Production Machining

NOV 2018

Production Machining - Your access to the precision machining industrial buyer.

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in diameter and use Beckho servodrive actuation for tool feeding and part clamping. "Targeted at the heart of the hydraulic cylinder market, the SHD is designed for volume production of relatively standard cylinders. For more specialized cylinders requiring a cross-hatch pattern for oil retention, honing is the preferred process," Mr. Hanna says. Candidates for the SHD skiving/ roller burnishing system include the agriculture, heavy-duty construction, mining, motion control and material handling industries and others that produce hydraulic actuation cylin- ders within the machine's capacity range. Within its targeted manufacturing market, most producers use tube stock as the raw material. Generally not pre-processed, the tube is simply cut to length and mounted on the machine for processing the ID. Skiving is able to accurately size bores despite variability in wall thickness. †e skiving/roller burnishing toolhead uses a hydraulically actuated expanding mandrel mecha- nism that is preset to the desired diameter size. †e toolhead ˆoats on the tool drive shaft to self-center, and the drive shaft itself uses a vibration damping system to elimi- nate chatter marks. On the SHD system, the skiving process is followed immediately by the roller burnishing process that uses the expanding mandrel mecha- nism as well. At the end of the stroke, the skiving tool extends through the bore so the burnishing tool can complete its stroke. †e Sunnen machine uses a unidirectional skiving/roller burnishing stroke. At the end of the cutting stroke, the skiving and burnishing tools retract and are withdrawn from the bore. †e retraction is su‹cient so that no contact is made on the walls of the Œnish bore, meaning there are no drag lines or scratches in the bore. †e rigidity of the machine and cutting/ Œnishing toolhead combination hit the size and Œnish toler- ances without the need for a cleanup pass. In the skiving/roller burnishing process, two tradition- ally separate operations are combined into one. A critical consideration to making this multitasking operation work is coolant and chip control. Skiving is a metalcutting process and therefore gener- ates chips. Depending of the variability of wall thickness of the sized tube stock being used, the amount of these often stringy chips can be signiŒcant. With the roller burnishing process immediately following the skiving process, and performing its surface Œnish opera- tion, the chips must be clear or there is a risk damaging the surface of the bore. In a two-step process, skiving followed by roller burnishing, this is less of an issue. However, to take advantage of the time savings of combining the two opera- tions into a single stroke, chip control is critical. †e SHD uses a speciŒc cutting oil or water-based coolant for this operation that works to ˆush the skiving chips toward the front of the machining stroke, ahead of the skiving tool, so the roller burnishing tool has a clear surface to work with. †e cutting tool head is plumbed in such a way that the cutting oil forms a jacket around the tool that ˆushes the chips ahead of the operation and out the end of the bore into a chip removal and oil recovery unit. Sunnen partnered with Prince Manufacturing on the development and testing of the SHD system in Prince's Lewis and Clark Hydraulics facility in Yankton, South Dakota, ensuring it met all of the critical needs of the market, from overall machine layout to the details on the control screens. Prince is one of the industry's premier manufacturers of hydraulic valves, pumps, cylinders and accessories, with Œve plants in the U.S. In a beta test at the Prince facility, a 3-inch ID by 12-inch long tube is successfully skived and roller burnished in 10 to 15 seconds with spot-on specs. "†at would take us 60 percent longer with honing," Mr. Hanna says, "which is why shops are looking at the skiving/roller burnishing process as an alternative for the right application." It's the ability to bring the various factors that comprise the system approach needed to perform a skiving/burnishing combination process that gives Sunnen a competitive edge. The company takes responsibility for the machine, tooling, workholding chip management and cutting fluid to provide a complete solution for production bore sizing and finishing operations of hydraulic cylinders. Sunnen Products Co. | 314-781-2110 | :: The combination skiving/roller burnishing tool is manufactured by BT Heller, a holly oned subsidiary of Sunnen Products Co. Here's another article on this topic: e Forgotten Art of Skiving Here's a look at one of the oldest and most e•cient meth- ods of screw machine production for parts that are long and slender, with close-diameter tolerances and -nishes, or parts that require truly spherical radii. LINK :: TECH BRIEF :: 25

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