Accuracy for CMMs and Machine Tools

Transcription

1 Systematic machine errors Rapid Calibration and Compensation of CMM and Machine ools: Recent Developments of the Lasertracer echnology Motivation Geometry errors he LaserRACER RAC-CAL for Error Mapping and Compensation RAC-CHECK for Accuracy esting Current developments Conclusions Accuracy for CMMs and Machine ools For CMM and machine tools accuracy is a key performance feature Highest accuracy cannot be achieved economically without numerical compensation While for CMMs full error compensation is used for 15 years successfully, it is now introduced in the machine tool world Classical methods for error mapping are time consuming and need operators with years of experience 5 axis machining introduces additional requirement for geometricaccuracy Heinrich Schwenke - CIMi21, Porto, Portugal Geometry deviations of a Cartesian Machine he EALON solution he LaserRACER RAC-CAL LaserRACER RAC-CAL RAC-CHECK Notation according to VDI (source: PB) Error mapping and compensation esting and qualification Interferometer with,1 µm resolution (1) Patented reference sphere (2) with form deviation <,5 µm Environmental compensation for temperature, pressure, humidity Length measurement uncertainty: U=.2 µm +.3 µm/m

2 Solving a linearized set of equations Specifications Weights and dimensions Weight LaserRACER Weight controller Height LaserRACER approx. 12 kg approx. 1 kg 2 mm he Principle: GPS- Principles for machine calibration C par Par = E ( d P E) K = L Norm ( d PNorm C * Par *) K = L par Operating range Angular range elevation axis - 2 up to + 85 ( C * d PNorm K ) M par = Angular range azimuth axis ±2 Measuring range.2 m up to 15 m Accuracy Frequency stability laser 24 h Stability of the reference sphere ±.1 µm Resolution interferometer,1 µm Uncertainty (k=2).2 µm+.3 µm/m Interferometrical length measurement from 4-6 positions Evaluation of all errors entirely based on length information Position of LaserRACER position and dead path need not be known Par * L [ M C ] = L M C Par * L = B L Mathematics Animation RAC-CAL Movie RAC-CAL Software for error mapping

3 Evaluation of parametric errors Comparison Vertical Machining center: Bevor and after compensation Comparison Horizontal Mill: Bevor and after compensation (Siemens) Comparison Middle Class Vertical Mill: Before and after compensatin (Fanuc) Comparison High End Vertical Mill: Bevore and after compensation(fanuc) Horizontal machining center before and after compensation

4 Summary Error Mapping with RAC-CAL Highest accuracy Position, straightness, pitch, yaw, tilt, squareness: All solelybased on the wavelength of a stabilized laser Suitable for error mapping of CMMs and machine tools Applicable for any size of working volume Fast execution (1-3 h) Simple setup and data handling Interfaces and error mapping format for many Controls/CMMs available (and library is expanding) Siemens Volumetric Compensation System for machine tools (VCS) Etalon software directly generates volumetric compensation data for SIEMENS Sinumerik controllers Compensation using EALON technology was tested by Siemens on various machines Etalon has become Siemens Solution Partner in April 28 Etalon is Zeiss Business- Partner for Compensation of CMM Zeiss employs Etalon technology for the calibration of differentproduct lines Zeiss certifies the Etalon format for customers and service providers Zeiss cooperates with Etalon in the further development of Etalon technology he EALON solution Machine esting with RAC-CHECK Cooperation with other machine tool controller manufacturers RAC-CAL LaserRACER RAC-CAL RAC-CHECK Principle: he LaserRACER operates in Static Interferometer Mode but the measurement direction is automatically aligned by machine motion Fanuc und Heidenhain have opened up there controllers for Etalontechnology Close cooperation with Heidenhain (Heidenhain also has purchaseda system) Increasingly good cooperation with Fanuc Error mapping and compensation esting and qualification Laser displacement measurement in any direction without manual alignment No cosine error Data evaluation according to ISO 136(CMM) or ISO 23(machine tools)

5 Principle RAC-CHECK Summary Machine esting with RAC-CHECK Highest accuracy Semi-automated execution No alignment of interferometer required Fast execution: Full geometry test in 3 minutes Complete report function satisfying highest traceability demands For CMMs: In accordance with latest revision of ISO For Machine ools: esting according to ISO 23-2 and 6 he EALON solution New 16 Cateye RAC-CAL LaserRACER RAC-CAL RAC-CHECK 63 mm Reflection angle: +-8 Uncertainty: U=.2 µm Mass: 94 g Limitation R < 2.5 m Error mapping and compensation esting and qualification

6 Development focus 1: Measurement On the Fly Measurement of rotary axes: Animation [µrad] 1 Position error ECC Radial error motion EXC Radial error motion EYC Axial error motion EZC [µrad] ilt error EAC [µrad] ilt error EBC

7 Real-time Multilalateration System Multilaterationsnetz Characteristics: Self-calibrating Sub µm accuracy 1 Nanometer resolution 32 khz bandwidth Applications: Mobile metrology for large high end parts (PB) hermal and dynamic analysis of machine tools (Fraunhofer) est installation in a laboratory Moving reflector Multilateration net of 4 Laserracer Comparison of spatial points Source: PB Source: PB Comparison: Multilaterationsnetz CMM system Z-axis Y-axis -2 differences CMM - M3D3 (bestfit) 1 µm X-axis 6 8 Deviations of positions Residuals M3D Summary With tracking interferometers GPS principles can be applied to CMM and machine tool calibration Volumetric compensation of machine tools is on its way to a standard procedure for high end machine tools Limiting factors for geometric accuracy of compensated machine tools are - temperature stability of the environment -heat load from machining process - repeatability of the machine (including backlash) - stability of the foundation Volumetric accuracy improvements between 5% -8% can be achieved by volumetric compensation of 3 axis machine tools On-the-fly interferometric tracking can reduce time for a complete error mapping down to 1 hour Real time multilateration system open up new approaches for research and 3D metrology Source: PB

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