A Prasa krawędziowa hydrauliczna CNC produces an accurate bend by driving two hydraulic cylinders under closed-loop control, positioning the sheet with a CNC back gauge, compensating bed deflection, and holding tooling and material inside a known window. The final result comes from how those systems correct one another during the stroke.
What Determines Bending Accuracy?
Bending accuracy separates into four outcomes that a fabricator measures on the finished part.
- Bend angle:how closely the achieved angle matches the drawing once the part has relaxed.
- Bend line position:where the bend sits along the sheet, which fixes flange length and the distance from a hole to the bend.
- Consistency along the length:whether the two ends and the middle of a long part carry the same angle.
- Batch repeatability:whether the hundredth part matches the first.
Two groups of variables decide those outcomes. Machine-side variables cover ram position and parallelism, back gauge positioning, deflection compensation, and tooling condition. Material-side variables cover thickness tolerance, tensile strength and hardness, batch-to-batch variation, and rolling direction. A press brake holds the machine-side variables stable; the material-side variables are managed through settings, first-article checks and, on some configurations, angle measurement during the stroke.
How CNC and Closed-Loop Hydraulic Control Keep the Ram Accurate
The ram sets how deep the punch enters the die, and bend angle follows that depth. Four links in the control chain hold that depth.
- Programmed target:the CNC stores the ram position for the required angle, and the machine returns to it on every part.
- Two cylinders, Y1 and Y2:one drives each end of the ram; equal positions keep the ram parallel to the bed, and any difference shows up as a long part bent tighter on one side.
- Linear scales (grating rulers): mounted on the frame, they read the actual position of each side of the ram.
- Proportional servo valves:the CNC compares each measured position with its target and meters oil into the cylinders, correcting continuously as load, oil temperature and friction change.
Each side runs its own feedback loop and the valves work separately, so a deviation on one side is corrected without disturbing the other. This electro-hydraulic synchronization decides whether the ram arrives accurately and stays parallel.
MYT builds the WE67K around this arrangement: closed-loop electro-hydraulic synchronized servo control, a DELEM DA66T controller, Rexroth hydraulics, a Siemens motor, and 4 to 8 axes (Y1, Y2, X1, X2, R1, R2, Z1, Z2) selected for the job. The NC press brake keeps the two ends of the ram aligned mechanically with a torsion bar and a forged, tempered shaft, which suits shops that bend simple parts and set the angle from job experience.
How the Back Gauge Controls Bending Position
The ram decides how deep the material enters the die; the back gauge decides where along the sheet the bend lands. Flange dimensions are a back gauge result.
- Oś Xsets the front-to-back position of the stop fingers, which fixes the distance from the sheet edge to the bend line.
- R axisraises or lowers the stop fingers so the sheet can sit flat on tall parts, stepped flanges or previously formed bends.
- Z1 and Z2move the two fingers sideways along the gauge beam, which covers parts of different widths and asymmetrical flange layouts.
- X1 and X2, R1 and R2appear where the two fingers must be positioned independently, as on tapered or angled parts.
Drive and structure decide how well the gauge repeats. A servo-driven back gauge with an imported ball screw and a double linear guide holds position against the force of repeated stops, and multi-stage stops extend the positioning range so a single setup can cover several bend positions. The gauge also has to reach each position without overshoot, because the operator feeds the sheet against the fingers on every cycle and feels any inconsistency at once.
MYT press brakes list back gauge options from Y1+Y2+X through Y1+Y2+X1+X2+R1+R2+Z1+Z2+V, so the axis count matches the parts the shop runs. On the Prasa krawędziowa CNC WC67K, the controller programs the X-axis back gauge and the Y-axis bending angle, with the R axis and V-axis compensation available as options.
How Crowning, Tooling and Machine Structure Maintain Angle Consistency
Crowning Compensation
Under bending load, the ram and the bed deflect, so a long bend receives slightly less depth at the middle than at the ends and the middle angle opens. Crowning applies a controlled curve to the bed or lower tooling so the effective gap stays uniform along the full bend length. Mechanical crowning moves wedges with a motor, hydraulic crowning uses a set of cylinders, and both are adjusted from the controller.
On the MYT full electric press brake, a motorized crowning system adjusts parallelism and straightness automatically. On the WE67K, compensation runs as closed-loop control: the CNC calculates the compensation amount for the job and sets it, which keeps the bending angle consistent over the full length of the part.
Tooling Accuracy
The V opening in the lower die sets the inside radius, the required penetration depth and the tonnage needed per metre. Punch and die straightness, wear on the die shoulders, and alignment between the upper tool and the lower die all transfer directly to the part, and segmented tooling must be assembled so the sections line up.
MYT press brakes are delivered with one set of upper punch and lower tooling, with lower tooling available as single-V or four-side V in 835 mm sections, and custom tooling can be made for a specific profile. Fast clamping holds the upper tool in position and shortens tool changes.
Machine Rigidity
Frame, bed and ram rigidity determine how much the machine deflects under load and how much the correction systems have to absorb. Every MYT press brake starts from a mono-block frame built from mill-certified high-yield steel. Each frame is welded and spliced, then annealed before the bed and mounting faces are finished on a floor boring and milling machine, which keeps the tool mounting surfaces true and gives the control systems a stable base to work from.
How Material Variation and Springback Are Compensated
A press brake can hold position and still produce a different angle on the next sheet, because the sheet itself changes what happens in the die.
- Thickness variation:a heavier gauge needs more penetration for the same angle and increases tonnage per metre.
- Tensile strength and hardness:a harder sheet resists bending and springs back further.
- Batch and supplier changes:the same grade from a different heat can behave differently at identical settings.
- Rolling direction:bending across the grain reacts differently from bending along it.
Springback is the elastic part of the deformation that returns when the punch lifts, so the finished angle opens relative to the angle formed under load. Production practice absorbs it in four ways: program the ram slightly deeper than the target angle requires, apply an angle correction parameter in the controller, check the first part of the batch and correct before the run continues, and, where the job justifies it, measure the angle during the bend. Laser check angle measurement is available as an optional configuration on MYT CNC press brakes, and CNC follower supports are available for large panels that would otherwise sag between the operator and the back gauge.
Software support matters here as well. Offline programming suited to the controller lets the shop prepare angle, depth and correction values away from the machine, so the first part starts from a calculated setting.
How These Systems Work Together During a Bend
A single part shows how the systems depend on each other.
- The CNC loads the program for the job, with the target angle, ram depth, tooling data and material correction already stored.
- The back gauge moves to the programmed X position, and the stop fingers take their R and Z positions.
- The ram descends quickly to the approach point and slows to the pressing speed.
- The linear scales on each side report the actual ram position continuously to the CNC.
- The CNC adjusts the proportional valves so Y1 and Y2 stay synchronized and the ram stays parallel.
- The crowning system holds the bed in the compensating curve it needs for the bend.
- The ram reaches the programmed depth, the punch penetrates the die to the calculated value, and the part forms.
- The angle is checked on the first part, the correction is applied if the material requires it, and the machine repeats the cycle for the rest of the batch.
Every step carries a possible error, and each system reduces the one in front of it. Back gauge positioning sets where the bend falls, ram depth sets the angle under load, crowning keeps that angle along the length, and the material correction brings the finished part back to the drawing.
Wniosek
Accurate bending on a CNC hydraulic press brake comes from the combination of precise ram positioning under closed-loop control, an accurately positioned back gauge, deflection compensation, sound tooling, and settings that account for the material in the batch. A machine specified with the right axis count, the right crowning method and suitable tooling for the part range gives the operator the control needed to hold angle and flange dimensions through a production run.
MYT builds NC press brakes, CNC press brakes, full electric press brakes and panel benders, and can review the part range, material mix and tonnage per metre of a job to propose a configuration. Contact the team to discuss the press brake specification for your workshop.
