What is Sheet Metal Stamping Process

sheet metal stampingToday we are surrounded by sheet metal objects like automotive parts, Car body, Disk-Brake, Gaskets, Door/ window hardware, Electronic appliances components, and cabinets, coins,  Cooking or serving utensils i.e. plate, spoons, glasses, etc. Almost every sheet metal product is made by Metal Stamping.

What is  Sheet Metal  Stamping Process?

As per Wikipedia

Sheet Metal stamping  (also known as pressing) is the process of placing flat sheet metal in either blank or coil form into a stamping press where a tool and die surface forms the metal into a net shape.

In simple words, we can understand it as

Sheet Metal Stamping or Cold Stamping is a Manufacturing process to produce the desired product from a flat metal sheet by a stamping press. Sheet Metal Stamping Process is also known as cold Stamping Process.

When the requirement of components exceeds 50,000 pieces, the product design engineer should consider the possibility to manufacture through sheet metal stamping due to its high degree of possible precision, high productivity, utilization of unskilled manpower and a resultant reduction in weight and cost.

7 Huge Advantages of Sheet Metal Stamping

The metal stamping Process is a modern & advanced technique of manufacturing. Sheet Metal Stamping process has the following  benefits or advantages :

  1. Less weight of stamped components.
  2. High Volume – Low-cost Production.
  3. High Efficiency of labour ( Upto 25000 to 40000 stamped parts per 8-hour shift ).
  4. A high degree of possible precision.
  5. Low-cost material.
  6. Uniformity of parts.
  7. Both complex and simple components such as washers, tanks, a cage of ball bearing & car body parts can be produced very easily.

All the above benefits have made the metal stamping a  prime manufacturing process in various industries such as automotive, electrical & electronics, aircraft and many more.

Metal Stamping Equipments

Sheet Metal Stamping Process is impossible without below-mentioned machines :

  1. Press Machine / Power Press
  2. Press Tools / Dies

Note : Lot of people think that Press Machine and Press Tool is a same thing. Here I must clear that Press machine and press tools both are different things. Press Tools are replaceable attachment of press Machines. The same press machine may produce different products  but press tools are designed to produce a specific product.

Press Machine or Power press

A Press Machine or Power Press is a modern-day hammer that generates and applies pressure to a press tool to deform metal sheet into a net desired shape.

Image source: indiamart.com

Classification of Power Press

Power presses are classified in various ways. They may be classified according to:

  • Source of Power: Mechanical and Hydraulic Press
  • Type of frame: Open frame and closed frame press
  • No. of slides: Single, double and triple action press

Source of Power: Mechanical and Hydraulic Press

The two main sources of power for applying the force to slide of press are Mechanical Press and Hydraulic Press.

Mechanical Press Vs Hydraulic Press

In Mechanical Presses, the linear movement of RAM is obtained by a heavy fly-wheel. The heavy flywheel continuously absorbs the energy from an electric motor and delivers it to ram and hence to the workpiece steadily. Mechanical presses have the following advantages over hydraulic presses:

  • Lower Maintenance Cost
  • Lower Capital cost
  • Run faster

In Hydraulic Presses, the linear movement of RAM is obtained by a hydraulic system. Hydraulic presses are a large cylinder and piston arrangement coupled to a hydraulic pump. Piston and press ram is one unit. The ram is moved by oil pressure on the piston in the cylinder. Hydraulic Presses have several advantages:

  • Easier to operate
  • Most Versatile
  • Tonnage capacity adjustment from zero to maximum
  • Constant pressure throughout the stroke
  • More powerful than mechanical presses
  • Safer than mechanical press, it will stop to a pressure setting.

Note: Hydraulic presses are slower than mechanical presses.

Type of frame: Open frame and closed frame press

Open frame Vs Closed frame Press

Due to their construction, there are two types of presses: the open frame and closed frame presses. Open frame presses are less strong and less rigid so they are useful for smaller work operations. These presses are available up to 200-tonne capacity and 90 to 140 strokes per minute.

Closed frame presses are highly strong, balanced and rigid presses for use in bigger work operations. These presses are available up to 3000-tonne capacity.

Note : Closed frame presses often have inclined press frame which allow removal of stamped part by gravity.

No. of slides: Single, double and triple action press

Single, Double & Triple action Press

According to the no. of slides, there are single, double and triple action presses.

A single-action press has only one ram which acts against a fixed bed.

A Double action press has two slides moving in the same direction to the fixed bed. Both the slides are assembled one in another ( Outer ram and inner ram). These presses are used in deep drawing operations.

A Triple action press has two slides moving in the same direction against the fixed bed as in double-action press and the third slide moves in an upward direction through the fixed bed.

Press Tools / Dies

As per Wikipedia

Press tools are commonly used in hydraulic, pneumatic, and mechanical presses to produce the sheet metal components in large volumes. Generally, press tools are categorized by the types of operation performed using the tool, such as blanking, piercing, bending, forming, forging, trimming, etc. The press tool will also be specified as a blanking tool, piercing tool, bending tool etc.

In simple words, Press Tools can be defined as

Press tool ( commonly known as die/ dies) is a assembly of die, punch, punch plate , punch back plate, stripper plate etc. to produce sheet metal components/ stamped parts. Press Tools have two assembled in two sections

  1. Upper section / Upper shoe
  2. Lower section /Lower shoe

Metal stamping press tools

Types of Press Tools / Dies

Dies may be classified according to the type of operation/process and method of operation.

Type of Press Operation or Sheet Metal Stamping Processes

The sheet metal Stamping may be divided into two following groups :

  1. Cutting Operations tools
  2. Forming Operations tools

Cutting Operations dies

 These dies are used to cut the metal sheet. In cutting operations, the work-piece is stressed beyond it’s ultimate strength. The stresses cause in the metal by the applied forces will be the shearing stresses. Cutting Operation includes the following main operations:

  1. Blanking: Stamping Operation of cutting a flat shape from sheet metal.
  2. Punching /Piercing: Cutting operation by which various shape holes are made in sheet metal.
  3. Notching: Operation by which Metal pieces are cut from edge of a sheet, plank or strip.
  4. Trimming: Cutting unwanted excess material from the periphery of the previously formed component.
  5. Shaving: Operation of removing uneven and rough edges to obtain accurate dimensions of the component.
  6. Slitting: Stamping process of making uncompleted holes in components.

Forming Operations dies

 These die changes the appearance or shape of blank without removing any stock. In the forming operations, the work-piece is stressed below its ultimate strength. Forming Operation includes the following important operations:

  1. Bending: Process in which flat sheet metal or strip is uniformly strained around a linear axis to make an arch.
  2. Drawing: The stamping process of forming a flat metal sheet into a hollow shape by pressing of punch into a die cavity.
  3. Squeezing: Application of compressive forces by the metal flows to all portion of the die cavity to form desired net shape.

Method Of Operations

According to these criteria, Press Tools may be classified as follows:

  1. Simple Dies
  2. Compound Dies
  3. Combination Dies
  4. Progressive Dies
  5. Transfer Dies
  6. Multiple Dies

Simple Dies

Single action press tool performs a single operation for each stroke. This operation may be any cutting or forming operation such as Bending, punching, Blanking or notching, etc.

Compound Dies

In compound press tools, there is two or more cutting operation performed at one station for each stroke. Like washer is made by one stroke by blanking and punching operation simultaneously at one station.

Combination Dies

Combination press tools are those tools by which one cutting operation is performed with one or more forming operation. Unlike compound dies where only cutting operations performed for each stroke at one station.

Progressive Dies

A Progressive tool or follow on tool consisting of a series of stations. At each station a single cutting or forming operation performed on a workpiece during the stroke. Between Stroke, the Metal sheet strip moved to next station by the feeder action. A Finish workpiece is produced at each stroke of the press. Progressive tools are highly efficient stamping dies as they performed multiple operations in one stroke.

Transfer Dies

In transfer dies the already cut blanks are fed mechanically from one station to another to produce a complete stamped part.

Multiple Dies

Multiple or gang press tools produce two or more workpieces at a single station. Generally, those workpieces are smaller in size.

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