Shops Benefit from Advanced Technology
Robots deliver cost-effective results in cells or out of cells
By Jim Lorincz
By now the accepted wisdom is that automation can improve spindle uptime in machining applications, provide 24/7 untended production and material handling, and configure diverse types of machine tools into productive cells. Small and midsized shops also have an opportunity to adopt automation as a ready-made and cost-effective solution to critical gaps in the availability of skilled workers for applications like welding, for instance. Although automation can and does take many forms, ranging from barfeeds and parts catchers to pick-and-place systems, and to floor, machine, or gantry-mounted robots, each type has its pros and cons. Descriptions of solutions range from inexpensive, simple and flexible to just the opposite. Matching the right solution to the application is critical and often inherent in the solution chosen.
Single Machine Cells on the Rise
The challenge of meeting increasingly tough competition has opened the eyes of US manufacturers to the opportunities that robotic cells, especially for single machines can offer. “Single machine cells have been very popular as of late,” said John Lucier, automation manager, Methods Machine Tools Inc. (Sudbury, MA). “I believe this is due to the progression of robotics in the machine tool field. For many years robotics on machine tools were used almost exclusively in the automotive and other high-volume sectors of the machine tool market. Automation in these types of fields tended to include many machines and processes tied together. Due to factors such as the competition coming from overseas, smaller manufacturers are now forced to look at ways to control their labor to stay viable in today’s market, even if they are not making a million parts.”
When it comes to creating a cell with a single machine, the JobShop Cell from Methods Machine offers the solution of a small cell with a single machine being serviced by a single robot. “Even though this product’s name literally suggests that a job shop will be using it, and it is quite often sold to shops with a medium-to-low volume of parts, including a high mix of different parts, we also find this cell very popular with manufacturers doing traditional automation with a higher volume, lower mix production,” said Lucier.
“A popular configuration is to have two different workholding setups on the table tasking the robot to flip the part between the first and second operations,” said Lucier. “In this example, the part enters in the raw state and exits finished. In a very high-volume scenario, multiple machines might be utilized for this. However, for a smaller shop where the cost of multiple machines might be prohibitive, or in a situation where the length of the job is only for months versus years, this multiple workholding setup with a robot has proven to be very useful.
“We’ve also augmented this type of setup using a fourth-axis table including a trunnion support which the two workholding configurations are mounted to. This provides the ability to have access to positions all over the part. In traditional high-volume machining, we would have normally used different machines for each operation, but in this situation we used multiple workholding setups in the same machine resulting in the part leaving the machine complete,” said Lucier.
According to Lucier, the size of the infeed/outfeed is a challenge that presents itself time after time in the design of a small cell. “The cell is small, so users expect the infeed/outfeed will be small as well. The infeed/outfeed can really be whatever size the end user needs. It can be small, but then the capacity and resulting untended run time will be limited. Conversely, it can be so big it can double the square footage of the cell. When designing a small cell, the end user tends to want things compact. To solve this challenge, we often use pallet conveyors and stackers which can hold a lot of parts in a small amount of space.”
Robotics Takes On Redundant Operations
“Pre-engineered platforms for welding cells have been available since the mid-1990s and have become a popular mainstay of manufacturing because they are portable and compact, readily available at a lower cost, and usually redeployable,” said Andy Glaser, vice president-sales, Yaskawa America Inc., Motoman Robotics Division (Miamisburg, OH). “The standard pre-engineered welding cell platform is a mature product at this point, but the same concept that makes it effective has been adopted in many other applications. Robots provide a solution when a reliable operator on the shop floor isn’t readily available for many redundant tasks, such as painting, packaging, deburring, grinding and assembly.”
Yaskawa Motoman also provides robots for machine tending and also part of integrated solutions for production machining. “A machine tool may have some automation on it like a pallet changer and large tool capacity so that they can be run for extended periods of time. Robotics, whether for a one-off application or in a pre-engineered platform for machine tending, is all about keeping spindle utilization as high as possible,” said Glaser. “The trend toward increased demand for automation has been around for a while, principally because Baby Boomers are retiring and there are fewer people entering the workforce with the skill sets for some of these types of trades that were available in the past. The combination of a shrinking workforce with fewer people entering the workforce to replace the retirees and the need to be competitive globally have increased demand for automation, probably more so than it ever has been,” said Glaser.
In Search of Uncomplicated Welding Cell Solutions
Simplifying single-purpose applications for robots continues to be a challenge in the highly competitive area of robotic welding cells. According to George Learmonth, vice president, ESAB Automation NA (Florence, SC), entering into a preferred partnership with KUKA Robotics (Shelby Township, MI) has enabled ESAB “to offer welding cell solutions in standard packages that have a lot of features without being so complicated that the end user would need an integrator to get up and running. Our approach is to offer some simple, straightforward equipment or solutions and help the end user, often a first-time user, get into using robotic welding solutions for their applications. This is something that you can buy off the shelf. You may or may not need an integrator to do tooling, but as far as the welding package or the robot package, you just need gas and power. We supply everything else.”
ESAB’s cell configuration is aimed at keeping the cost of the robotic solution down. “Our welding cell solutions have all the features that are designed to improve quality and speed of the process without adding costly features," said Learmounth. "The welding cells also satisfy the need that some shops may have when they have difficulty in finding qualified skilled welders, which, depending on where the shop is located, can be a challenge. In the oil patch in the Midwest, there are shortages of skilled welders, for example.”
A recent product entry from ESAB Welding & Cutting Products is the Swift Arc series of robotic welding cells available in three models (angle-load, front-load, and side-load) that are delivered ready-to-weld. The cell features a KUKA KR-5 Arc Robot with PC-based KRC-2 controller with 11 lb (5-kg) payload and 55.5" (1.5-m) reach. Versatility of welding cell design can be seen in the three models that are available. Swift Arc AL has easy-open manual doors for two independent working locations. Tooling can be changed on one side while welding takes place on the other side. The Swift Arc FL features a servo table that indexes small-to-medium parts at high production rates. Loading and unloading can take place during the welding process. The Swift Arc SL robotic cell is designed for high production of larger parts. Dual trunnions manipulate the parts, allowing welded parts to be unloaded and new parts to be loaded during the welding process.
Rental Program for Robotic Welding Solutions
Miller Electric Mfg. Co. (Appleton, WI) has introduced a robotic welding cell rental program that allows end users to test automation in their own welding operation before purchasing equipment. The program minimizes risk and the need for large capital expenditures, helping businesses meet short-run production demands. Cost to the user is estimated to be about 5% of the system list price.
The program is designed to reduce the risk for companies that are interested in robotic welding, but are uncertain whether the technology is right for them. The program is also well-suited for companies that receive contract work for short runs of parts that don’t warrant the capital expenditure for a robotic welding cell or those that have a sudden need for automation and are unable to justify the expense quickly enough. Rental contracts are for a three-month minimum. For companies that prefer the option, Miller also rents robotic welding cells onsite and will oversee short runs of parts in its own facility.
The Miller PerformArc robotic welding cell at the center of this program is Robotics Industry Association (RIA) compliant, is fully assembled and able to be moved with a forklift. The cells can be optimized for robotic TIG or MIG welding and welding on aluminum or thin-gage materials. As part of the program, Miller offers a full assessment prior to rental to determine that the parts to be welded are repeatable and able to benefit from automation. They also preprogram the PerformArc robotic welding cell and set up any necessary tooling. End users with 3D models of parts are especially benefited by this assessment and programming support.
Renters who also implement ITW Welding components such as Miller power sources, Hobart filler metals or Tregaskiss robotic MIG guns can build residual value toward the purchase of the rental cell should they decide to keep it. Fifty percent of the rental payments apply to the purchase price. For those renters who use other components, 25% of the rental payments will apply.
Single Panel Controls Robot and Machine Tool
Through Siemens’ recent collaboration with KUKA Robotics, the operator of a machine tool with a KUKA robot can run both the machine tool and robot from a single control panel. Key to this latest development is the machine builder’s ability to integrate mxAutomation from KUKA directly through the Siemens Sinumerik CNC platform.
The motion sequence of the robot is entirely engineered within the Sinumerik 840D sl CNC, then transferred by the 840D sl’s PLC function to the mxAutomation interpreter on the KR C4. All program changes to a six-axis robot can easily be input on a second channel of the CNC and fully operated. This scenario provides the ability to not only run a machine tool’s automation sequence more efficiently, but also make more changes on-the-fly to minimize machine downtime, without special knowledge of robot programming language. During the operation of the machine tool, all changes made can be visualized directly on the CNC screen.
In operation, the KRC4 integrator and mxAutomation convert the robot language into the same commands used for multiaxis machine tool functions. A single Profinet cable runs between the robot and the CNC. KUKA’s Andrea Schuhbauer, key technology manager for machine tool automation (Augsburg, Germany) said, "mxAutomation allows the machine tool builder a single I/O language for integrating robotics on the CNC, while the end-user operator can run both the machine tool and the robot from a single screen on the control."
mxAutomation for Sinumerik CNC was a joint development between KUKA and Siemens. KUKA created plug-in function modules for the Siemens Step 7 PLC engineering software and provided its robot knowledge to Siemens for creation of the second channel logic on the CNC. All safety functions and test functions for load/unload, brake test, gripper, robot communication and safe operation of the robot are provided through the Siemens Profinet and Profisafe platforms.
Siemens is the first CNC supplier to achieve this capability for single-screen operation of the machine tool and robotic materials handling on the CNC. Future developments for mxAutomation are planned, including a wider application range for robots in the CNC machine tool environment. ME
This article was first published in the September 2013 edition of Manufacturing Engineering magazine. Click here for PDF.