Progressive stamping

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Progressive (punch and blanking) die with strip and punchings ProgressiveDieToyota-strip-scrap.jpg
Progressive (punch and blanking) die with strip and punchings

Progressive Die is a metalworking method that can encompass punching, coining, bending and several other ways of modifying metal raw material, combined with an automatic feeding system.

Contents

The feeding system pushes a strip of metal (as it unrolls from a coil) through all of the stations of a progressive stamping die. [1] Each station performs one or more operations until a finished part is made. The final station is a cutoff operation, which separates the finished part from the carrying web. The carrying web, along with metal that is punched away in previous operations, is treated as scrap metal. Both are cut away, knocked down (or out of the dies) and then ejected from the die set, and in mass production are often transferred to scrap bins via underground scrap material conveyor belts.

The progressive stamping die is placed into a reciprocating stamping press. As the press moves up, the top die moves with it, which allows the material to feed. When the press moves down, the die closes and performs the stamping operation. With each stroke of the press, a completed part is removed from the die.

Since additional work is done in each "station" of the die, it is important that the strip be advanced very precisely so that it aligns within a few thousandths of an inch as it moves from station to station. Bullet shaped or conical "pilots" enter previously pierced round holes in the strip to assure this alignment since the feeding mechanism usually cannot provide the necessary precision in feed length.

Progressive stamping can also be produced on transfer presses. These are presses that transfer the components from one station to the next with the use of mechanical "fingers". [2] For mass production of stamped parts which do require complicated in-press operations, it is always advisable to use a progressive press. One of the advantages of this type of press is the production cycle time. Depending upon the part, productions can easily run well over 800 parts/minute. One of the disadvantages of this type of press is that it is not suitable for high precision deep drawing which is when the depth of the stamping exceeds the diameter of the part. When necessary, this process is performed upon a transfer press, which run at slower speeds, and rely on the mechanical fingers to hold the component in place during the entire forming cycle. In the case of the progressive press, only part of the forming cycle can be guided by spring-loaded sleeves or similar, which result in concentricity and ovality issues and non uniform material thickness. Other disadvantages of progressive presses compared to transfer presses are: increased raw material input required to transfer parts, tools are much more expensive because they are made in blocks with very little independent regulation per station; impossibility to perform processes in the press that require the part leave the strip (example beading, necking, flange curling, thread rolling, rotary stamping etc.). [3]

The dies are usually made of tool steel to withstand the high shock loading involved, retain the necessary sharp cutting edge, and resist the abrasive forces involved. [4]

The cost is determined by the number of features, which determine what tooling will need to be used. Engineers keep the features as simple as possible to keep the cost of tooling to a minimum. Features that are close together produce a problem because it may not provide enough clearance for the punch, which could result in another station. It can also be problematic to have narrow cuts and protrusions.

Applications

A representative example of the product of a progressive die is the lid of a beverage can. The pull tab is made in one progressive stamping process and the lid & assembly is made in another, the pull tab simultaneously feeding at a right angle into the lid & assembly process. Also various car brake calipers have plates that are bent into shape, possibly cut too using these methods. [5]

See also

Related Research Articles

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<span class="mw-page-title-main">Perforation</span> (Making) a small hole in a thin material

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<span class="mw-page-title-main">Sheet metal</span> Metal formed into thin, flat pieces

Sheet metal is metal formed into thin, flat pieces, usually by an industrial process. Sheet metal is one of the fundamental forms used in metalworking, and it can be cut and bent into a variety of shapes.

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<span class="mw-page-title-main">Punch press</span>

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<span class="mw-page-title-main">Punching</span> Metal forming process to create a hole

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<span class="mw-page-title-main">Stamping press</span>

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<span class="mw-page-title-main">Deep drawing</span>

Deep drawing is a sheet metal forming process in which a sheet metal blank is radially drawn into a forming die by the mechanical action of a punch. It is thus a shape transformation process with material retention. The process is considered "deep" drawing when the depth of the drawn part exceeds its diameter. This is achieved by redrawing the part through a series of dies.

Hemming is a technology used in the automotive industry to join inner and outer closure panels together. It is the process of bending/folding the flange of the outer panel over the inner one. The accuracy of the operation significantly affects the appearance of the car’s outer surfaces and is therefore a critical factor in the final quality of a finished vehicle.

<span class="mw-page-title-main">Photochemical machining</span> Process that uses chemicals to machine sheet metal

Photochemical machining (PCM), also known as photochemical milling or photo etching, is a chemical milling process used to fabricate sheet metal components using a photoresist and etchants to corrosively machine away selected areas. This process emerged in the 1960s as an offshoot of the printed circuit board industry. Photo etching can produce highly complex parts with very fine detail accurately and economically.

<span class="mw-page-title-main">Blanking and piercing</span> Shearing processes

Blanking and piercing are shearing processes in which a punch and die are used to produce parts from coil or sheet stock. Blanking produces the outside features of the component, while piercing produces internal holes or shapes. The web is created after multiple components have been produced and is considered scrap material. The "slugs" produced by piercing internal features are also considered scrap. The terms "piercing" and "punching" can be used interchangeably.

<span class="mw-page-title-main">Roll forming</span> Continuous bending of a long strip of sheet metal into a desired cross-section

Roll forming, also spelled roll-forming or rollforming, is a type of rolling involving the continuous bending of a long strip of sheet metal into a desired cross-section. The strip passes through sets of rolls mounted on consecutive stands, each set performing only an incremental part of the bend, until the desired cross-section (profile) is obtained. Roll forming is ideal for producing constant-profile parts with long lengths and in large quantities.

A punching machine is a machine tool for punching and embossing flat sheet-materials to produce form-features needed as mechanical element and/or to extend static stability of a sheet section.

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.

References

  1. DOE Workshop on Research and Development Needs for Bipolar Plates for PEM Fuel Cell Technologies (14 February 2017). "Bipolar Plate Cost and Issues at High Production Rate" (PDF).
  2. Occupational Safety and Health Administration (11 February 2022). "1910.217 - Mechanical power presses".
  3. BlechMal GmbH (11 February 2022). "Bleche nach Mass" (in German).
  4. Johnson, Carl-Johan (August 2021). "DESIGN KNOWLEDGE REUSE IN DESIGN OF PROGRESSIVE STAMPING TOOLS: A QUALITATIVE STUDY" (PDF). INTERNATIONAL CONFERENCE ON ENGINEERING DESIGN, ICED21: 1053–1062. Retrieved 1 August 2023.
  5. Thomas Engineering (17 November 2015). "Progressive Metal Stamping".