Problem In order to run a machining process it is necessary for part tolerances to fall within the shortterm capability of the machine tool. Implementing Patterns such as AP203 (Job set-up), AP301 (Cutter parameter update) and AP302 (Dynamic re-machining) can help a machine tool adapt to real production conditions in order to maintain process capability. However, some sources of process variation cannot be accounted for using such methods. For example: • Where no mechanism exists to adjust an error, even when the error and its magnitude have been correctly identified. For example, it may not be possible to correct for extreme backlash on machine axes, or to automatically correct in instances where a piece of swarf causes gross part mis-alignment • Where the variation in error changes at a rate faster than it is possible to correct for it, for example extreme temperature variation AP206 Machine capability check Solution Use an inspection probe to perform a machine capability test before machining. Commence machining only if the machine is within the capability limits defined for the component. Measuring known reference features shows the machine is capable of positioning itself accurately and repeatably, or if there is a capability problem. Benefits • Programs can automatically alert an operator if the machine appears to be out of alignment • Machining will not begin unless confidence in machine capability has been established Perform machine capability checks No, halt machining Is machine within defined capability limits? Yes, continue machining Machine capability check For example, the following scenarios may be checked: • A fixture is automatically loaded and clamped on a machine tool. Occasionally, swarf may become trapped between the fixture and the clamp, causing an angular error which can be measured • It may be known that extreme temperature variation causes a particular machine tool to vary in performance. It is possible to test for thermal effects immediately before a cutting cycle by measuring a known artefact, ‘golden part’ or machine reference feature Case study Renishaw uses workpiece inspection probes in its own factories to establish machine capability. The Renishaw Advanced Milling Turning and Inspection Centre (RAMTIC) is a vertical machining centre equipped with standard Renishaw probing technology, custom fixture, indexing trunnion and tooling loading systems. RAMTIC machines are also loaded with an artefact: a known ‘golden part’ which is regularly calibrated and used as a reference part for machine checks. RAMTIC systems perform machine capability checks with three tests: • Indexer repeatability test: measure artefact features with artefact on top of indexer, perform indexer moves away from and back to measurement position, re-measure and compare artefact features, stop machining process if the difference is out of tolerance. • Indexer alignment test: measure points on the top of the artefact spanning the X-axis with the artefact at positions either side of the indexer top position, compare centre points at each inspection position, calculate indexer misalignment, stop machining process if out of tolerance. • Checks for thermal distortion: measure key features on the artefact to establish reference points for thermal tracking, stop machining process if thermal drift is out of tolerance - see AP303, Thermal correction - machine drift and AP306, Thermal Correction - workpiece expansion for information about correcting for thermal effects. Example: checking the correct orientation of an automatically loaded pallet table Only continue machining if the A and B axes are correct to within 1° Sample Productivity+™ probe software program Measure plane and establish X, Y, Z position data. Using data from measured plane, determine if the absolute angle error in A or B axes is greater than or equal to 1°. If yes, the program jumps to Out_of_Alignment label and a machine alarm is raised. If error in A and B axes is less than 1° the component is machined before jumping to the end of the program. The statement referenced by the ABS function within the Condition Builder of Productivity+ Active Editor Pro must be surrounded by parentheses - round brackets. Even if the target NC platform requires square brackets, the Condition Builder must use round brackets; the post processing process will convert them as necessary for the target machine. Sample Inspection Plus software program N10 T01 M06 Select the probe G54 X0. Y0. Start position G43H1 Z100. Activate offset 1 and go to 100 mm above G65 P9810 Z10. F3000 Protected positioning move to Z10 G65 P9818 Y50. Z0. Measuring cycle IF[ABS[#144]GT1.]GOTO100 If the angle error is greater than 1° jump to an alarm G65 P9810 X0. Y110. F3000 Move to next position G65 P9810 Z-10. F3000 G65 P9843 X0. D50. Measuring cycle IF[ABS[#144]GT1.]GOTO100 If the angle error is greater than 1° jump to an alarm G65 P9810 Z10. F3000 G65 P9810 X110. Y0. F3000 Move to second position G65 P9810 Z-10. F3000 G65 P9843 Y0. D50. Measuring cycle IF[ABS[#144]GT1.]GOTO100 If the angle error is greater than 1° jump to an alarm G65 P9810 Z100. G0 G91 G28 Z0. Return to home position G90 GOTO110 N100 #3000=99(AXIS OUT OF ALIGN) Alarm for the axis alignment N110 (END) RENISHAW ACCEPTS NO RESPONSIBILITY FOR ANY PROBLEMS OR DAMAGE ARISING FROM THE USE OF ANY SAMPLE CODE AND ADVISES THOROUGH CHECKING OF OUTPUT VARIABLES FOR THE SELECTED INSPECTION PACKAGE AND THE AVAILABILITY OF SPARE AND UNUSED VARIABLES FOR INDIVIDUAL APPLICATIONS. SAMPLE PRODUCTIVITY+™ PROGRAMS ASSUME THE USE OF ACTIVE EDITOR PRO 1.70.20 SAMPLE INSPECTION PLUS PROGRAMS ASSUME USE WITH FANUC TYPE CONTROLS Renishaw plc New Mills, Wotton-under-Edge, Gloucestershire GL12 8JR United Kingdom T +44 (0) 1453 524524 F +44 (0) 1453 524901 Euk@renishaw.com www.renishaw.com About Renishaw Renishaw worldwide Renishaw is an established world leader in engineering technologies, with a strong history of innovation in product development and manufacturing. 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Products include: • Dental CAD/CAM scanning and milling systems. • Encoder systems for high accuracy linear, angle and rotary position feedback. • Laser and ballbar systems for performance measurement and calibration of machines. • Medical devices for neurosurgical applications. • Probe systems and software for job set-up, tool setting and inspection on CNC machine tools. • Raman spectroscopy systems for non-destructive material analysis. • Sensor systems and software for measurement on CMMs (co-ordinate measuring machines). • Styli for CMM and machine tool probe applications. Hungary T +36 23 502 183 E hungary@renishaw.com India T +91 80 6623 6000 E india@renishaw.com Indonesia T +62 21 2550 2467 E indonesia@renishaw.com Israel T +972 4 953 6595 E israel@renishaw.com RENISHAW HAS MADE CONSIDERABLE EFFORTS TO ENSURE THE CONTENT OF THIS DOCUMENT IS CORRECT AT THE DATE OF PUBLICATION BUT MAKES NO WARRANTIES OR REPRESENTATIONS REGARDING THE CONTENT. RENISHAW EXCLUDES LIABILITY, HOWSOEVER ARISING, FOR ANY INACCURACIES IN THIS DOCUMENT. © 2010-2011 Renishaw plc. All rights reserved. Renishaw reserves the right to change specifications without notice RENISHAW® and the probe emblem used in the RENISHAW logo are registered trademarks of Renishaw plc in the UK and other countries. apply innovation, Productive Process Pyramid, Productive Process Patterns, Productivity+, AxiSet, Rengage, Trigger Logic, ToolWise, Sprint, MicroHole, PassiveSeal and SwarfStop are trademarks of Renishaw plc. All other brand names and product names used in this document are trade names, service marks, trademarks or registered trademarks of their respective owners. *H-5650-4010-02* Issued 0912 Part no. H-5650-4010-02-B