Press Fundamentals

To expand or establish a stamping operation, businesses must choose the right press for the job

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According to economic forecasts, the global metal stamping market is poised to grow in the coming years. Depending on the research firm analyzing its potential, CAGR estimates for the industry range from 3.7 to 5 percent. Businesses operating in a variety of industries – from automotive and industrial machinery to consumer electronics, aerospace and defense – are understandably readying their operations to take advantage of market opportunities. New businesses, as well, will enter the space to share in the market’s growth potential.

To properly expand their stamping capacity and capabilities, business owners must fully understand the equipment options that are available to them. Primarily, those options include mechanical presses, hydraulic presses and servo presses. But which press should a business choose? The answer, of course, depends on several factors, but the following rules generally apply:

  • A traditional mechanical press can achieve the highest production speeds, especially for flatter, progressive die work.
  • A hydraulic press offers versatility and outstanding ability for deep-drawing operations.
  • A mechanical servo press offers versatility and higher production speeds, even higher than mechanical presses in certain applications.
Stamtec’s GTX two-point straight side press is designed for stamping relatively long, narrow parts at high single-stroking rates or in continuous mode, using either blanks or coil stock. 

Traditional mechanical presses

Traditional mechanical press can achieve the greatest production speeds, especially when running relatively flat parts with simpler, shallower forming requirements. These parts are typically processed from coil stock through a progressive or transfer die. Many automotive, appliance and hardware parts fall into this category. Characteristics of a traditional mechanical press are:

  • fixed stroke length (although variable stroke length presses are available from some press manufacturers)
  • special slide motions (i.e., link motions) are available, specific to a particular press
  • variable slide velocity, although slide velocity profile within a single cycle of the press is fixed
  • working energy is dependent on flywheel mass and speed
  • full press capacity near bottom dead center of stroke
  • simplicity of setup and operation
  • in general, the highest stroking speeds
  • high accuracy and repeatability
  • relatively low initial cost

Hydraulic presses

Hydraulic presses do not generally achieve the high cycling speeds of similar-sized mechanical presses, but they do offer greater versatility with a variable stroke length, die space and pressure. Hydraulic presses are often the best choice when producing parts with deep, complex forms that require a lot of material flow and are not dependent on production speed.

Parts such as tanks, cylinders and bowl shapes as well as parts that require a “dwell” at the bottom of the stroke (including plastics) are often run on hydraulic presses. Characteristics of a typical hydraulic press are:

  • variable stroke length
  • slide motion and position control throughout the range of the stroke length
  • variable slide velocity, even within a single cycle of the press (typically configured as fast approach, slow press, fast return)
  • full working energy at any speed
  • full press capacity at any point in the stroke
  • adjustability of all the above
  • in general, slower than a traditional mechanical or mechanical servo press
  • in general, lower accuracy and repeatability than a mechanical or servo press
  • relatively low initial cost
The range of stroke profiles and parts that can be achieved with the stamping process is greatly expanded with the use of a servo press.

Mechanical servo presses

Mechanical servo presses offer much of the versatility of hydraulic presses at production speeds often approaching traditional mechanical presses. The stroke, slide motion, slide position and speed are programmable to allow many different combinations that can work with a variety of dies, part types and production speeds. Characteristics of a mechanical servo press (where a flywheel, clutch and brake are replaced by high-capacity motors) are:

  • variable stroke profiles
  • precise slide motion and position control throughout the range of the stroke length
  • variable, precise slide velocity control, even within a single cycle of the press stroke
  • full working energy, even at very slow stroking speed
  • programmability of all the above
  • full press capacity near bottom dead center of stroke
  • in general, greater cycle speeds than a hydraulic press, in many cases approaching or exceeding the speeds of a traditional mechanical press
  • high accuracy and repeatability
  • relatively high initial cost

Proprietary press controls specifically designed for the servo press achieve a variety of stroke and slide movement profiles while supplying full working energy even at low speeds. Preprogrammed profiles can include:

  • traditional crank
  • coinin
  • drawin
  • in-die heating
  • feeder
  • fine blanking
  • pulse (extruding)
  • swing forging
  • pendulu

Unique profiles can also be created by the user to meet their specific needs.

The advantage

With full working energy at any speed and the ability to dwell anywhere in the stroke, mechanical servo presses are taking a big bite out of the drawn and formed parts pie. However, servos are still mechanical presses at heart and, therefore, achieve full tonnage capacity near the bottom of the stroke. In many cases, hydraulic presses with full tonnage and energy throughout the entire stroke still have the advantage.

Watch the video to see a recent full press line installation provided by Stamtec and its team of engineers.

While traditional mechanical presses are still the fastest, they lack flexibility. And while hydraulic presses allow more versatility in drawing and forming of complex parts, they’re slow. Mechanical servo presses have many of the best characteristics of both.

Beyond the characteristics of each type of press, remember that in the end, the chosen equipment needs to align with the business’ goals, budget constraints and operational requirements. Taking the time to thoroughly research and analyze the options will contribute to a more successful and sustainable investment. Also remember that consultations with industry experts, engineers and professionals, such as those at Stamtec, can provide valuable insights that will ultimately lead to an informed decision.

Stamtec Inc.

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