Replacing CNC Restores Gear Hobber to Full Productivity

March 8, 2010
NUM CNC replaces Gleason machines automation package, without a separate gearbox

Automation upgrade specialists MasterControls Inc. and Southern Technical Services have jointly retrofitted a Gleason 782 gear hobber with a new CNC control system from NUM.

The new operator panel features a large, easy-to-read 15-inch LCD screen and full membrane keyboard, and a 61-button machine tool builder’s panel.

An internal view of the gear hobber, showing the complex multi-axis system and the hob shaft.

An aerospace components manufacturer that produces spur, helical, and crown gears with complex profiles had a problem with declining productivity. Its Gleason 782 gear hobber was showing its age, becoming unreliable, especially in regard to its process controls.

Gleason Corp. specializes in gear-making machinery, or “hobbers.” Typically, these machines have two non-parallel shafts, one mounted with a blank workpiece and the other with a cutting tool that has teeth in a helical arrangement. This “hob” makes a series of cuts in a workpiece. The relative rotational speed of the shafts determines the number of teeth that are cut, thus forming the gear to specification.

The Gleason 782 gear hobber is a widely installed “workhorse” design. But, the unreliable control system in this specific installation was driving up the machine shop’s maintenance costs, diminishing productivity, and forcing unacceptable downtime.

This machine’s seven CNC axes were controlled by an Allen Bradley 8600 CNC system and an external electronic gearbox. After several months of intermittent operation, the operators approached two automation specialists, MasterControls Inc. and Southern Technical Services, to restore the machine to peak condition. The success of the project gave the machine shop the effect of a new machine at a fraction of the cost.

MasterControls Inc. (MCI) and Southern Technical Services (STS) quickly ascertained that the Gleason 782 was in excellent mechanical condition, but would benefit from new CNC control hardware and software, a new operator’s panel, and some associated control modules. The customer requested that the machine’s existing drives, motors, and feedback devices (all of which were serviceable) should be retained, and stipulated no change to the machine footprint. MCI and STS accommodated this latter demand by developing an entirely new sub-panel containing the new NUM CNC, power supplies, circuit breakers and contactors, which was subsequently mounted inside the machine’s existing control cabinet.

As explained by MCI president Jeff Petry: “To minimize disruption at the customer’s premises we built the sub-panel off-site, and then arranged a convenient time for installation. Since swap-out time was going to be important, we chose to use NUM breakout boards in the new sub-panel, which made it very easy to connect to the machine’s existing drives – and by using machine I/O boards with terminal strips, we were able to land all the existing wiring without any trouble whatsoever. In fact, much to our customer’s satisfaction, we were able to remove all the obsolete control hardware and complete the wiring stages of the installation – including the sub-panel, CNC control, new operator’s panel and the magnetic cabinet – in just over three days.”

The neat installation that MCI and STS accomplished will significantly simplify future maintenance efforts, according to Petry.

The retrofit was based entirely on NUM technology and equipment. It includes a new seven-axis CNC controller; a new PC based operator’s panel, with an easy-to-read 15-inch LCD screen and a full membrane keyboard; and a 61-button machine tool builder’s panel with a hand pulse generator. For convenience, an industrial mouse was mounted on the operator panel.

The new NUM CNC machine software includes the NUMGear package. This program performs all of the functions that previously required an external electronic gearbox, thereby reducing the complexity of the system and the number of parts that require maintenance.

NUMGear features a highly intuitive graphical user interface. Using the HMI, the operator simply fills in fields on a graphical representation of the part, and then selects a hob tool: the program is generated automatically. All customer parts and hobs can be stored in memory according to part number, for simple recall when the part needs to be produced again. Hob programs can be stored on external USB memory devices.

The NUMGear package also makes it possible for an operator to monitor hob tooling. Once the values are entered into the HMI’s shift data fields, the software automatically handles all hob shifting. It informs the operator when to check or replace the hob, so tooling costs can be minimized. Hobs can be sent for regrinding and recoating many times before wearing out.

The new CNC control system also performs all of the functions that previously demanded an external electronic gearbox.

After installing the new hardware and verifying the wiring, MCI and STS powered-up the machine and immediately started verifying its operation. Within a day a full set of gear types was produced, each one passing the customer’s quality control inspection. They conducted operator training simultaneously, and the new user interface proved so intuitive that the operators were able to handle their own set-ups by the end of the day, including entering all part and hob data. The machine is back in full-time production — operating like new, but at considerably less cost.

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