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Sensor Frankensteins, Mutants and Zombies

By: George Keremedjiev

Friday, June 01, 2012
 

The economy has been incubating a sensor-and-controls nightmare the likes of which I have not seen in decades, if ever. Plant closures, auctions, offshoring, takeover dies, retirement of many of our skilled tradespeople and even eBay have resulted in shop floors partially if not fully populated with sensor and controls monstrosities. Let’s look at some examples.

Presses

Bought at auction or otherwise acquired, used presses with various controls and die-protection systems are being mixed and unmatched. Where at one time many pressrooms featured equipment with a common, standardized set of electronic controls for press and die-protection functions, I am taken aback to see the various hybrid systems being used in stamping shops. On a recent plant tour, I saw presses with controls from no less than four suppliers, as well as homemade controls. The presses appeared to be mechanically sound machines but with disparate electronic controls for both the press and die-protection functions. What a nightmare for the maintenance folks as they scramble to find the required instructions, schematics, manual—any form of formal documentation applicable to all of the electronic systems being used. Of course, each press has its own connectors and cables for the in-die sensors.

Dies

On another recent shop visit, I saw one die on the shelf with yellow cables and connectors dangling from its side, and another die with a massive rectangular connector and thick cabling for its sensors—seemingly outfitted to handle 240 VAC at several amps, rather than low sensor voltages with milliamp currents. A few shelves to the right was a die with a rat’s nest of wires and banana plugs of various pretty but oily colors. And on the backwall shelving were dies with no electronic sensors for die protection, but instead littered with arrays of mechanical switches and homemade actuators.

The king of this messy hill: A die with six standard power cables, the kind typically attached to home power drills or saws. Each cable powered a separate sensor in the die. I imagined a power strip on the side of the press, connected to the die-protection control, as the most likely candidate for the mating set of receptacles for the die-sensor cables. What a motley crew of dies to try and run with discipline, consistency and repeatability.

Sensor Types

Dies are flowing from shop to shop at a growing pace, as takeover tooling is sent globally not just for offshoring but for reshoring as well. Thus, on the same shelf may sit American, Chinese, Korean and Slovenian dies, each with its own particular sensor setup. Under normal, stable conditions, it is common for the bread-and-butter die-protection sensors and their mounting/probing techniques to be standardized, or at least be vaguely familiar from application to application. However, during yet a third recent press-shop tour, each sensor installation was cobbled by a committee of severely mechanically impaired individuals, each with his own ideas of how a sensor should probe the target. No two dies shared a similar approach to feed sensing or stripper and part-out monitoring. This variety of probing mechanisms was matched by the numerous brands of sensors populating the dies. Thus, a veritable zoo of sensor technologies arrives at the toolroom with every request for maintenance.

What’s going on?

In one word: survival. Many stamping shops worldwide are being asked to be fully fluid and flexible with their dies and presses. As OEMs, at furious and unprecedented rates, shift component production among domestic and international suppliers, dies are being yanked and moved globally with the ease with which amazon.com ships books. Bankruptcies and the resultant auctions are flooding stamping shops with used presses outfitted with varieties of controls.

The resulting extreme mixing and mismatching of dies, presses, sensors and controls is a relatively recent phenomenon. I expect that it will be quite awhile before the situation stabilizes. Adjust your toolroom activities accordingly. MF

 


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