Soffiaggio melds ‘simplicity’ with new blow moulding line

Italian blow moulding manufacturer S.T. Soffiaggio Tecnica SRL has recently introduced a new series of machines model ISIT, which are designed primarily for industrial packaging application and technical articles.

The company coined the acronym ISIT to identify this new range of machines for extrusion blow moulding.

ISIT is a combination of “ISI”, which is generally how locals pronunciation the word, “easy”; and the abbreviation of the Italian adjective, IT.

With the brand, the company intends to convey that while they simplify technology, theu are not cutting corners in terms of quality.

The new range features clamping units with two columns in diagonal support and make the platens slide.

“Diagonally because, looking frontally the machine, a column is at the top left and the other at the bottom right, on the side of components extraction. In this way, the gripper and extraction of the blown product from the mould finds no obstacle even in the case in which the piece and the respective mould are higher than the platens.”, explained Soffiaggio of the design.

The clamping unit is based on three plates: one is to support each half mould and the third one is attached with the only hydraulic cylinder, which moves the other two plates.

The clamping force is applied to the rear of the latter through a bending bar, which avoids the transmission of unbalanced forces and any deformation. The platens can reach very large openings and are guided at the bottom by means of prismatic guides with widely oversized roller bearings.

The single screw extruder is based on High Output Extrusion (HEX) technology and has a high plasticising capacity. Therefore, it was possible to reduce the diameter of the screws without affecting the capacity, also thanks to a special profile, thus allowing decreasing the involved powers, all to the advantage of the energy savings.

A system of electric heating elements, with a level of efficiency almost equal to 1, allows transferring the heat to the material in an optimum manner.

The heater bands are insulated to avoid the dispersion of heat into the environment and the screw does not overheat the material, even when it rotates at maximum speed.

The plasticising cylinder does not need cooling by means of special fans, neither the cooling bush of the feeding zone requires an intensive cooling, with further benefits in terms of reduction of the machine’s overall energy requirements.

The lack of overheating also allows the optimum control of the melt temperature.

The accumulator head with two cardioids is of FIFO type (First In First Out) and is equipped with a diverter, which provides the balanced stratification of the parison. More in detail, in the section of the hydraulic head, which allows the extrusion through an ejection piston, a transducer controls the amount of accumulated material while the extrusion speed and the parison thickness are checked on 500 points. The intermediate section of the thermal division has a water-cooled flange of union of the ejection piston, whose flow is controlled by a pneumatic valve. The accumulation and material ejection section is instead equipped with evacuation windows for carbon residues.

The blowing unit is provided with a structure connected to the main frame through a guide with ball bearing, a solution that, during the mould change, allows to "move" the blowing unit under one half of the mould and to accurately adjust the blow pin position.

The vertical movement is motorised and controlled by a linear transducer and the position can be stored. A column of reinforcement closes the group so that it can also be used with the inclined pin.

The basic structure includes a hydraulic cylinder (for blow pin with fixed single stroke) and a pneumatic one (spreader); both can be inclined on conical elements. The pneumatic cylinders (supported on linear guides) are used to stretch the parison and the stroke adjustment in the positions of opening and closing is carried out independently by means of a shock absorber.

The extraction gripper of the blown part is height adjustable to vary the distance between the taking points and the head, so as to minimise the production scrap. The gripping arms, pneumatically controlled and synchronised by means of toothed wheels, are supported by prismatic guides with recirculation ball bearings.

A rod less pneumatic cylinder with integrated valves provides the translation.

The device does not need any lubrication, avoiding the product contamination resulting from the fall of oil or grease. The grippers are water-cooled; the water passes through a circuit obtained inside them.

Currently, the clamping forces range from 30 to 150 tonnes, the head accumulation volume from 3 to 40 litres and the screws from 50 to 120 mm of diameter (all with L / D = 30).


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