A New Extrusion Concept

A New Extrusion Press Concept

Paolo Fraternale, Danieli & C., Officine Meccaniche S.p.A., Breda Division, Cinisello Balsamo, Italy

ABSTRACT – Downsizing and energy savings are key words in the automotive industry. Danieli Breda & C.’s R&D department studied a way to quench the cylinders’ thirst for oil between the empty dead cycle time and the extrusion phase, and has patented a 23MN extrusion press prototype that completely discards the old dead cycle time. The project is based on twin containers laterally shifting. During extrusion, the billet that waits to be processed can be loaded outside the extrusion axis; at the end of the extrusion, the twin containers shift laterally and the new extrusion can start immediately. In this way, the cylinders’ oil demand is balanced during dead cycle time and extrusion phase, so that the number of installed pumps depends just on the extrusion speed. Last but not least, the dead cycle time is drastically reduced. PROJECT INTRODUCTION Evolution or revolution? It is not easy to answer to this question. The new T-WIN® Extrusion is a mix of front loading and back loading design, simplifying the design being free of shears and loading devices. This is a press for horizontal extrusion, equipped with twin containers positioned transversely to the extrusion center line, to allow loading of the next billet into the empty container during the extrusion of the former one. In conjunction with the movement of the container (lateral shifting), the butt is cut off by blades installed between the two containers on the die side. The target of reducing dead cycle time and minimizing the installed power has been reached by modifying the extrusion cycle. The following is a brief description of the project’s main features:

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MAIN DATA

Type of Press:

Horizontal hydraulic direct type press with four pre-stressed columns

Work Cycles: • Manual • Maintenance – using key selector • Semi-automatic (step by step) • Automatic – with no air outlet • Automatic with air outlet using N.B.E. system

Use:

Extrusion of aluminum and aluminum alloy profiles (civil and industrial)

Construction:

Conform to European norms and regulations

Patent:

Worldwide

TECHNICAL CHARACTERISTICS

Maximum nominal capacity:

23MN (2350MT)

Working pressure:

31.5MPa

Maximum force main cylinder:

21.4MN

Side cylinder shifting force:

1.6MN

Maximum force main cylinder:

21.4MN

Side cylinder shifting force:

1.6MN

Billet dimensions : • Diameter • Maximum length for 7” and 8”

7” (178mm) - 8” (203mm) 1200mm

Maximum extrusion speed:

15mm/sec

Minimum extrusion speed :

0.8mm/sec

Butt:

10mm up to 250mm

Pre-filling valve: • Diameter • Flow rate

12” (305mm) 20.000l/min

Dead cycle time upon pre-filling valve shutting:

9-10 seconds ± 3 percent (The N.B.E. system may be used here – with no air outlet – by leaving the front cylinder ajar in the closing mode and fixed on the container command)

Automatic lubrication type block: Fixed (single-block with magnetised disc for container cleaning)

Press weight:

120 t.

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REQUIREMENTS

Electrical Energy Powered by six electric motors:

411kW Inductive load

Billet loader for 7” and 8”:

1kW Inductive load

Twin container heating:

80kW Resistive load

Total power installed:

500kW

Energy saving from power absorbed by the inductive load :

Reduced by 25 percent

Motor input voltage:

400V AC

Control input voltage: • PLC (Allen Bradley) • Electro valves • Signals and switches • Automation system

230/110V AC 24V DC 24V DC BreDanext ® (Levels 1 and 2 extendable to Level 3)

Frequency:

50Hz ± 2%

Cooling Water Flow:

30m3/h (connection value)

Pressure:

0.3MPa to 0.4MPa

Maximum temperature:

30°C

PH:

7 to 8.5

Maximum hardness:

5°F

Compressed Air Flow:

9Nm3/h (connection value)

Pressure:

0.4MPa to 0.6MPa

Hydraulic Oil Type:

HLP-ISO VG 68

Quantity:

10.000 l (Maximum filling including piping)

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THE MACHINE The machine is the front runner in a new family of multi-task presses for the extrusion of various metals (aluminum, copper, brass, steel, titanium). The prototype press is equipped with twin sliding containers, and has a maximum nominal force of 23MN (2350MT). It has been designed to extrude 7” to 8” (178mm to 203mm, with a length of 1200mm) aluminum billets. A press for the extrusion of 9”to 10” will follow in the very near future to complete this range of products.

ADVANTAGES

The main advantages of the new family of T-Win® (abbreviation for “To Win”) presses: • Reliability: billets are no longer misaligned during loading • Reduction in dead cycle time performed at lower speed • Billet loading directly from the furnace/saw with aerial loader: no billet loader at the floor level • Reduced gap between the container/billet, including shadow loading • Shorter dead cycle time: the shearing phase is deleted • Energy savings • Easy maintenance: container change-over and resistance outside of the press • Container can be scraped clean off-line: perfect for cycles in which container scraping is necessary • Extended container life, since it is subject to less thermal stress • High productivity and reduced fixed and variable industrial costs.

A starting solution to reduce energy is to install inverters on the main pumps; this basically allows the

“switching off” of one or more pumps during the extrusion cycle; all the pumps are energized immediately before dead cycle time. This clearly indicates that very often the number of pumps installed is not dictated by the extrusion speed, but rather due to the requirement of reducing dead cycle time. Typically, the dead cycle time in a conventional 23-MN extrusion press influences total cycle time by only 20 percent. This means that for 80 percent of the cycle, the number of installed pumps is superfluous. Using the above as a reference point, Danieli Breda’s R&D department tried to find a way to quench the cylinders thirst for oil between dead cycle time (17 sec.) and extrusion cycles time (approx. 60 sec.). The problem already was apparent; therefore, the challenge was to find a solution which would also optimize the dead cycle time.

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Here are our results:

23-MN Conventional

23-MN T-Win

Billet:

8” X 1.100mm 8” X 1.200mm

Total installed power:

900kW 500kW

Dead cycle time (inc. burp):

17 s econds 10 seconds reduction = -7 seconds/billet

Hydraulic circuits:

Main pumps

4 x 160kW 3 x 110kW

Container Sealing Pump

1 x 15kW 1 x 15kW

Pilot pumps

-- 1 x 55kW

Auxiliary pumps

2 x 75kW --

Oil conditioning/cooling

1 x 30kW 1 x 11kW

Container

40kW 2 x 40kW

Billet Loader

25kW 7kW

Total (approx.)

900kW 500kW INSTALLED POWER

However, the most critical advantage and influence to a plant’s overall operation and profitability

(excluding savings in energy consumption) is the extreme reduction in dead cycle time enabled by the new press concept. Reduction in Dead Cycle Time

A simple calculation makes clear the potential competitive edge given by a 23-MN twin-container press, with an average hourly production of 25 billets of 80kg each, and considering a three-shift operation over 220 days/ year results in at least 8,800 tpy. By reducing the dead cycle time by 7 seconds/billet, we will save at least 770,000 seconds/year, which is 214 hours/year. The following applies: 214 hours/year x 25 billets/hour x 80kg/billet = 430.000kg/year of added production. Reduction in Energy Consumption 23-MN Conventional

23-MN T-Win Delta

Energy consumption (kWh)

277.28 242.66 -12.49%

Production (kg)

2577.91 2729.55 +5.88%

Specific energy consumption (kWh/kg)

0.108 0.089 -17.35%

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TECHNICAL DESCRIPTION

The press is hydraulic type, direct, with four pre-stressed columns for the extrusion of aluminum profiles. The mechanical frame, as for Breda tradition, is made in forged steel, Class D. All components have been studied using the finite element method (FEM). The hammer-headed columns (on the front platen side) are equipped with armor-plated resistances (on the cylinder side) to heat the columns. They are assembled for pre-loading and supplied installed, thus ready in case of maintenance activities.

The roto type die-changing unit is situated outside of the press and connected to the front platen, which

reduces die changing time to a minimum. Lubrication points are incorporated into all main movable parts. Main technological innovation of this new machine can be summarized in:

• Billet loading and extrusion cycle • Container shifting system • Clean design of the front platen • Energy-saving design.

A brief description follows. Billet Loading and Extrusion Cycle

The billet is loaded into the container by an aerial-type loader equipped with two pushers. No additional time is required for this activity during the dead cycle time, since it occurs during the extrusion cycle. The movement of the twin containers allows for the alternation of containers from one billet to the next, and therefore no time is lost.

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At the end of the extrusion cycle, the main piston starts the return stroke, the containers are opened slightly, and the container side stroke movement starts.

The second container, which during extrusion was outside of the extrusion axis, takes up its position at the front of the die with the billet loaded. The butt shear blades (which substitute for the traditional butt shear) are positioned between the two containers on the front side, toward the die.

During the container side shifting movement the butt is sheared off from the die. Once the side movement has been completed, the twin containers move toward the die with a minimum stroke and a new extrusion cycle is started. Dead cycle time is drastically reduced using this cycle.

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Actual times: • Piston return • Container shifting movement and piston advancing.

Aligned cycle times where there is no influence on timing: • Container opening • Shearing • Container closing • Billet loading.

Container heating is controlled by tristors. Resistance heaters are placed longitudinally and located in

different areas. Thermocouples control the temperature. Container Shifting System

Container opening and closing cylinders are mounted onto a solid structure, avoiding the housing of the cylinders, or in the front or in the cylinder platen and therefore, reducing frame flexion fatigue.

Traditional presses have different container opening and closing forces, depending on how the cylinders have been assembled. In this case, the opening and closing force is the same.

Cylinders assembled onto the front platen (closing force is half that of the opening force).

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Cylinders assembled onto the main cylinder platen (closing force is double that of the opening force).

Advantages using this new system for cylinder assembly are:

• Equal force between opening and closing • The cylinders are extremely small, since both front and back forces are calculated • Absolute precision in the opening part (shearing phase); the container shifting cylinder is used • Using the N.B.E. system (no air vent), the front cylinder operating in the closing mode is not closed

completely; hence, no other expensive systems are implicated.

Sliding Container Carrier Structure during Construction

Shown above, hydraulic cylinders for container opening and closing.

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Container Sliding System

The unit is comprised of a moveable platen, a container sliding device, and containers holder.

This view shows the opposite side of the container sliding device.

Blades for butt shearing can be seen in the center.

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Front Platen

The main function of the front platen is to contrast the force of the main and side cylinders, thus rendering the press a hyperstatic system. Apart from of the system’s hyperstatic state, platens usually have a flexion of 0,6/1,2mm (flexions of 1,5mm and above can also be reached).

With the twin container’s platen design, the container shifting cylinders are not housed in the front platen, therefore flexion is reduced.

Front platen deflection negatively influences profile dimensional tolerances, since the die also bends and the final dimensional tolerances of profiles changes considerably (particularly with tubular and special profiles). Oil Tank

The oil tank is positioned above the main cylinder and is designed for the installation of all main components necessary for press functioning.

Hydraulic parts are installed on the tank cover:

• Main pumps immersed and directly coupled to the relevant electric motors • Logic element type forged steel hydraulic blocks • Heat exchangers • Filters and cooling • Dust filters including accessories

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All components are hydraulically and electrically interconnected with high- and low-pressure piping.

Manometers (six) control the pressure of the most important machine elements. Hydraulic power is composed of three groups of motor pumps, which include servo control and a digital control card for flow control in closed loop condition, and of groups for container sealing piloting and filtering. All electric components assembled on the tank cover are connected to an electric panel containing a rack remote from the PLC.

The oil tank also includes all components necessary for safety and control: oil level indicator, automatic transducer for oil level, and temperature transducer including alarm and preheating timer. The staircase and walkways are fitted with protective railings. The pre-fill valve with command cylinder is assembled between the main cylinder and tank. A soundproof hood may be fitted if required to reduce noise levels.

Side views of tank cover (in the final stages of preparation) ready for assembly on the press body.

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Tank Cover

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Billet Loader and Pusher

The press frame is fitted with a suspended billet loader, which picks up heated billets from the furnace and introduces alternatively on the right and left side, the billets directly into the container bore. The aerial billet loader can be coupled with a log shear or log saw.

The system is completed by a further structure composed of a billet holder and a pusher for introducing the billet into the container. Pusher movement is controlled by a hydraulic cylinder.

There is no billet loader around the press, improving the access for maintenance, the foundation works

and the possible misalignment between container and billet loader.

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ELECTRICS Electric Cabinet and Pulpit

The electric command cabinet is composed of a group of connected boards with IP55 grade protection (dimensions are 6800 x 2200 x 600) with a 1250 A main switch. Both the cabinet and main pulpit of the press are equipped with air conditioning. The cabinet also has a number of single-phase 220V power outlets in various areas of the cabinet. Three-phase line voltage is 400V AC – 50Hz.

The cabinet includes: • Container resistance power supply • Starter for feeding the oil tank heat resistances • Electronic modules for main hydraulic pump proportional valve control • Control system for safety gates • Control instruments are applied on the cabinet door • PLC area.

Space has been left available for introducing more machinery as required by the customer.

The command pulpit conforms to Rittal standards (IP55 protection). Industrial monitors, touch screens with luminous columns that are assembled onto the summit are included. Additional Accessories

Electrics include other accessories which are installed onto the machine: • Auxiliary panel – installed onto the side of the front platen • Panels (three) – installed on the opposite side of the billet loader/platen on the extrusion side, and on

the billet loader and oil tank

• Emergency switches (three) – installed on the press’ main function emergency accessories. Energy Savings

As shown in the table “Requirements – Electric Energy,” installed electric power (inductive loading type) has been reduced, compared to that of any press functioning normally. Further reductions of 25 percent can be obtained through absorbed power (inductive loading). These results are made possible

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through insertion of electronic devices in the electric cabinet for controlling absorbed energy. Each device is a different size, depending on the power of the electric motor to which it is connected. Devices act in relation to the load on the voltage; consequently, losses in winding are reduced, and installed motor efficiency is increased.

Energy-saving device.

AUTOMATION – HARDWARE AND SOFTWARE

The BreDanext® Level 1 and Level 2 automation systems are used on this press, and automation can be extended to Level 3. Hardware includes an Allen Bradley PLC and an industrial computer, which are connected. The PC acts as supervisor and manages and controls all press functions, thus facilitating the location of any possible signals of breakdown.

The operator can follow the progress of the main measures attained from the press via the monitor. These are available in both the numerical and histogram form. Each stage of the extrusion process can be viewed on the computer screen (each page applies to one single topic).

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CONCLUSIONS

Apart from the advantages mentioned above, the press could also have advantages in copper and brass applications, since container scraping is performed offline.

Twin containers provide an additional benefit in the extrusion of hard alloys, since improved extrusion

temperature control is permitted and container life is also lengthened considerably. Another important advantage of the twin containers is the added time available to introduce a new

billet, thus allowing a reduction in tolerance between the container bore and billet diameter. This also brings about a reduction in dead cycle time (upsetting phase) and blisters in extruded profiles.

Finally, the problem of billet sticking to the container liner during loading will become a distant

memory.

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