrs, stamping, and polishing?
This video compares several metal stamping processes.
Video Credit: harveyvogel
Making medals, computer parts, precision tools, automotive parts, cutlery, and power tools.
Todd, Robert H., Dell K. Allen, and Leo Alting. Manufacturing Processes Reference Guide. New York: Industrial, 1994. Print.