Nabtesco: robust joints for fast sprinters

Just like a competitive athlete, a fast delta robot also needs robust and "well-lubricated" joints. The French robot manufacturer Machines Pagès, headquartered in Foncine-le-Haut, therefore relies on the gear heads of the new RF-P series from Nabtesco. The advantages of the cycloidal gears are fully utilised here.

Machines Pagès is a manufacturer specialising in robot systems for the high-speed sector. The robots are primarily used in the following areas Packaging and medical technology as well as in parts production. They are not only suitable for particularly fast Pick-and-place applicationsbut also for moving or Positioning of injection moulds or stack moulds. There are currently over 1,200 Machines Pagès systems in use worldwide, around half of which are in the IML sector. The company carries out all phases of production, from design, parts production and software development through to assembly and commissioning, in order to guarantee its customers the highest possible product quality and operational reliability.

Six metres per second with high precision

The Delta robotwhich are used in the pick and place area of food packaging, impress with their high performance, precision and reliability. The arms of the high-speed robots are made of lightweight carbon fibres and move at a speed of over six metres per second in some cases. With such high dynamics, precise and at the same time Durable gearboxes indispensable. So far, planetary gearboxes have been used. However, they have a major disadvantage, which is particularly noticeable in dynamic pick & place applications: Their service life is very limited. "Planetary gearboxes wear out quickly in these applications," says Marcus Löw, Sales Director at Nabtesco.

"By switching to cycloidal gears, Machines Pagès expects a significant increase in the service life of the gears with increased precision in continuous operation. This will also extend the maintenance intervals of the robots and thus reduce maintenance costs, summarises Pagès. Marcus LöwSales Director at Nabtesco Precision Europe GmbH.

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Cycloidal gears extend service life

As part of a current project, Machines Pagès is therefore Cycloidal gearbox of the new RF-P series from Nabtesco. Eccentric gearboxes of this type essentially consist of four componentsThe first stage consists of a drive shaft, three eccentric shafts, two cam discs and an output shaft. In the first stage, the rotary motion of the drive is transmitted to the spur gears via the input shaft. The speed is reduced according to the reduction ratio of the input shaft to the spur gears. For the second reduction stage, a cam profile corresponding to the cam discs is incorporated on the inside of the housing. The cam profile in the housing has one more recess than the cam discs. Pins, which are arranged between the cam discs and the cam profile in the housing, transmit the rotary movement to the output shaft in a rolling motion. Once the eccentric shafts have completed a full rotation, the cam discs rotate off-centre by one pitch.

Cycloidal gearboxes such as the RF-P series from Nabtesco come in the second stage without gear wheels off. Sudden shock-induced failures are therefore ruled out. The even load distribution within the gearbox, high shock absorption and roller contact between the cycloidal disc and the housing ensure particularly low-wear operation. "Compared to conventional planetary gears, cycloidal gears have a significantly longer service life," emphasises Marcus Löw. Another advantage over planetary gears is the reduction ratio: as cycloidal gears do not require additional preliminary stages, they allow reduction ratios of 30:1 to over 300:1.

Installation kits to replace planetary gearboxes

The new RF-P series is based on Nabtesco's RV reduction gearboxes with a two-stage reduction principle and is Especially for use in the arm axes of Delta and Scara robots designed. The gearboxes offer high output speeds of up to 200 min^-1 and, thanks to their compact dimensions, come with Small installation space from. Their design ensures very good gearbox behaviour in terms of dynamics as well as high repeatability and path accuracy - even with very fast and abrupt movements, which are common in pick & place applications in modern automation. These gearboxes can also maintain this accuracy over a longer period of operation - a decisive advantage over planetary gearboxes, where a considerable increase in backlash can also be observed over the course of their service life.

Nabtesco offers the installation kits in different versionsRF-19P and RF-32P. They can withstand even high shock loads of up to 570 and 960 Nm respectively. This corresponds to three times their permissible nominal torque. The RF-19-P variant is an extension of the RF-32P gearbox and is designed for lower torques. In very fast robots for handling tasks with particularly small parts (for example in the Packaging of small parts and blister packs), the 32-P version would be oversized. The cycloidal gears of the RF-P series have been successfully in use at Machines Pagès for several months and the French company is considering switching to cycloidal gears from Nabtesco across the board in the medium term.

[infotext icon]Today, Nabtesco is the world's largest manufacturer of Precision gearboxes in cycloidal design. The manufacturer's cycloidal gears are used in around 60 per cent of all industrial robots around the world. With more than 5,000 employees in numerous production facilities and sales and service centres around the world, including the European headquarters in Düsseldorf, Nabtesco offers comprehensive customer service for individual needs.