TPT January 2022

AR T I C L E

Fives

OTO 608H tube mill from Fives aims to address specific automotive and mechanical tube makers’ requirements By Luca Ferraguti, product manager, Fives OTO SpA

The OTO 608H tube mill, a heavy and precise machine capable of forming tubes up to 60mm OD and 8mm WT, provides the lowest possible D/T ratio. It allows the user to minimise the number of required drawing cycles in order to bring the tube to the desired final size, resulting in significant cost saving for customers. New technical features The main technical feature of the OTO 608H tube mill is a completely new stand specially designed to reach the required D/T ratio, ensuring the maximum precision of tube sizes. The new stand has a very strong frame, with robustness that is comparable to 6" machines and at the same time allows the user to keep the distance between the stands significantly short to ensure the best effectiveness on small diameters and to reduce the material springback, resulting in an overall excellent quality and high speeds. To further achieve this goal – meeting the highest standards required for the automotive application – the OTO 608H tube mill is equipped with special devices to take out backlash/ clearances between the rolls and the shafts, as well as between the shafts and the adjustment system, that could affect the final tolerance. The welding box has also been redesigned in order to allow a quick roll change and adjust a roll diameter to the tube measures in order to minimise the energy losses and tube overheating.

Automotive and mechanical tubes are made from high steel grades and feature low outer diameters and high thicknesses, which require the utmost precision. In order to reach the strict tolerances required for such applications, while minimising the drawing process cost, tube makers need a customised robust mill to produce low D/T tubes with perfect inner scarfing suitable for the subsequent Drawn Over Mandrel (DOM) process. It is of paramount importance to have a perfect smoothness of the inner tube surface, for the drawing process itself and for all applications where drawn tubes serve as housings for shafts. Such tube production processes requires that, before being drawn, the produced tube has very precise diameter dimensions. It is often required to be at one half of the limit imposed by EN10305 regulation. In order to make the drawing process as inexpensive as possible, tube makers also have an interest in subjecting tubes that already have a small diameter to the drawing process. Heavy and precise tube mill Fives, an international engineering group, designed an OTO 608H high precision tube mill featuring robust frames and equipped with the best fitting technologies to minimise drawing process expenses and make the whole process precise and repeatable.

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JANUARY 2022