RETROFIT BRINGS MASSIVE FLOOR-TYPE MILL UP TO MODERN STANDARDS

Mine of Information: This old Gray horizontal boring mill used in the mining industry was electrically upgraded to higher precision, compatibility with RS274 G-code programming, probing functionality, and an industrial PC front-end with unlimited program storage and networking . . . all for a fraction of the cost of a new machine.

CNC technology from NUM Corporation (Naperville, IL) has been used to bring the programming software and motion control system on an old floor-type horizontal boring mill originally manufactured by Gray up to state-of-the-art standards. The electrical upgrade was performed by automation systems integrator MasterControls LLC Inc. (MCI; Pendleton, IN) and was part of a complete mechanical rebuild of the mill by a major U.S. machine rebuilder. The machine is now in production with an end-user working in the mining industry.

The mill, which has a massive 42 ft travel on the main horizontal axis and weighs over 100,000 lb (greater than 45,000 kg), had originally been converted from manual to CNC operation back in the 1970s. However, the control system was primitive by today’s standards, with numerous drawbacks that included limited CNC functionality, a very small memory size, and no networking capability.

MCI and its rebuilder customer performed an extremely comprehensive electrical and mechanical rebuild on the mill – even adding a secondary X-axis. By choosing a NUM CNC kernel, the integrator has been able to bring the mill’s CNC functionality up to modern standards. New capabilities include compatibility with RS274 G-code programming, probing functionality, and an industrial PC front-end providing unlimited program storage, as well as networking.

The introduction of a tandem drive arrangement on the X-axis made a major contribution to the machine’s performance and accuracy, increasing torque dramatically for the main axis of the machine. The two axes are now synchronized in a master-slave arrangement, with the new secondary axis set to lag the primary axis very slightly in order to maintain tension in the geartrain and eliminate backlash.

The flexibility of the drives and control software that allowed this configuration was an important reason behind the decision to base the upgrade on NUM technology, because its drives support master-slave architectures. As this was a critical element of the project, the integrator visited the Naperville facility during the development of the control system to physically test the tandem control, as well as to get the CNC vendor’s feedback on the proposed control and programming scheme.

Improving the underlying precision and accuracy of the heavily-built mill was a major feature of the control system upgrade, and MCI additionally implemented a table with laser measurements of axis positions to compensate for other variations in the mechanics. Other key factors in choosing this particular CNC system was the ability to upgrade the servomotor drives to advanced digital operation with absolute feedback that enhanced precision a step further. This also eliminated the need for homing moves that free the end user from having to reference the machine on power loss or after shutdown.

All of the control system engineering and panel building was done off-site. When the retrofit control system was complete, the systems integrator took the package to the customer rebuild site and started installation. This phase was achieved in just three days.

After testing and training, the whole machine was then disassembled and shipped to the end user. According to managing partner Jeff Petry of MCI, “The refurbished mill now has both a machining accuracy and a rich programmability that is comparable with a brand new mill, but at a fraction of the cost. The technical support provided by NUM, who often partners with us on applications like this, makes us comfortable taking on these types of major projects.”

MCI has become well known for automation upgrades on machine tools. The system integrator has over 25 years of experience in the business, replacing legacy CNC systems on lathes, mills, grinders, gear hobbers and other capital equipment. One reason behind the integrator’s significant share of the U.S. machinery rebuilding market is its willingness to retain existing analog-interfaced servomotor drives on CNC systems – for economy . . . although this was not a factor in this latest project where the demand was for optimum precision.

In turn, the integrator relies on close relationships with a number of reliable control system equipment partners, including NUM for CNC applications because of the programming flexibility their system provides and their willingness to supply in-depth technical support. “Strong engineering support and a partnership approach has always been a major element of our business philosophy,” adds Steve Schilling, the general manager of NUM. “That is one of the reasons behind our success with small to mid-sized machine tool OEMs, and system integrators and upgrade specialists.”

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

MasterControls Inc. LLC, 10951 S. 100 E., Pendleton, IN 46064, 765 533-6719 or 765-425-4249, Mastercontrols.us.