Press brake back gauge

01

Choose the axes and the accuracy each one holds

Cincinnati's 5-axis back gauge retrofit gives independent control of two front-to-back axes (X1, X2), two left-to-right axes (Z1, Z2) and one up-down axis (R). It lists a horizontal range of 0–24 in at 1,200 IPM with ±0.001 in positioning accuracy and repeatability; a vertical (R) range of 8 in at 300 IPM with ±0.005 in accuracy and ±0.003 in repeatability; and lateral (Z) positioning at 3,000 IPM with ±0.015 in accuracy and repeatability. [1]

Selmach explains that automated back gauges arrived in the 1970s moving on the X axis only, and that today each axis, up to six, can have its own DC motor travelling on ballscrew spindles, with axis sets such as X, X-R and X-R-Z1-Z2. Its X-axis back gauge has a 1,000 mm range and a maximum travel speed of 330 mm/s. [2] Cincinnati states that its gauge uses closed-loop servo drives and is designed for material up to 1/4 in thick that one or two operators can handle, with thicker parts up to 150 lb processed with reasonable care. [1]

Editorial calculation: 1,200 IPM is 1,200 × 25.4 / 60 = 508 mm/s, and ±0.001 in is ±0.025 mm, ±0.005 in is ±0.127 mm and ±0.015 in is ±0.381 mm. Accuracy is quoted per axis, so the lateral (Z) and height (R) figures are looser than the X figure in the same listing; ask for each axis separately rather than one number for the gauge. [1]

Give the supplier the press brake make, model, length and control, the axes required, X stroke and the longest flange to gauge, the thickest and heaviest part, the finger types and number, required accuracy and repeatability per axis, guarding, and the control's gauge and collision functions.

02

Plan retract and finger-to-die clearance

Delem's DA-66T reference manual (version V0311) states that the back gauge retract starts when the beam is pinching the sheet. A 'wait for retract' setting decides whether the beam keeps moving through the clamping point while the gauge retracts, or stops there until the retract is complete and then moves on. [3]

The same manual computes a minimum X position for each die where an R axis is fitted, to prevent finger-to-die collision: X-safe = FS + ½V, where FS is the flat section behind the V groove and V the opening, plus 0.5 mm extra. The die safety zone is SZ = X-safe + SD, where SD is a safety distance defined by the machine supplier. When the gauge must move to a new Z position from inside that zone, it first moves to an 'intermediate X'; when X must move inside the zone, R can first go to an 'intermediate R'. [3]

Delem also describes 'lay-on' levels for fingers on a moving R axis, which change the X and R axis positions so the sheet rests on a different finger step while the gauge position stays the same, and a per-line precision option that chooses the back stop position for the highest accuracy or for a closing dimension, at the cost of longer production time. [3]

Editorial calculation: with an assumed die of V = 16 mm and FS = 5 mm, X-safe = 5 + 8 + 0.5 = 13.5 mm, so flanges shorter than that cannot be gauged against fingers that drop to die height without changing die or finger level. The die values are an example; use your tooling drawings. [3]

03

Match the back gauge configuration to the press brake

Salvagnini's B3 electric press brake page offers its back gauges in six different types, from 4 to 9 axes, and states that all axes slide on linear guides. The same page lists the machine data the back gauge must work within: table lengths of 2,040 to 4,250 mm across the 80/2000 to 170/4250 models, throat depths of 350 to 520 mm, a maximum approach and return speed of 250 mm/s (180 mm/s on the 170/3000XL) and a bending speed of 15 mm/s. Its optional safety system, a laser transmitter with an HD camera, can reduce the speed-change position to as little as 2 mm from the sheet. [4]

Compare the axis count and travel offered here with the 5-axis retrofit figures, the finger and axis guidance, and the controller retract settings above. [1] [2] [3]

Editorial calculation: a 4-axis and a 9-axis configuration differ by five independently driven axes; at 250 mm/s the ram covers its 300 mm maximum stroke on the 80/2000 in about 1.2 s, the time window in which the gauge must reposition between bends.

State the axis count you need (for example X1, X2, R1, R2, Z1, Z2), the travel and speed of each axis, and whether the gauge runs on linear guides, and ask how these match the throat depth and table length of the press brake it will be fitted to.

04

Press brake builders offering multi-axis gauges

The listings are press brake builders offering multi-axis back gauges on their own machines; ask whether a gauge can be supplied as a retrofit and which control it runs on.

05

X, R and Z drives, fingers, guarding and control

06

Stroke, speed and accuracy per axis, then force, drives and guides

Cincinnati, Selmach and Salvagnini figures fill the stroke, speed, accuracy and axis-count rows; finger force, motor, enclosure and guide rows have no published value and must come from the supplier.

07

Send the machine, axis and part data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Machine: [press brake make; model; length; control]
Axes: [X1/X2; R; Z1/Z2; others]
Per axis: [stroke; speed; accuracy; repeatability]
Parts: [thickness; largest and heaviest part; shortest flange]
Fingers: [type; steps; number]
Control functions: [retract; safety zones; lay-on]
Safety: [rear guarding; interlocks]
Supply: [new machine or retrofit; installation]

See manufacturer records Send an enquiry through CNFX