How to raise the precision of numerical control machine tool

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As the flying development of our country economy, numerical control machine tool regards new generation as machine tools, in machinery wide application already received in making, of the rapid development of accurate processing technique and precision of spare parts treatment rise ceaselessly, also raised taller requirement to the precision of numerical control machine tool. Although the user is when machine tool of numerical control of choose and buy, value the positional precision of the machine tool very, especially the fixed position precision of each axis and repeat fixed position precision. But the precision of numerical control machine tool in these use after all how? Many statistic data makes clear: 65.

The new machine tool of 7% above, its technology index is not accorded with when installation; The 90% numerical control machine tools in using are in lose standard work status. Accordingly, to the machine tool working status undertakes monitoring is mixed undertake to machine tool precision often the test is very necessary, so that seasonable discovery is mixed,solve a problem, raise a spare parts to machine precision. At present of precision of position of numerical control machine tool examine to use international standard ISO230-2 or national level GB10931-89 to wait normally. Same table machine tool, differ as a result of adoption level, gets positional precision is not same also, because this is when the precision target that chooses numerical control machine tool, also want to note the level that it uses. The positional level of numerical control machine tool points to the retrorse deviation of axis of each numerical control and fixed position precision normally. To this both determine and be being compensated is the necessary way that raises treatment precision. One, retrorse deviation is on numerical control machine tool, as a result of component of the drive on catenary of drive of feed of each reference axis (enter electromotor to wait like motor of hydraulic pressure of servo electromotor, servo and pace) drive of retrorse dead band, each mechanical movement the existence of the error such as deputy backlash, cause each reference axis to be in by turning to motion retrorse deviation is formed when be retrorse motion, also weigh backlash normally or lose momentum. To using the numerical control machine tool of servo of half closed circuit, the exists to be able to affect a machine tool fixed position precision of retrorse deviation and repeat fixed position precision, affect the treatment precision of the product thereby. If be when G01 cutting motion, retrorse deviation can affect the precision that interpolation moves, if deviation passes to be able to be caused greatly " round insufficient circle, square not quite square " case; And in motion of G00 fast fixed position, retrorse deviation affects the fixed position precision of the machine tool, make bore, bore hole the between each aperture position loss of accuracy when treatment waiting for aperture. In the meantime, throw the growth of run time as equipment, because wear away,retrorse deviation still can follow those who create kinematic pair gap increase gradually and increase, because this need is fixed,to the machine tool the retrorse deviation of each reference axis undertakes determine and be compensatinged. Of retrorse deviation determine of retrorse deviation determine method: Inside the journey that measures reference axis, xiang Zhengxiang or retrorse shift are apart from and stop the position to be with this beforehand fiducial, give certain shift instruction value in same way again, made shift is apart from one paragraph, be apart from identically toward opposite way shift again next, gauge the difference that quits the position and standard position. The midpoint that standing by the journey and 3 positions of two end undertake for many times determining respectively (it is) 7 times commonly, beg piece individually locally average, with earning average medium maximum is retrorse deviation measured value. A paragraph of distance must move first when be being measured, cannot get correct retrorse deviation is worth otherwise. When the retrorse deviation that measures sharp movement rod, measure a tool to be collected normally have dial gauge or dial gauge, if the condition allows, can use interferometer of double frequency laser to undertake metrical. When using dial gauge or dial gauge to undertake metrical, those who need an attention is a watch do not extend with watch lever exorbitant too long, because measure when because cantilever is longer, watch suffer power shift easily, cause computation to forbid, compensation cost is truthless also. If use implementation of process designing law to measure, can make measure a process to become more convenient more accurate. For example, the retrorse deviation of X axis is measured on machine tool of 3 coordinate vertical, can pin the watch the columnar surface of main shaft first, run following programs to undertake metrical next: N10 G91 G01 X50 F1000; Workbench is right move N20 X - 50; Workbench is left move, eliminate transmission clearance N30 G04 X5; So that time-out observes N40 Z50; N50 X-50 of get out of the way of Z axis drive up: Workbench is left move N60 X50: Workbench is right move restoration N70 Z-50: N80 G04 X5 of Z axis restoration: So that time-out observes N90 M99; Those who need an attention is, in workbench the place below different traversal speed measures the result that give to be able to differ somewhat. Usually, of low speed measure a value to want to compare high-speed big, it is especially when bear of machine tool axis and athletic resistance are greater. Speed of motion of the workbench when low speed moves is inferior, had happened not easily to rush exceed Cheng (opposite " backlash " ) , because this measures a value bigger; When high speed, because workbench rate is higher, incidental too strong exceed Cheng, measure so that the value slants small. The measurement technique that retrorse deviation measures circumgyrate movement rod and straight bobbin are identical, just use at detected instrument to differ just. The compensation of retrorse deviation is homebred numerical control machine tool, fixed position precision has many > 0.

02mm, but did not compensate a function. To this kind of machine tool, below certain circumstance, law of usable process designing realizes one-way fixed position, cleared backlash, in mechanical part changeless circumstance falls, want low speed only one-way fixed position arrives at interpolation initial drop, next resumptive interpolation treatment. Encounter in interpolation feed retrorse when, be worth again formal interpolation to backlash, can raise the precision that interpolation machines, basically can make sure the public errand of the spare parts asks. To the numerical control machine tool of other category, set in memory of numerical control device normally a certain number of address, offer memory only the backlash value of each axis. When a certain axis of the machine tool is dictated to change athletic way, numerical control device can read the backlash cost that takes this axis automatically, to coordinate displacement statement cost undertakes compensating, amend, make the machine tool locates well and truly in the instruction locally, eliminate or reduce the retrorse deviation adverse effect to machine tool precision. Only single backlash compensation cost can supply system of ordinary numerical control use, for give attention to two or morethings the athletic precision of tall, low speed, besides should do weller on machinery beyond, the retrorse deviation value that when will moving quickly, can measure only is worth an input as compensation, because this accomplishs balance, give attention to two or morethings hard,precision of fast fixed position is mixed the interpolation precision when cutting. Wait for numerical control system to FANUC0i, FANUC18i, useful at rapid movement (G00) and motion of feed of low speed cutting (the compensation of two kinds of backlash of G01) can be offerred choose. According to feed means different, numerical control system chooses automatically to use different compensation value, finish relatively the treatment of high accuracy. The test rapidity that the backlash that G01 cutting feed motion measures is worth A to input parameter NO11851(G01 but the cutting feed speed with commonly used basis and machine tool character will decide) , the backlash that measures G00 is worth B to input parameter NO11852. Those who need an attention is, if want numerical control system to carry out the backlash compensation that specifies respectively, should parameter number the 4th of 1800 (RBK) set is 1; If RBK set is 0, do not carry out the backlash compensation that specifies respectively. G02, G03, JOG and G01 use same compensation value. 2, the fixed position precision of machine tool of numerical control of fixed position precision is the positional precision that the component of machine tool motion that shows place is measured controls next motion to be able to be achieved in numerical control system, it is numerical control machine tool has fasten a at general accuracy machine tool important precision, the geometrical precision of it and machine tool is collective main to generation of precision of machine tool cutting effect, the pitch error in be being machined to hole especially has conclusive effect. Machine tool of a numerical control is OK the fixed position precision that can achieve from it sentences the treatment precision that gives it, undertake to the fixed position precision of numerical control machine tool compensation is the necessary way that assures to machine quality detecting mixing so. Of fixed position precision determine to use Shuang Pin to laser interferometer detects to the machine tool and handle an analysis more at present, use laser interference to measure a principle, with laser real time wavelengh is measure fiducial, raised test precision to reach so enhanced suitable scope. Detect the method is as follows: Install interferometer of double frequency laser; The machine tool reference axis that measures in need installs optical measurement unit on direction; Adjust laser head, make measure axes and axes of machine tool shift in all line or parallel, be about to collimation of smooth road preliminary adjustments; The input after waiting for laser warm-up measures parameter; Those who press a regulation measure program motion machine tool to undertake metrical; Data processing and result are outputted. If the compensation of fixed position precision is measured so that the fixed position error of numerical control machine tool exceeds error limit, must undertake to the machine tool the error is compensated. Commonly used method is computation gives pitch error to compensate a watch, the hand uses system of CNC of input machine tool, eliminate fixed position error thereby, as a result of numerical control machine tool 3 axes or four-axle compensation point may have hundreds of on 1000 a little bit, so the hand moves compensation to need to spend more time, and make mistake easily. Pass RS232 interface to rise the computer and connection of controller of machine tool CNC now, the interferometer of laser of control of automatic calibration software that writes with VB and synchronism of numerical control machine tool work, those who realize precision of pair of fixed position of numerical control machine tool is automatic detect reach automatic pitch error to compensate, its compensate a method to be as follows: In backing up CNC controls a system already had compensating parameter; The program of machine tool CNC that by the computer generation has pointwise locates precision is measured, convey CNC system; Measure fixed position error of each bits automatically; Produce a group of new compensating parameter according to designation compensation point, convey CNC system, automatic compensation finishs pitch; Repeat C.

Undertake precision test and verify. According to numerical control machine tool the precision state of each axis, use pitch error to compensate function and backlash compensation function automatically, choose to allocate each axis compensation point reasonably, make numerical control machine tool achieves optimal precision status, rose to detect greatly the efficiency of precision of machine tool fixed position. Fixed position precision is a of numerical control machine tool main index. Although be bought in the user,the machine tool with precision tall small error can choose as far as possible when choosing, but as equipment devoted use time grows more, equipment wears away fiercer, the fixed position error that causes a machine tool is bigger and bigger, the spare parts of this pair of treatment and production is having deadly effect. Use above method to the machine tool precision of the retrorse deviation of each reference axis, fixed position undertakes accurate measure and compensate, can be reduced well or remove the retrorse deviation adverse effect to machine tool precision, raise the fixed position precision of the machine tool, make the machine tool is in optimal precision condition, assure the treatment quality of the spare parts thereby. CNC Milling CNC Machining