Counting system raises Stanley's productivity
Tape rule assembly line gets a far more precise measure of the numbers of incoming parts, thanks to high-resolution scale technology.
By Staff -- Modern Materials Handling, 7/1/1998
Stanley Hand Tools is the world's leading supplier of tape rules-each year it distributes some 10 million tape rules to a variety of industries and end users. To maintain that competitive position, however, Stanley must ensure that each step in its manufacturing process is designed for peak productivity, and, equally important, high accuracy.Helping keep Stanley precisely on target in the step that requires moving tape rule cases from plating to assembly is where high-resolution counting scale technology (Setra Systems) figures prominently. Higher productivity and a counting accuracy that's gone up, from 92% to 97%, are the results from the new scale installed.
Why accuracy counts
The specific model of scale now on the end of the plating line where cases are boxed before transport to assembly has a counting resolution as fine as one part in 750,000 (see sidebar). This degree of accuracy ensures that there will be a precise count of the number of cases per box (a box averages 300 cases) that go to assembly.
"If assembly receives an inaccurate number of cases in a box, they have to stop the process to get another box," explains Mark Staranchak, a plating supervisor. "With guaranteed accuracy, the efficiency of the assembly operation has been noticeably improved," he adds.
"We run this system 24 hours a day, six days a week. If we're not sending the correct number of cases in each box to assembly, it could translate to a serious productivity problem down the road."
Performance from the scale technology now installed at Stanley contrasts sharply with that of the scales the manufacturer had used previously. Besides problems with accuracy, and thus inventory count, the antiquated scales were difficult to program. Recalibration of each scale was a lengthy and complicated process.
Now, however, recalibration of the counting scales is accomplished simply by the push of a button.
When it came to selecting scales to replace the antiquated models previously used, Stanley's Staranchak found that the percentage of error (or a standard deviation of ±0.00005 lb) was lower than with any other scale in the same price range.
In order to compare the model chosen versus other scales on the market, the Stanley supervisor tested all the scales for accuracy by repeatedly weighing known amounts of cases. "This scale produced no errors; the others were not only erroneous, but inconsistent as well," he says.
Accuracy and consistency were important for another reason: Stanley's Hand Tools Division, of which the tape rules unit is a part, was applying for ISO certification at the time. The decision to upgrade to better scale technology was made partly to enhance chances for certification. Subsequently, Stanley's performance met the ISO requirements.
Improving operations
Efforts to enhance efficiency have extended to other operations as well. The conveyorized handling process that transports finished cases to packaging is a direct outgrowth of Stanley's efforts at improvement.
Similarly, a review of the past method of electroplating cases led to a switchover to vacuum metalizing the plastic cases. The materials used in metalizing are better for the environment. "And because the metal immediately dries, our overall efficiency is increased," says Staranchak.
Now Stanley's materials handling process starts with receiving tape rule cases, which then go to a carousel, followed by travel to the metalizing system. Finished cases then move via conveyor toward an empty box that rests on the high-resolution scale. As more cases are added to the box, the scale computes the total number until the box reaches capacity.
Finally, there's an intangible gain from use of this new scale technology: It's more user friendly. "Workers don't feel the same level of stress they once did when it comes to recalibration, entering average piece weights, or other operations," Staranchak observes. "That's a benefit we really can't put a price on."
A scale that counts by weighing
Stanley Hand Tools' Tape Rule Department now uses a high-resolution scale to achieve very accurate counts of parts (tape rule cases) moving to an assembly line. Here's how it works.
An onboard computer runs custom software and teams up with the scale's ceramic load cell and its capability to provide an internal counting resolution of 1 part in 750,000.
What distinguishes this scale technology from others, according to the manufacturer, is the combination of both high sensitivity and high capacity in one scale.
For Stanley's application the model chosen (Setra 70 CP) has a 70 lb capacity and a precision of ±0.0005 lb. Counting accuracy is selectable, from 90% to 99.99%, with this scale. Stanley achieves 97% accuracy in its specific process application.
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