Automated CMMs Help Build Best-In-Class Engines

May 20, 2003
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International Truck and Engine Corp. (International)—the operating company of Navistar International Corp. and the world's largest producer of mid-range diesel engines—has achieved new levels of quality verification, system productivity and flexibility. By incorporating word-class equipment and processes, the company has gained valuable insight into finding ways to make its manufacturing processes more productive. The company is set to meet the needs of its customers and offer products with an edge over its competitors.

Set on building the most reliable, best-in-class diesel engine, Inter-national remodeled its 680,000-square-foot manufacturing facility in Huntsville, AL. Together with its sister engine plant in Indianapolis, International currently produces the next generation V-8 diesel engine for International brand trucks.

At each location, diesel engines make their way through machining and assembly production lines that are nearly one mile long. The process includes multiple integrated manufacturing quality verification stations where line operators conduct quality checks. In addition to the integrated quality verification checkpoints, components undergo random in-process and final product inspections using coordinate measuring machines (CMMs).

When International developed the manufacturing processes at its Huntsville and Indianapolis facilities, it incorporated a first-of-its-kind, fully automated, quality verification process for engine crankcases, cylinder heads and crankshafts that combine Prismo CMMs from Carl Zeiss IMT Corp. (Minneapolis) and an overhead gantry loading system from Fibro Inc. (Rockford, IL). The verification system measures part dimensions to ensure accurate machining, supporting process control and production volume objectives.

Set up in an enclosed, fully automated turnkey workstation, the Prismo CMMs are automatically loaded using an overhead gantry system and pallet loaders. The safety glass enclosures equipped with safety light curtains surround the CMMs. Photo: Carl Zeiss IMT

Meeting complex requirements

“We needed an optimized CMM verification system without the complexities and throughput hindrances that a quality lab sometimes includes,“ says Chuck Sibley, business team leader, machining and assembly, in Huntsville.

While the Huntsville product represents a low-volume, high-complexity focus, and the Indianapolis product is the outcome of a high-volume, lower-complexity system, the CMM verification process must function efficiently within both plants. Other strategic design objectives for the verification processes included high functionality, operational control, automated material handling and a safety module.

“We knew that there were automated CMMs on the market that incorporated loading systems using automated pallets or pick-and-place robotics, but we required a solution that would increase throughput,“ says Donald Brown, International's senior manufacturing engineer. “The system had to fully automate the CMM inspection process, optimizing manpower and providing efficient, accurate inspections on production lines.“

Brown brought the quality verification system to several CMM manufacturers. “In addition to fully automated inspection capability and the option to be used in a stand-alone capacity, the CMMs needed to provide accurate measurement and real-time inspection results to verify the consistency and quality of our products,“ he says. “We also needed adequate capacity for the CMMs to support our 85% up-time goal for production equipment.“

Brown predicted that a CMM equipped with scanning technology and a library of software programs could provide both the accuracy and real-time results for which he was looking.

Working with a concept from International's John Foley, Steve Zike and their manufacturing engineering team, the design team of Carl Zeiss, International, Fibro and TAC developed a CMM inspection strategy that would complement the integrated process validation checkpoints at each facility and contribute to a robust manufacturing process overall.

“Our quality verification system required scanning CMMs to ensure measurement accuracy, product functionality, and support of our up-time goal,“ Brown says. “The ZEISS Prismo with VAST scanning technology proved capable of capturing thousands of data points in minutes, which afforded us with the accuracy and efficiency we needed in a CMM.“

Each CMM is equipped with 18 probe configurations and measurement programs to verify the thousands of features on each crankcase, cylinder head and crankshaft. Measurement time depends upon process or product complexity with results for each feature downloaded and sent electronically to the manufacturing line's real-time shop-floor application to let machine operators know when to change worn tools or make alignment adjustments.

Design layout

The Huntsville plant uses four automated CMMs and the Indianapolis facility uses three automated CMMs. The automated systems use overhead gantry loading and computerized controls and each manufacturing process is verified at a frequency documented by the control plan for each process.

Components are loaded and unloaded at a station outside an environmentally controlled enclosure. Parts are loaded on the load shuttle pallet that hold the crankcase, cylinder head and crankshaft. Operators enter sample data at the load control station, using operator prompts and bar codes. The load shuttle delivers the sample into the room and to the gantry system through an automated door. The gantry then picks the part from the load shuttle and places the sample in one of three locations on each storage seat. As many as 24 samples can be loaded to fill the system. The system selects samples by priority and order and then delivers the sample either to the next available CMM shuttle or to a selected CMM. Based upon the sample data entered, the CMM performs the specified program and returns the CMM shuttle to the gantry for post-inspection storage. The operator receives the report via the Intranet.

“We believed a single overhead gantry system would enable us to load parts for inspection on a CMM without disrupting the routines of the other CMMs,“ Brown says. “Unlike pick-and-place robotics, the overhead gantry can handle the larger part size and weight to easily transfer the part from the queue to one of the four CMMs.“ The four Prismo CMMs at International's Huntsville plant are positioned in the corners of a rectangular room, with two CMMs facing each other at each end. The gantry runs above the CMMs and the pallet system runs between them. The three Prismo CMMs at International's Indianapolis plant are set in a straight line, with the gantry above loading the pallets below.

The Prismo CMMs are equipped with 18 different probe configurations and different measurement programs to measure features on an engine block and cylinder head. Photo: Carl Zeiss IMT

The library

The CMMs are equipped with ZEISS UMESS, HOLOS, KUM, and Strata software programs. UMESS programming software, along with the KUM and HOLOS graphical software programs, enables International to report inspection results several ways.

UMESS software from Carl Zeiss supports true geometric tolerancing, which considers both the size and the position of holes that are critical in measuring machined bores on the engine crankcases, cylinder heads and crankshafts. The system measures size and hole positions to within 0.0002 of an inch. In addition to using scanned data points to produce a 3-D digital image of a part, UMESS networks with other CAD systems. This provides the capability to download CAD files to the CMM to develop automated inspection programs. UMESS also can create a CAD file by using reverse engineering capabilities to digitize dimensions directly from an unknown part profile.

ZEISS HOLOS software enables part analysis by comparing CAD data to scanned measurement data. The software creates CAD data from digitized measurement data without using other programs. The Strata software provides statistical process control (SPC) to compare data to precise engineering specifications. Information from Strata gives International insight into ways in which to improve production for better accuracy. Strata communicates measurement results to a real-time, shop-floor SPC package.

International had a two-fold purpose in establishing world-class verification at both manufacturing facilities. “We wanted the identical quality verification system in two locations so the systems can support each other in every conceivable way,“ Sibley says. “We now have a powerful system that meets all requirements and allows us produce a reliable, best-in-class diesel engine.“

Carl Zeiss IMT Corporation
(763) 744-2409 Reply 10
www.zeiss.com/imt

BENEFITS

• A fully-automated, quality verfication process uses CMMs and a gantry system to check engine crankcases, cylinder heads and crankshafters without slowing throughput.

• Scanning CMMs in an environmentally-controlled enclosure capture thousands of data points in minutes.

• Each CMM is equipped with 18-probe configurations and measurement programs to verify thousands of features.

• A software library includes programs that download CAD files to develop inspection programs as well as compare manufactured parts to CAD files. In addition, SPC data is generated and results are made available in real-time.

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