New versatile gauging system

Published by: Mike Excell – Fri 06 May 2011
Feature Type: Accessories

A new gauging system from Renishaw provides a radical new alternative to traditional dedicated gauging. It promises to cut purchase, maintenance and fixture costs, can be pre-programmed for multiple parts and quickly re-programmed for design changes. Equator has been conceived and developed by Renishaw, working closely with automotive, aerospace and medical gauging users, alongside their manufacturing machines. The result is a lightweight, fast and highly repeatable gauge that provides operators with ‘push-button’ simplicity. Equator can switch between parts in seconds, so is ideal for flexible manufacturing processes, or accepting parts from multiple machines.

Equator Organiser – operator front end with ‘push-button’ simplicityBased on an easily scaleable and adaptable ‘parallel kinematic’ structure, Equator allows high speed scanning and rapid moves between features, while retaining the stiffness required for point-to-point repeatability, critical for accurate gauging. Installation takes minutes, and an operator can switch between gauging different parts in seconds. Re-configuration of the system to cater for part design changes, or to measure new parts, is much faster than with conventional custom gauging, using the comprehensive industry standard DMIS programming.

Easy operation, easy programming
Equator systems are available with two levels of software: a programmable version for production engineers to create DMIS programs; and a lower price shop floor system which allows those programs to be executed but prevents operators from making modifications.

Both software levels include the intuitive MODUS Organiser operator front-end software, requiring little or no training, while on the programmable system the comprehensive MODUS Equator programming software allows engineers to rapidly create gauging routines for any part - simple or complex, prismatic or free-form. MODUS Equator features the ability to easily program scanning measurements and touch points, using the industry-standard Renishaw SP25 compact scanning probe. By scanning, thousands of data points can be taken to define a feature, allowing true form analysis of any feature. By taking the dongle provided with the programmable system and plugging it into a shop floor system, full programming functionality is activated on that shop floor system, ideal for engineers to adjust programs but also retain control.

Though its appearance is unusual, the Equator system uses the comparison method of mastering and measuring familiar to anyone who uses dedicated gauging systems.  A master component with features of known dimensions is used to ‘zero’ the system, with all subsequent measurements compared to this part. Re-mastering is as swift as measuring a production part and immediately compensates for any change in the thermal conditions of a shop-floor environment.

Equator can be used in factories with wide temperature variation - simply re-master and the system is ‘re-zeroed’, ready for repeatable comparison to the master. The key to the Equator system is a highly repeatable and radically different metrology mechanism based on a parallel kinematic structure. This mechanism is lightweight, allowing rapid motion, yet is very stiff and repeatable. The system uses Renishaw touch and scanning probes, styli and stylus change racks, and MODUS Equator programming software.

Master parts do not need to be expensive custom parts like a traditional gauge; users can simply take a production part and measure it on a CMM to establish feature variation from CAD or drawing nominals. The results from any CMM, operating with any CMM programming software, can be configured to be used directly within the Equator software.

Effectively, the calibrated absolute accuracy of the CMM (which may be located in a temperature controlled room) can be extended onto the shop floor to provide calibrated traceability to Equator measurements. With the calibration file loaded into the Equator software, measurements made in the Equator system can be referred back to the CAD or drawing nominals. This allows true process control with SPC packages.

Equator controller
The Equator controller is a powerful dedicated control system that provides a secure and robust environment for running the gauging system software. It is similar to machine tool control systems, with the added ability to run Equator-specific Windows applications. Designed for Equator, it incorporates all the necessary electronic boards and software in one package. The user can create and execute DMIS measurement programs, change measurement settings and transfer data or programs. An additional PC is not required when operating the Equator, reducing cost to the customer and eliminating the chance of incompatibility or un-predictable performance arising from the wide variation of PC architectures.

Equator cuts fixture costs compared to dedicated gauging. By using fixturing that positions parts to within 1mm of where the master was measured, which has no significant effect on system repeatability, and by establishing the part orientation and datums on the part itself, the need for expensive precision fixtures is removed.

Further versatility is offered by the Equator-specific stylus changing rack, allowing automated in-cycle changing of SM25 stylus modules. The SM25 modules couple to the industry-standard SP25 CMM probe, allowing Equator users to swap stylus configurations without re-qualifying each time. Up to six stylus combinations can be loaded into the rack at any time. These can be used on a single complex part or with multiple parts of varying geometries.

Equator can be integrated into automated cells, using the optional I/O interface to connect it to a robot, or by outputting the gauging results to an SPC package. Some SPC packages also offer the ability to connect to certain modern machine tool controls to update offset values, for true automated process control.

Softening up hard gauge costs
Cincinnati-based aero-engine component maker Meyer Tool undertook a pre-launch application for Equator. The company’s practice has been to  design, build, and maintain dozens of costly hard gauges for in-process measurement; one Equator gauge has eliminated at least four of these in a new work cell.  “And that’s just the beginning of the impact the company anticipates for its inventory of custom hard gauges, which can cost up to $20,000 each to design, build and maintain” says Quality Manager Beau Easton; “down the line, design changes can add another $3,000 - $10,000 to re-configure and qualify an existing gauge.”

For in-process dimensional measurement, the company principally relies on work-cell-based point-to-point contact gauges, using pneumatic digital probes.  Hard gauges in the machining cell give very fast feedback but are expensive.  Design/build of the part nest can cost $6,000, plus probes at $500 each, verification studies, and maintenance, Easton explains: “If we are producing a make-complete nozzle, there could be six to ten fixtures, each with six to twenty probes, and if a feature or tolerance on the part changes, it adds time for the gauge to be altered and verified.”

When shown Renishaw's Equator comparative gauge and offered a pre-launch trial, Easton and SPC Manager Bridget Nolan immediately recognised the potential. “We got involved with Renishaw’s introduction of the system and provided parts. Renishaw programmed them, and the results matched our CMM results”  says Nolan.

The Equator system is currently assigned to a lean machining cell in Meyer Tool’s shop. Demonstrating its adaptability, it integrates with Meyer’s Orion SPC system, maintaining a familiar look for machinists and shortening the learning curve. Orion communicates with the Equator’s MODUS software, presenting the operator with results in the form of dimensional data, SPC charts, etc. “Keep in mind the machinist sees variable data and can compare the current part with recent measurements, so it’s not just a pass/fail determination,” Nolan explains. The parts must meet tolerances of ±0.001 to ±0.003 inches. Inspection time varies with the part but typically takes two to six minutes, well within the TAKT time of the cell so the system easily keeps pace with machining operations.

“We already gauge five part numbers for two different engine programs, so we have multiple fixturing tiles for the Equator setup and qualified,” says Nolan. “We try to combine as many different operations on one tile as possible to limit our qualifications, and we’re currently working on one tile that will combine three. We are doing GD&T true positions, notches, hole diameters, profiles, runout, and such with touch probing, though we are implementing contact scanning with the SP25M probe. We have the stylus changing rack and use at least four different styli - frequently star styli - so it's very convenient not to have to requalify with every change.”

Quality-driven
The Equator measurements at Meyer are correlated with those from a CMM, using a CMM-calibrated master part. “The master part sets the values the Equator expects to find inside its measuring envelope while the software automatically applies the compensation values from nominal taken by the CMM.  It must check within 10% of allowable tolerance from nominal,” Nolan explains.  There is no need to re-master on every part change, Meyer has decided to re-master on a 3-hour schedule to compensate for changes in the plant’s temperature. “The Equator system memorises the master parts and validation scores, so we can switch parts as many times as needed during the 3-hour window, and not have to re-master.”

Meyer Tool is a leading producer of hot-section jet engine components for aerospace OEMs, employing more than 1000 at ten locations. The Cincinnati headquarters specialises in new parts; principal workpiece materials are super alloys, nickel and cobalt-chromium based.
With nearly 500 fast-hole EDM drillers, the company is North America's largest EDM-based manufacturer; it EDM-drills over 1.75 million holes per day, and with one blocked hole out of hundreds capable of causing failure on military high-pressure blades, Meyer Tool is fanatical about quality.

With well over 100 hard gauges costing $10-20,000 each throughout its facilities, Meyer Tool recognizes the potential cost advantages of a flexible, software-driven gauging system. “We are still expanding our knowledge and capabilities with the Equator system, but have high expectations it will ultimately alleviate a large part of our cost burden for hard gauges,” concludes Beau Easton. 

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