What Are the Different Press Brake Bending Methods?

What Is Air Bending and How Does It Work?

Air bending does not bring the sheet into full contact with the die because the bend angle is determined by the Y-axis penetration depth of the punch, not by the geometry of the die walls. 

The sheet contacts only the punch tip and the two V-die shoulders — the center of the sheet floats freely above the die cavity floor.

The mechanism works in three stages:

First, the punch descends and contacts the sheet at the punch tip and V-die shoulder edges, leaving the sheet bottom unsupported.

Second, the punch continues downward to a programmed depth, bending the sheet to the target angle without pressing it against the die cavity walls.

Third, the ram retracts and the sheet springs back slightly from the bent position, which the CNC system compensates by programming slightly beyond the target angle.

The practical advantages of this method are significant.A single set of 88°/86° tooling can produce bend angles from 90° to 175° by adjusting only the ram depth.Force requirements are the lowest of all three methods, reducing wear on tooling and the machine frame.

Accuracy is the challenge: results depend on material consistency, and springback variation across a batch of material with inconsistent thickness will produce angular variation across parts.

Modern CNC press brakes use laser angle measurement systems to provide real-time bending angle data during the stroke, enabling automatic springback correction without operator intervention.

What Is Bottoming and When Should You Use It?

Bottoming reduces springback because the ram forces the sheet to conform fully to the die walls through three-point-to-three-point-plus-surface contact, imprinting the die geometry directly onto the workpiece. Angles in bottoming are defined by die geometry, not by ram penetration depth — a fundamentally different control mechanism from air bending.

The practical consequence is higher angular accuracy and reduced springback compared to air bending.This makes bottoming the appropriate choice when air bending’s springback variation cannot be compensated by CNC correction alone — particularly with thinner gauges of stainless steel or hard aluminum alloys where springback variation is pronounced.

The trade-off is force: bottoming requires 1.5–2x the bending force of air bending, which increases load on the machine frame and tooling with every cycle.One firm limitation: each target angle requires a dedicated die. You cannot produce a range of angles from a single die the way air bending allows.

What Is Coining and When Is It Required?

Coining delivers zero springback because extremely high pressure imprints the exact die shape into the workpiece through cold flow at the microscopic level, fracturing and rearranging the metal lattice structure and thinning the compressed areas permanently.

Coining forces — 10–30x higher than air bending — are sufficient to disrupt the internal stress structure of the metal entirely, eliminating the elastic recovery that causes springback in other methods.

What this looks like mechanically: the punch descends with enough force to cause cold flow rather than elastic-plastic deformation. Metal lattices fracture and rearrange at the bend zone. The material thins in compressed areas. The result is maximum precision and zero springback — the finished angle equals the die angle without any compensation required.The cost of this precision is significant.

Coining imposes severe wear on both tooling and the machine frame, substantially reducing their service life compared to air bending or bottoming.It is therefore limited to ultra-precise, small-part applications where zero springback is an absolute requirement and the volume justifies the accelerated tooling replacement cost.

The three bending methods represent a fundamental trade-off principle: precision in press brake bending always costs more in one of three currencies — bending force, tooling investment, or machine lifespan. Coining maximizes precision by spending all three.