Case Studies: Operator Interface Facilitates Blade Inspection
Goodrich produces complete rotating assemblies for turbine engine manufacturers, major airlines and the industrial gas turbine market. The company specializes in grinding all types of high-production turbine airfoils for both low- and high-pressure applications; manufacturing stationary components such as vanes, vane rings, shrouds and nozzle segments; and machining rotating components such as disks, impellers and integrally bladed rotors.
Goodrich has the ability to grind complex geometries by implementing advanced technology using multi-axis conventional grinding and CBN (Cubic Boron Nitride). The company's quality management system is certified to ISO 9002 and AS9100 in addition to NADCAP approvals for special processes. A major part of the quality system is the 100% inspection of turbine blades for process control purposes.
Building a Shop Floor ProgramFor years the company used a combination of in-process inspection and inspection on coordinate measuring machines to gather dimensional data used to control the grinding process. Recently, the company purchased two Brown & Sharpe coordinate measuring machines (CMMs), a Global Image 575 located in the company's metrology laboratory and a ONE 577, both equipped with PC-DMIS measurement and inspection software.
"The goal was to set up a shop floor inspection program that would provide the level of accuracy and repeatability we need to ensure precision grinding, while at the same time being easy and inviting for the operator to use," says Steve Meredith, Goodrich Turbomachinery Products quality engineer/CMM programmer. He was able to reach that goal using the two CMMs and PC-DMIS measurement and inspection software.
The Global Image CMM, located in the company's metrology laboratory, is equipped with PC-DMIS CAD++ software. Meredith uses the capabilities of this software, along with customer-provided computer-aided design (CAD) models, to create part programs on the Global CMM. When completed, the programs are downloaded to the ONE CMM located in a manufacturing cell on the shop floor. That machine is running PC-DMIS PRO software with the Display CAD option.
"The challenge was in creating an interface that didn't intimidate the operator, and that did, in fact, encourage the operator to use the ONE CMM," Meredith says. "I wanted to get away from the coded language based interfaces that were necessary for operating our other CMMs."
Using PC-DMIS programming tools, Meredith constructed the operator interface. All the programs follow a common structure, and are accessible through the ALLGUI program available on the PC-DMIS Web site. The interface was designed to make the inspection process quick and easy. Each button on the interface shows a picture of the blade, the part number, the revision letter and an internal program serial number. Because many blades look similar, a color-coding system is also used. When selecting a blade, the operator is asked what function he would like to perform. The opening setup screen provides for probe calibration, fixture setup and part measurement selections. Sub-routines in PC-DMIS PRO prompt the operator through each of the selections.
"When the measurement of parts is selected, the operator can choose which operation he would like to check. Each individual machining operation is programmed into each part program, as well as a complete inspection of the blade," Meredith says. "This way, an operator has the freedom to inspect a blade at different stages in the operation within the same setup. For example, one operator could select Operation 50 from the interface and another operator could select Operation 120."
Before the measurement routine begins, the operator is prompted to identify which fixtures have blades in them. The program is written to run up to four blades at one time, using four root fixtures on the CMM table. The fixtures in use at Goodrich are duplicates of the fixtures used by its customers for the same part families to help ensure accurate alignment of the parts and correlation to customer inspection results. The operator selects any combination of fixtures that contain blades, presses continue and then walks away from the machine to continue machining the next run of blades.
An electronic inspection report is prepared for all inspections and saved on the company's intranet. In some cases, paper reports are prepared as well. Electronic data is also stored in a DataPage statistical process control (SPC) database so that it can be analyzed at a later date.
A typical inspection routine takes about 4 minutes per blade if measuring all the machined surfaces on the part. Individual operational checks can take less than 1 minute per part. If any blade is out of tolerance, the operator can see at a glance which one it is and can check the report for that blade to see specifically what corrections need to be made to the machining operation.
"The programs are written to allow machine operators to use the ONE CMM with minimal training," Meredith says.
Advanced ProgrammingThe programming for this inspection routine uses a number of advanced capabilities of PC-DMIS software including subroutines with variables, iterative alignments, hyperview reporting with variable parameters, SPC data collection, conditional branching, file input/output, and external coordinate systems.
"Some people might be a little timid about using the advanced programming features of measurement and inspection software, but this is where the true functionality of coordinate metrology lies. Any CMM can gather data. It's about how you do this in a way that is fast and friendly and doesn't compromise the measurement. That's how to take advantage of the technology," Meredith says.
This project is just now getting off the ground at Goodrich and Meredith said he expects to see improvements in inspection throughput and scrap reduction as the program unfolds. "By becoming less dependent on in-process gaging, which can be subject to operator influence, we are seeing an improvement in measurement accuracy using the ONE CMM in the cell," he says.
The company has already purchased Brown & Sharpe Global and ONE CMMs for its operation in Guymas, Mexico, and Meredith plans to send part programs to the operation in Mexico to be run as they are in Arizona.
"We're running the programs in just one of our seven manufacturing cells, and, in the future, we want to expand this inspection approach to other part families in other cells," Meredith says. "We believe this approach to inspection will have a significant impact on our ability to control our manufacturing processes and on our efforts to continuously improve throughout the organization."
Brown & Sharpe
Benefits• By becoming less dependent on in-process gaging, which can be subject to operator influence, Goodrich is seeing an improvement in measurement accuracy using the ONE CMM.
• A typical inspection routine takes about four minutes per blade if measuring all the machined surfaces on the part. Individual operational checks can take less than 1 minute per part.
• The programs are written to allow machine operators to use the ONE CMM with minimal training.