Synchronized Press Brake or Torsion Bar Press Brake

30th April 2019

Press Brake choices

Press Brake, there are 3 possible specification options:
1) Synchronized Hydraulic
2) Synchronized Electric
3)Torsion Bar Hydraulic

Which Press Brake specification is the best option?

for your requirements:- operator safety, functionality, precision, your company budgetary requirements ??

Synchronized Press Brakes

Synchronization is:
Positional balancing of a Press Brakes
bending beam at [Y1+Y2] axis positions

The required bending beam level position is monitored by the reading of two individual linear encoders situated at the [Y1 +Y2] axis

Therefore the function of the linear encoder is to keep the top bending beam level at all times. This applies to both Hydraulic & Electric Press Brakes. Synchronized Press brakes, therefore, allow multiple bending tooling setups along the full length of the Press Brake tooling.

Both Hydraulic and the latest Electric models are of a high build standard, with the latest technology equipment, and design thinking. They are generally backed up with 2 years parts and labour warranty.

Synchronised Press Brakes offer a full range of 8 number automatic axis, these being: [Y1+Y2+X1+X2+R1+R2+Z1+Z2 ] + [X5] axis option, with a variety of 2D or 3D CNC control options, with offline programming software. [See our CNC control page].

Synchronised Press Brakes offer many ‘ancillary equipment’ options for safer operation, improved productivity, easier operator functionality.

A Synchronised Press Brake offers precision repeatability of the [Y1+ Y2] axis = 0.01mm [+or-], when ‘Optical’ linear scales are used its possible for a 0.02 mm difference between 2 beam strokes

When Magnetic linear scales are used [Y1+Y2] axis = 0.08mm [+or-]

Accuracy example: Optical linear scales
‘V’ opening of 16mm, the accuracy of 0.01mm = 0.14°[+or-] each bend so it’s possible for a 0.28° angle difference between 2 bends

All other axis: X, R, Z = 0.01mm [+ or -] per axis movement

Synchronised Press Brake operator guarding has generally moved away from the Infra-Red Guarding systems, the majority of the metalworking industry now prefers to fit Laser guarding. Laser guarding for Press Brakes offers 2 major improvements, these being:

a) The Laser beam is directly positioned under the top tool nose this, therefore, allows the operator(s) to be positioned up close to the bending beam/tooling.

b) improved productivity, smaller Press Brakes 20/30/40 ton capacity can benefit from an ‘upgraded’ Laser Guarding system, that allows the top beam to drop quickly, stopping at a reduced ‘mute’ position, thus saving
around 2 seconds per bend, this upgraded system is not for every application but is very effective when a suitable application arises.

Torsion Bar Press Brakes

3) Torsion Bar Press Brakes are an older technology, generally no longer offered by Western manufacturers, the Chinese remain the only manufacturer.

a)Torsion Bar Press Brakes require that all the bending is positioned in the middle of the Press Brake top beam, therefore this does not allow for multiple tooling setups along the top & bottom beams. Bending done off centre will eventually have the result of causing a positional discrepancy between the 2 Hydraulic cylinders that require a positional recalibration of each hydraulic cylinder.

b) Torsion Bar Press Brakes are not generally viewed as high accuracy, high specification Press Brakes, the number of automatic CNC Controlled axis is generally limited to 3 number These being [Y+X+R], the [Z] axis generally manual, some manufacturers of Torsion Bar Press Brakes do offer automatic [Z1+Z2] axis, its a rare request  Choice of CNC controllers is generally limited to non-graphical, occasionally with to 2D graphics

The Torsion Bar Press Brake achieves the required bending position of the upper beam [the single Y axis], via a motorised thread and nut [known as dead stops] that are incorporated into each of the 2 individual [Y] axis hydraulic cylinders. The revolutions of the dead stop nuts are driven with a motorized central single gearbox, the gearbox revolutions are measured by a rotary encoder. With this system, the accuracy of achieving the target bend position of the combined [Y] axis is [+or- ] 0.10 mm each stroke of the bending beam, so its possible for a 0.20 mm difference between 2 beam strokes

Torsion Bar Press Brake precision repeatability of [Y]axis
[Y] axis = 0.10mm [+or-] each bend

Accuracy example:
‘V’ opening of 16mm, accuracy of 0.10 = 1.14°[+or-] each bend
so it’s possible for a 0.28° angle difference between 2 bends

All other axis: X, R, Z = 0.2mm [+or-] per axis movement

Torsion Bar’ press brake manufactured in China, are always model W67Y

So in conclusion

As you can see from the 2 accuracy examples that the Synchronised Press Brake is 10 times more precise in the positioning of the bending beam axis than a ‘Torsion Bar’ Press Brake resulting with a more precise bend angle when would a ‘Synchronized’ press brake be a correct choice, simple, almost every application assuming your company has the Budget when would a ‘Torsion Bar’ press brake be a correct choice.

Generally, it’s not a correct choice if you intended to use the Press Brake for high volume precision parts, or high volume production in general Torsion Bar’ press brakes are slower than Synchro Press Brakes and not sufficiently accurate.

Where a Torsion Bar Press Brake can be the correct option is:-

Lower volume products, that tends to be fabrication parts where the bend angle accuracy requirements are not to tight, where axis speeds are not very important, Where budgetary requirements are a major consideration.  Tonnage application to the top beam A significant point to consider when purchasing a press brake, whether its a Synchronized or Torsion Bar Press Brake, is the required tonnage, Please consider this technical point.

If you decide that you require a press brake with a bending length over tooling of say 3100mm with a tonnage requirement of 200 tons, then please be aware that the top beam is unlikely
to have been designed to withstand the Press Brakes full tonnage [200 tons] over short lengths.

The manufacturer’s rule of thumb is that you only apply a % of the available tonnage to the same % of the available beam length.

i.e using 1/3rd of the Press Brakes beam length, then you can only use 1/3rd of available tonnage [66,6 Tons ].

Why, over time the constant overloading of the bending beam may cause it to deflect forward & not spring back, then requiring the bending beam re straightening, the top tool seating