Oil-Shear Clutch/Brake Saves $26,000 for Auto Parts Maker

A high-volume manufacturer of steel elbows for automobile sun visors experienced a nasty kink in its operations. About monthly, a dry clutch/brake driving the cut-off shear in the elbow manufacturing work cell would fail, stopping production an average of 2.5 hours for replacement of the clutch/brake with a new $650 unit.

Each month the manufacturer lost approximately $1,875 in production, $650 on the clutch/brake, and an average of $187.50 on labour costs for removal of the old unit and replacement with the new. Altogether, dry clutch/brakes were costing the manufacturer about $2,700 per month.

The company had come to view dry clutch/brakes as a disposable, commodity item. Plant operations people were frankly skeptical when Force Control Industries proposed replacing the dry clutch/brake with its Posidyne X2 oil-shear clutch/brake — especially at a higher price of $825.

The supplier explained that the oil-shear design, created and tested for 40-million lifetime cycles, would repay the differential in purchase price if it outlasted a dry unit by just one week, but should deliver well over a year of reliable 24/7 service.

The company agreed to put the productive-time argument to the test, replacing a dry friction unit with the Posidyne X Class oil-shear clutch/brake. Eleven months later the oil-shear brake was still running non-stop in 24/7 service and the company had converted six more lines to the new brakes. The company calculated total savings to date at $26,948 from converting just the first line to the oil/shear clutch brake.

HOW IT WORKS

Unlike dry friction brakes, the oil-shear design squeezes a thin film of transmission fluid between a series of alternating friction discs and steel drive plates before achieving full surface contact.

As the oil is squeezed, it cushions the engagement, minimizing shock on drive components. The oil absorbs the heat of engagement, which minimizes wear on friction elements.

In addition, Force Control’s proprietary oil-shear design uses a stack of smaller-diameter discs in place of the two mating discs for typical dry clutch/brakes. The small diameter disc pack has lower inertia, reducing the load on drive motors while enabling higher cycle speeds and acceleration/deceleration.

The sun visor elbow cell is set up so that coil stock of 0.310-in.-dia tubular steel is processed into L-shaped elbows. Processing begins with tubular stock of 0.05-in. wall thickness indexing into a Tube Cut-Off Station. A cut-off press driven by a 2 hp electric motor and the Posidyne X clutch-brake shears the tubular stock into selected lengths. A vertical ram mounted to an overhead counter-weighted horizontal crank drives the notched shear down to cut the tube to length.

Sheared segments are then placed on an indexing conveyor. The conveyor indexes the tubes to two tube end crimpers that reform and debur the tubes. Next, the segment is conveyed into a servo press to form flats on to the tube. The formed tubes index into the next station for bending to preset specifications. The finished product exits the sun visor elbow manufacturing work cell down a drop chute into a finished parts bin.

The cell produces sun visor elbows at 1.2 seconds per part with a value of $0.25 each.

The manufacturer calculated the savings from the 11 months of trouble-free production by the oil-shear clutch brake based on:

1. Recovered production of 2.5 hours per month from avoiding downtime for clutch/brake replacement.

2. Dry Clutch Brake — 2.5 hours x 11 times = 27.5 hours x 60 min/hr = 1,650 min x 60 sec/min = 99,000 sec.

3. Oil Shear Clutch Brake — 2.5 hours x 1 times = 2.5 hours x 60 min/hr = 150 min x 60 sec/min = 9,000 sec.

4. (99,000 sec – 9,000 sec) / 1.2 sec/ part = 75,000 parts x $0.25/part = $18,750 in lost production savings.

Clutch/Brake costs were calculated as follows:

Dry Clutch Brake — $650 each x 11 Units = $7,150. Oil-Shear Clutch Brake — $827 each x 1 Unit= $827. The result is $6,323 in clutch brake savings.

Maintenance savings were calculated as follows:

For removal and replacement of a clutch/brake: $75 hr/labour x 2.5 hr= $187.50 per changeover. With the Dry Clutch Brake it amounted to $187.50 x 11 times = $2,062.50. With the Oil Shear Clutch Brake, it was $187.50 x 1 time= $187.50. Total maintenance savings were $1,875.

Total savings after 11 months of oil-shear clutch/brake production amounted to $26,948, for a payback period of 1/3 month.

The oil-shear clutch/brake also generates savings in reduced air demand that are not included in the calculations. The X2 Oil Shear Posidyne engages at 30 psi, whereas a worn dry fiction unit may take as much as 100 psi.

Since adopting the oil-shear clutch brake, SCFM demand has been reduced on the sun visor manufacturing work cell. The reduction in compressed air demand has generated additional dollar savings and compressed air capacity for the company.

The manufacturer has begun to upgrade all its clutch/brakes to the oil-shear design. Six lines have been converted to date with additional lines to be addressed at a later date.

For additional information, contact Force Control Industries Inc. of Fairfield, Ohio, at 1-800-869-3244, or visit the website at www.forcecontrol.com.