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Shot Blasting

Blast Machines Ready for Aluminium

| Author / Editor: Stéphane Itasse / Janina Seit

There are two aspects that contribute to the increasing significance of aluminium for manufacturers of blast machines: For once, workpieces are more frequently made of aluminium and secondly, aluminium is also popular as a blast abrasive.

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In its test centre, Agtos has studied aluminium in greater detail and even developed machines specially designed for this purpose.
( Source: Agtos )

Aluminium is increasingly used as a material for workpieces that have to be manipulated in airless blast cleaning machines. In this area, aluminium die casting is especially important. This material is, however, also an interesting blast abrasive. One reason for this occurs during the further processing of the workpieces: If hard abrasive material such as stainless steel remains in inaccessible areas of the workpiece, this could result in damages to the tools during subsequent further processing. It is also for this reason that aluminium blast abrasive is a preferred material for non-ferritic blast processes. A further benefit of aluminium as an abrasive material is the fact that surfaces that have been treated with this metal have an attractive look — an effect that is much appreciated by the automotive industry.

Aluminium Is also a Popular Blast Abrasive

An increasing number of aluminium workpieces are also blasted with this type of metal. Although it offers certain advantages, there are also consequences that have to be considered in the construction of the blast machine. Due to its physical characteristics, for instance the lower specific weight of aluminium compared to steel abrasive, special details must be kept in mind in the design of the blast machine. This starts with the determination of the repose angle, which has an impact on some assembly parts, such as the funnel and the bunker. The volume of certain assembly parts must be adjusted as well. In a further step, the turbines have to be optimized. During this process, the specific flow behaviour of aluminium abrasive is a very important factor. That is why the turbines are designed in a way that ensures that they can handle various types of aluminium graining without any problems. The aluminium abrasive has to be handled gently. An elevated temperature inside the turbines must also be avoided, as this could destroy the aluminium abrasive.

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Shot blast machines from Agtos largely avoid that the aluminium abrasive is destroyed inside the machine and would lose its efficiency as a tool for the surface treatment. These machines also prevent the loss of abrasive material. Following the blast process, a blow-off unit removes the abrasive from the workpieces, thus avoiding the discharge of material. In this way, the blast machine works economically at comparatively low operating costs.

The blast technology should be aligned with the internal flow of material. It is for this reason that wire mesh blast machines are frequently asked for by operators of automated plants. The biggest advantage of these machines is their ability to treat workpieces from above and below, without the need to flip or hang the parts manually.

Wire Mesh Blast Machines Are Very Robust

In this machine type, the workpieces are placed on a wire mesh belt, which moves them through the machine, by means of an automatic transfer system or a manipulator — in rare cases also manually. First, they pass through the entry vestibule which seals the chamber from the outside. Inside the blast chamber, high-performance turbines shoot the abrasive material onto the workpieces at high velocities. The wire mesh belt is designed in a way that ensures that the workpieces are optimally treated with the abrasive material from both sides. After completion of the blast process, the abrasive material and dust are blown off the workpiece. While the dust is separated by a filtering unit, the abrasive material is returned to the processing cycle of the machine,

An automatic abrasive dosing system is installed above the turbines. It ensures that the blast process only begins when a workpiece is located inside the blast area. The wear and tear of the blast unit is also reduced. A blow-off unit removes the abrasive material from the surface of the workpieces.

In many factories, the workpieces are transported in a hanging position. For these applications, Agtos has developed continuous overhead rail shot blast machines for aluminium workpieces and with aluminium as a blast abrasive. The company also offers conventional, non-continuous hanger type blast machines.

* Ralf Walterman is head of construction, Ulf Kapitza is head of sales + marketing at Agtos Gesellschaft für technische Oberflächenbehandung mbH in 48282 Emsdetten, Germany

This article was first published by Maschinen Markt.

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