Production Accelerated by CNC Refurbishment of Gear Shaper

July 7, 2011
Linear actuator enables wind-turbine gear profile changeovers in minutes, not hours
The refurbished Stanko gear shaper uses a NUM Axium Power CNC system to control all five axes.
The gear shaper is currently being used to manufacture large internally cut gears for the wind turbine industry.

Advanced gear shaping software and motion control hardware from NUM has been used to bring an older, manually controlled gear shaping machine up to modern control standards. The five-axis Stanko machine is controlled by a NUM Axium Power CNC system, using electronic gearbox techniques to synchronize the rotary cutter, gear blank and stroking axes. It also incorporates a novel programmable replacement for the stroking axis, which reduces product changeover time from hours to minutes - significantly improving productivity.

NUM works with customers to improve their machining operations by developing “high-end CNC applications.”

The gear shaper was bought by DePe Gear Company, an English manufacturer that specializes in design, production, and refurbishment of gears and gearboxes for multiple industrial and commercial applications, including the steel processing, rail, mining, quarrying and aeronautical industries. The company operates a considerable number of gear cutting, shaping and grinding machines at its Stoke-on-Trent plant and is no stranger to NUM: three of its gear cutting machines are equipped with NUM Axium CNC systems and NUMgear software. In this particular case, DePe Gear Co. purchased the Russian-built Stanko gear shaper initially for manufacturing large internal gears for wind turbines, and subsequently commissioned machine tool engineering company Euro CNC to carry out the necessary refurbishment work.

Euro CNC specializes in retrofitting, rebuilding, and upgrading machines. Very often this involves equipping manual machines with partial or full CNC systems, and the company consequently maintains a close working relationship with NUM, providing it with access to the latest CNC technology, control software, digital drives and motors. In recent years, Euro CNC has built up considerable knowledge of machine tools for gear production, and now handles a wide variety of gear hobbing and shaping machines.

Euro CNC quickly ascertained that although the machine was fully mechanically serviceable, it would benefit from being equipped with new motors and drives, including high performance digital units for all axes, together with a CNC system for operational flexibility and a customized HMI to replace outmoded mechanical switchgear.

Traditionally, gear shaping machines employ a complex, cam-driven ‘nodding’ axis arrangement to move the cutting tool up and down the gear blank as it is cut, the stroke of which needs to be synchronized to the rotation of the tool and the blank. This approach suffers from numerous disadvantages: it can involve up to three axes of movement, each subject to error, and is extremely difficult and time-consuming to set up, which does not sit well with the fast and flexible changeover requirements of modern manufacturing. So, Euro CNC decided to develop an entirely new form of stroking axis, based on a fully programmable linear actuator. The end position, length and speed of the stroke can be freely changed under software control.

In addition to the stroking axis, the gear shaper has three rotary axes – to rotate the cutting tool and the gear blank, and to retract the cutting tool on the up stroke – together with a linear positioner based on a motor and ballscrew, which drives the gear blank to the cutting tool. All of these axes are controlled by NUMDrive C servo drives and NUM brushless motors.

Euro CNC chose to use a NUM Axium Power CNC system to control all five machine axes, networked to a NUM industrial PC and a large touch-sensitive screen. The software includes NUM’s powerful NUMgear package, but in this instance it is used mainly to provide the electronic gearbox functions for synchronizing the cutting tool rotation, gear blank rotation and linear stroking axes. The HMI for the gear shaper machine is primarily created by a special version of NUM’s PC ProCam software, which was developed jointly by Euro CNC and NUM’s USA operation, specifically for this type of application. The software combines an intuitive graphical user interface using common gear shaping terminology with a ‘conversational’ style of programming, so operators who are not familiar with CNC-based machines are able to become proficient very quickly.

The refurbished Stanko gear shaper was installed at DePe Gear Company in Stoke-on-Trent recently, and aside from a few minor initial issues the operators say it has performed flawlessly.

Nigel Parker, DePe Gear Company technical director, explained: “We are using the gear shaper for a variety of internally cut gears, including spur gears for wind turbine generator gearboxes and a variety of splined gears. Although it is too early to provide quantified data, we are definitely seeing a reduction in setup and operating times.

“Like our other CNC machines,” he continued, “the most significant benefit comes from the sheer versatility of this all-digital approach, which enables us to switch freely from manufacturing one type of gear to another under software control. Machine operators no longer need to laboriously count the number of teeth being cut, but simply push the appropriate button on the menu, which helps maximize throughput.”

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