机械设计制造及自动化专业毕业设计（论文）文献翻译1. 英文Shapers, Drilling and Milling Machines A shapers utilizes a single-point tool on a tool holder mounted on the end of the ram. Cutting is generally done on the forward stroke. The tool is lifted slightly by the clapper box to prevent excessive drag across the work, which is fed under the tool during the return stroke in preparation for the next cut. The column houses the operating mechanisms of the shaper and also serves as a mounting unit for the work-supporting table. The table can be moved in two directions mutually perpendicular to the ram. The tool slide is used to control the depth of cut and is manually fed. It can be rotated through 90 deg, on either side of its normal vertical position, which allows feeding the tool at an angle to the surface of the table. Two types of driving mechanisms for shapers are a modified Whitworth quick-return mechanism and a hydraulic drive. For the Whitworth mechanism, the motor drives the bull gear, which drives a crank arm with an adjustable crank pin to control the length of stroke. As the bull gear rotates, the rocker arm is forced to reciprocate, imparting this motion to the shaper ram. The motor on a hydraulic shaper is used only to drive the hydraulic pump. The remainder of the shaper motions are controlled by the direction of the flow of the hydraulic oil. The cutting stroke of the mechanically driven shaper uses 220 deg. Of rotation of the bull gear, while the return stroke uses 140 deg. This gives a cutting stroke to return stroke ratio of 1.6 to 1. The velocity diagram for a hydraulic shaper shows that for most of the tool during cutting stroke is never constant, while the velocity diagram for a hydraulic shaper shows that for most of the cutting stroke the cutting speed is constant. The hydraulic shaper has an added advantage of infinitely variable cutting speeds. The principal disadvantage of this type of machine is the lack of a definite limit at the end of the ram stroke, which may allow a few thousandths of an inch variation in stroke length. A duplicating device that makes possible the reproduction of contours from a sheet-metal template is available. The sheet metal template is used in conjunction with hydraulic control. Upright drilling machines or drill presses are available in a variety of sizes and types, and are equipped with a sufficient range of apindle speeds and automatic feeds to fit the neds of most industries. Speed ranges on a typical machine are from 76 to 2025 rpm., with drill feed from 0.002 to 0.020 in.per revolution of the spindle. Radial drilling machines are used to drill workpieces that are too large or cumbersome to conveniently move. The spindle with the speed and feed changing mechanism is mounted on the radial arm; by combining the movement of the radial arm around column and the movement of the spindle assembly along the arm, it is possible to align the spindle and the drill to any position within reach of the machine. For work that is too large to conveniently support on the base, the spindle assembly can be swung out over the floor and the workpiece set on the beside the machine. Plain radial drilling machines provide only for vertical movement of the spindle; universal machines allow the spindle to swivel about an axis normal to the radial arm and the radial arm to rotate about a horizontal axis, thus permitting drilling at any angle. A multispindle drilling machine has one or more heads that drive the spindles through universal joints and telescoping splined shafts. All spindles are usually driven by the same motor and fed simultaneously to drill the desired number of holes. In most machines each spindle is held in an adjustable plate so that it can be moved relative to the others. The area covered by adjacent spindles overlap so that the machine can be set to drill holes at any location within its range. The milling operation involves metal removal with a rotating cutter. It includes removal of metal from the surface of a workspiece, enlarging holes, and form cutting, such as threads and gear teeth. Within an knee and column type of milling machine the column is the main supporting member for the other components, and includes the base containing the drive motor, the spindle, and the cutters. The cutter is mounted on an arbor held in the spindle, and supported on its outer extremity by a bearing in the overarm. The knee is held on the column in dovetail slots, the saddle is fastened to the knee in dovetail slots, and the table is attached to the saddle. Thus, the build-up the knee and column machine provides three motions relative to the cutter. A four motion may be provided by swiveling the table around a vertical axis provided on the saddle. Fixed-bed milling machines are designed to provide more rigidity than the knee and column type. The table is mounted directly on the machine base, which provides the rigidity necessary for absorbing h