How a diverse group of players joined forces to build a winning production cell.
Sta-Rite boosted cycle times 40% for its pump suction parts by combining multiple operations into one setup on a Daewoo Puma 230 MB turning center.
A glimpse inside the machining envelope for the suctionparts-machine.
An external view shows the single machine that performs turning, milling, and drill-and-tap operations on pump-suction parts.
One setup is the goal of NorthTech's special chuck, which I.D. grips Sta-Rite's suction parts.
A 30-station Wes-Tech table gives the suction-parts machine a lot of flexibility.
Sta-Rite's finished suction parts sit in special quick-change fixturing plates.
In a two-machine cell, the first-op machine cuts O.D. threads on the pump discharge parts.
This transfer unit links the first and second-op machines in the discharge-parts operation.
Daewoo added this quick adjustment feature in the transfer area of the twomachine cell to simplify part changeovers.
When Sta-Rite Industries decided to automate production of a part family, it knew that it needed help. The parts, which had always been manufactured in an operator-driven process, required multiple setups, and many were made of a tough stainless steel. While each part presenteda particular machining challenge, the company wanted a turnkey system along with a partner that could customize it to exacting specifications. The company got its turnkey—and added a whole lineup of partners in the process.
"We knew that automating production of our 4-in. submersible pumps would improve throughput," says Matt Servant, process manager at the Delavan, Wis., company. "But we needed someone who could do the complete turnkey application based on strict criteria from a processcontrol standpoint." The company soon found its lead partner in Daewoo Heavy Industries America Corp., West Caldwell, N.J.
"We've been making these parts forever, so we worked closely with Darryl Smith and Shane Richards at Daewoo to brainstorm different ideas for the cell," remarks Servant. "I headed up a fourperson Sta-Rite team that included Antonio Angeles, manufacturing engineer; Bob Busbey, tool engineering manager; and Eric Bilau, process manager."
"When we visited Sta-Rite," recalls Smith, manager of Daewoo's automation group, "we looked at two different styles of pump parts.
One was the 'suction' end; the other was the 'discharge' portion. Each presented its own set of difficulties." The suction parts, for example, are made of 304 stainless steel and have an interrupted cut that was tearing up Sta-Rite's existing twinspindle machines and tooling. The discharge side, which is also made of 304 stainless, requires threads on part I.D.s and O.D.s.
Smith says that Sta-Rite wanted to do some of the work in one setup, and the rest in two. This required three machines, a single Daewoo Puma 230 MB turn-mill center and a two-machine cell consisting of two Puma 230 MBs. To improve process flow, Sta-Rite wanted to separate the operations so that it could group two different suction parts on the single machine and all 10 discharge pieces on the two—machine cell.
One machine, one gripping
The integration for the suction machine was complicated by machining challenges associated with the part — the first of which was turning an interrupted cut. Rather than turn the part, Daewoo suggested Sta-Rite mill it, thereby increasing both machine and tooling life.
Daewoo's next task was doing the suction parts in one setup. So, in addition to making the interrupted cut, the machine had to drillandtap. "Our old operation, which ran on twin-spindle machines, was operator driven," says Servant. "The machines would run the first cycle, then the operator would have to remove the part, flip it, put it back in the machine, and restart the operation." All this took roughly 5 min. During this 5-min cycle, operators also performed drill-and-tap operations on another machine.
Daewoo knew it could handle all the necessary machining operations, but it needed some assistance with Sta-Rite's workholding concept, which entailed gripping part I.D.s "Although we used O.D. workholding on the old machines, we knew I.D. workholding would let us do all the part features without flipping the part," says Servant. "But we didn't have the capabilities to do this workholding internally."
At this point, Daewoo brought in partner NorthTech Workholding Inc., Schaumburg, Ill., which made the I.D. gripping a reality. "We needed someone to design chuck jaws that could grip in one chucking for the suction parts," says Smith. This was critical to machining all features in one setup on one machine.
NorthTech quickly proved itself up to the challenge. Ervin Vallejo, a NorthTech design engineer working on the project, customized a PW-style chuck for I.D. gripping. The lightweight chuck uses jaws made from aircraft aluminum rather than carbon steel. "Reducing the weight is important when you grip something on the I.D.," says Vallejo. "That's because the gripping force increases when the chuck rotates at a high rpm, which can deform a part. If you make the jaws/top tooling of a lightweight material, then the effects of I.D. gripping at a high rpm are less damaging."
After designing the chucks in CAD, NorthTech used FEA analysis to see just how gripping pressures would affect the part. "We checked the deflection and the distortion based on the pressures
we would apply with that chuck, per each part," comments Jon Steinfeldt, NorthTech's OEM account manager. "That was a big plus because we could show the engineers at Sta-Rite that the gripping system worked."
NorthTech's software also helped Daewoo tweak its machine design. " Because the parts are thinwalled and the jaws are gripping on the I.D., NorthTech recommended that we change out the actuator," says Smith. "The change gave us the gripping pressure we needed without deforming the part and still maintaining quick chuck open-close."
With the machine and chuck in place, Daewoo then turned to the integration of other features that would streamline Sta-Rite's operations. "We started with the base machine and added a gantry loader," says Servant. "This was a stock option for the Puma, but we went further with a 30-station table that gives us the flexibility to handle different parts." The table is from Wes-Tech Inc., Buffalo Grove, Ill.
Topping the table are custom-designed quickchange locating fixtures. Daewoo gave its design criteria to P. Smith Design Associates in Berwyn, Pa., which designed the quick-change plates.
"The fixtures are basically templates mounted to the table," says Servant, "which we can quickly change for different jobs."
Once the Puma machines a part, Daewoo's gantry transfers it to a 3-ftlong Lipe vibratory table. "Daewoo brought us a neat concept," remarks Servant. "The part vibrates across the table to a larger Lipe accumulation table, which also vibrates the parts. As parts evacuate the system, they don't get dinged or damaged from metal-on-metal contact."
Automating for two machines
For the discharge parts, Daewoo also equipped the two-machine system with its gantry loader, a Wes-Tech table, special fixturing plates, and Lipe vibratory tables. However, it had additional work to do as the discharge operation requires two machines linked by a transfer station.
"The part on the two machine cell has both I.D. and O.D. threads," says Servant. "The first operation does the O.D. threads. The part is then dropped on the transfer table. A robotic arm—not the gantry loader—comes down and picks up the part, does a swivel, flipping the part orientation."
The second machine does the I.D. thread, some boring, and cleans up the part.
Workholding, again, was key to the performance of the two-machine system. "NorthTech was instrumental in designing the jaws and making sure they fit," observes Smith. "This was important so that the entire population of parts was chucked properly. Plus, our goal was to ensure Sta-Rite could change over parts with little operator involvement and a minimum chance for operator error."
Smith's partner on the Sta-Rite project was Shane Richards, applications/ projects engineer. He says ease-of-use is a main concern for any cell Daewoo integrates. "The easier it is to do a setup, the faster it is, the less likely you'll have mistakes, and the more likely you'll have a better quality of parts. We aim to take the guesswork out of the setup and make it easier for the operator."
A winning partnership
The three Daewoos are now up and running at Sta-Rite, with good results. According to Servant, the suction machine has already reduced cycle time as much as 40%—from roughly 5 min to a little over 2 min. And that time includes the drill-and-tap operation, which wasn't even counted in the previous arrangement.
"We added another machining center to the cell," comments Servant, "which brings it to a total of four machines." One operator runs the robot-driven Daewoos and performs a manual operation on a part-time basis.
"We added the fourth machine without adding a person," says Servant. "This lets us streamline operations, decrease staffing, and increase throughput. We went from one operator running two machines to one operator handling four."
And the new equipment delivered tighter tolerances. "We eliminated the second operation on the one part, which we now do complete. So there were fewer stackup tolerances," explains Servant.
The gantry loader was a new technology for Sta-Rite, but Servant says Daewoo followed through on training. "Daewoo's application engineer was out here nearly a month—training, setting up the machines, and problem solving. He trained both shifts and the operators on those shifts, as well as our maintenance personnel."
All in all, Servant says he's happy with the relationship between Sta-Rite and Daewoo. "From the beginning, Daewoo was good at keeping me in the loop in regards to weekly activities," he comments. "And like any new process, we have had some hiccups since the installation in November. But together, we are working through these. What's important is that the machines are running full steam and producing good parts."
The tooling partner
Daewoo spearheaded Sta-Rite's turnkey, bringing NorthTech, Wes-Tech, and others-into the project. But to standardize its tooling, Sta-Rite brought another player to the table.
The new Daewoo Pumas use Capto quickchange tooling from Sandvik Coromant, Fair Lawn, N.J. Changeovers are so quick, an operator needs only 10 to 15 sec to remove and replace tools.
The quick changeovers are only part of the picture, says Daewoo's Darryl Smith. " Sandvik has done a lot to improve perishable tooling, optimizing tools between cycle time and perishable tool life." In addition, the tool company had a role in an important aspect of the turnkey development — the suction machine's one-op setup. When Daewoo and NorthTech were working on the chuck, they ran into issues with tool clearance. "We modified our Capto tools, based on a suggestion from Darryl Smith, so there was enough clearance to get behind the part," says Robert Nieman, OEM specialist with Sandvik. "We shaved a good 1/4 in. off the back of the tool so that it would fit down between the part and the face of the chuck."
Sandvik's involvement dates from the earliest stages of the Sta-Rite project, but its role greatly expanded after the machines were installed. "We only looked at 25 parts for the runoff," notes Nieman. "But now Sta-Rite is working with part lots of 300 to 400. This makes it easier for Dave Feivor, our local Sandvik rep, to investigate ways to further increase tool life and productivity."
Nieman adds that Sandvik works closely with both builders and customers for turnkeys such as the one at Sta-Rite. "The builders don't necessarily have the expertise in tooling that we offer—especially the new tooling. We close the loop and keep the machines running."