hydraulic systems for scrap presses and scrap shears

RE 08107Edition: 2020-09Replaces: 2009-09

RE 08107, Edition: 2020-09, Bosch Rexroth AG

Content

General Information 2Description of a Scrap Press 2Description of a Scrap Shear 3Requirements 3Cylinder Controls 4‒ Vertical Cutting 5‒ Vertical Pressing 5‒ Horizontal Pressing 6‒ Alternating Loads (Pressing) 6Possibilities for Pressure Supply 7‒ High Pressure/Low Pressure (HP/LP) 7‒ Pump with Horse Power Control 7 ‒ Electronically regulated Pumps 8‒ Pressure Supply with two Pump Groups 9

Hydraulic Systems forScrap Presses and Scrap Shears

Technical Information

Rexroth Components 10‒ Power Units, Motor Pump Groups 10‒ Pumps 11 - 12‒ Oil-Air Cooler 13‒ Hydraulic Manifold Blocks 13‒ 2-way Cartridge Valves 14‒ Cylinder 15Questionnaire for Scrap Presses/Scrap Shears 16 - 18Service Industrial Hydraulics 19

2/20 Technical Information | Hydraulic Systems for Scrap Presses and Scrap Shears

Bosch Rexroth AG, RE 08107, Edition: 2020-09

General Information

Scrap presses and scrap shears are an important part of the recycling cycle. Re-usable materials or products are compressed for better transport and storage until they are further processed for reuse.The demand for machines such as scrap presses and scrap shears is increasing and they have to work faster and more energy efficient.Bosch Rexroth has established itself as the specialist forhydraulic controls and drive technology for forming,baling and recycling presses and develops solutions inclose partnership with machine manufactures in thisfield.The product range extends from individual componentsand modules to a wide range of drive systems.

The necessary know-how for project planning and imple-mentation has been bundled in our application centresfor decades.All necessary drive components, such as power units,valve control blocks, cylinders including their control, are offered from a single source. In addition, the most modern calculation and simulation options are available to optimally implement customer-specific requirements.Together with the local sales department, the applica-tion center converts customer requirements into drive solutions.For this, Bosch Rexroth applies proven products and systems with high quality in order to ensure a longproduct lifetime.

Description of a Scrap Press

A scrap press is used to compact scrap material, which reduces the volume of the supplied material. When several pieces are compacted together, a single block is produced. This process makes transport, storage and disposal easier and more efficient.In order to compress the scrap as uniformly as possible it is pressed from all sides – from the side, from the end and from above. After pressing the gate is opened and the compressed scrap is pushed out (see diagram below). Typically four hydraulic cylinder axes are used.

This results in a high degree of standardization of scrap press systems on the market. In order to reduce the total cycle time these machine are often fitted with a “skip“. During the working cycle of the press theskip is filled by means of a crane with the next charge of scrap. The pressing chamber is refilled by a tipping process and the cycle starts from the beginning. The skip also functions as a “measuring jug“ in order to ensure that the press is always filled with the optimum amount of scrap.

Typical layout of a scrap press

Lid/Vertical press Cylinder 2

GateCylinder 4 Skip

Cylinder 6

Side pusherCylinder 3

End pusherCylinder 1

Hydraulic Systems for Scrap Presses and Scrap Shears | Technical Information 3/20


Typical layout of a scrap shear

End pusherCylinder 1

Lid/Vertical press Cylinder 2

ShearCylinder 5

SkipCylinder 6

Hold down cylinder/StamperCylinder 4

Side pusherCylinder 3

Description of a Scrap Shear

With a scrap shear the scrap is first compressed in a similar way as with a scrap press. The compressed scrap is then pushed out in small steps by means of the end pusher and cut off with a scrap shear.

In order to optimize the cutting process, the scrap is pre-compressed directly at the shear by a hold-down cylinder and fixed during cutting. This cutting into parts of equal size is preparation for the next stage in the recycling process.

Requirements

High forces, robustness, reliability and short cycle times mean that only hydraulic can be considered for this application.

When designing the system, the following additional requirements must be taken into account: ▶ Fast, shock-free switching of large volume flows ▶ Fast, shock-free decompression ▶ Avoidance of cutting shocks ▶ Low energy consumption ▶ Low initial procurement costs

The mechanical principle of different manufacturers of scrap shears hardly differs in concept. The performance and quality of the system is therefore significantly influenced by the used hydraulics.



Cylinder Controls

Valve circuits can be divided into four different functions – vertical (cutting), vertical (pressing), horizontal (pressing) and alternating loads (pressing).These functions can be achieved by means of a circuit based on four 2/2-way logic valves.With these four logic valves the function of a 4/3-way directional valve is imitated but with the following advantages:

▶ Nominal sizes for “P” to “A”, “P” to “B”, “A” to “T” and “B” to “T” can be selected individually to match exactly the volume flows actually required

▶ The times of event at which the valves are switched can be set independently of each other. This enables fast and shock-free switching and decompression.

▶ In order to save costs and space several functions can be integrated into one valve e.g. directional function with additional pressure limiting, check-valve, pressure cut-off function etc.

In order to make full use of these advantages a PLC control system is necessary.



Vertical cutting – simplified circuit

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Characteristics: ▶ Fast approach with regenerative circuit and automatic change-over to cutting mode when

the piston side pressure reaches the set switching pressure ▶ Pressure limitation at the rod side ▶ Load holding/counterbalance at the rod side

Vertical pressing – simplified circuit

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Characteristics: ▶ Pressure limitation at the piston and rod sides ▶ Load holding/counterbalance at the rod side

Cylinder Controls



Horizontal pressing – simplified circuit

Alternating loads (pressing) – simplified circuit

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Characteristics: ▶ Pressure limitation at the piston and rod sides ▶ Load holding/counterbalance at the piston and rod

sides

In the past proportional valves were seldom used in scrap presses and scrap shears because of the rough environmental conditions and high costs.

This restriction no longer applies to current generations of proportional pressure valves, so they can be used in today’s circuits. Proportional valves offer significant advantages over normal switching valves, especially for decompression.

Characteristics: ▶ Pressure limitation at the piston and rod sides ▶ Brake force adjustment at the piston side

Cylinder Controls



Possibilities for Pressure Supply

Double pumps are often used in this solution. One pump for LP - large volume flows (normally a fixed displacement pump) and one pump for HP ‒ small volume flows (power or pressure controlled). Rapid movements are performed at low pressure with all pumps simultaneously while pressing and cutting

movements only with the HP pumps.Due to this configuration, the electric motor load remains approximately constant. As LP constant flow pumps are considerably cheaper than HP variable dis-placement pumps, the initial purchase costs are lower with this solution.

High pressure/low pressure (HP/LP):

High pressure/low pressure – simplified circuit

Example:Low pressure: 150 l/min @ 120 bar + 300 l/min @ 120 bar = 90 kW

High pressure: 150 l/min @ 315 bar + 300 l/min @ 10 bar (circulation pressure to tank) = 84 kW

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Switching pressure

In this solution all pumps are identical in construction. The pump volume is automatically adjusted via the power controller depending on the pressure. This solution is very energy-efficient as the pumps automatically adapt to the operating conditions:

It is guaranteed that the available maximum pump flow or the available maximum power is always fully utilized.

As an option, a special total power controller (so-called cross-sensing power controller CR) is available. With two pumps of the same nominal size in different working circuits, the CR controller ensures that the total output is limited and (like the normal output controller) operates with a fixed maximum output along the output hyperbola. The mutual override of the controllers ensures that the total output is divided between the two pumps according to requirements.

Pump with horse power control – simplified circuit

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LR (CR) LR (CR)

Pump with horse power control




Electronically regulated pumps

In this solution the pump volume is adjusted by an electronic control. These electronics can also be used to control the pressure and limit the output. Such a control system allows the infinitely variable adjustment of cylin-der speeds and system pressure. The pressure reduction or decompression is normally still carried out via a valve control.

This solution is the most flexible and gives the best results, but it is rarely used in scrap presses and scrap shears because of the relatively complicated electronics. On the left side the possibility with an internal control oil supply is shown, on the right side an external control oil pump is required.Both versions can be realized.

Electric swivel angle control – simplified circuit

For axial piston pumps, an electric swivel angle control is available. This allows the flow rate of the pump to be infinitely variable. In the most cases this controller is combined with our hydro-mechanical power and pres-sure controllers. This allows the pump drive to be opti-mally designed for use with scrap presses or scrap shears.

In principle, Rexroth pumps can be combined with the advantages of speed control in terms of energy savings and noise, as long as this appears technically and eco-nomically feasible.

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Pressure supply with two pump groups – simplified circuit

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Cylinder 1 Cylinder 2

In order to reduce the cycle time, it is possible to move two or more axes simultaneously. In this case, the axes which are to operate simultaneously must be supplied from separate pressure sources. The pumps must therefore be divided into two or more groups. If a movement requires more pumps than available in one group, the pump groups must be connected together. Simultaneous movements only make sense if not all pumps are required for at least one of the movements.

Extending (valve switched on):First cylinder 1 with 6 pumpsthen cylinder 2 with 6 pumps.

Retracting (valve switched off):Cylinder 1 and cylinder 2simultaneously with 3 pumps each.




Rexroth Components

Power units

In the branch of industrial hydraulics Bosch Rexroth manufactures customer specific and large power units to uniform standards in several locations. The increasing need of customers for shorter delivery times is met in industrial hydraulics by the development of standard ABMAXX units and sub-assemblies.

This modular concept covers power units, motor-pump assemblies, oil tanks, filter-cooler-heating units, accumulator assemblies and pressure relief blocks for pumps. This reduces the amount of work required in project engineering, design, logistics and assembly.

ABMAXX

Reservoir: 2000 l up to 12500 l Pressure: Up to 315 bar Qmax: 345 l/min up to 2160 l/min (A4VSO and A10VSO)

For more information see RE 08140.

Motor pump groups

▶ Electric motor size 90S up to 400M ▶ IE2 and IE3 ▶ Electric motor with foot and flange mounting, design type

B3/B5 ▶ Pumps mounted on the motor with pump carrier and

coupling ▶ For assembly on oil reservoir, base frames or free standing ▶ Low operating noise levels ▶ Maintenance friendly design ▶ Optionally with fixed or variable displacement pumps ▶ Pump combinations for multi-circuit systems possible

For more information see RE 51170, RE 51171, RE 51174, RE 51175, RE 51180, RE 51181, RE 51182,RE 51184.



Rexroth Components

Pumps

Bosch Rexroth offers a complete range of pumps and motors of all types. In particular axial piston pumps, internal gear pumps, fixed and variable displacement vane pumps as well as external gear pumps and radial piston pumps. If required, speed control can also be implemented with our pumps.

Axial piston pump A4VSO ▶ Nominal size 40 up to 1000 ▶ Axial piston swash-plate design ▶ Open circuit ▶ Long bearing life ▶ Comprehensive range of controllers and adjustment

devices ▶ Through drive for the attachment of further pumps

up to the same nominal size


Axial piston pump A15VO ▶ Nominal size 110 up to 280 ▶ Axial piston drive unit in swash-plate design ▶ Open circuit ▶ Long bearing life ▶ High efficiency ▶ Low operating noise levels ▶ Special controller for scrap press and scrap shear

applications (LR-CR) ▶ Universal through drive for mounting units up to the

same nominal size, i.e. 100% through drive ▶ Approved for use with HFD fluids ▶ Optionally available with charge pump (A15VLO).

Suitable for speeds up to 2160 rpm for example for the following applications:

– Drive with diesel engine – Use with speed control (Sytronix) – For poor suction conditions

– Installation at high altitude (e.g. Mexico) – Cold start – High viscosity




Rexroth Components

A20VFO 260 ▶ Axial piston drive unit in swash-plate design ▶ For hydrostatic drives in open circuit ▶ Compact design for drives with large flow requirements ▶ Combination of variable and fixed pump

(HA4VSO 260 + HA4FO 260) with advantages regard-ing input speed and noise development

▶ One common inlet port ▶ Suitable for drives with variable input speeds ▶ Short response times ▶ Lower overall costs for installation

Further information on request.

Pumpen

Internal gear pump PGH-3X ▶ Nominal size 20 up to 250 ▶ Low pulsation of the flow ▶ High efficiency also at low speed and viscosity

through sealing gap compensation ▶ Suitable for a wide viscosity and speed range ▶ All frame sizes and sizes can be optionally combined

with each other ▶ Can be combined with internal gear pumps PGF,

vane pumps and axial piston pumps




Rexroth Components

▶ High quality standard (in manufacture and assembly) ▶ More than 50 years of experience in the manufacture

of hydraulic manifold blocks ▶ High speed machining with special tools and fixtures ▶ Machining of all block sizes (<1 kg up to >10 t) ▶ Use of modern CAD-CAM-DNC manufacturing tech-

nology ▶ Implementation of customer requirements with the

application of standards ▶ Realization of special solutions


Hydraulic manifold blocks

Oil-air cooler ▶ Developed and manufactured by Bosch Rexroth ▶ Cooling power data according to DIN EN 1048 ▶ Max. operating pressure 26 bar ▶ Special lamella design reduces clogging of the

cooling element ▶ High quality standard e.g. powder coating ▶ Low noise levels (to DIN 45635) ▶ Optimum airflow (inlet nozzle) ▶ With axial or radial fan wheel:

– 3 kW up to 120 kW cooling power – Max. flow 400 l/min – Freely selectable mounting position

(horizontal and vertical)


Oil-air cooler



Rexroth Components

2-way cartridge valves with directional function ▶ Nominal size 16 up to 160 ▶ Standard mounting cavity to DIN ISO 7368

(up to size 100) ▶ Standard areas ratios 2:1 and 14,3:1 ▶ “High-Flow” as standard ▶ Valve poppet with or without damping nose ▶ Various opening pressures ▶ Various types of adjustment for stroke limiter ▶ Control cover optionally with shuttle valve, various

possibilities for pilot stage ▶ Optional limit switch monitoring ▶ Variable arrangement of orifices ▶ Optional valve spool seals ▶ Logic cover fixing screws included in supply


2-way cartridge valves with pressure relief function ▶ Nominal size 16 up to 100 ▶ Standard mounting cavity to DIN ISO 7368 ▶ Unloading, isolation and selectable pressure stage

circuits are possible ▶ Valve with seat poppet or spool poppet ▶ Various pilot valves for manual and/or electro-propor-

tional setting of pressure ▶ Various opening pressures ▶ Various types of adjustment for manual setting of

pressure ▶ Variable arrangement of orifices ▶ Optional valve spool seals ▶ Logic cover fixing screws included in supply


2-way cartridge valves



The development of customer specific solutions is carried out by highly specialised cylinder designers:Special cylinders matched to the industry sector requirements are conceived together with the customer, tested and, when ready for series production, manufactured in the required version.


Cylinder

Rexroth Components



Questionnaire for Scrap Presses/Scrap Shears

1. Customer:

Project:

Contact:

2. Machine type: Scrap press Scrap shear

Functions:

End pusher (cylinder 1)

Vertical press (cylinder 2)

Lid 1 (cylinder 2)

Side pusher (cylinder 3)

Lid 2 (cylinder 3)

Hold down cylinder/gate (cylinder 4)

Shear (cylinder 5)

Skip (cylinder 6)

Additional functions:

3. 3. General data:

Fluid Outdoors/indoors

Cooling fluid (water/air) Mobile/stationary

Ambient temperature Safety regulations

4. Electric motor:

Power (kW) Voltage (V)

Speed (RPM) Frequency (Hz)

Quantity Mounting type

Protection class



5. Key parameters:

Addit

iona

lfu

ncti

ons

Ski

pC

ylin

der

6S

hear

C

ylin

der

5

Hol

d d

own

cylin

der

/gat

eC

ylin

der

4

Lid 2

/ S

ide

pus

her

Cyl

inder

3

Lid 1

/Ve

rtic

al p

ress

Cyl

inder

2

End p

ushe

rC

ylin

der

1

Num

ber

of

cylin

der

s

Tota

l fo

rce

(kN

)

Max

. pre

ssur

e (b

ar)

Pis

ton

dia

met

er (

mm

)

Rod

dia

met

er (

mm

)

Cyl

inder

str

oke/

wor

king

str

oke

(mm

)

Max

. spee

d, r

apid

adv

ance

(m

m/s

)

Max

. spee

d, c

utti

ng/p

ress

ing

(mm

/s)

Fast

ret

urn

(mm

/s)

Effe

ctiv

e w

eigh

t ac

ting

on

cylin

der

–P

ullin

g (k

g)

Effe

ctiv

e w

eigh

t ac

ting

on

cylin

der

–P

ushi

ng (

kg)





6. Sequence diagram:Please also include a sketch of the machine.

Pos

itio

n

Cyl

inder

1

Cyl

inder

2

Cyl

inder

3

Cyl

inder

4

Cyl

inder

5

Cyl

inder

6

2448

72

96

tim

e in

s



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Bosch Rexroth AGIndustrial HydraulicsZum Eisengießer 197816 Lohr am Main, Germany Phone +49 (0) 93 52 / 40 30 20 [email protected]

© All rights reserved to Bosch Rexroth AG, also regarding any disposal,exploitation, reproduction, editing, distribution, as well as in the event ofapplications for industrial property rights.The data specified above only serve to describe the product.No statements concerning a certain condition or suitability for a certainapplication can be derived from our information. The information given does not release the user from the obligation of own judgment and verification. It must be remembered that our products are subject to a natural process ofwear and aging..

hydraulic systems for scrap presses and scrap shears

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