The direct control of contrail of motion of cutting tool of fictitious axis machine tool

Time:2023-06-20 15:02:37
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source:PURELIFE CNC Machining

Of machine tool of fictitious axis numerical control appear to be considered as this century to provide revolutionary machine tool to design a breakthrough most. This kind of new-style machine tool broke the concept of structure of traditional machine tool completely, abandoned to secure slideway cutting tool oriented means, turn and introduce drive of orgnaization of 6 lever paralell connection, comb-out cantilever structure, consequently not only its stiffness can raise fivefold left and right sides than traditional machine tool, make machine precision and treatment quality to rise greatly, and its feed speed and acceleration also rise than groovy machine tool multiple above, often be helpful for realizing high speed and freeboard from and rather than fast treatment. In addition, light, raw material uses up weight of whole of this kind of machine tool treatment capacity is little, little, plus rigid structure simple, rate of component generalization, standardization is high, great and convenient the economization batch production of machine tool production manufacturer. Have afore-mentioned numerous advantages in view of fictitious axis machine tool, use a machine tool to pushing, make and the development of relevant course and industry has important sense, its research takes seriously extensively what got world each country with development, already became the machine tool on international to study a heat of the domain to pass the analysis of pair of fictitious axis machine tools, can see, the biggest characteristic of this kind of machine tool is rigid structure simple and control is complex. Accordingly, the fictitious number of axle that should combine national condition development to have Chinese distinguishing feature controls machine tool product, must solve its to control a problem above all, study development gives system of high-powered numerical control of fictitious axis machine tool. Because fictitious axis machine tool has 6 motion freedom to spend, exist on control relation serious nonlinear with deepness coupling, make existing numerical control algorithmic cannot undertake to its linkage is controlled directly, also use software of process designing of existing numerical control to produce input information for its hard, the promotion that the development that controls a system to its consequently increased difficulty and affected machine tool of this kind of new-style numerical control applies. To solve this problem, the article offers the direct control means of contrail of kind of motion of cutting tool of fictitious axis machine tool, its are basic the thought is the craft that be mixed by the geometrical information of treatment spare parts information inputs a machine tool to control a system, by control algorithm is generated be machined apparently cutting contrail and instruction of control of cutting tool sport, and instrument appearance journal the article was received in November 1998. Realize much to the machine tool freedom to spend athletic control accordingly, a variety of issues that removed pair of fictitious axes to the machine tool undertakes leaving line process designing and be brought not only thereby, and the treatment precision that raised a part effectively still and treatment efficiency, the open up of process capability of efficient high accuracy that to fill cent develops fictitious axis machine tool a new approach. Contrail of motion of cutting tool of fictitious axis machine tool is direct pilot fundamental is fictitious if kind of typical structure of axial machine tool pursues 1 is shown. The main shaft unit of this machine tool is propped up by lever of drive of 6 alterable length at workbench upper part. The other end of 6 drive lever originallies to go up on fundamental frame. Adjust the length of 6 drive lever, can make main shaft and cutting tool make 6 freedom spend campaign, include an edge to the translation of X of 3 linear and fictitious axes, Y, Z moves and turn along 3 among them fictitious axis A, B, whirligig. So, answer how to control the length of lever of these 6 drive, ability makes the athletic contrail of cutting tool and attitude satisfy treatment to ask this is problem of core of pilot of fictitious axis machine tool. The main train of thought that solves this problem divides a pace, pace is according to inputting information first in empty axis space direct interpolation makes march range in real time contrail of cutting tool motion, beg solution to give each hope motion of fictitious axis to measure, map of false or true of repass of the 2nd pace changes the hope motion volume of empty axis the hope motion that is solid axle to measure, calculate in real time namely the hope length that gives 6 drive staff. Through solving Ou follow-up control makes the actual length of drive lever and hope length are sent finally, and by machine tool structure implicit the fact of implementation is changed to the inversion of empty, the contrail of cutting tool motion that can receive a demand. According to afore-mentioned train of thought, the article puts forward kind of multistage to give rank control program, the principle is shown 2 times like the graph. The introduction is made to among them main module below. Method of cutting of cutting method program is surface of workpiece of edge of drop of cutting tool cutting the path that mobile place should follow, it is the base that builds contrail of cutting tool motion. Cutting method plans to solve how the input information according to numerical control system, if be waited for by the geometrical information of treatment spare parts, craft information, beg expression of solution cutting method, decide its concern parameter. It is with machining free curved surface below exemple, introduce the course seeking solution of the problem. Set a spare parts to be able to be used by treatment surface curved surface expresses pair of 3 second batten, the geometrical information that inputs control system can use P of geometrical coefficient matrix to give out, its expression is: The P in type -- B batten curved surface piece P can build reference point basis to be machined the expression of the face: The S in type (U, v) -- B batten curved surface assumes office the positional vector of the dot -- invariable matrix S (U, v) coordinate function is called in the heft of direction of coordinate of X, Y, Z, its expression is: The P in type -- the craft information that the matrix cutting way that makes by the heft of each element in P of geometrical coefficient matrix plans to need basically has: Dimension of direction of position removing a knife, direction taking a knife, feed of means taking a knife, travel, cutting tool, allow error of instrument appearance journal to wait. According to these information can begin to fix the tool cutting edge plane of each cutting from initiative position: The plane of these mutual parallel and surface of spare parts treatment intersect earning curve is workpiece namely apparently cutting method. Set J tool cutting edge plane and surface of spare parts treatment intersect if the cutting method of earning pursues 3 are shown, criterion expression of region of its U V is: 4 cutting contrail generates cutting contrail to create the crucial problem that should solve in real time is will (5) the cutting contrail that the has nothing to do with time cutting method that type gives out changes the disperse that fastens to connect with time to change. The train of thought that finishs this job is a basis given feed speed and allow an error to produce interpolation linear paragraph of L K, .

, approach cutting way with its, get each disperse nods K on its stage by stage, .

coordinate value. Apparent, this is kind of direct interpolation of pair of free curved surface. Because interpolation computation is not the geometrical computation of kind of static state, it not only must make current interpolation dot and before the distance between interpolation dot satisfies feed speed to reach impose the requirement such as decelerate, and make sure the interpolation between this 2 o'clock is straight even line segment and be in by the error between interpolation curved surface given inside allow poor limits. To satisfy afore-mentioned requirements, the article is adopted it is control target with instantaneous feed speed, in order to allow the direct interpolation algorithm that the error is tie condition, its are basic the process is as follows. Above all, divide by the F of instantaneous feed speed that adds decelerate computation to give out) , with computation leaving type current sampling cycle hopes mediumly chord (without the interpolation when the tie linear end length is spent) . L of the δ in type -- hope chord (millimeter) T -- sampling is periodic (millisecond) at the same time, press a plan according to allowing an error 4 in error relation computation restrains chord: The E in type -- the permission between actual cutting contrail and hope cutting contrail error R -- if the average curvature radius of contrail of the hope between solstice of radius of ball head cutting tool hopes chord is less than tie chord, make current interpolation straight line segment length: 1, take Δ L otherwise next, the basis joins the susceptibility that variable changes to chord, choose (8) type or (9) dot of P of type plan cipher out is in U (or V) take a cost again U) era enters type (5) take a cost actually what can solve an additional ginseng variable to be in in P. Because interpolation frequency is taller, the arc length in sampling cycle and chord are very adjacent, when be being calculated actually so, can make L of Δ of U / of Δ of Du /ds ≈ .

Take U increment Δ U so, beg the Δ L that gives correspondence next, can get what what need to also can be begged with manage finally, amount to U and generation type into coordinate function table (3) , the coordinate that can get P is nodded is worth X (contrail of motion of cutting tool of computation of contrail of motion of U 5 cutting tool is to show some is nodded on cutting tool (center of the head that be like a ball) athletic contrail. Of contrail of cutting tool motion beg take need to be finished via two paces, bu Xiangen occupies information of treatment surface geometry, beg take cutting to nod N of unit normal vector (U, v) , its expression is: The 2nd pace is mixed according to cutting tool information again the law arrow information that already got is begged take the contrail of cutting tool motion that answers relatively with cutting contrail. When milling cutter of use ball head, along R of radius of cutting tool of deflection of law arrow direction, the contrail of cutting tool motion that can get with cutting tool ball the function table of coordinate of direct control heart of contrail of motion of cutting tool of fictitious axis machine tool is shown. The N in type -- the heft in direction of reference axis of X, Y, Z will nod N of unit law arrow the value of place takes the place of to go up type, the coordinate that the dot answers relatively with the dot on contrail of attainable cutting tool namely is worth, namely the motion of linear and fictitious axis controls an instruction. By type (11) visible, use the cutting tool of different measurement, although the contrail of cutting tool motion of generation is different, but can maintain cutting contrail however changeless. This is meant, contrail of this kind of cutting tool controls a method to be able to realize the real time compensation of dimension of three-dimensional cutting tool conveniently directly. Computation of stance of campaign of 6 cutting tool is in fictitious axis machine tool, l of vector of axes of usable cutting tool describes the attitude of cutting tool. Task of calculative of stance of cutting tool campaign is mixed according to machine tool structure namely treatment requirement, by foregone current cutting the dot is in the N of unit normal vector of workpiece surface, beg L of vector of axes of the quarter cutting tool when solution gives this take a cost. Ball head milling cutter is used more when curved surface is being machined like, to assure the treatment of spare parts surface quality needs to make cutting rate constant, this is located in heart of ball of the arbor in nodding normal to be with cutting, cutting tool to be acme with respect to axes of requirement cutting tool and on the taper seat that half vertex angle is φ . In the meantime, to make the machine tool is in better state getting power in machining a process, should make the included angle of cutting tool axes and axis of machine tool Z as far as possible small. Accordingly, use the following method to beg attitude of solution cutting tool. Building origin to be located in the cutting tool coordinate of heart of cutting tool ball is, axis of the X that X of its reference axis fastens with machine tool coordinate respectively, Y, Z is parallel. Heart crossing a sword nods plane to make its include Z axis and cutting dot normal, cross knife heart to be nodded on this plane next linear, the included angle that makes should nod law space with cutting point-blank is equal to cutting tool axes to be in φ of conic half vertex angle, this is feasible cutting tool axes namely point-blank. Beg the 3 heft L Z that gives L of vector of cutting tool axes through leaving type, defined the cutting tool attitude of current hour mensurably namely. Those who need to point out is, when cutting dot normal is close to with Z axis need to transfer when parallel processing, its algorithm is trivaller, will draft additionally only civil introduction. Control of sport of solid axle of control of solid axle sport includes computation of solid axle motion to reconcile Ou follow-up control two measure. Calculative of solid axle motion is main the task is the hope motion amount that seeks solution to give 6 drive staff according to statement of empty axis exercise. Show a process to be as follows actually: When setting initiative condition, cutting tool axes and Z axis are parallel, = L of cutting tool attitude.

Change platform attitude correspondingly with this (with the whirl that circles an axis coordinate A expresses) for A = 0.

The structure according to using platform is attainable 6 drive lever props up the end points that uses platform (move end points) the initiative position in department of cutting tool coordinate: Be like K hour, cutting tool attitude turns into L Zk, can beg dispatch the corner coming back that platform circles X axis: Its corresponding change coming back changes matrix to be: Can beg with manage dispatch the corner coming back that platform circles Yt axis: Its corresponding change coming back changes matrix to be: Because move platform to circle the corner coming back of Z axis,be 0, reason change coming back changes matrix: From this calculable 6 drive lever moves this hour end points fastens medium seat in cutting tool coordinate: Then, in this hour, 6 drive lever moves end points to fasten medium coordinate value to be in machine tool coordinate: The 6 drive lever that gets above the basis uses end points coordinate and foundation the coordinate of static end points with machine tool foregone structure, press (21) the hope value that type can get length of journal of appearance of instrument of each drive lever, get statement of solid axle exercise is worth thereby. The X in type -- the coordinate cost of static end points of 6 drive lever in department of machine tool coordinate is final, through solving Ou follow-up control makes sure the actual length of drive lever and hope length are sent, the solid axle linkage that can achieve contrail of contented cutting tool to ask is controlled. Show a method to already had made detailed introduction in article actually. The validity of the means that emulation test result offers for place of test and verify and feasibility, undertook for many times emulation an experiment. The experiment is in undertake in order to gallop on the numerical control system that personal computer develops for core. This system is used advocate the direct control of the contrail of motion of cutting tool of fictitious axis machine tool that frequency is 266 Hz is algorithmic with the language means of mixture process designing of 32 assembly language comes true. Form. In the graph, photograph node of the curve is free curved surface model value drop, in all 361. The graph shows the contrail of cutting tool motion that arises to control software and attitude of cutting tool motion 6 times (express with vector of cutting tool axes) . Be clear about to show, the cutting tool contrail in the graph and attitude show all right to lie between. Graphic representation result and result of data spot check make clear, the means that article place offers is correct. The course checks, pilot of the real time that finish computation is periodic (an interpolation on computational curved surface is linear motion of value of answering coordinate of dot of cutting tool contrail and solid axle measures Duan Hexiang) place is 3s about with time.

Such, a sampling in numerical control system odd 2s is returned inside cycle, still have the other function that system of the numerical control that finish can use when the machine of 40 namely, if the graph shows, control of capacity of interactive, information processing, switch. This explains, it is completely OK that contrail of this kind of cutting tool controls a method directly come true in the N system that is based on high-grade personal computer. Conclusion is fictitious the biggest characteristic of axial machine tool is rigid structure simple and control is complex. Accordingly, want to combine national condition to develop the fictitious number of axle that has Chinese distinguishing feature to charge a machine tool, must solve its to control a problem above all, study development gives system of high-powered numerical control of fictitious axis machine tool. Be aimed at characteristic of pilot of fictitious axis machine tool, the article offerred the direct control means of contrail of motion of cutting tool of fictitious axis machine tool, this method can be mixed according to information of spare parts geometry treatment craft information, straight deliver a child hopes into cutting tool orbit and empty axis motion dictate, realize the linkage control of pair of solid axles through map of false or true, make sure actual contrail and hope contrail photograph send cutting tool effectively thereby, the efficient control open up that is fictitious axis machine tool a new approach. Theoretical analysis proves with emulation experiment, the principle that article place advances and method are feasible, laid necessary theory and technical foundation to develop system of numerical control of machine tool of new acting fictitious axis. CNC Milling