A machine that forms or cuts sheet metal by driving a die downward with stored flywheel energy.
01 / Definition
What a Power Press is
A power press forms or cuts sheet metal by driving a die down onto it. A motor spins a heavy flywheel continuously, storing rotational energy. When the operator trips the clutch, that stored energy is coupled to the crankshaft, which converts rotation into the up-and-down travel of the ram. The brake then stops the crank at top dead centre, ready for the next stroke.
The important point is that the press does not make its force evenly through the stroke. Rated tonnage is available only near the bottom, typically in the last few millimetres of travel, because that is where the crank geometry gives maximum mechanical advantage. A press asked to deliver full tonnage higher up the stroke is being overloaded even though the tonnage gauge looks fine, and that is how crankshafts and frames crack.
Also called
02 / Anatomy
The parts that matter
The components a technician reaches for when this machine stops working.
Flywheel
Stores the energy for the stroke. Its inertia, not the motor rating, is what delivers the blow.
Clutch and brake
Couples the flywheel to the crank and stops it at top dead centre. The single most safety-critical assembly on the machine.
Crankshaft and connecting rod
Convert rotation into ram travel and set the stroke length and the tonnage curve.
Ram and slide adjustment
Carries the upper die, with adjustment to set shut height for different tooling.
Gibs
Guide the ram and hold it square. Worn gibs let the ram rock, which ruins die life before it ruins parts.
Safety systems
Two-hand controls, light curtains, interlocked guards — plus the brake monitor that proves stopping time is still within limits.
03 / Applications
Where it is used
Blanking, piercing, bending and deep drawing of sheet components for automotive, appliance and electrical parts.
04 / Failure modes
How it fails
What actually goes wrong on Indian shop floors, and what each fault looks like to the operator.
FM_01
Brake stopping time lengthening
Worn linings or failing air valves. Safety-critical, because every guard distance was calculated from the original stopping time.
FM_02
Double stroking
Clutch not releasing cleanly, so the press makes a second unwanted stroke. Immediate danger to the operator.
FM_03
Ram rocking or off-square
Worn gibs or uneven die loading, producing burrs on one side and uneven die wear.
FM_04
Frame or crank cracking
From repeated overload, off-centre loading, or running full tonnage too high in the stroke.
FM_05
Snapthrough shock on blanking
The sudden release as the slug breaks through, which hammers the whole machine on thick material.
05 / Onsite
What our technician checks
A methodical path to root cause, not a scattergun of part swaps.
- 01Measure brake stopping time and compare it against the figure the guard distances were set from
- 02Test the clutch for clean engagement and release, and check for any tendency to double stroke
- 03Check gib clearance and ram parallelism to the bolster across the full width
- 04Verify shut height and die height against the tooling, and confirm the work is centred on the bolster
- 05Inspect the frame and crank area for cracks, especially around the tie rods and at radii
- 06Confirm every safety device functions: two-hand control, light curtain, interlocks and brake monitor
06 / Get it fixed
Related services
The MachineryFix services that cover this equipment.
07 / Questions
Frequently asked questions
Why does my press sometimes make two strokes?+
The clutch is not releasing cleanly — worn friction material, a sticking valve or low air pressure. Double stroking is one of the most dangerous faults a press can have, because the operator is reaching in. Take the press out of service until it is fixed.
Does the press give full tonnage anywhere in the stroke?+
No. Rated tonnage is available only near the bottom of the stroke, where the crank geometry gives maximum advantage. Asking for full tonnage higher up overloads the crank and frame even though nothing on the gauge looks wrong.
Why does brake stopping time matter so much?+
Because every safety distance — where the light curtain sits, how far the guard stands off — was calculated from the stopping time when the press was commissioned. As linings wear, stopping time grows and those distances quietly stop being adequate.
What causes burrs on one side of the part only?+
The ram is not landing square, from worn gibs or from the die being loaded off centre on the bolster. It wears the die unevenly too, so correcting ram parallelism saves tooling as well as part quality.
Written & reviewed by MachineryFix — last reviewed — questions? Call +91 70133 33007