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Decisions Depend on Dollars

 

Calculate the value added to processes


By Jim Lorincz
Senior Editor 

 

Automation projects of the type that can dramatically improve the productivity of machine cells, production lines, and possibly entire factories are desired and sought for their ability to improve manufacturing competitiveness.

The ultimate measure in metal-cutting operations is keeping spindles turning. That's when money is made, and return on investment (ROI) is justified for automation that adds value to the production of piece parts. For other processes, such as painting, welding, and gluing, automation can similarly add value, and is evaluated by measured improvement in productivity and the quality of the work that is done.
The DA20 dual-arm robot has human-like movement for tasks such as machine tending, assembly, and part transfer—tasks that formerly could only be done by people.

In some cases, use of robots may be mandated, as it is in for many of the more hazardous production processes employed in the automotive industry, such as painting and welding. For other applications, careful analysis is required to justify the capital investment.

Robots seem to be the flavor of the day in automating technologies. "When robots are directly involved with adding value to the part, such as in welding, cutting, painting and gluing, they're much easier to justify," explains Roger Christian, vice president, Motoman Inc. (West Carrollton, OH).

Gantry loading of blanks to lathes, grinders, and other machine tools increases productivity through untended operation.

The first half of the year has been a good one for the robot industry. Sales of robots are up 39% from last year, with 76% of growth due to automotive plants and their Tier One and, to a lesser degree, Tier Two suppliers.

"The big five or six have started investing in new lines," says Christian. "Each automotive plant makeover or new plant involves buying 500–1000 robots." Motoman serves all of the areas involved. About 45–50% of its business is automotive, principally in the arc welding, spot welding, paint, and powertrain areas.

"Robots have increased in reliability with service life easily measured in 10–15 years; whereas many capital budgets for automation restrict companies from investing in robotics if they don't pass the two-year justification hurdle," Christian explains. "Even if they capitalize the robot over five years, they're looking for a two-year payback, which, to my way of thinking, is a little short-sighted."

Motoman has developed analytic tools that compare all of the costs associated with a robot against labor and other considerations, giving the results in cashflow study.

For talking purposes, Christian cites the example of a robot with a price tag of say $50,000. Adding a gripper, putting it in a safety enclosure, and outfitting it for work, loading a machine or welding a workpiece, will add another two and a half times the purchase price, or an additional $125,000.

"Our analysis will show that over ten years, the benefits of the automation can add up to millions of dollars from one or two robots. It's a pretty compelling story," Christian says.

The likelihood that the robot will be productive for that long is virtually assured these days as robots have become much more reliable. One reason: they are less complex and contain far fewer components than those of years ago.

"Typical MTBF is well over 60,000 hours, or ten years between failure running three shifts a day," says Christian.

Several years ago, Motoman adopted a strategy of providing process-specific robots, optimized for arc welding, spot welding, palletizing, and painting. These robots are designed with process-related cabling, hoses, fittings, etc. integrated through the robot arm, which reduces interference, simplifies programming, and greatly reduces cable-related wear and maintenance.

The most recent product introduction involves their Dual Arm (DA) series of robots, one with 13 axes, (two six-axis arms with a 20-kg payload per arm), and one with 15 axes, (two seven-axis arms with a 10-kg payload per arm). One application targeted: bolting during final assembly of a car. One arm grabs the part; the other has a nut runner to attach the part to the body of the car. In the near future, these dual-arm robots will include seamless 3-D vision and force with sensing on each arm so that the robot can "see and feel" what it is doing.

"Automation is being adopted by a greater number of shops, some surprisingly small, but if automation is slowing down processing, i.e. allowing spindles to stand idle, there is something wrong with the automation solution chosen," says Jeff Thomason, manager of the turnkey department, Hardinge Inc. (Elmira, NY). The axiom is clear: an idle spindle isn't making money.

Thomason points to the improvement in reliability of automation for machine tools. "One of the important things that has happened is that the software for integration is more powerful and easier for people to apply and integrate with machine tools."

With the longer periods of untended operation that today's manufacturers require, engineers have focused on improving error-proofing of automation for the overall system. "Today there are few excuses for a system not to work as it should, i.e. churning out parts," Thomason says.

"There are gages and sensors that can tell if a part was loaded properly. You can use broken tool detection systems to make sure that parts are coming off in tolerance, and you're not making a lot of scrap. Automatic postprocess gaging and traffic control sensors for material handling systems have gotten better and more reliable."

The trend in the last four years toward lean manufacturing has reached into smaller contract manufacturing shops, with increasing use of automatic devices such as palletizers, automatic gripper systems, and vision systems for batch manufacturing.

"Automation has even been recommended for and integrated into 3–4-man job shops. It allows them to run untended third-shift operations, or to run through the weekend without having to increase staff support, and that type of ROI is significant, regardless of the size of the shop," he says.

Manufacturers continue to abandon older ways of mass production based on transfer lines. This development is driven by the need to meet the short product and model life cycles and changes that are required today. "They are choosing the flexibility of CNC turning/milling/grinding centers and cells coupled with automation," says Thomason.

"Today, you need the flexibility to make families of parts and family-type parts that are similar but have subtle changes. You need to be able to run 100 of these today and 100 of those tomorrow. With the automation and the number of programs that most controls can hold, this sort of flexibility is within grasp."

Placing robots in front of the machine is one option. Hardinge's turnkey department offers several designs that do just that. Putting the robot on an overhead gantry rail so it can work from above the machine tool buys floor space and improves operator ergonomics. Operators can roam the line and look in machine windows while the machines are in operation, if the system is designed properly.

"With a two-axis rectilinear gantry, when you try to add a function, gaging for example, or have it service more than one or two machines, everything has to be in a plane," Thomason points out. "You've only got two axes of programmable motion. If you have a couple of lathes in that line one of the lathes is going to become the master set point, and then everything else must fall within that same line."

The overhead robot can be programmed with buffering zones between machines that allow machine redundancies, and more machines can be serviced with a gantry-mounted robot. "Taking a machine out of service for downtime maintenance or tool change is no problem. The gantry ignores the machine and follows through with the rest of the program," Thomason points out.

Palletech Manufacturing Cells designed and manufactured by Mazak Corp. (Florence, KY) continue to evolve in their capability to deliver palletized parts to machining centers. The latest developments are intended to increase the flexibility of automation by increasing the mix of different-sized machines.Palletech manufacturing system delivers supercharger end caps, housings, and custom wheels for five-axis machining on a Variaxis 630 high-speed VMC at K-M-S Industries (Middleburg Heights, OH).

At EMO, a Palletech system was shown loading/unloading two different-sized pallets, 400 and 500-mm pallets. "This way, the manufacturer is able to address a wider mix of part variation across the cell," explains Chuck Birkle, marketing vice president of Mazak's Cybertec Div. Also located at this system was a stand-alone robot next to one machine's automatic tool changer. This provided untended tool load/unload from tooling carts enabling higher tool counts. In addition, Palletech has been designed with a new tandem shuttle that has two pallet stands on the car.

The fact that Mazak manufactures its Palletech system directly addresses the issues of floor space and layout that users face when considering automation installations. "We produce our own Palletech so that we can design in modular configurations around floor layout issues such as pillars, posts or loading docks," Birkle points out.

Palletech manufacturing systems can be designed to accommodate machines that are in-line, opposed, or staggered. "Floor space is at a premium today, particularly given the lean thinking of manufacturers. Palletech systems can be configured in one, two, or three levels high, and systems are matched to the requirements of the machine. If the machine has a 39" (990-mm) swing, the Palletech has the same."

Mazak has introduced its new PMC Web Server cell controller software, which is able to create more flexibility and expandability to the system. The browser-based Windows system concentrates the cell control into one PC that can handle all of the functions associated with untended operation of the cell. They include the cell controller, pallet management scheduling, tool management, and tool transportation.

"All of these functions previously required a number of PCs. The PMC Cell Controller provides the confidence that these functions can be controlled on site or remotely for untended operations. It addresses the need for running different size pallets and fixtures, multiple kinds of workpieces, different types of scheduling, and everyone's favorite—interruptions," says Birkle.

Mazak follows a policy of proving out technology in its own manufacturing facilities that will be used by its customers. Robot technology is the latest technology to be proven out for its multitasking machines.

Mazak has installed two robot cells in its Florence, KY, plant. "The nuance of the eBot 720 cells is the 720 hours of non-stop automatic operation per month that they provide in loading and unloading workpieces on machines for producing shafts and turrets for our turning centers," says Birkle.

ThDesktop modules no wider than a single sheet of paper use Rexroth TS1 conveyor modules for transporting palletized workpieces in a prototype 'Desktop Factory' for use in a Bosch factory in Waiblingen, Germany. The small footprint ensures that no WIP inventory is stored on the conveyor.e vision system enhances the performance of the cell's load/unload system. The robot picks up a workpiece and presents it to the camera, which takes a picture that is identified and compared to a template. The part is oriented and is loaded into the chuck and calls up the appropriate machining program," Birkle explains.

"The eBot 720 is enabling us to marry automation technology to multitasking machines just as automation was married to high-speed machining capability in the past," Birkle says. "That will enable us to reduce setup, increase throughput, and take the valuable productivity that multitasking offers to the next level."

Lean thinking has become such a powerful force in manufacturing that it has challenged adoption and justification of such a traditional automation device as the conveyor. Kevin Gingerich, director, marketing services, Linear Motion and Assembly Technologies Div., Bosch Rexroth Corp (Buchanan, MI) explains: "Lean manufacturing in its purest sense to this way of thinking is regarded as a way to eliminate waste in all its forms."

In lean thinking, putting things on a conveyor and moving them around a plant may be regarded as another form of WIP. The conveyor may be in motion but something is standing on it, in another form of queue, piling up.

Bosch Rexroth has developed a Lean Production Resource Kit that is offered on its web site that includes practical guidebooks that are designed to enable manufacturers to implement the principles of lean manufacturing in their operations. They are Lean Production and Material Flow in Medical Manufacturing and Efficient Material Transport in Lean Production.

Selecting the most suitable production system is illustrated on a matrix that graphically displays Product Mix against Quantity Requirements. Choices include manual production system, automated production cell not linked, flexible modular system with automation added as needed, and fully automated complete solution. Here's how the process is described in the guidebooks:

"Today, lean production is usually associated with manual production systems. Such systems are successfully integrated into many assembly processes and in various sectors of industry. Lean production does not, however, eliminate automated transport. Transferring parts manually can cause a drop in quality, for example, or a loss of valuable time resulting in an increase in per piece costs. Finding the most economically efficient transport solution depends on the following production factors:

  • Batch size and variety of models
  • Production cycle time
  • Part weight and size
  • Takt time

"Automated production or, in other words, the automated transfer of parts, is always the right choice if one can cut costs and increase process reliability in comparison to a manual solution. The savings gained through automation must offset the higher investment costs. Of course, in many situations, the best solution is a combination of manual workstations linked by automatic systems. Finally, certain production processes are simply uneconomic to automate; for example, when quantities are too small or the product mix changes too frequently."

Gingerich explains: "Manual workstations mean having people do the work. There are some processes that you can't do without positioning parts very precisely such as welding, painting, and gluing. If you are going to put a bead of glue around a headlamp, for example, it might be a better idea to have a robot or a Cartesian system or some kind of automation system position a part that is delivered by a conveyor very accurately and firmly.

"We have had some companies such as automotive suppliers build new facilities that have replaced the conveyor approach with manual workstations and maybe manual roller conveyors. Then a few years later they discovered that the quality they needed wasn't there, and they came back to us looking for conveyor solutions."

 

This article was first published in the December 2007 edition of Manufacturing Engineering magazine. 


Published Date : 12/1/2007

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