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New Robots 'Load' Quality and 'Unload' Costs

Stäubli Robotics

With every one of the new robots that Minco Manufacturing has installed in its Colorado Springs plants, the company has improved product quality and kept costs down. Within a few months, the company will have 16 new Stäubli robots producing identically perfect fuser rollers for copy machines.

'In this day and age most people don't want to run a machine, so we have trouble finding enough qualified employees,' said Brian Duff, manufacturing engineer. 'The fact that we can increase production by incorporating robots is a huge benefit for us.'

Minco, a subsidiary of Katun Corporation in Minneapolis, MN, primarily manufactures aftermarket and OEM (original equipment manufacturers) TEFLON®-coated upper fuser rollers for copiers. The company also refurbishes drum units and produces picker fingers for copiers.

Solves labor shortage

'With robots, we save the training and other employee-related costs and we save the part quality,' Duff explained. 'Every time we hire a new operator we go through a learning curve. Unfortunately, sometimes as soon as a new operator is up to speed, he leaves the company and we start all over again.'

Minco manufactures 260,000 fuser rollers per month to precise specifications. 'We remove part variability by having a robot load and unload, because we don't have an operator tweaking the settings,' Duff explained. 'We're taking a lot of the quality variables and potential for damage to machine tools out by replacing the operator with a robot.'

Robots keep labor costs down allowing Minco to compete internationally. 'By using robots and reducing labor costs here, we can compete with companies that make parts in China, for example,' Duff said. 'We are able to keep the work in the United States and still be competitive with the cheaper labor rates in Asian countries.'

They keep the work in the states and they keep the workers. 'That's one of the hardest parts about integrating robots - as soon as people get wind of it, they think their jobs are on the line. We don't look at it as a reason to get rid of employees; we just look at it as a reason to give them more challenging jobs,' Duff explained. 'Adding robots allows Minco to grow the business without growing the head count.'

Precision makes tight fit possible

Robots are not new to Minco's operation. They have been using robots to load and unload parts between lathe centers since 1992. But their latest installation is the result of a long search to find a robot to do the more precise work of loading and unloading parts in their end finishing lathes.

'In our end finishing process, we have to load the part 10 inches deep into the draw tube. We tried it with our older version robots, but the accuracy was not good enough because it is a tight fit.'

In their effort to find a robot to perform this application, the company researched the major robot manufacturers. 'I developed a matrix of all the robots on the market comparing accuracy, speed, repeatability, etc., and then talked to all the robot companies on whether they could perform the function,' Duff said. 'Stäubli did a computer-generated mock-up of how the process would work and gave us their assurance that their robot would perform.'

Minco bought just two Stäubli RX130 robots in May 2001. 'We did not want to make a wholesale jump into it until we could prove that it would work,' Duff said. The test was successful, so Minco installed 10 more robots in the fall and has four more on order. 'With the introduction of the Stäubli RX130 robot, we have now overcome the obstacles and can load that end finishing process with the robot.'

Saves one lathe and 50% space

Most of the Stäubli robots currently in-house are used in OEM work cells that finish the ends and surface of the rollers. One cell consists of three robots and five lathes - two robots on the ends feed two end finishing lathes each, and the middle robot services one finishing lathe.

Watching the operation is like watching three alien creatures in a strange but perfectly synchronized dance, with the two end robots taking turns to present an end finished part to the middle robot at just the precise moment that it turns to accept it. Normally, when the robots are running, the only human participation in this performance is the worker who stages raw material, removes full transfer totes of parts from the cell and performs quality checks.

'With the Stäubli robots, once you get them set up, they just run. That frees up the operator to do inspections and move parts in and out of the cell, instead of having all these people loading lathes for 10 to 12 hours a shift,' Duff said.

Stäubli robots are known for high-speed performance, and this speed also generated savings. Before the Stäubli robots were installed, this process required an additional finish turning lathe. 'We had an operator manually feeding two lathes to work the ends and then feeding a third lathe to do the finish turn work. The finish turning machine was actually capable of twice the production than was possible by hand,' Duff explained. 'With three robotic cells currently running, we've saved three lathes that we can transfer into making another cell.'

They've also saved about 50 percent more floor space. The tightly configured cell is possible due to the robot's six-axis articulation, which gives it an almost completely spherical work envelope. 'This is a big benefit. It allows us to design extremely compact work cells,' Duff said.

Repeatability ±0.02mm (±.001')

The quantity of fuser rollers produced and the level of quality needed, demand repeatability as well as speed.

'Repeatability is key to the robot's performance in this application because of how we are locating the part into the draw tube. If we don't place the part against the stop very accurately then we would have too much fluctuation and we could not control the quality of the roller,' Duff said. 'We need to meet a length accuracy of less than .005 of an inch, but we're not seeing even that much variation. We're seeing .002 or less.'

Two features that contribute to the robot's repeatability are the rigid structure and zero backlash. 'Even more than rigidity, backlash in a robot affects the robot's repeatability and how well it's going to position itself,' Duff explained. 'Stäubli has developed a unique gearing system that virtually eliminates all the backlash. That was key to us.'

Flexibility for multiple uses

While Minco awaits delivery on four more Stäubli robots, management has not yet decided if the additional robots will be put into OEM or aftermarket work cells. And that's OK, according to Duff, because the versatility of the Stäubli robot features means the company can be flexible on where they use the robots.

'In the OEM business we currently make seven different fuser roller models, but they are almost identical in raw material size, so there is virtually no set up or change over to do these parts,' Duff explained. 'All we do is bring in the new material and load a different program in the lathe. The aftermarket business is more challenging because we have so many different roller models, but we're working on designing cells to minimize set-up changes.'

Unlimited potential for more

After the initial 16 robots are installed, Minco's plan is to integrate robots into other processes that could benefit from automation; then the company will start replacing their older robots.

'We've talked to Stäubli about adding robots to load the initial paint station. It is very labor-intensive, because every roller we make gets painted. Rollers weigh up to eight pounds so it is exhausting work. We get a lot of operator fatigue and production begins to drop,' he said.

The company is also considering installing robots to unload rollers off a conveyor after the coating has cured. 'This is very labor intensive, but also has to be done very carefully. At this stage the rollers cannot get nicked or scratched,' Duff said. Robots are also ideally suited for Minco's packaging process.

According to Duff, they are not looking at other robot manufacturers at this point. 'We could consider less sophisticated robots for the packaging application, but we have to consider how much variation we want to enter into our automation. With every robot we would have to deal with different programming languages, training on multiple robots, etc. The Stäubli robots can do what we want to do - and more - so we want to stay with them.'


This work cell at Minco Manufacturing, Colorado Springs, CO, consists of three Stäubli RX130 robots and five lathes. The tightly configured cell is possible due to the robot's six-axis articulation, which gives it an almost completely spherical work envelope.


The Stäubli robot loads a part into the chuck, inserting it 10 inches deep into the draw tube. Minco tried to use their older robots to perform this function, but the accuracy was not good enough.


After one end of the part is finished, the robot removes it from the lathe and puts it into an indexer to flip and re-orient it in preparation for finishing the other end.


An end robot places a part onto the transfer stand, which orients the part for the middle robot.


The robot loads the part between centers in the finish turning lathe.


After three lathe operations, the robot loads the finished part into a transfer tote to be removed from the cell. At this stage it is critical that the finished parts are loaded precisely so the surfaces are not nicked or scratched.


After three lathe operations, the middle robot loads the finished part into a transfer tote to be removed from the cell. At this stage it is critical that the finished parts are loaded carefully so the surfaces are not nicked or scratched. In the background an end robot places a part onto the transfer stand, which orientates the part for the middle robot.


Brian Duff (left), manufacturing engineer for Minco, and an operator inspect a copy machine fuser roller. Robots help Minco manufactures 260,000 fuser rollers per month to precise specifications.


Editor's Note
From labor and training cost savings to asset maximization; from quality improvement to productivity gains, justification for robot technology abounds. This story highlights more than just a supplier, it speaks to the variety of opportunities to improve manufacturing in application areas and industries not always considered mainstream. And we are reminded once again that robot technology can help a company compete internationally, and in fact grow their business, without abandoning its domestic roots.

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