Laser gaging aids cellular machining: a production bottleneck in inspection and gaging can be a disaster in a cellular machining strategy. Here's what two plants are doing to "unclog" the production value stream.
There's a sign hanging in every department at Mitchel & Scott Machine Company (M & S) (Indianapolis), which reads: "Quality Is Built Into A Product, Not Inspected Into It." Nevertheless, over time the company has amassed a battery of more than 17,500 active gages, including 16 optical comparators (14" through 30"), fully equipped inspection stations in each production department, a temperature and humidity controlled gage lab equipped with contour, surface finish and roundness gages for circular geometry and straightness, and a CMM. So to suggest that M & S, with some 250,000 sq.
-ft.
of manufacturing space and more than 300 employees, is preoccupied with inspecting parts is, perhaps, an finishing understatement. Gaging is, after all, a good thing. Especially if you ship more than 20 million components and assemblies a year to a roster of very demanding customers in the heavy truck, off-road, agricultural and automotive industries. Satisfying these customers is a very critical and time consuming proposition.
However, a recent gage acquisition, a LaserMicro100 laser micrometer from Blum LMT (Fort Mitchell, KY), isn't just the latest tool in the gage arsenal; it's much more and less. [ILLUSTRATION OMITTED] [ILLUSTRATION OMITTED] Population Reduction "The reason we initially bought the LaserMicro100," says Bill Steward, M & S gage coordinator, "was to help us keep up with the flow of some of our shaft-type parts--fuel pump drive shafts, supercharger shafts, water pump shafts. We installed it in our first cellular manufacturing center and dedicated it to a single part family.
Soon, we were running eight different part numbers across it, and when we added a second cell, the laser took it on as well." Before the laser technology, the operator had to deal with a large number and mixture of gages, attribute and variable, plus standard micrometers. "He'd have to write down the gage data and then manually input the data into a computer so it could be downloaded to our central SPC system, Steward says.
" All of which took considerable time.
Now, however, all 17 ODs are gaged in 34 seconds, down from eight minutes. And, the single LaserMicro100 has eliminated 41 separate gages. "Running a family of eight parts and having to cope with up to 70 gages," Steward says, "has been replaced by simply selecting the part program from the laser's touch screen, loading the shaft and pressing the start button.
That's how difficult it is to change from one part to another. Plus, the SPC data are downloaded directly to our central computer without operator intervention, which eliminates the potential for error by manual data input." More Than Precise Steward notes that when they first took delivery, representatives of Blum spent two days on site overseeing installation and providing training.
Such support continues today, Steward says, with regular follow-up calls from Blum nearly every month. The shafts run across the laser micrometer range from 0.625"-1.25" in diameter and 3.50"-4.50" long. Materials are 1215 and 1144 free machining steel, and typical tolerances are [+ or -]0.
0025" - [+ or -]0.
004" with a standard machine finish of 125 Ra. A sample is pulled every 15 minutes, minimum, and each part requires the gaging of 17 different diameters. To be acceptable, the laser had finishing to pass a gage R & R study.
Final acceptance tests conducted on samples of the part families to be run resulted in a variation of no more than 0.000021". Further, double-X and triple-X master setting disks were used during initial assessments, and the results correlated very closely with those of digital SuperMics. Also, a number of different pieces were gaged with varying surface finishes, ranging from 16 Ra-125 Ra.
The LaserMicro100 was unphased by changes in surface, with the notable exception of being readily able to detect very fine tool lines on a shaft surface. "This is an important point," says Steward. "Being precise enough to detect the appearance of tool lines has become an invaluable tool in process control.
It allows us to address an upstream problem before it becomes a downstream source of scrap." The LaserMicro100 is configured such that the gage readouts are color-coded: green, yellow, and red. When the operator sees readouts drifting into yellow, he knows that something is changing--the surface finish or the part size.
Which means that there's a tooling issue that needs to be addressed, a tool that's beginning to wear or is near failure. "This type of real-time process data has proven indispensable to our ongoing commitment to cellular part-processing," says Steward. Cycle Time Impact In the shaft cells, four distinct operations take place.
The four machines that metal feed the laser micrometer are multi-spindle automatics that perform forming and shaving operations. After sampling, the parts proceed to a CNC turning operation, a drilling operation, and a polygon milling operation. The reason that gaging is done after forming and shaving is to ensure that all subsequent steps are performed on a shaft that's proven to be in final OD spec tolerance.
[ILLUSTRATION OMITTED] "Laser measurement technology became part of our machining strategy at a time when we made our initial commitment to cellular manufacturing," says Steward. "Without a fast, efficient and reliable way to gage, the production advantages of machining in cells could easily be lost." He explains that prior to the cellular strategy, cycle time was dependent on the cycles of the multi-spindle automatics, plus the time required to gage the samples coming off them.
This wasn't predictable.
And unpredictability does not lead to process efficiency. The need to use so many separate attribute gages, for example, could very well produce a significant backlog in inspection, which in turn would result in upstream down time. "With the addition of the LaserMicro100," says Steward, "we now can achieve quick changeover and the production efficiencies we'd hoped for in adopting a cellular approach.
Our move away from an abundance of fixed gages, plus the ability to download gage data automatically and seamlessly, removes the inspection process from cell cycle time. Cycle time is now machine cycle time, and nothing more. And the predictability of the laser affords a high level of confidence in the quality of the 375,000 shaft parts we run every year in these cells.
" Cells Of A Different Sort York, NE is home of one of Hamilton Sundstrand's (a United Technologies Company) production facilities. This is a precision machining operation, running three shifts a day, employing 225, with expertise in 3- and 4-axes CNC milling, drilling, CNC turning, precision grinding, spline cutting, metal finishing, and assembly. Materials processed include stainless, carbon and tool steels, cast iron and nickel based alloys such as inconel and nitronic, and aluminum.
Prismatic parts and components are generally less than a 12" cube, and round parts less than 12" diameter and 14" length. Charlie Sanders, Hamilton's area manager, technical support, which includes engineering, quality and purchasing, is intimately involved in the production of shaft-type parts for use in rotating applications, many of which are used for aerospace power generation. "In order to meet plant-wide initiatives to reduce cost, cycle time, inventory, and WIP, and improve quality, delivery and customer satisfaction," Sanders says, "we amended our machining strategy to include supply-chain production cells.
In the process we invested significant capital and resources in technology improvements. We looked at everything--new tooling technology, grinding wheels, machine tools, and advanced gaging. "We had to become faster, more efficient, more flexible.
What we had finishing to do, and thus far we've seen considerable good results, is squeeze every bit of waste out of the production/value stream. One island in that stream is metrology." Rotor Shaft Cell Many of the shaft-type parts produced in this cell become critical performance components--for example, generator rotor shafts for aircraft electrical power generation systems. Hamilton Sundstrand's Electric Power Enterprise (Rockford, IL) is the site where rotor shafts produced in Nebraska are assembled into generators, thoroughly tested and then shipped.
"Our first customer," Sanders says, "is Hamilton Sundstrand assembly operations, and we have to stay keenly focused on the quality of product--and the value of that product--that we ship to our customer." The rotor shafts are finish ground on Studer S40cnc cylindrical grinders. Common to each shaft is that three different points on two-to-four critical OD dimensions have to be checked and constantly validated.
Shafts range in length from 0.
630"-10.
165" and in diameter from 0.
788"-3.
741".
Acceptable diameter tolerances are from 0.0002"-0.0005". Surface finishes range from 6 Ra-32 Ra. Annual production is approximately 15,000 shafts, and each shaft is inspected at 12 inspections per piece for approximately 180,000 points gaged a year. "In our drive to become leaner, more efficient and more flexible, we knew we'd need to move up to a level of gaging technology that would allow us to meet these kinds of demands, while keeping costs down and quality and productivity high and predictable," says Sanders.
"It's at this point that we began to look at the LaserMicro100." Speed, Accuracy, Repeatability These are three qualities that Sanders and his team needed in new gage technology. The previous method involved bench comparators that, with the new emphasis on cellular machining, no longer could make the mark.
"With the comparators," Sanders says, "it might take 15-30 minutes just to gather up the gages, set, and prep them. Then if you have three different ODs to check, you'll need three different bench comparators with a disk set. Plus, with the bench comparators, you have only 0.
002" range, so your have to reset them for each operation. With the LaserMicro100, you simply select the program, load the part, push the button and walk away. The entire process takes less than a minute.
" Further, Sanders says that recalibration time was an issue, which is done at least once per shift and perhaps four times a day. The laser recalibrates itself within 10 seconds; the bench comparator, about three minutes. The real test, however, was the gage R & R analysis.
Preliminary studies determined that to meet goals and objectives a gage R & R on 0.0003" could be no higher than 20%, or a variation of no more than 0.000060". Anything above this would indicate an unacceptable drift in part accuracy.
The LaserMicro100 came in at 7%; the bench comparators, 35%. "With the laser mic, we've got variation down to about 0.00002", which is well below acceptable Hamilton Sundstrand standards," says Sanders.
Defect Reduction According to Sanders, in addition to speed and accuracy, a new gage had to have superior reliability and repeatability. Reliability, in that the gage had to be able to survive the plant floor environment, and repeatability, in that it had to perform exactly the same, from shift-to-shift, from operator-to-operator. Without these, the efficiencies and benefits of cellular machining might very well never materialize.
"Laser technology not only fit the demands of our new cellular machining strategy," says Sanders, "but it has also contributed to the 75% reduction in defects that the machining operation has realized over the past three years. Which is not only helping to eliminate waste but also adding real value to our production processes and the quality of the parts we deliver to our customers." Blum
-ft.
of manufacturing space and more than 300 employees, is preoccupied with inspecting parts is, perhaps, an finishing understatement. Gaging is, after all, a good thing. Especially if you ship more than 20 million components and assemblies a year to a roster of very demanding customers in the heavy truck, off-road, agricultural and automotive industries. Satisfying these customers is a very critical and time consuming proposition.
However, a recent gage acquisition, a LaserMicro100 laser micrometer from Blum LMT (Fort Mitchell, KY), isn't just the latest tool in the gage arsenal; it's much more and less. [ILLUSTRATION OMITTED] [ILLUSTRATION OMITTED] Population Reduction "The reason we initially bought the LaserMicro100," says Bill Steward, M & S gage coordinator, "was to help us keep up with the flow of some of our shaft-type parts--fuel pump drive shafts, supercharger shafts, water pump shafts. We installed it in our first cellular manufacturing center and dedicated it to a single part family.
Soon, we were running eight different part numbers across it, and when we added a second cell, the laser took it on as well." Before the laser technology, the operator had to deal with a large number and mixture of gages, attribute and variable, plus standard micrometers. "He'd have to write down the gage data and then manually input the data into a computer so it could be downloaded to our central SPC system, Steward says.
" All of which took considerable time.
Now, however, all 17 ODs are gaged in 34 seconds, down from eight minutes. And, the single LaserMicro100 has eliminated 41 separate gages. "Running a family of eight parts and having to cope with up to 70 gages," Steward says, "has been replaced by simply selecting the part program from the laser's touch screen, loading the shaft and pressing the start button.
That's how difficult it is to change from one part to another. Plus, the SPC data are downloaded directly to our central computer without operator intervention, which eliminates the potential for error by manual data input." More Than Precise Steward notes that when they first took delivery, representatives of Blum spent two days on site overseeing installation and providing training.
Such support continues today, Steward says, with regular follow-up calls from Blum nearly every month. The shafts run across the laser micrometer range from 0.625"-1.25" in diameter and 3.50"-4.50" long. Materials are 1215 and 1144 free machining steel, and typical tolerances are [+ or -]0.
0025" - [+ or -]0.
004" with a standard machine finish of 125 Ra. A sample is pulled every 15 minutes, minimum, and each part requires the gaging of 17 different diameters. To be acceptable, the laser had finishing to pass a gage R & R study.
Final acceptance tests conducted on samples of the part families to be run resulted in a variation of no more than 0.000021". Further, double-X and triple-X master setting disks were used during initial assessments, and the results correlated very closely with those of digital SuperMics. Also, a number of different pieces were gaged with varying surface finishes, ranging from 16 Ra-125 Ra.
The LaserMicro100 was unphased by changes in surface, with the notable exception of being readily able to detect very fine tool lines on a shaft surface. "This is an important point," says Steward. "Being precise enough to detect the appearance of tool lines has become an invaluable tool in process control.
It allows us to address an upstream problem before it becomes a downstream source of scrap." The LaserMicro100 is configured such that the gage readouts are color-coded: green, yellow, and red. When the operator sees readouts drifting into yellow, he knows that something is changing--the surface finish or the part size.
Which means that there's a tooling issue that needs to be addressed, a tool that's beginning to wear or is near failure. "This type of real-time process data has proven indispensable to our ongoing commitment to cellular part-processing," says Steward. Cycle Time Impact In the shaft cells, four distinct operations take place.
The four machines that metal feed the laser micrometer are multi-spindle automatics that perform forming and shaving operations. After sampling, the parts proceed to a CNC turning operation, a drilling operation, and a polygon milling operation. The reason that gaging is done after forming and shaving is to ensure that all subsequent steps are performed on a shaft that's proven to be in final OD spec tolerance.
[ILLUSTRATION OMITTED] "Laser measurement technology became part of our machining strategy at a time when we made our initial commitment to cellular manufacturing," says Steward. "Without a fast, efficient and reliable way to gage, the production advantages of machining in cells could easily be lost." He explains that prior to the cellular strategy, cycle time was dependent on the cycles of the multi-spindle automatics, plus the time required to gage the samples coming off them.
This wasn't predictable.
And unpredictability does not lead to process efficiency. The need to use so many separate attribute gages, for example, could very well produce a significant backlog in inspection, which in turn would result in upstream down time. "With the addition of the LaserMicro100," says Steward, "we now can achieve quick changeover and the production efficiencies we'd hoped for in adopting a cellular approach.
Our move away from an abundance of fixed gages, plus the ability to download gage data automatically and seamlessly, removes the inspection process from cell cycle time. Cycle time is now machine cycle time, and nothing more. And the predictability of the laser affords a high level of confidence in the quality of the 375,000 shaft parts we run every year in these cells.
" Cells Of A Different Sort York, NE is home of one of Hamilton Sundstrand's (a United Technologies Company) production facilities. This is a precision machining operation, running three shifts a day, employing 225, with expertise in 3- and 4-axes CNC milling, drilling, CNC turning, precision grinding, spline cutting, metal finishing, and assembly. Materials processed include stainless, carbon and tool steels, cast iron and nickel based alloys such as inconel and nitronic, and aluminum.
Prismatic parts and components are generally less than a 12" cube, and round parts less than 12" diameter and 14" length. Charlie Sanders, Hamilton's area manager, technical support, which includes engineering, quality and purchasing, is intimately involved in the production of shaft-type parts for use in rotating applications, many of which are used for aerospace power generation. "In order to meet plant-wide initiatives to reduce cost, cycle time, inventory, and WIP, and improve quality, delivery and customer satisfaction," Sanders says, "we amended our machining strategy to include supply-chain production cells.
In the process we invested significant capital and resources in technology improvements. We looked at everything--new tooling technology, grinding wheels, machine tools, and advanced gaging. "We had to become faster, more efficient, more flexible.
What we had finishing to do, and thus far we've seen considerable good results, is squeeze every bit of waste out of the production/value stream. One island in that stream is metrology." Rotor Shaft Cell Many of the shaft-type parts produced in this cell become critical performance components--for example, generator rotor shafts for aircraft electrical power generation systems. Hamilton Sundstrand's Electric Power Enterprise (Rockford, IL) is the site where rotor shafts produced in Nebraska are assembled into generators, thoroughly tested and then shipped.
"Our first customer," Sanders says, "is Hamilton Sundstrand assembly operations, and we have to stay keenly focused on the quality of product--and the value of that product--that we ship to our customer." The rotor shafts are finish ground on Studer S40cnc cylindrical grinders. Common to each shaft is that three different points on two-to-four critical OD dimensions have to be checked and constantly validated.
Shafts range in length from 0.
630"-10.
165" and in diameter from 0.
788"-3.
741".
Acceptable diameter tolerances are from 0.0002"-0.0005". Surface finishes range from 6 Ra-32 Ra. Annual production is approximately 15,000 shafts, and each shaft is inspected at 12 inspections per piece for approximately 180,000 points gaged a year. "In our drive to become leaner, more efficient and more flexible, we knew we'd need to move up to a level of gaging technology that would allow us to meet these kinds of demands, while keeping costs down and quality and productivity high and predictable," says Sanders.
"It's at this point that we began to look at the LaserMicro100." Speed, Accuracy, Repeatability These are three qualities that Sanders and his team needed in new gage technology. The previous method involved bench comparators that, with the new emphasis on cellular machining, no longer could make the mark.
"With the comparators," Sanders says, "it might take 15-30 minutes just to gather up the gages, set, and prep them. Then if you have three different ODs to check, you'll need three different bench comparators with a disk set. Plus, with the bench comparators, you have only 0.
002" range, so your have to reset them for each operation. With the LaserMicro100, you simply select the program, load the part, push the button and walk away. The entire process takes less than a minute.
" Further, Sanders says that recalibration time was an issue, which is done at least once per shift and perhaps four times a day. The laser recalibrates itself within 10 seconds; the bench comparator, about three minutes. The real test, however, was the gage R & R analysis.
Preliminary studies determined that to meet goals and objectives a gage R & R on 0.0003" could be no higher than 20%, or a variation of no more than 0.000060". Anything above this would indicate an unacceptable drift in part accuracy.
The LaserMicro100 came in at 7%; the bench comparators, 35%. "With the laser mic, we've got variation down to about 0.00002", which is well below acceptable Hamilton Sundstrand standards," says Sanders.
Defect Reduction According to Sanders, in addition to speed and accuracy, a new gage had to have superior reliability and repeatability. Reliability, in that the gage had to be able to survive the plant floor environment, and repeatability, in that it had to perform exactly the same, from shift-to-shift, from operator-to-operator. Without these, the efficiencies and benefits of cellular machining might very well never materialize.
"Laser technology not only fit the demands of our new cellular machining strategy," says Sanders, "but it has also contributed to the 75% reduction in defects that the machining operation has realized over the past three years. Which is not only helping to eliminate waste but also adding real value to our production processes and the quality of the parts we deliver to our customers." Blum
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