Www Americanmachinist Com Content Site304 Articles 07 01 1998 Software0100png 00000002777

Jet-engine CNC data collection takes off

July 1, 1998
Software adds new level of data access and programming convenience for CNCs.

Software adds new level of data access and programming convenience for CNCs.

Using GE Fanuc's Cimplicity HMI, GE Aircraft Engines verifies jet-engine quality and maintains extensive documentation for each machined part.

On a new Campbell grinder, the GE Aircraft Engines engineering team used GE Fanuc's Windows-compatible technology running on a high-speed, fiber-optic network.

A GE Fanuc Series 15B CNC is integrated with the Cimplicity HMI system for monitoring and CNC programming.

The GE Aircraft Engines control teams configured Cimplicity HMI to read data directly from the Series 15B CNC. The process did not require custom code or SQL database programming and it supports full data-analysis capabilities.

The automated system helps GE Aircraft Engines gather and archive more than 600 different values during the grinding operation to show that tolerances are met within 60.001 in.

Verifying the quality of jet-engine components is critical for the GE Aircraft Engines plant in Raleigh-Durham, N.C. The company maintains extensive documentation for each machined part, which involves gathering more than 600 different values during the grinding operation to show that tolerances are held to within 6 0.001 in. Fortunately, teaming PCs with Cimplicity HMI (human machine interface) and Series 15 CNCs (computer numerical controls) from Charlottesville, Va.-based GE Fanuc Automation North America Inc., has simplified data collection.

"Automatic data collection is no longer limited to programmable controllers," says David Smither, assembly engineer for GE Aircraft Engines. "We have simplified CNC data acquisition for our grinders by using personal computers and Cimplicity HMI. Our CNC programming, process monitoring, and data analysis is now accomplished on generic, Pentium-grade computers."

GE Aircraft Engines uses the program to collect and track data from touch probes on three Campbell CNC radial grinders. After each machine grinds a feature, the probe verifies that the part meets blueprint tolerances. The data is then uploaded to a PC for display and automatically archived on a file server for future statistical process control analysis. The information not only helps GE Aircraft Engines verify quality, but also gives a picture of actual cycle times to assist with scheduling and capacity planning.

Grinding away
Depending on the type of jet engine, the grinding process can take from 12 to 24 hr for just one assembly such as an array of turbine components used in an engine's hot section. Such an assembly incorporates up to 12 different features.

Grinding one feature averages one hour of machine time, and the plant processes between 200 and 300 assemblies a year.

"The time involved in grinding is considerable," Smither emphasizes . "Jet-engine assemblies are made of high-temperature, heat-resistant metals that are difficult to machine. Plus, we are removing a lot of stock in a sequential, grind-and-inspect, grind-and-inspect process."

Before grinding begins, pieces of the assembly are shipped to the Raleigh-Durham plant. Technicians build the assembly and load it into a holding fixture. With the fixture secured to a 80-in. machine table, the operator selects the appropriate feature to grind. Selections may include inner diameters up to 40 in., outer diameters, axial features, or various other characteristics of the particular part.

When grinding is complete, the machine automatically picks up the Renishaw touch probe from the tool changer and measures the feature. This data is then sent to Cimplicity HMI at the PC. A tower light signals the operator that the machine is ready for the next process. The operator selects the new feature; the part rotates on the table; and grinding begins again.

Automatic pilot
Two of the Campbell grinders have GE Fanuc Series 15A CNC controllers featuring an open architecture compatible with PC hardware and software. The controls team used GE Fanuc MMC-I software to develop custom programs that capture CNC data and send it across a serial link to the host PC, which displays and stores the data in text form. Because of the slow-speed serial link, it takes about 10 min to transmit data before the next grinding process can begin.

For a new grinder installed in early 1997, the engineering team moved to GE Fanuc's Windows-compatible technology running on a high-speed, fiber-optic network. The grinder itself is equipped with an automatic tool changer that holds the touch probe, miscellaneous grinding wheels up to a maximum diameter of 14 in., and various end mills. A GE Fanuc Series 15B CNC controller is integrated with the Cimplicity HMI system for monitoring and CNC programming.

"With this system, a direct, high-speed, fiber-optic link connects the GE Fanuc Series 15B CNC with the PC running Cimplicity HMI," says Smither. "Data transmission is instantaneous, which eliminates the 10-minute-per-feature wait."

The network uses a fiber-optic high-speed serial bus (HSSB) to shuttle data to and from the CNC at speeds up to 25 Mbyte/sec. The CNC racks and the PC include HSSB boards to provide ports for the fiber-optic cable. The cable runs from the CNC controller to the PC operator stand. All together, the network employs about 150 feet of fiber-optic cable.

Opening Windows
"With GE Fanuc's open-architecture CNCs and HSSB, we can easily collect data from our Campbell grinders on common DOS or Windows-compatible PCs," Smither says. "By running in a Windows environment, Cimplicity HMI makes data collection and analysis easy. To a machine operator, it's as friendly as a home computer, thanks to a point-and-click, mouse-driven, graphic interface."

Cimplicity HMI provides pre-built and pre-configured screens that can be used or adapted to individual applications. The GE Aircraft Engines controls team configured 72 screens using builtin graphic tools. According to Smither, screen setup is similar to a PowerPoint application.

"I created pictorial diagrams of three engine-assembly models," he says. "Each picture shows what the part looks like and functions as a simplified blueprint. The user clicks on a feature in the drawing, which pulls up another screen to show the data. If more detailed data is desired, a second data screen can be opened."

Items incorporated into the screens include alarms, trends, and logs. Cimplicity HMI for CNC also supports active operator messages, active CNC alarm messages, as well as CNC parts program upload and download. The controls team also configured Cimplicity HMI to read data directly from the Series 15B CNC. This process requires no custom code or SQL database programming and supports full data analysis capabilities.

Data analysis takes off
For data analysis, Cimplicity HMI is configured to automatically log data to Microsoft Access. Operators can search the database, compare grinding events against blueprint tolerances, and print reports to track quality control.

Cimplicity HMI for CNC provides access to a variety of data from within the CNC. Data items include: axis positions relative and absolute, machine and distance to go, pitch error compensations, active program number, skip data, actual spindle speed, and work offset table.

Dimensional data is stored in the CNC custom macro variables. When a feature is within blueprint tolerances, the part program initiates a trigger to the HMI, which reads and archives the data into the Access database. The same functionality is responsible for displaying the "just-sampled" data on the PC monitor.

Part programming for CNCs
GE Aircraft Engines also uses the PC as a convenient way to edit the part program for the CNCs. According to Smither, Cimplicity and the HSSB can transfer a part program from the PC to the CNC faster than the older systems.

"Since Cimplicity supports out-side applications, a button to click and run the CNC part program transfer utility was created," he says. "The necessary edits on the PC can be made and then send it back to the CNC."

Convenient remote access is also possible from Smither's Cincinnati office. Plans call for taking advantage of the HMI's inherent client/server support to perform enterprise-wide data access and remote CNC programming.

"With Cimplicity HMI, we have a window into the process," Smither explains. "We know what grinding wheel was used, the speed, the wear rate, and stability of the grinder to help us calibrate the machine for optimum performance. It's a whole new level of data access and programming convenience for CNCs that improves quality and productivity."

Latest from CAD and CAM