机械工程专业英语文本施平10

第10 次课的教学整体安排2.教学内容与讨论、思考题、作业部分可合二为一。

14 Lathes车床Lathes are widely used in industry to produce all kind of machined parts. Some are general-purpose(通用的) machines, and others are used to perform highly specialized operations.Engine Lathes普通车床Engine lathes, of course are general-purpose machines used in production and maintenance shops all over the world. Sizes range from small bench models to huge heavy-duty(重型的) piece of equipment. Many of the larger lathes come equipped with attachments not commonly found in the ordinary shop, such as automatic stops for the carriage.Tracer or Duplicating Lathes仿形/靠模车床The tracer or duplicating lathe is designed to produce irregularly shaped parts automatically. The basic operation of this lathe is as follows: A template(模板、模型) of either a flat or three-dimensional shape is placed in a holder. A guider or pointer(仿形指) then moves along this shape and its movement controls that of the cutting tool. The duplication may include a square or tapered(锥形的) shoulder(台肩), grooves, tapers(锥体), and contours. Works such as motor shafts, spindles, pistons, rods, car axles, turbine shafts, and a variety of other objects can be turned using this type of lathe.Turret Lathes 转塔车床A Turret lathe is basically similar to an engine lathe except that the conventional tool post is replaced with a hexagonal turret, which can be rotated around a vertical axis as required. Appropriate tools are mounted onthe six sides of the turret. The length of each tool is so adjusted that by simply indexing(转动) the turret, any tool can be brought in exactly the desired operating condition. Those cutting tools can, therefore be employed successively(依次地) without the need for dismounting the tool and mounting a new one each time, as the case with conventional engine lathe. This result in an appreciate saving in the time required for setting up the tools. Also, on a turret lathe a skilled machinist is required only initially to set up the tools. (对刀) A laborer with limited training can operate the turret lathe thereafter and produce parts identical to those that can be manufactured when a highly skilled machinist operates the lathe.Automatic Screw Machine自动切丝机Screw machine are similar in construction to turret lathe, except that their heads are designed to hold and feed long bars of stock. Otherwise, there is little difference between them. Both are designed for multiple tooling, and both have adaptations for identical work. Originally, the turret lathe was designed as a chucking lathe for machining small castings, forgings, and irregularly shaped work piece. The first screw machines were designed to feed bar stock and wire used in making small screw parts. Today, however, the turret lathe is frequently used with a collet attachment, and the automatic screw machine can be equipped with a chuck to hold castings.The single-spindle automatic screw machine, as its name implies, machines work on only one bar of stock at a time. A bar 16 to 20mfeet long is fed through the headstock spindle and is held firmly by a collet. The machining operations are done by cutting tools mounted on the turret and on the cross slide. When the machine is in operation, the spindle and the stock are rotatedat selected speeds for different operations. If required, rapid reversal of the spindle is also possible.In the single-spindle automatic screw machine, a specific length of stock is automatically fed through the spindle to a machining area. At this point, the turret and the cross slide move into position and automatically perform whatever operation are required. After the machined piece is cut off, stock is again fed into the machining area and the entire cycle is repeated.Multiple-spindle automatic screw machines have four to eight spindles located around a spindle carrier. Long bar of stock, supported on the rear of the machine, pass through these hollow spindles and are gripped by collets. With the single-spindle machine, the turret indexes around the spindle. When one tool on the turret is working, the others are not. With a multiple-spindle machine, however, the spindle itself indexes. Thus the bars of stock are carried to the various end-working and side-working tools. Each tool operates in only position, but all tools operate simultaneously. Therefore, four to eight work pieces can be machined at the same time.Vertical Turret Lathes立式转塔车床A vertical turret lathe is basically a turret lathe that has been stood on its headstock end. It is designed to perform a variety of turning operations. It consists of a turret, a revolving table, and a slide head with a square turret for holding additional tools. Operations performed by any of the tools mounted on the turret or side head can be controlled through the use of stops. Machining Center(MC加工中心)Many of today’s more sophisticated lathes are called machining centers since they are capable of performing, in addition to the normal turning operations,certain milling and drilling operations. Basically, a machining center can be thought of as being a combination turret lathe and milling machine. Additional features are sometimes included by manufacturers to increase the versatility of their machines.(FMS F lexible M anufacturing S ystem柔性制造系统)(HSC H igh S peed C utting 高速切削)。