Eliminating the stall
At Cummins Engine, the installation of new AGVs and a power-and-free conveyor has created for the first time a synchronized, continuous flow in manufacturing.
By DAVID MALONEY -- Modern Materials Handling, 10/1/1999
Custom production of diesel engines for over-the-road trucks, buses, bulldozers, and marine vehicles is what Cummins Engine does best. But at its Jamestown, N.Y. facility, production always got stalled between the main assembly line, the testing department, and final assembly and painting.That's not the case since an upgrade of its automatic guided vehicles (AGVs) and power-and-free conveyor. Not only is there a synchronous flow of engines through all the key stages now, but productivity has increased and engine quality improved at the same time as labor costs declined. In addition, the new materials handling scheme eliminated one work shift in the testing area.
"Before the upgrade we had three areas of assembly as opposed to one integrated system," explains Ron Padd, manufacturing engineer in the assembly and test area. "It was not a good set-up and was extremely costly."
Flexibility and efficiency have improved to the point that "we can literally take an order and build it in a day if necessary," says Gene Wilston, head of Cummins test/assembly area.
The Jamestown Engine Plant makes most of the major components used in their engines, from cylinder heads to flywheels and crankshafts.
Each engine is assigned a serial number that corresponds to a summary bill of materials (SBM). The SBM has specific instructions as to which parts go on which engine. There are literally thousands of variations available on Cummins engines. They range from 270 horsepower diesel generators to large 635 HP marine engines that power large cabin cruisers.
"This is a custom plant," says Mike Brinkley, manufacturing engineering technician. "We probably have 16 different oil pans alone."
All engine models move down the tow assembly line together. Parts and sub-assemblies for each engine are sequenced on racks or in containers at the assembly stations to correspond to the SBM. Each part is marked according to the build sequence.
After the pistons, gaskets, and all other engine parts are assembled at the 56 workstations along the line, the engine is sent to a test area to evaluate for leaks. Once an engine passes the leak test, it is tagged and moves onto the hot test area.
In this test, engines are fired up and run to assure proper perfor-mance. Computers measure and record the results.
This area had been the major bottleneck in the facility. While the assembly line was running only one shift, two shifts had been required in the hot test area. Engines stacked up outside the cells until they could be tested.
"That was a lot of money just sitting on the floor," says Padd.
One of the main reasons for the bottleneck was an antiquated system of AGVs used to transport engines on test pallets to and from test cells. The original units, installed in 1985, were constantly breaking down and required 1Þ technicians full time to keep them running.
The upgrade involved the addition of four new roller-deck AGVs (Rapistan Systems) specially designed to accept or deliver engine test pallets from either end of the units. This saves time, as the old units had to turn around to accomplish the same task. The new AGVs are also more efficient, as they meet the design parameters of being able to pick up and deliver the engines within 2 minutes.
A quick repair area was added to take care of minor problems with engines that did not meet specs, and the test pallets that hold the engines were also upgraded to work with the new systems.
As an engine enters the test area, it is first hoisted from the build cart that carried it through assembly onto one of the 16 custom-designed test pallets. Next, a rigging station connects measurement lines, air hoses, exhaust hoses, and wires from the engine to outlets on the pallet. Oil and lube are also added to the engine.
The test pallet and engine next roll from the rigging station onto the AGV's conveyor deck for transport to one of the six diesel test cells. As the AGV enters the cell, the test pallet rolls off and is married to connections on the test equipment. The engine is then started. The test measures critical areas such as manifold pressures, oil pressure, fuel consumption, and running temperature.
Engines that do not pass the tests are immediately transported to the repair area, while the next stop for acceptable engines is de-rigging. There, the oil is drained and recycled and the test hoses and wires are removed.
The other major part of the upgrade was a large expansion of a power-and-free conveyor. It picks up the engine at the de-rigging station and carries it through final parts assembly, paint preparation, and the paint booth. The power-and-free then transports the engines to the post-paint assembly area before they are off-loaded onto returnable skids for shipping.
There are actually three chain pulls within the power-and-free conveyor, two are fast chains and the other is a slow drive. The faster chains carry the engines from the test zone through final parts assembly. The slow chain transports the 63 carriers in the system through a pre-paint wash and then through the paint booth. The total system covers 2,585 ft. Controls were also upgraded.
A shorter power-and-free conveyor (1,745 ft.) had existed prior to the upgrade. It basically carried the engine though a few post-test assembly stations and was located a good distance from the hot test cells. Engines had to be transported manually there on build carts, which means that there was double handling involved.
"The person delivering the engines always came back with an empty cart," notes Padd.
The new system has greatly reduced the number of engines in process at Cummins. Before the upgrade the plant averaged 200 engines in process. Now that figure is about 125.
The new system has also provided synchronous flow. As a result, the facility is now approaching its throughput goal of 250 engines per day. Throughput time has gone from 18 hours to only 6 at peak.
"We have taken a day out of our process time, and that gives us more time to adapt," says Wilston.
The greatest savings have been in the test area, where there has been a 30% improvement in the cost per piece of conducting the hot engine tests. Cummins managers acknowledge that at current production levels savings add up quickly.
The system upgrade has also eliminated a full shift from the test area and has allowed Cummins to increase quality while meeting customer orders on time by getting engines built more quickly. Damage has been reduced as a result of less nual handling.
"The automation really helped us manage the process," adds Wilston.
Benefits at a glance:
- Synchronous flow established
- Increase in capacity
-Labor savings
-Increase in quality with 7% fewer engines needing re-working
-Reduced testing cycle
-Work in process reduced by 30 engines
Manufacturer Profile
CUMMINS ENGINE PLANT, JAMESTOWN, NY
Facility established in 1975
1-million square feet
Over 1,000 employees
205 engines built daily
Engines range from 270 horsepower to 635 HP
EQUIPMENT SUPPLIERS
AGVs and tow conveyor
Rapistan Systems 616-451-6200
Power and free conveyor
Automatic Systems 816-356-0660
Forklifts
Clark 606-288-1200
Hyster 217-443-7548
Toyota 310-781-2963
Hoist
Dalmec 847-364-9090
Coleman 201-375-6000
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