Assembly in Action: Arm Speeds Inspection
Morton Metalcraft Co. (Morton, IL)--a large contract fabricator of sheet metal parts for manufacturers of farming, off-highway and industrial products--faced this obstacle when it teamed with John Deere & Co. to develop two cab frames for a new G Series backhoe.
Producing the new cab frame was daunting, particularly from the inspection standpoint. Although the company had relied on state-of-the-art digital inspection equipment and CMMs, these were too slow to meet the production requirements. Something faster and simpler was needed.
To qualify for the new cab contract, the company had to manufacture and inspect each unit at the required rate. This includes checking surfaces for parallelism; hole patterns; position of attachments, such as headliner hangers; and gross dimensions.
Testing their previous digital inspection system on a cab mockup, engineers discovered that it would take two men approximately 4.5 hours to fully inspect each unit. At the projected volume, total inspection of every unit would require 270 man-hours per day. Inspection would need paring down to a fraction of that, with inspectors checking only key characteristics. However, to prove that the company had the capability to make and deliver the product, it had to demonstrate inspection of all units, 100 percent if necessary.
"If we had to rely on our previous inspection system, we would never have gotten the job," explains Eric Johnson, division manager of quality services. "We had to find a new way to attack the problem."
To address the need, Morton installed FARO Technologies' (Lake Mary, FL) FaroArm digital measuring system. This digital measuring system, called Control Station, uses the same electromechanical components as a conventional FaroArm. However, a new computer and software speeds up and simplifies dimensional inspections.
The FaroArm is set on or near the product, and is mounted magnetically or by clamps. The Control Station is equipped with a touch-sensitive monitor that is attached to the base of the arm. This displays the part, or section of the part, that is being inspected, and it can be swiveled for easy viewing. Measurement accuracy is ±0.001 inch depending on the size of the part. When mounted inside the backhoe cab, the arm can reach all the required measuring points without being repositioned.
The points to be measured are embedded in the software, and operators are directed to these points. Thus, the need for an operator to search for key points is eliminated.
The Control Station software programs, known as Softcheck Tools, are written for individual products or parts. The routine screen presents the operator with a series of product photos that show full inspection or several partial inspections. The operator makes a selection by pressing the screen. The screen defaults to the selected inspection routine's first step. A photo of this selection fills the screen. Small colored balls, which are the measurement points, then appear superimposed on the photo. A highlighted instruction line appears on the screen and tells the operator where to touch the cab with the arm's stylus.
To take the measurement, the operator touches the point and presses a button on the stylus handle. This records the dimension, the computer acknowledges the completion, and the first green ball disappears. A broken arrow appears and points to the next measuring spot.
For points with critical tolerances, or when there are many points to check and the inspection process is hurried, the Softcheck Tool has a "target acquisition" mode. This helps operators find the exact spot to measure.
When the inspection is complete, two types of reports are available. Inspection reports, showing point-by-point tolerance data, are provided in spreadsheet format. Also, SPC graphical reports can be produced to show process trends.
One advantage of this software-directed inspection is repeatability. "I can run the system on one shift, then turn the equipment over to someone on the next shift, knowing that we will both be measuring the same points," explains Frank Lewis, an inspector.
With this system, the company cut inspection time from 4.5 hours, for two operators, to less than 45 minutes, using only one operator.
For more information on digital measuring systems, call FARO Technologies at 800-736-2771, visit www.faro.com.