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Press Review Animal Feed

Focus on micropitting, design and heat treatments

Micropitting is considered a phenomenon and not necessarily a damage to the gear and that it is not yet possible to calculate this phenomenon since there is not a sufficiently large database to understand all the real cases obtained from laboratory studies.
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Magazine: ORGANI DI TRASMISSIONE
Publishing house: TECNICHE NUOVE
Month of publication: JANUARY 2012
Article Title: FOCUS ON MICROPITTING, DESIGN AND THERMAL TREATMENTS
Article author: Carlo Gorla
Summary by: Zuolo Filippo
Institute: I.I.S. MEUCCI
Class: 3 ^ AM


This article talks about the Fall Technical Meeting of the AGMA, held in Cincinnati from 30 October to 1 November 2011, immediately followed by the Gear Expo which took place from 1 to 3 November.

The topic that most attracted the interest of the participants was micropitting, that is the superficial irregularities of the gear caused by wear.
This aspect is not yet completely clear and for this reason he is given much attention. In the past it was concluded that the time was not yet ripe for the issue of a standard for the calculation of standardized wear. In this regard, Carlo Gorla states that, shortly, an article on micropitting will be published with four practical examples of numerical calculation.
Micropitting is considered a phenomenon and not necessarily a damage to the gear and that it is not yet possible to calculate this phenomenon since there is not a sufficiently large database to understand all the real cases obtained from laboratory studies; so it is difficult to give due weight to the results obtained from the calculations.

A further aspect to verify is if micropitting does not necessarily represent a cause of failure since it often settles without giving rise to any malfunction; but sometimes it can be the origin of more serious failures such as macropitting or tooth breakage.
The factors that prevent the phenomenon of micropitting are lubrication and surface finishing. To understand how much these two factors are important to prevent the onset of micropitting a test was carried out on two equal aeronautical transmissions with two different surface finishes: one had a honing finish (it is surface sanding performed after heat treatment) and the other an isotropic superfinishing (ISF) (it is a non-abrasive mechanical / chemical process that results in a series of beneficial properties that go well beyond the reduction of friction).

The honing finish transmission showed signs of micropitting after 150 hours of use; while the transmission with the isotropic superfinitura gave signs of micropitting after 2000 hours of use.

It has also been found that the use of a high performance lubricant can stop micropitting.
At the Fall Technical Meeting, Dr. Stadtfeld presented the new Coniface system for cutting and grinding Face gears or equivalent to them from the point of view of use. This system does not require additional very expensive special equipment. Another innovation presented at this event was the Convoloid teeth, whose geometry aims to optimize the connection between the pinion and wheel teeth.
Further studies have been done on the efforts that affect each individual tooth and the effect that generates the different angle of the helix on the stresses to the foot.
Another important component in power transmission is the bearing whose life is influenced by multiple factors including the dynamic load factor and mounting in the box.

Even if bearings are not the main source of losses in a gearbox, they can have a significant impact on the overall performance, so that thanks to their optimization, improvements of up to 30% can be achieved.
In the last ten years, the introduction of the heat treatment within the gear production cycle has taken place to guarantee efficiency, flexibility and economy. Finally, with the latest equipment developed it is possible to create a piece that passes automatically from the cutting station, to the heat treatment and popi to the finish.

Furthermore, the simultaneous use of high and medium frequency induction highlights its potential.
All these researches are supported by a further study on the materials to be used to produce gears such as high-hardenability steels that allow treatment processes characterized by limited distortions and therefore require less grinding allowances, thus increasing productivity.
The next edition of the Fall Technical Meeting will be held in Dearborn, nrl, Michigan, October 28-30, 2012.

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