Offset bending tools
Z-bend geometry, press-brake insert systems, progressive offset forming and manufacturer-specific limits.
Tags: tooling, sheet-metal, bending, press-brakes
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For a 3 mm rise modeled with two sharp opposite bends in a zero-thickness centerline, a 45° inclined segment is 4.243 mm long and projects 3.000 mm horizontally. At 30°, it is 6.000 mm long and projects 5.196 mm. Equal step height can require different clearance. Actual blank development also needs bend radius, sheet thickness and bend allowance.
Definition and geometry
WILA’s press-brake Z tooling makes two opposite bends in one stroke, including closely spaced bends. Replaceable inserts fit a separate holder. WILA Z-bending
Specify offset height at its drawing datums, along with angle, inside radius and bend spacing.
Wilson Tool describes changing the offset height with one air-bending tool set when the angle can vary. Wilson Tool, air bending with offset tools
Press-brake tool systems
Mate's December 14, 2016 article describes replaceable inserts and holders for its Trumpf-Wila, European precision and bevel-tang systems. It states interchangeability among its own offset-holder styles. The article lists 26 standard sizes and 90°, 140°, 150° and 160° insert angles, plus flattening inserts. Those are the manufacturer's catalog choices at that date; they do not establish cross-brand mounting compatibility or a current complete assortment. Mate Z-offset inserts
Check the holder’s tang, seating and retention against the machine. Insert geometry determines the form.
WILA describes its tools as using an upward sweeping action for air forming and bottoming, and distinguishes horizontal offset designs. Its largest standard Z15 example corresponds to roughly V20 and up to 3 mm mild steel within the tool's load limit. For its stated 90° forming approach, WILA relates V openings of 6–8 thicknesses to an offset around four thicknesses; an offset equal to one thickness calls for more open angles. These are scoped WILA relationships, not universal limits for all offset-forming systems. WILA tool principles and FAQ
Progressive forming on punching machines
TRUMPF's punching-tools catalog distinguishes two alternatives to a full-length press-brake stroke. Its 0699200 stepping tool forms straight or curved steps by nibbling. The 0699368 roller offsetting tool forms continuously and requires the machine's roller-technology option. Both are designed for a specific sheet thickness. TRUMPF catalog, printed pp. 58–59
| Catalog example | Listed height | Selected conditions |
|---|---|---|
| Stepping tool 0699200 | H = 1–5 mm | Listed section angle 45°; H2 example permits sheet thickness 1–2 mm |
| Roller offsetting tool 0699368 | H = 1.5 or 3.0 mm | Listed section angle 45°; minimum travel radius 25 mm |
For the roller example, listed thickness ranges are 0.8–2.5 mm aluminum, 0.8–2.0 mm steel and 0.8–1.5 mm stainless steel. These ranges describe the catalog offering, not one thickness-independent setup. The 25 mm travel radius concerns the tool path, not a bend's inside radius. TRUMPF roller offsetting entry, printed p. 59
Process comparison: a progressive tool follows the feature's length over successive contacts; a press-brake pair forms the engaged length in one stroke. Their travel, support, access and dimensional constraints therefore differ. A catalog height common to both does not make their processes interchangeable.
Forming force and capacity
Mate states that press-brake offset forming requires more than twice the tonnage of a single bend. This is its application guidance, not a calibrated multiplier covering every material, angle and contact condition. Mate offset-forming load discussion
As engineering interpretation, two bends occurring together do not justify simply doubling an unrelated air-bending estimate. Material strength, thickness, contact geometry, forming method and engaged length affect demand. Punch, die, insert holder and machine ratings describe available capacity, each with its own conditions. Force per unit length and total machine force are different quantities.
Worked geometry: equal height, different angle
Original idealized calculation. Represent two equal, opposite sharp bends by a zero-thickness centerline with a straight inclined segment of length L. Let θ be its inclination to the parallel outer segments, H its rise and X its horizontal projection:
H = L sin θ X = L cos θ
For H = 3 mm:
θ = 45°: L = 3 / sin 45° = 4.243 mm; X = 3.000 mm
θ = 30°: L = 3 / sin 30° = 6.000 mm; X = 5.196 mm
The same rise can therefore occupy different horizontal distances. This model excludes bend radii, thickness, springback and tool contact. L is the ideal inclined centerline segment, not a production blank allowance or an insert dimension; θ is not necessarily the catalog's included-angle convention.
Coverage and source dates
Mate's cited article explicitly carries December 14, 2016. The TRUMPF catalog carries identifier 1798794_EN_202204_S; that identifier is retained without inferring an issue date. No technical publication dates were established for the WILA or Wilson pages.
These sources cover selected press-brake and punching-tool arrangements. They do not establish a universal minimum offset, tonnage, bend radius, blank development, achievable tolerance or mounting interface. Tool specifications and general forming relationships do not establish a particular shop's installed equipment or approved production settings.