: Production :

Design, construction and automation of industrial machineries and plants: automatic winders for plastic films, polymer gear pumps, reduction gearboxes for single and twin-screw extruders.


                                     :: Gear boxes | Single screw extruder | Twin screw extruder


Riduttore mano



ALFATECH’s long experience in special reduction gearing boxes for single-screw extruders is born from the studies and research carried out on particular capacity and application problems in co-operation with leading National and International manufacturers of extrusion and coextrusion systems for plastic materials. Innovative project and construction concepts distinguish this new series. Thorough working specifications and dimensional control methods, as well as strict selection of the materials used have developed absolute reliability. This essential condition is required by the technological specifications defined during the project and confirmed by the relevant complex calculations made by RIDEST to simulate the operative environment of each reduction gearing. RIDEST under Windows is available on request. The software will select the most suitable reduction gearing and define the working conditions for the following:

Loading capabilities
Gear service factor according to the A.G.M.A. 218.01 standards and relevant specifications regarding control calculation of the bending stress at the basis of the teeth and of the specific face pressure. Other special algorithms are also applied to determine the geometrical factors defining correct toothing mathematically;
gear efficiency;
thermal capacity;
heat transfer.

Dynamic conditions of the elements
• Elastic line of all the shafts displayed in the following diagrams:
• deflection;
• bending moment;
• shearing stress;
• bending stress;
• combined bending and torsion stress;
• shearing force;
• theoretical life of all the bearings;
• peripheral speed of gears;
• bending critical speed of high-speed shaft;
• tensile strength of thrust block bars;
• dynamic loads on anchor bolts.

Construction characteristics
Based on modular concepts and allowing both horizontal or vertical assembly according to the specific application, the reduction gearing feature the following:
• two-piece casing in good quality cast iron;
• front plate in carbon steel with coupling gate to the extruder;
• thrust block back plate in carbon steel;
• thrust block bars in carbon steel with front extension (on request) for securing the extruder as an alternative to the flanging with the front plate;
• gears in compound, forget, case-hardened and tempered steel with helicoid toothing and refaced outline. The DIN <=6 (ISO<=5 or AGMA >=11) rating prescribed by the technical specifications is ascertained by strict electronic tests on the outline, helicity, pitch, eccentricity, and others certified by the respective diagrams;
• low-speed shaft in hardened and tempered steel with axial boring allowing for the extrusion screw that can be extracted through the gearing box with substantial advantages, especially in coextrusion applications where this device avoids disassembling the elements situated after the extruder or displacing the whole line forward;
• high-speed shaft with cylindrical ends allowing motor direct coupling either on front or back sides;
• screw coupling box in compound, hardened and tempered steel with grooved internal profile or with boring on request. Thanks to this flexibility, selection of the reduction gearing box is made according to the torque that must be transmitted and does not depend on the screw diameter, this means that a gearing box can couple to various types of extruders. Furthermore, the coupling box can be mounted on the front or the back side; according to the desired application;
• each shaft is supported by a pair of radial roller bearings and by an axial bearing to guarantee the calculated theoretic life of all the bearing regardless of the direction of the axial loads that vary according the gear rotation direction. Great care was given to the interchangeability of the low-speed shaft axial bearing situated in the back. This will substantially expedite maintenance as there is no need to disengage the extruder. Furthermore, the bearing itself comes in 4 different sizes for each type of gearing box according to the theoretical life required.

Because of the wide range of possible working conditions and mounting configurations offered, a standard lubrication system cannot be defined . Therefore either forced-circulation by means of an electric pump or splash and oil-washed lubrication is applicable. In some cases, and when required by particular environmental conditions, oil cooling by heat transfer is also available.

Our Technical Division is at your disposal for advice on the most suitable lubrication system for your particular application.

1 Informations


ALFATECH S.r.l. Via Lecco, 12 - 21049 Tradate (VA) - ITALY - P.I. e C.F. IT01857710121 Reg. Soc. VA16931 - C.C.I.A.A. V 212333 Cap.Soc. € 98.800 i.v. © 2010. All Rights Reserved.