A gear hobber is a special type of milling machine, used for producing gears. Typically, the machine will have 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.
The hobber’s new CNC software includes the NUMGear package, which features a highly intuitive graphical user interface to help maximise productivity. This software also performs all of the functions, which previously required an external electronic gearbox, thereby reducing the complexity of the system and the number of parts that require maintenance.
Gleason Corporation is a world leader in gearing technology; the company was founded in1865, and nowadays its machines are ubiquitous. The Gleason 782 gear hobber is no exception- widely regarded as an industrial workhorse, it enjoys a very large customer base. This particular machine is used by a large aerospace components manufacturer in Chihuahua, Mexico, to produce spur, helical and crown gears with complex profiles. It’s control system was showing signs of age. In this case, the gear hobber has seven CNC axes, which were controlledby an Allen Bradley 8600 CNC system and an external electronic gearbox, both ofwhich had become outdated, unreliable and difficult to maintain. After several months ofintermittent operation, the company solicited the help of MCI and STS to restore the machine to peak operational condition at a fraction of the cost of a new machine.
MasterControls Inc. (MCI) and Southern Technical Services (STS) quickly ascertained that the gear hobber was in excellent mechanical condition, but would benefit from newCNC control hardware and software, together with 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 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 minimise 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 MasterControls and Southern Technical Services have jointly retrofitted a Gleason 782 gear hobber, used by anaerospace components manufacturer in Chihuahua, Mexico, with a new CNC control system. Case Study Power in Motion - September 2010 12 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 toour customer’s satisfaction, we were able to remove all the obsolete control hardware andcomplete the wiring stages of the installation- including the sub-panel, CNC control, new operator’s panel and the magnetic cabinet - injust 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 NUMequipment. As well as the new seven-axis CNCcontroller, this includes a new PC based operator’s panel, which features a large, easy-to-read15-inch LCD screen with a full membrane keyboard,and a 61-button machine tool builder’s panel with a hand pulse generator. An industrial mouse was also mounted on the operator panel, for convenience of the operator.
The supplied NUM CNC software includes the NUMGear package, which features a highly intuitive graphical user interface. The operator simply fills in fields on a graphical representationof 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 also provides close monitoring of the hob tooling; the operator merely enters values into the shift datafields 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 verifyingits operation. Within a day they were producing a full set of gear types, all of which passed inspection in the customer’s quality controllaboratory. At the same time, they conducted operator training, and the new user interfaceproved so intuitive that by the end of the day the operators were able to handle their own set-ups, including entering all part and hobdata. The machine is now back in full time production.
