Sunnen Products Company’s quantum improvement in a key manufacturing process for cast-iron hydraulic valve bodies using a precision single-stroke honing process that achieves cylindricity/straightness with less than 2 microns in bores as much as 10 times longer than diameter. Developed in Europe to meet leak-free requirements for high-pressure hydraulic systems, the high precision single-stroke honing process is almost 200 percent more accurate than anything previously achievable for long, small diameter, tandem bores.
Single-stroke honing is a single-pass process that sizes and finishes a bore with a series of progressively larger superabrasive tools adjusted to a preset diameter. Single-stroke honing tools rotate while passing through the bore one time and then withdrawing. The machine's servo-controlled stroking system provides flexibility with adjustable speed and various feed profiles, such as pecking, short stroke, dwell, and so on. Column feed and spindle speed can be varied throughout a cycle using the machine control.
The single-stroke honing tool consists of a tapered arbor with an expandable diamond-plated abrasive sleeve mated to it. The external profile of the sleeve is designed for the application. Single-pass honing is especially suited for solid bore parts with length-to-diameter ratio of 1:1 or less. Parts with much larger length-to-bore ratio can be honed under certain circumstances. Bores that have interruptions allow better chip flushing and reduce the load on the abrasive sleeve. In the case of cast iron valve bodies, bore length-to-diameter ratios of 10 or more can be single-pass honed.
The high precision, single-stroke process utilizes a combination of tool processing, toolholding, workpiece fixturing and process parameters, without any penalty on cycle time. It is already in use by manufacturers of hydraulic valves in Turkey, Italy, Germany, Switzerland, Brazil, Sweden and the U.S.