feature story

Power drawbar gives old vertical turret lathes new life

Advanced Machine & Engineering built a special power drawbar, over 3,000mm in height, for handling the tool changes and spindle interface on this Bullard Vertical Turning Lathe, showing the rotating work table, ram assembly and tool changer.

New or rebuild? That’s a question being asked more often in light of the economic downturn. What’s a company to do for a vertical turret lathe?

Essex Machine Tool Services, New Britain, CT, poses a solution to get better performance from an old machine than a new one.

Essex rebuilds and remanufactures conventional VTLs to CNC. It also provides spare parts for the legacy line of Bullard vertical turret lathes.

Operated by Dana Budney and Chester Perry, the company specializes in remanufacturing VTLs from the ground up, saving only the old quality cast iron frame and incorporating all-new spindle drive systems, tool changers, ram/drawbars, axis positioning, new hydraulics, lube systems and other components in the process.

“Sometimes customers can get a new machine for 30 percent more than the cost of a remanufactured machine which has the same functions,” Budney explained.

“The remanufactured machine can outperform the new machine for less money,” he added. “In the past, that wasn’t always the case, but, today, with the advanced CNC, motor, drives and technology available, a machine can actually be made to run better than when it was new.

Superior positioning and new way liner materials with heightened feedback and accuracy make the remanufactured VTL’s technology advanced in a way that was impossible in bygone days.

Another of the key components used to achieve the highest levels of functionality on the remanufactured VTLs is a power drawbar from OTT-Jakob, a leading supplier in Europe. This company has been represented in America for nearly 30 years by Advanced Machine & Engineering of Rockford, IL, itself the home to many top names in the machine tool industry, including the current OEM for the VTLs remanufactured at Essex, the DeVlieg-Bullard Services Group, now part of Bourn & Koch.

By using the OTT-Jakob power drawbar, Budney said, the VTL can be modified for use with virtually any tool clamping system, including HSK, KM, and 50 or 60 taper. As this drawbar design is relatively recent, it marks another example where the remanufactured VTLs with the advanced drawbar actually bring the machine tool to a higher level of performance than when it was new.

The OTT-Jakob universal inside spindle contour was an important step toward achieving totally modular tooling, as it allows the rebuilder and its customer the flexibility to use different steep taper HSK 60 tools with air blast coolant-through functionality, by simply exchanging the gripper unit.

Unique features of the OTT-Jakob power drawbar include an intensifying mechanism that amplifies the pull force of the springs to approximately 3½ times as well as a signal ring to sense positioning and special front and rear inserts to accept the drawbar.

Since the ram unit is stationary and the work table rotates on the Bullard VTL, hydraulic and air lines are likewise stationary in this application. AME also designed a front and rear insert to accept the gripper unit without removing the drawbar from the ram. With the drawbar in place in the ram, the changeover of gripper units could be done quickly and with assured proper positioning. To further aid the position integrity, the drawbar also provides a signal ring to sense positioning.

In addition, another supplier innovation was designed into this drawbar assembly. An intensifier mechanism amplifies the pull force to 3½ times greater than the spring stack, which allows the drawbar’s use in a considerably smaller space. Given the massive size of this ram and the weight of the tooling involved, this represents a design and performance advantage for Essex, according to Paul Vitols, chief engineer at Essex Machine Tool.

Essex Machine Tool Services

OTT-Jakob / Advanced Machine & Engineering Co.