CNC UPGRADE RESTORES GEAR HOBBER TO FULL PRODUCTIVITY

A gear hobber is a special type of milling machine used for producing gears. The typical machine has two non-parallel shafts, one mounted with a blank work-piece and the other with a cutting tool featuring helically arranged teeth, known as a hob. The hob makes a series of cuts in the work-piece, and the relative rotational speed of the shafts determines the number of teeth, which will be cut. Compared to other gear cutting processes, hobbing is relatively fast and inexpensive, which is why it used extensively throughout the industry.

Gleason Corporation (Rochester, NY) is a world leader in gear manufacturing technology. Founded in 1865, its machines are now ubiquitous. Their 782 gear hobber is no exception. It is widely regarded as an industrial workhorse and enjoys a very large customer base. One of these machines is used by a large aerospace components manufacturer in Chihuahua, Mexico, to produce spur, helical and crown gears with complex profiles.

However, this particular gear hobber?s control system was showing signs of age. It has seven CNC axes which were controlled by an Allen Bradley 8600 CNC system and an external electronic gearbox, both of which had become outdated, unreliable and difficult to maintain. After several months of intermittent operation, the company solicited the help of automation upgrade specialists MasterControls Inc., LLC (MCI; Pendleton, IN) and Southern Technical Services, LLC (STS; Oviedo, FL) to restore the machine to peak operational condition at a fraction of the cost of a new machine.

MCI and STS quickly ascertained that the gear hobber was in excellent mechanical condition, but would benefit from new CNC control hardware and software, together with a new operator's panel and some associated control modules. They jointly retrofitted the machine with a new CNC control system from NUM Corporation (Napierville, IL).

Prior to the retrofit, the machine's control system had become increasingly unreliable, resulting in high maintenance overhead and unacceptable downtime. The machine's new CNC software includes the NUMGear package that features a highly intuitive graphical user interface to help maximize productivity. This software 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.

The customer requested that the machine's existing drives, motors and feedback devices ? all of which were perfectly serviceable ? should be retained, and also stipulated that the machine footprint should not be changed. 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.

According to Jeff Petry, president of MCI, "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 overall result is a very clean installation, which will contribute significantly to ease of future maintenance."

The retrofit package is based entirely on NUM equipment. As well as the new seven-axis CNC controller, this includes a new PC-based operator panel that features a large, easy-to-read 15 in LCD screen with a full membrane keyboard, and a 61-button machine tool builder panel with a hand pulse generator. An industrial mouse was also mounted on the operator panel, for convenience of the operator.

The NUMGear software package features a highly intuitive graphical user interface. The operator simply fills in fields on a graphical representation of the part on the HMI and selects a hob tool ? the program is then generated automatically. All customer parts and hobs can be saved on the system by part number, so that they can easily be recalled when the part is needed for production again, and hob programs can easily be archived onto an external USB memory device.

The NUMGear package provides close monitoring of the hob tooling: the operator merely enters values into the shift data fields displayed on the HMI and the software then handles all hob shifting completely automatically, informing the operator when it is time to check or replace the hob. This tight control approach enables tooling costs to be kept to a minimum ? hobs can be sent out for grinding and recoating many times before they are worn out. The new CNC control system also performs all of the functions that previously demanded an external electronic gearbox, as previously mentioned.

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 they were producing a full set of gear types, all of which passed inspection in the customer's quality control laboratory. At the same time, they conducted operator training, and the new user interface proved so intuitive that by the end of the day the operators were able to handle their own set-ups, including entering all part and hob data. The machine is now back in full-time production.

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NUM Corporation, 603 East Diehl Road, Suite 115, Naperville, IL 60563, 630-505-7722; www.num.com.

MasterControls Inc., LLC, 10951 S. 100 E., Pendleton, IN 46064, 765-533-6719; MasterControls.com.

Southern Technical Services, LLC, 5709 Aloma Woods Boulevard, Oviedo, FL 32765, 407-971-0196, www.SouthernTechnicalServices.com.