Aluminum extrusion press selection – 2

This is the second part of an overview of the extrusion press selection process by materials., primarily, from [1].

Characteristics of the components and systems of the press

Also part 1 and part 3.

Fig. 1 – The identification of the components of an direct extrusion press [2]

Fig. 2 – Specifications of a direct extrusion press [3]

Plates, plunger, container

Cast or forged?

On early aluminum extrusion presses, many important components (front and back crossbars, the main rams, containers) cast from cast iron or steel.
Currently, most of these components are made of forged steel. Forged steel is much easier and, the main thing, reliable control for various defects, and so the provider can confidently guarantee their quality.
Machining of a forging is done only if there is no certificate of passing complex ultrasonic and magnetic tests for the absence of defects..
components design quality of the press necessarily supported by complex calculations, based, usually, on the finite element method.

Fig. 3 – Machining a main cylinder for a new press (Presezzi Extrusion) [2]

The thickness of the front plate

The front plate of the press should be as thick as practicable, to minimize die deflection (Fig.. 2)
The rigidity of the front cross member should be, to limit the deflection of the matrix at maximum load no more than 0,25-0,40 mm [2]

Pre-stressed tie rods

Four columns (“rod”) connect the front and rear cross members. Their fatigue failure was common for presses early designs.
At the present time it is practically impossible due to the installation of the special sleeves and pre-loading of the entire length.

The cycle of idling

Losses from idling of the press are the main factor in its performance.
In recent years, this cycle is greatly reduced thanks to the computer control, improvement of hydraulic systems, shift to designs of presses with a short stroke and in front-loading, as well as other innovations.
It must be borne in mind, that press suppliers often claim the shortest idle cycles. It is important to apply the same definition of this very “idling”, when you compare them to the various presses. Different vendors may or may not include such as a decompression process steps, precipitate preform and air outlet.
Need to request an idle chart, where all its components will be displayed in the Timeline.

Hydraulic system

The hydraulic system requires the consideration of many issues.

A supplier of hydraulics

It is good to, if hydraulic equipment received from an acquaintance supplier, which already have experience, including, equipment maintenance and spare parts supply.
The best thing, to spare parts are common with existing presses.
It is important to clearly state in the contract, what responsibility assumes provider for maintenance of equipment after installation, and, if necessary, staff training.
The supplier of the press should be ready to take into account your preferences (if any) for the supplier of hydraulic equipment. This preferred supplier can be useful in the preparation of the technical requirements for the hydraulic system for the new press.

The number of main pumps

It is necessary to consider the possibility of increasing the number of the main pumps to improve performance and reduce the duration of idling.

Location pumps

The pumps can be placed on the oil tank above the press, on the floor of the press, in a separate pit or even a separate room (Fig. 4). Their location affects the noise level, serviceability and efficiency of the hydraulic system.

Oil filters and cooling oil

Proper filtering of the oil is critical to the life and normal operation of the hydraulic system .
It must be ensured, that filters and heat exchanger design, and temperature control system corresponds to the actual climatic and other conditions of your plant.

Pipes and accessories

You need to consider the types and location of pipelines, valves and other auxiliary equipment in order, to reduce water hammer in the system and leakage of oil.

Fig. 4 – Floor-mounted pump layout with three main pumps, three auxiliaries, one spare,
“kidney loop” filtration, and plate-type heat exchanger at rear (Presezzi Extrusion) [2]

Automated control of the press

All modern presses are controlled by automated control systems based on programmable logic controllers (PLC).
Need to know exactly, what parameters are included in the control scheme of the new press.

The supplier

Will this Siemens or someone else - have to deal with supplier, who know your specialists and will provide you with technical support.

Features and Integration

Today's automated control system can be integrated into the computer system of the enterprise with the collection and storage of data, and even the acceptance of orders in real time. The capabilities of these systems is enormous and continues to grow. We need to make, that their potential will really give a new press any advantages.

Diagnostics

Special displays can report potential problems before, they happen. for instance, on some new presses allow constant measurements of the alignment state (alignment) of the container relative to the ram. Remote Display Network allows you to monitor the status of the press and to report deviations from the normal operation. With the help of such systems, it is possible to carry out diagnostics of the press even from another hemisphere of the globe [1].

Fig. 5 – Modern control desk for entire press line with graphic operator interface (Presezzi Extrusion) [2]

Fig. 6 – Inside a modern press PLC control cabinet (Presezzi Extrusion) [2]

Container alignment system

Most modern presses used container alignment system, which can be put on the outside of the frame press. These systems make it possible to align the axis of the container in the vertical and horizontal planes (Fig.. 7).

Fig. 7 – Container Housing and flat guide system (Lake Park Tool) [2]

Heating and cooling the container

new press, especially large sizes, differentially heating the container offer several zones, as well as control the temperature of many points of measurement. It is believed, it is reasonable to divide the container into the lower and upper zones. The thing is, that the upper part has a tendency to heat up more than, lower than.
Some suppliers offer a container, which can be cooled, to reduce the temperature, when it exceeds the set limit.

Type the die carrier

Two types of die carrier are mainly used (Fig. 8):

rotary and
longitudinal-transverse.

Here are the key selection considerations of available space to accommodate.

Fig. 8 – Die carrier. (a) Die slide. (b) Rotary die head (Schloemann-Siemag) [3]

Type blanks loader

For conventional presses loader is well suited as a carriage, which delivers the workpiece (solid or split) to the center line of the press.
For compact or short-running presses applied load from the top and / or robotic loader.

The mechanism of removal of the discard

Separation mechanism of the discard should include a pneumatic chipper for quick removal of the cut of the discard.

Fig. 9

Replacement of the container and ram

When using more than one billet diameter, provide the design for quick change of the container and ram.

Fig. 10 – Stem quick-changing device [3]

Optional equipment

Pressing without venting

The container is kept open during the precipitation workpiece to eliminate or minimize the length of the air discharge cycle.

Positioning the die

Clamping die in the horizontal and vertical directions at the time of shearing press residue, to provide a uniform and smooth cutting surface.

Fig. 11 – Die-positioning device for accurate shearing [3]

Sources:

Seven Steps for Selecting An Extrusion Press /Al Kennedy // Seminar Materials ET2008
Extrusion Press Maintenance Manual, ed. Al Kennedy
Aluminum Extrusion Technology / P. Saha