Application of the hottest CAD in the design of ma

The application of CAD in the scheme design of machining center and flexible line

Abstract: combined with several application examples, this paper focuses on the importance, necessity, superiority and development prospect of the application of CAD in the scheme design of machining center and flexible line

Keywords: CAD; FMS； Machining center; Scheme design

the scheme design referred to in this paper mainly refers to the scheme design of Application Engineering (also including the scheme design in the project bidding process). Machining centers and flexible lines are used for multi variety processing. Its characteristics are that there are many kinds of parts, great process changes, and the workload of scheme design is much larger than that of general modular machine tools. Using the traditional manual design method, it takes a lot of manpower and time, and it is often difficult to complete within the required time. If CAD technology is introduced and its advantages are brought into play, the effect will be very significant. In this regard, we have done some work and made a preliminary application attempt

firstly, according to the actual needs, the relevant data and graphics of machine tools, cutters, tools, pallets, rail cars, trackless cars, raceways, cleaning machines and cutting parameters commonly used in the scheme design of some machining centers and flexible lines are summarized and sorted out, and some graphic libraries, databases and mathematical models are established. On this basis, we have made a preliminary application attempt of these achievements and achieved good results. Here are two examples as follows:

example 1: Our Institute has provided Anshan Thermal Instrument Factory with a processing center k6307 for processing 49 different valve bodies. These valve bodies have 7 different diameters and 4 different pressures, and the size changes greatly. See Table 1 for the diameters and pressures of 49 valve bodies. Table 1 valve body classification table

type tee and cross pressure path 25 ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ ∨ therefore, variety change is very frequent in the production process. Sometimes the order quantity of a valve is only a few pieces, and the fixture, cutter, program, etc. need to be replaced or adjusted every time the variety is changed. Their process diagram, processing diagram, fixture adjustment diagram, etc. must be complete and clear, so as to ensure the smooth work of operators. Because there are 49 different parts, the design workload is very large. We have introduced CAD technology. According to the actual needs, we first make various modules, and then draw the fixture adjustment diagram and processing schematic diagram required by various parts. The time required is greatly shortened, while the quality of the graph is greatly improved

1) draw the workpiece process diagram of various parts (Fig. 1)

Fig. 1 workpiece process diagram

2) draw the fixture adjustment diagram (Fig. 2)

Fig. 2 fixture adjustment diagram

this figure shows that the fixtures used in processing the valve body JP are 21 groups of fixtures. Two parts can be installed on each fixture. The selected adjusting pad is 2146 (PAD height 32.392), and the V-shaped blocks located at both ends are adjusted to 66.5 away from the fixture edge. The 21 sets of clamps can be used for tee valve bodies with diameters of 40 and 50 (a total of 8 kinds). The figure also shows that the part program number that CNC should call up when machining the valve body is. The operator will select and adjust the fixture according to this figure. If you change the type, you only need to change the adjusting pad and change the distance from the V-shaped block of an experimental machine with good performance to the fixture edge

3) draw the machining diagram

the fourth chamfer (see Figure 3)

Figure 3 the fourth sequence chamfer processing schematic diagram

the figure shows one of 49 parts (valve body JP), a 50 diameter tee valve body with a pressure of 4MPa, which is positioned by three flange excircles. The thick solid lines in the figure show the surfaces and holes required to be processed, and indicate the dimensions and tolerances to be processed

the special chamfering cutter is used in this sequence, and the position of its cutter head can be adjusted greatly. When machining various valve bodies, it can be called out according to the dimensions indicated in the machining diagram (including the extension dimension of the knife tip and the dimension from the knife tip to the center of the knife bar). Since this knife is used for many parts, the worker will adjust the knife according to this size

7th order milling thread

for large threads, thread combs are usually used on FMC. As shown in Figure 4, threads with different diameters can be milled by planetary milling with a 30 comb (M64 in the figure × 1.5). The path of the tool center is shown in the left figure, which is divided into 1 ~ 5 segments. The first segment of the tool feeds laterally from the hole center to r30.688, and the second segment feeds to r32.212 in the 90 ° area. At this time, the cutting of the tool has been completed, the third segment completes planetary milling for one week within the 360 ° range, and the fourth and fifth segments are exit. As the thread comb cutter is a new type of cutter, in order to facilitate the operators and field technicians to understand the program, the cycle diagram of this cutter is drawn

Figure 4 Schematic diagram of thread milling in the seventh sequence

because each part has four different materials, such as cast iron, cast steel and stainless steel, several different cutting parameters are filled in the figure

a total of 49 sets of the above drawings are designed, one set of each kind of parts, more than a dozen pieces per set, a total of more than 700 pieces, which are highly praised by the operators of the user factory. If the traditional method is adopted to design, it will take several times or even more than ten times to complete, and the quality of the drawings is relatively poor

example 2: a flexible production line scheme designed for a factory in Chongqing

the factory requires a flexible production line to process six different transmission shells. There are also many faults in the process of using this instrument. The production line needs 14 vertical machining centers and 2 horizontal machining centers. Since most of the bidders are foreign manufacturers, users have high requirements for the scheme of the bid, and they are required to draw the scheme diagram of each machine tool, each part and each installation (see Figure 5 ~ 7)

Figure 5 Schematic diagram of transmission housing processing for scheme 1

Figure 6 schematic diagram of transmission housing processing for scheme 2

Figure 7 transmission housing flexible production line

figures 5 and 6 show the schematic diagram of a certain part processed on a processing center. The figure shows the machining position, size and accuracy, positioning method and selected tools on the machine tool. For 16 machine tools and 6 kinds of reducers in the flexible line, about 100 such drawings are needed (some processes are long, and one drawing is not enough, such as Figure 5). For the cutting parameters of the tool shown in the figure, another table is required. For example, the parameters of the processing content shown in Figure 5 are given in Table 2. Table 2 processing time calculation table

auxiliary time (s)

note: t change = 82.5, t set = 33, t install = 20, t auxiliary = 67.8

t machine plus = 94.7, t total = 16, the stable value with the difference within ± 2 is 2.5

generally, the time of project bidding is very short, and it is impossible to make a large number of such drawings manually in a short time. Our CAD scheme is among the best among many bidders, and has reached the same level as foreign manufacturers

recently, we have made a FMS scheme for processing the overall reducer housing for an automobile factory, which has also been highly praised by the user factory

the work we have done in this area is only a preliminary application. Most of the information, data and experience are accumulated in practical work, and the basic work is also gradually carried out in practical application. Further applications can only be realized after doing a lot of work. Therefore, we should improve all kinds of databases and graphic libraries, enrich the basic parts, develop all kinds of management software, call all kinds of modules according to different needs, and improve the automation of design. Its goal is to make full use of CAD technology in similar application projects, speed up the design speed, improve the design quality and enhance the competitiveness, so that we can stand firmly in this field and remain invincible. (end)