Heading Tonnage

Heading tonnage is the maximum compressive force a progressive header can apply at the die face during the forming stroke. It is the single most important specification when evaluating whether a machine can produce a given part, and it is always expressed in metric tons (ton) or kilonewtons (kN).

1 metric ton of forming force ≈ 9.81 kN

What Determines the Required Tonnage?

The force required to cold form a part depends on four primary factors:

1. Material Flow Stress

Every metal resists plastic deformation with a characteristic force per unit area — the flow stress (σ_f), expressed in N/mm² or MPa. Higher strength materials require greater forming force for the same geometry. Wire rated at 600 N/mm² tensile strength — the standard for Manzoni machine specifications — requires substantially more force than 300 N/mm² wire.

2. Part Cross-Section and Volume

The larger the cross-section being formed, the greater the total force required. Heading tonnage scales approximately with the area of the punch face contacting the material.

3. Operation Type

Different operations have different force requirements:

• Upset (open): lower force, material flows freely outward
• Upset (enclosed): highest force — material must fill a confined cavity completely
• Forward extrusion: moderate force, depends on area reduction
• Backward extrusion: high force, especially for deep holes

4. Number of Simultaneous Stations

On a progressive header, all active stations form simultaneously in a single stroke. The total heading tonnage is the sum of the forces across all stations. If five stations are each requiring 50 ton, the machine must deliver at least 250 ton — with a safety margin.

Manzoni Machine Range

Series	Max Wire Ø	Heading Tonnage
MA	8 mm	70 ton
MB	11 mm	100 ton
MC	20 mm	200 ton
ME	33 mm	650 ton
MF	42 mm	700 ton

Under-Tonnage vs Over-Tonnage

Under-tonnage (machine too small for the part): the machine stalls, slows, or the part is not fully formed. Tooling can be damaged. The motor struggles to re-supply energy between strokes.

Over-tonnage (machine far too large): the machine works below its capacity, which is generally not harmful but represents unnecessary capital investment and higher energy consumption per part.

Correct sizing means selecting the smallest machine series that covers the required tonnage with a reasonable safety margin (typically 20–30% headroom).

The Role of the Vector Motor

On Manzoni machines, the Double Encoder Vector Motor with Torque Control provides real-time torque monitoring throughout the forming stroke. This allows the machine to detect over-load conditions before damage occurs, and to supply power only when needed — resulting in energy savings of up to 50% compared to conventional motors with fixed-speed drives.