A New Design Enhances the Performance of Screws

In order to reach high performances with its ball screws and planetary roller screws, even in the most critical applications, the Bergamo branch of Moog Italiana, a manufacturer of high-performance solutions for motion control, turned to MICROingranaggi Srl in Buccinasco (MI). The partnership proved successful not just from a technological standpoint, but also in terms of delivery times and flexibility.

di Alma Castiglioni

A multinational company with branches in 26 countries worldwide, specialized in the design, production and sale of high-performance solutions for motion control. We are talking about motion control solutions based on electro-mechanical, hydraulic or hybrid technologies. Namely, the Bergamo branch of Moog Italiana, a part of Moog Inc, deals with the design and production of ball screws and satellite roller screws, both standard and inverted. Companies turn to Moog when they cannot find “the solution” they need on the market, not merely from a technical standpoint, but also in terms of other factors such as sales support, delivery times, production flexibility and so on. Realizing solutions for motion control – screws, in the case of the Bergamo branch of Moog Italiana – therefore implies paying the utmost attention to these factors. As a consequence, looking for valid technological partners becomes essential to reach corporate objectives.

The issue: avoiding failure in more demanding applications
Screws manufactured by Moog Italiana are used in the automotive, railway, but especially metal forming sectors, the later taking up about 40% of production.
“About six or seven years ago – Roberto Donghi, Site Manager of Moog Italiana’s Bergamo branch – “we began to notice performance issues due to a design weakness in the satellite roller screws we were producing. As long as these components were used in “normal” conditions there were no problems; if however the application required higher, not standard, performances, brakages or failures often occurred which inevitably risked creating larger problems. The market analyses we carried out, besides, had shown that these components would have been increasingly in demand in the years to come”. At this point Moog realized that it was imperative to rethink the complex gears of these mechanical components: this led to the necessity of finding a supplier capable of providing a valid support from a technical standpoint, capable of guaranteeing long-term reliability”.

The solution: a new design for gears and crown gears
Moog Italiana decided to turn to MICROingranaggi, an Italian concern specializing for over forty years in the design and production of mechanical and electro-mechanical precision micro-components for all sorts of industries, as well as in mechanical machining for third parties. The reasons for selecting this partner were the willingness on the part of MICROingranaggi to follow a synergetic process, as well as the technical competence shown. “We needed – Donghi carried on – to cont on a technical partner capable of providing us with the correct suggestions. This is why we gave rise to a technological partnership based on the union of our know-how, and this allowed us to find the solution to our problems, and to reach excellent performances even in highly critical applications for planetary roller screws.
Planetary roller screws are rolling systems made up by a shaft with a profiled thread and a threaded nut which contains a certain number of rollers. These rollers, which rest on the threaded profiles of the screw and of the nut, follow a rolling path making use of two crown gears placed at the ends of the nut and, thanks to the large contact area on the thread, allow a particularly high load to be applied in a small area, thereby offering a greater competitive advantage. Today the rollers are produced internally by Moog in its Bergamo branch, while the gears found on the end of the roller and the crown gears are manufactured by MICROingranaggi.

To conclude…
“Another aspect which allowed us to have a further confirmation that MICROingranaggi was the right partner”, Roberto Donghi concluded, “was the flexibility which we noticed during our cooperation. During the first two years we doubled the production volume of satellite roller screws. This means that within three years the productivity requirement actually increased fourfold and MICROingranaggi was by our side in the best way, investing when necessary, to increase in turn its production capacity, in spite of the uncertainty of the market which often does not allow to determine beforehand what the real needs will be”.
Roberto Donghi’s words were echoed by Stefano Garavaglia, president and CEO, MICROingranaggi: “This partnership immediately seemed to be a very interesting challenge. Not just from a technological standpoint, but also at a more general level. The increase in the production of satellite roller screws which Moog had to face of course affected us too, since – as a technological partner – we had to outline a carefully planned investment strategy allowing us to support hem as best we could”. Investments carried out by MICROingranaggi concerned two new EMAG Koepfer 160 CNC gear cutters, flanked by the brand new Koepfer HLC150 H CNC gear cutter, showcased as a preview at the last EMO in Hannover and installed in October. “In general – Garavaglia added – these are very rigid and precise machines which allowed us, also by means of the implementation of gripping equipment and tailor-made tools, to create components suitable for the very demanding applications typical of mechanical components produced by Moog”. MICROingranaggi allocated part of the investments to gear control systems, specific equipment and software dedicated to these products’ requirements.