sổ tay cơ khí và bản dịch tạm (Handbook of die design 2nd edition ) là một tài lệu tất cần thiết cho các sinh viên và kỹ sư cơ khí. Nó bao gồm bản tiếng anh nguyên gốc và tạm dịch một số chương cho các bạn kém tiếng anh
[...]... slightly more difficult to obtain and will increase production costs Tolerances 0.0127mm (0.0005 in.) or smaller require good equipment and skilled operators and add significantly to production costs Utilize standard components as much as possible Preshape the workpiece, if appropriate, by casting, forging, welding, etc Utilize standard preshaped workpieces, if possible Employ standard machined features 84... finished product and, less importantly, the roughmachining time, b The rate for the machine tool and operator c The power available for machining and the specific cutting energy of the work material d The nonproductive times— especially for smaller components, e The surface area to be finish machined, f The recommended finishmachining conditions, which are in turn affected by the work material and tool... assembly tasks It also simplifies the design of the special-purpose workfixture Avoid the need for reorienting the partial assembly or for manipulating previously assembled parts These operations increase the robot assembly cycle time without adding value to the assembly Moreover, if the partial assembly has to be turned to a different resting aspect during the assembly process, then this will usually... special robot tools or grippers, special-purpose feeders; and special magazines, pallets, or part trays The average assembly cycle time—that is the average time to produce a complete product or assembly The cost per assembly of the manual labor involved in machine supervision,loading feeders, magazines, pallets, or part trays and performing any manual assembly tasks 15 SV:HOÀNG HỮU BÁCH Phương pháp&Tiến... cost of production and cost of raw material) Utilize raw materials in the standard forms supplied Try to design the component so that it can be machined on one machine tool only Try to design the component so that machining is not needed on the unexposed surfaces of the workpiece when the component is gripped in the work-holding device Avoid machined features the company is not equipped to handle Design. .. 67 actual cost and extra allow-ance should be made Loading of magazines: The time needed to hand-load one part into a magazine can be estimated to be the part-handling time, obtained from the data in Chapter 3, plus 1 s Alternatively, a typical value of 4 s may be used Reduce part count— this is a major strategy for reducing assembly ,manufacture, and overhead costs irrespective of the assembly system... with robots, special-purpose workheads, and manual assembly stations as appropriate The total cost of all the general-purpose equipment used in the system,including the cost of robots and any transfer devices and versatile grippers—all of which can be employed in the assembly of other products if necessary The total cost of all the special-purpose equipment and tooling, including specialpurpose workheads,... 69 70 71 two assembly operations Note that the use of screw fasteners always results in the need for tool changes since robot wrists can seldom rotate more than one revolution Design products so that they can be assembled in layer fashion from directly above (z-axis assembly) This ensures that the simplest, least costly, and most reliable 4 degreeof-freedom robot arms can accomplish the assembly tasks... one requiring adjustment According to kinematic design principles only three point constraints are needed together with closing forces Clearly, the redesign shown in Fig 3.43 is simpler, requiring fewer parts, fewer assembly operations, and less adjustment In many circumstances designs where overconstraint is involved result in redundant parts In the design involving overconstraint in Fig 3.44 one... proceeds with 50% efficiency while one arm remains immobile Design parts so that they can all be gripped and inserted using the same robot gripper One major cause of inefficiency in robot assembly systems is the need for gripper or tool changes Even with rapid gripper or tool change systems, each change to a special gripper and then back to the standard gripper is approximately equal to 18 SV:HOÀNG HỮU . thiết kế Product Design for Manufacture and Assembly Số thứ tự Lời khuyên Hình minh họa 1 Providing a tool for the designer or design team which assures that considerations of product. experienced design engineer and arranging it conveniently for use by less-experienced designers. 4 Establishing a database that consists of assembly times and cost factors for various design. allow assembly of the sensor, and therefore none of the three criteria are met and the strap becomes a candidate for elimination. For the strap a zero is placed in the column for minimum