The practice that implements USB interface to transform to machine tool of economy numerical control is explored (one)
- source:FINKEL CNC Machining
1 with MAP3.
O makes automation agreement, it is the industrial network with at present more extensive application, it broadband technology, bus line technology and passive workstation be in harmony is an organic whole, make sure information is transmitted without the fault thereby. But when should asking MAP implementation and treatment synchronism transmit NC order, it is very inaccessible requirement of real time sex, because MAP uses 7 whole agreements,this is, the network accesses charge sex of low, real time differs tall, transmission efficiency, because this is unsuited the couplet net at CNC Machining equipment. By go up the analysis is knowable, asynchronous is serial communication interface RS232 is communication interface of the most commonly used numerical control system, almost all numerical control systems contain this port. Same, graph 1 medium DNC interface board also is adoption RS232 interface. In computer technology change quickly today, RS232 interface is in in computer application domain be replaced by a kind of new USB interface place, arrive from clavier, mouse printer, scanner, numerous the peripheral that is based on USB replaced the device that uses RS232 interface in former days, so in numerical control system, whether can you also use a such new USB interface technology? In DNC communication system, machine some at the same time when equipment of much stage CNC Machining when complex part, because NC program is huge, the memory of numerical control system cannot deposit whole NC program, can adopt DNC to transmit means treatment only, this appears likely CNC Machining equipment machines idle phenomenon because of lacking NC program temporarily, this kind of phenomenon is called " communication competes " . Communication competition often can produce serious consequence in actual production, for example, the midway halt that the car enclothes a punch mould to be versed in inscrupulously can be caused enclothe local " get together smooth " phenomenon, affect quality of punch spare parts directly thereby. The element that poses communication competition is as follows roughly: Participate in the quantitative M of the CNC Machining equipment of couplet net, the amount is more, the possibility that poses communication competition is larger. Spot bus line transmits T of C of rate, transmission efficiency and node switch serve time. Transmission efficiency is to point to the scale that transmits effective byte number to occupy total transmission byte. The Vi of communication transmission rate of equipment of each CNC Machining and transmission efficiency Ei(i=1 ～ M) . Vi is 9600b/s normally, but complex model face antrum finish machining asks to admit achieve 19200b/s above. Program of numerical control system uses up rate Pi, namely every second implements numerical control system of the program (Bit) number. Pi wave motion is bigger, but every system has a value of more certain the biggest Pi; The size Qi of BUFFER of buffer of data of communication of numerical control system. The size Si of BUFFER of buffer of odd metadata of front of each DNC communication. Si is the quantity that need optimizes, through building mathematical model, can get: 1.
By type (1) is knowable, the upper limit of S of buffer of odd metadata of DNC communication front and Q, V, C, P is relevant: Q, V, C is bigger, p is smaller, criterion S upper limit is bigger. The floor level of S returns related to M, T: M, T is smaller, criterion the floor level of S is smaller. Type (equipment of identical CNC Machining of join of system of communication of DNC of 2) watch palpability and the largest amount that does not produce communication competition: V, C is bigger, p, T is smaller, criterion M is bigger. If DNC corresponds,the platform of CNC Machining equipment of systematic couplet net counts dissatisfaction sufficient type (2) , should be unified calm meeting occurrence communication competes, can pass only at this moment reduce all or the method such as the feed speed of equipment of partial CNC Machining with reducing machine program use up rate P, perhaps use higher transmission rate, raise V namely, the communication competition issue in collecting appliance to the USB bus line that transmits rate higher and interface can solve DNC communication system so. 2, photograph of interface of technical analysis USB depends on to the advantage of RS232 interface: USB bus line offerred 3 kinds of different data to transmit rate: 1.
The low speed data of 5Mb/s is transmitted, of 12Mb/s amain data is transmitted, the high speed data of 480Mb/s is transmitted (USB2.
0 support) , and the rate of RS232 is top have 20kb/s only, USB is machining the curved surface with curvature very big change when, high speed number has clear advantage according to transmitting. USB is theoretic supportable amount to 127 peripheral, join to the dot relative to the dot at RS232, the system that uses USB interface realizes a PC to control much stage NC likely, can improve efficiency greatly thereby, reduce cost, facilitating control, more be helpful for coming true to be made in coordination. The significant link distance of USB is 5m, can pass collect line implement patulous join, can expand at most 5 class, achieve the distance of 30m, and the largest when data is transmitted space is RS232 only 15m. Icron company developed Exterme USB technology, can expand USB equipment the distance is in for 500 ～ 2000m more. Another of USB marked characteristic is to support heat to unplug insert, this kind of character special apply to manufacturing distribution to adjust frequent environment. Just think, should need NC of increase and decrease or when NC occurrence breakdown needs shutdown maintenance, can accept facility the system directly, can make manufacturing settling time is reduced greatly certainly. USB still is had use low price, easily, transmission data has better fault tolerance sex to wait for a characteristic. Graph the 2 network develop after using USB interface attack the structure is analysed from above not ugly piece, numerical control system uses USB interface have a lot of advantage, opposite at RS232 interface it is a kind of technologies rise. We put forward a kind further convenient medium or small the mode that machines production network, if pursue,2 are shown. CNC Milling