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Robotics Case Studies

FANUC Robotics Dross Removal Case Study

by Cathy Powell
FANUC America Corporation


Skimming the dross from a zinc metal bath on a 24/7 production schedule with temperatures up to 878 degrees Fahrenheit is hot, dangerous, back-breaking work. This labor-intensive task with its quality and cost implications gives you all the justifications you need for a great robotic application.

That is exactly what one of the world's leading hot dip galvanizers of automotive coiled sheet steel found when it turned to robotics to perform the laborious task of dross skimming.

The FANUC Robotics Model M-710i robot is the solution of choice to perform the laborious task of dross skimming at DNN Galvanizing of Windsor, Ontario. According to DNN, backaches, muscle pains and lost time associated with manual dross skimming have been eliminated thanks to the addition of an industrial robot to their production team.

Prior to robotic dross skimming, DNN Galvanizing had annually rotated employees through the task of skimming the dross (metal oxides) that form on the 6 foot by 13 foot surface of the zinc galvanizing bath through which they dip more than 147,000 lbs. per hour of sheet steel. According to DNN, this hot, physically demanding job had to be done almost continuously to maintain the quality of the zinc bath. Dross skimming requires an operator to manipulate a skimmer (a large 'spoon' with holes in it attached to a ten foot long handle) across the entire surface of the zinc bath in multiple passes. The skimmer stops frequently to lift up to 33 lbs. of dross that accumulates on the tool and drops the dross into a small holding pot for off-site recycling.

DNN's search for a total turnkey robotic dross skimming system lead them to FANUC Robotics. DNN contacted FANUC Robotics to review the requirements and provide a proposal. After the careful evaluation of all bids, FANUC Robotics Canada Ltd. of Mississaugua, Ontario was contracted to provide an automation solution consisting of:

  • M-710i six axis industrial robot, all-electric, servo motor driven, with model R-J2 controller 
  • HandlingTool™ Application Software package 
  • Stainless steel robot end-of-arm-tool (EOAT) 
  • Two position manual slide for the robot mechanical unit 
  • Removable molten metal splash cover for the two position slide and robot base 
  • Wire mesh safety enclosure with interlocked gate 
  • Project Management, engineering and manufacturing 
  • Classroom training on the robot and controller 
  • Complete on-site robot start-up and programming 
  • On-site supervision of initial production run 
  • On-site system training 
  • System documentation

The M-710i robot is programmed to make multiple passes across the surface of the zinc bath similar to the way the manual operator did the job. After every pass, the robot lifts the skimmer out of the zinc bath and makes a motion just above the surface of the metal bath to move the skimmer closer to the dross pot. During this motion the liquid zinc passes out through the holes in the skimmer, falling back into the zinc bath and leaving the dross in the skimmer. The robot makes a short move from the edge of the metal bath to a position over a dross pot located beside the robot. The robot turns its wrist and dumps the contents of the skimmer into the dross pot. The robot skims the entire surface of the zinc bath within approximately 40 skimming motions in a period of about 15 minutes. In a typical 12-hour shift the robot fills an average of six dross pots.

A number of production issues and were easily addressed due to the nature of flexible automation inherent in robotic systems. Some manual labor is still required to operate the robot and to augment the process, and DNN employees were skeptical of the robot early in the project because they were concerned that the robot wouldn't be able to perform as well as an operator. But after a short period of time, the employees became comfortable with the successful robotic skimming operation.

DNN has logged a reduction in lost time due to the elimination of physical problems associated with manual dross removal. The robot has freed the former skimming operators to do other tasks that are less strenuous, physically taxing and tedious. DNN has not been able to quantitatively measure the improvement in employee morale from the dross skimming robot. However, they are certain that the feedback of the employees who work with and around the robot is the best measure. DNN employees are said to be happy with the newest member of their production team, the Dross Skimming Robot and they speak positively about the job it performs. In a manner of speaking, the dross removal robot is skimming up more profits for them and their company by performing the most labor intensive, back breaking and monotonous job in their facility.

DNN Galvanizing opened its hot dip galvanizing and galvanneal line (HDGL) in Windsor, Ontario in 1992. NKK Iron and Steel Engineering Ltd. (NKK-SE) supplied the HDGL process equipment. The company is a joint venture and is operated as a limited partnership managed by a general partner, DNN Galvanizing Corporation, coating steel for Dofasco and National Steel on a toll-coating basis. The venture is owned 50% by Dofasco, 40% by NKK and 10% by National Steel.

FANUC Robotics North America, Inc. designs, engineers and manufactures innovative robots and robotic systems that impact business performance for global customers.  FANUC Robotics is the North American robotics industry leader and is a subsidiary of FANUC Ltd. in Japan.  The company has facilities in Chicago; Los Angeles; Charlotte, N.C; Cincinnati, Ohio; and Toledo, Ohio; Toronto; Montreal; Mexico City; Aguascalientes, Mexico; and Sao Paulo, Brazil.   FANUC Robotics can be found on the Internet at www.fanucrobotics.com or by calling 800-47-ROBOT.


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