1、组合机床论文中英文资料外文翻译文献中英文资料外文翻译文献TRANSFER AND UNIT MACHINE While the specific intention and application for transfer and unit machine vary from one machine type to another, all forms of transfer and unit machine have common benefits. Here are but a few of the more important benefits offered by TRANSFER A
2、ND UNIT MACHINE equipment.The first benefit offered by all forms of transfer and unit machine is improved automation. The operator intervention related to producing workpieces can be reduced or eliminated. Many transfer and unit machine can run unattended during their entire machining cycle, freeing
3、 the operator to do other tasks. This gives the transfer and unit machine user several side benefits including reduced operator fatigue, fewer mistakes caused by human error, and consistent and predictable machining time for each workpiece. Since the machine will be running under program control, th
4、e skill level required of the transfer and unit machine operator (related to basic machining practice) is also reduced as compared to a machinist producing workpieces with conventional machine tools.The second major benefit of transfer and unit machine technology is consistent and accurate workpiece
5、s. Todays transfer and unit machines boast almost unbelievable accuracy and repeatability specifications. This means that once a program is verified, two, ten, or one thousand identical workpieces can be easily produced with precision and consistency.rd benefit offered by most forms of transfer and
6、unit machine tools is flexibility. Since these machines are run from programs, running a different workpiece is almost as easy as loading a different program. Once a program has been verified and executed for one production run, it can be easily recalled the next time the workpiece is to be run. Thi
7、s leads to yet another benefit, fast change over. Since these machines are very easy to set up and run, and since programs can be easily loaded, they allow very short setup time. This is imperative with todays just-in-time (JIT) product requirements.Motion control - the heart of transfer and unit ma
8、chineThe most basic function of any transfer and unit machine is automatic, precise, and consistent motion control. Rather than applying completely mechanical devices to cause motion as is required on most conventional machine tools, transfer and unit machines allow motion control in a revolutionary
9、 manner2. All forms of transfer and unit machine equipment have two or more directions of motion, called axes. These axes can be precisely and automatically positioned along their lengths of travel. The two most common axis types are linear (driven along a straight path) and rotary (driven along a c
10、ircular path).Instead of causing motion by turning cranks and handwheels as is required on conventional machine tools, transfer and unit machines allow motions to be commanded through programmed commands. Generally speaking, the motion type (rapid, linear, and circular), the axes to move, the amount
11、 of motion and the motion rate (feedrate) are programmable with almost all transfer and unit machine tools.A transfer and unit machine command executed within the control tells the drive motor to rotate a precise number of times. The rotation of the drive motor in turn rotates the ball screw. And th
12、e ball screw drives the linear axis (slide). A feedback device (linear scale) on the slide allows the control to confirm that the commanded number of rotations has taken place3. Refer to fig.1.Fig.1Though a rather crude analogy, the same basic linear motion can be found on a common table vise. As yo
13、u rotate the vise crank, you rotate a lead screw that, in turn, drives the movable jaw on the vise. By comparison, a linear axis on a transfer and unit machine machine tool is extremely precise. The number of revolutions of the axis drive motor precisely controls the amount of linear motion along th
14、e axis.How axis motion is commanded - understanding coordinate systemsIt would be infeasible for the transfer and unit machine user to cause axis motion by trying to tell each axis drive motor how many times to rotate in order to command a given linear motion amount4. (This would be like having to f
15、igure out how many turns of the handle on a table vise will cause the movable jaw to move exactly one inch!) Instead, all transfer and unit machine controls allow axis motion to be commanded in a much simpler and more logical way by utilizing some form of coordinate system. The two most popular coor
16、dinate systems used with transfer and unit machines are the rectangular coordinate system and the polar coordinate system. By far, the more popular of these two is the rectangular coordinate system.The program zero point establishes the point of reference for motion commands in a transfer and unit m
17、achine program. This allows the programmer to specify movements from a common location. If program zero is chosen wisely, usually coordinates needed for the program can be taken directly from the print.With this technique, if the programmer wishes the tool to be sent to a position one inch to the ri
18、ght of the program zero point, X1.0 is commanded. If the programmer wishes the tool to move to a position one inch above the program zero point, Y1.0 is commanded. The control will automatically determine how many times to rotate each axis drive motor and ball screw to make the axis reach the comman
19、ded destination point . This lets the programmer command axis motion in a very logical manner. Refer to fig.2, 3.Fig.2Fig.3All discussions to this point assume that the absolute mode of programming is used6. The most common transfer and unit machine word used to designate the absolute mode is G90. I
20、n the absolute mode, the end points for all motions will be specified from the program zero point. For beginners, this is usually the best and easiest method of specifying end points for motion commands. However, there is another way of specifying end points for axis motion.In the incremental mode (
21、commonly specified by G91), end points for motions are specified from the tools current position, not from program zero. With this method of commanding motion, the programmer must always be asking How far should I move the tool? While there are times when the incremental mode can be very helpful, ge
22、nerally speaking, this is the more cumbersome and difficult method of specifying motion and beginners should concentrate on using the absolute mode.Be careful when making motion commands. Beginners have the tendency to think incrementally. If working in the absolute mode (as beginners should), the p
23、rogrammer should always be asking To what position should the tool be moved? This position is relative to program zero, NOT from the tools current position.Aside from making it very easy to determine the current position for any command, another benefit of working in the absolute mode has to do with
24、 mistakes made during motion commands. In the absolute mode, if a motion mistake is made in one command of the program, only one movement will be incorrect. On the other hand, if a mistake is made during incremental movements, all motions from the point of the mistake will also be incorrect.Assignin
25、g program zeroKeep in mind that the transfer and unit machine control must be told the location of the program zero point by one means or another. How this is done varies dramatically from one transfer and unit machine and control to another8. One (older) method is to assign program zero in the prog
26、ram. With this method, the programmer tells the control how far it is from the program zero point to the starting position of the machine. This is commonly done with a G92 (or G50) command at least at the beginning of the program and possibly at the beginning of each tool.Another, newer and better w
27、ay to assign program zero is through some form of offset. Refer to fig.4. Commonly machining center control manufacturers call offsets used to assign program zero fixture offsets. Turning center manufacturers commonly call offsets used to assign program zero for each tool geometry offsets.Fig. 4 Fle
28、xible manufacturing cellsA flexible manufacturing cell (FMC) can be considered as a flexible manufacturing subsystem. The following differences exist between the FMC and the FMS:1. An FMC is not under the direct control of thecentral computer. Instead, instructions from the centralcomputer are passe
29、d to the cell controller.2. The cell is limited in the number of part families itcan manufacture.The following elements are normally found in an FMC: Cell controller Programmable logic controller (PLC) More than one machine tool A materials handling device (robot or pallet)The FMC executes fixed mac
30、hining operations with parts flowing sequentially between operations. High speed machiningThe term High Speed Machining (HSM) commonly refers to end milling at high rotational speeds and high surface feeds. For instance, the routing of pockets in aluminum airframe sections with a very high material
31、removal rate1. Over the past 60 years, HSM has been applied to a wide range of metallic and non-metallic workpiece materials, including the production of components with specific surface topography requirements and machining of materials with hardness of 50 HRC and above. With most steel components
32、hardened to approximately 32-42 HRC, machining options currently include: Rough machining and semi-finishing of the material in its soft (annealed) condition heat treatment to achieve the final required hardness = 63 HRC machining of electrodes and Electrical Discharge Machining (EDM) of specific parts of dies and moulds (specifically small radii and deep cavities with limited accessibility for metal cutting tools) finishing and super-finishing of cylindrical/flat/cavity surfaces with appropriate cemented carbide, cermet, solid carbide, mixed ceramic or polycrystalline cubic boron nitride (PC
