The impact of stroke length on press productivity is often not well understood in factories. Press operators frequently state reasons without explaining, “This task can only be done on this mechanical press” or “We cannot run this task as fast as it should be.” Although there are many reasons, most of the time the cause lies in the integrity of the pressure and the stroke length.

Four Reasons for the Shortest Possible Stroke

Ram Position-Crank Angle Diagram Figure 1 — Ram Position-Crank Angle Diagram

  1. Minimize wasted time — Unnecessary ram movement leads to time and energy wastage. Shorter strokes reduce friction losses and slide wear.
  2. Minimize dynamic forces — Moving the ram over a shorter distance within a specific period reduces dynamic forces and fatigue effects within the press body and drive system.
  3. More precise shaping — The shaping time is inversely proportional to the stroke length. As seen in Figure 1, for a 300 mm stroke (gray), the ram intersects the material thickness line at 173° of crank angle, while for a 100 mm stroke (blue), it intersects at 165°. This means a press with a 100 mm stroke has an 8° longer shaping time, equivalent to 38 milliseconds at 35 strokes/min — a 114% increase in shaping time.
  4. Longer tool life — Shorter strokes reduce the speed at which die punches make contact with the workpiece. At 1.26mm above BDC, a 300mm stroke press has ram speed of 130 mm/s, while a 100mm stroke press has 80 mm/s.

Ram Position-Speed Graph 300mm Figure 2 — 300mm stroke

Ram Position-Speed Graph 100mm Figure 3 — 100mm stroke

In mechanical presses, the optimal stroke is the shortest possible stroke achievable.

Benefits of Short Stroke Operation

  1. Less stamp breakage in the mold
  2. Reduced need for tool sharpening
  3. Improved shaping quality
  4. Extended press life
  5. Less vibration
  6. Reduced noise

Common Causes of Suboptimal Pressing Operations

Improper use of equipment:

  • Running a job with the available equipment rather than the right equipment
  • Purchasing equipment that is not suitable by management decision

Significant changes in working conditions:

  • Changes in production volumes or batch sizes
  • Narrowing of product specifications or part tolerances

Outdated equipment:

  • Lack of newer technologies
  • Lack of automation or spare parts

Loss of precision:

  • Damages from operational errors
  • Material fatigue, improper repairs, machine wear

Emrah Demirezen — Metal Forming Specialist, Press Designer
info@demirezenengineering.com