Application Stories

Robotic Welding Increases Productivity In Unlikely Applications
 

Crown Equipment manufactures electric lift trucks used to transport materials and goods in warehouses, distribution centers and manufacturing facilities worldwide. Nearly 92 percent of the truck parts are made on site, requiring more than 1,500 parts to be manually welded.

CHALLENGE
• 1,500 individual parts per lift truck had to be welded in one of only nine welding stations.
• Increased downtime associated with changing welding procedures and fixtures for each part.
• Manual MIG and stick welding processes resulted in inconsistency and variable weld quality.

SOLUTION
• Lincoln Electric System 30 Robotic Cell
• Lincoln Electric System 30HS Robotic Cell
• Lincoln Electric Power Wave® 455M
• Lincoln Electric SuperArc® L-56

RESULTS
• 80% decrease in lift truck production time.
• More consistent welds of a higher quality—passing destructive testing after each run.
• Reduction in welding stations enabled the addition of a new production line and increased manufacturing capacity without adding more employees.
• Robotic programs made operator’s job easy with the simple entry of a code, placing the raw material in the fixture, and pressing start.

Many fabricators are discovering the benefits of robotic welding in areas they never before suspected.

While robotics was once considered a means exclusively for mass production, companies such as Crown Equipment Corp. have  dispelled that myth and continue to find substantial gains welding as few as one unit for a variety of separate parts using automation.

Crown manufactures electric lift trucks worldwide as high as 45 feet to assist in a variety of material handling and manufacturing applications. The company’s trucks are used to transport materials and goods in warehouses, distribution centers and manufacturing facilities.

 Crown Equipment

In a unique production model, the company produces nearly 85 percent of all its truck parts within the company. Each part is often made in small quantities – as few as one to twenty at a time, to meet real-time demand on the assembly line.

For years, however, the Greencastle, Indiana location had manually welded more than 1,500 miscellaneous parts in nine welding stations using MIG processes, along with the welding of the frame of four different models of lift trucks. Five years ago the company began reevaluating that strategy.

Crown Equipment 

Crown Chooses Lincoln Electric
A Crown manufacturing engineering team began looking into automation. The first step was to ask for an automation survey of  Crown, its parts and its processes by a team composed of Crown personnel and experts from the welding and robotic industry. As a result, Crown invited FANUC Robotics, The Lincoln Electric Company and several other automation and welding companies to review their operations.

They discovered hundreds of parts could in fact be welded better, faster and more consistently with robots, despite the small unit quantities.

The invited companies performed a twoday review of Crown’s complete welding operations and procedures, both manual and robotic. They discovered hundreds of parts could in fact be welded better, faster and more consistently with robots, despite the small unit quantities. Moreover, the data showed Crown that the investment would pay for itself in a matter of months.

Lincoln Electric tested its assessment in its Cleveland headquarter laboratories and presented Crown with the final results.

Crown engineers took those findings to its senior management team and purchased the first of three FANUC Robotics robots and Lincoln Electric welding cells, with Lincoln Electric Power Wave® 455M power sources and SuperArc® L-56 MIG wire.

The Welding and Material Handling Process
But the changes didn’t stop there. Crown engineers, using a universal mounting and fixture plate system, started building dozens of robotic welding fixtures for the new welding cells. They were all built on common fixture plates that matched up with the locating pins on the frames and tables in the robotic weld cells for easy installation and removal. This allowed every welding fixture the ability to be quickly changed in and out as needed or moved from one robotic weld cell to the other.

As soon as a new fixture is installed into the welding cell, an operator calls up the stored programming code for the part to
be welded by entering a three digit code using a thumbwheel switch on the operator panel of the robotic weld cell. This automatically loads the stored program into the robot’s teach pendant that corresponds to that specific fixture.

FANUC Robotics robots and Lincoln Electric power sources interface with each other so that operators need only enter one code into the robot. This stored code retrieves all the previously programmed instructions for both the robot and power source for each part, including travel path, travel speed and arc characteristics, such as constant voltage or Pulse-on-Pulse®.

The programs can even be designed to change arc characteristics within a single program. For instance, the robot and power source can instantly switch to Pulse-on-Pulse® process when the arm shifts to a vertical weld. When the arm swings back to a horizontal weld, the power source can instantly change back to constant voltage.

This is one reason that despite the small unit production, robotic welding has helped Crown’s overall process. Crown reports dramatic improvement in productivity – by a factor of at least three or four. Welds are more consistent and are overall better in quality. Crown performs destructive testing on the first run of each part and periodically there after, and the improved quality is clear.

Quantifying Productivity
According to Crown, the robot’s speed outperforms manual welding so well that it overcomes any downtime associated with  automation, even when producing a single unit. The new fixtures have been designed to eliminate the need for tack welding previously used in their manual operations, providing additional time savings.

Companies such as Lincoln Electric and FANUC Robotics routinely perform free welding evaluations for companies to determine a variety of needs. The process can increase productivity and in some cases, even improve the quality of the finished product without spending a dime.

The survey begins when robotic welding specialists audit operations and first identify immediate opportunities for cost savings and productivity gains. If automation is seen as a viable option, Lincoln Electric can actually simulate a specific automated welding process in its Cleveland laboratories and determine realistic costs savings in each case.

“Customers really appreciate seeing their parts welded first-hand. It allows production personnel to see how a proposed welding process performs with actual travel speeds and cycle times – and how forgiving a process might be for expected gaps, fixture tolerance, or if improvement in component part fit-up is needed to make the application a successful one,” said Geoff  Lipnevicius, Automation Engineering/Development Manager for Lincoln Electric. “This gives companies a sense of expected productivity gains in an effort to avoid any surprises after the purchase. It also allows the finance committee, prior to the commitment of an investment, to make an informed decision with real data to insert into payback or return on investment (ROI) calculations.”

Crown’s first robotic welding cell, a Lincoln Electric System 30, paid for itself in just four months. The second cell, a Lincoln Electric System 30HS, paid for itself in nine months. Both of these successes resulted in the company looking to add more  automation, and a Lincoln Electric System 50HP has recently been purchased and installed. The automation survey provided Crown with a sense of due diligence and an independent assessment, which its engineers could provide to senior management to support their own estimates.

Robotic welds tackle a variety of Crown’s work on carbon steel in thicknesses ranging from 16 gauge to ¾ inch. Crown uses Lincoln Electric SuperArc® L-56 wire in .035 and .045 diameters.

 Crown Equipment

Raw plate steel first enters the plant, where it is laser cut, formed, machined and, in many cases, welded into the final part. From there, it is painted and sent to assembly for final installment. Parts production had been slower before automation, but organizing the entire process accomplished several improvements. Crown first organized the production process overall, as well as precise procedures for each part. It reduced the space of the welding area, organized the fixtures for easy retrieval and dramatically increased product flow to assembly.

Return on Investment
The average welding time of each part dropped from five to ten minutes down to two to three minutes. The Lincoln Electric robotic cells are a System 30, a System 30HS and a System 50HP. All are dual station cells, which allow the robotic arms to alternate between two work areas.

As work is replaced on one side, the robot welds on the other, and vice-versa. The operator simply replaces finished product with the component parts to be welded next. In doing so, the robot is always kept in motion resulting in total time savings of nearly 80 percent. This newfound productivity has allowed Crown to begin new production in the Indiana facility without a significant impact on employment.

“Lincoln Electric and Fanuc Robotics really helped us realize this change, and it was their experience finding these kinds of opportunities and making them work, along with the equipment design and integration, that ultimately resulted in Crown choosing Lincoln Electric and FANUC,” said David Besser, Crown Senior Vice President – Manufacturing. “And quite frankly we have not had a single equipment failure with any of these products. We are very pleased with all the results.”

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