Crane National Vendors
Automated Conveyors Doubles Production Capacity
Hytrol Engineers guided us to the right components for the system. With the exceptions of the transfer car and a pneumatic lift table, every component of the new system was a catalog item. The use of off-the shelf items really cut lead time dramatically.
Manufacturing capacity limitations can hamstring any manufacturer, stretching out delivery times and requiring frequent juggling of production schedules. For Crane National Vendors (CNV), the solution was a straightforward one: convert a gravity-conveyor-based assembly operation to one based on automated powered roller conveyors for the Snack machine assembly line- CNV’s highest volume product.
Crane National Vendors produces a broad line of merchandising machines at its Bridgeton, Missouri, plant. The facility’s output includes Snack, Hot Drink, Cold Drink, Food Multi-Purpose, and Specialty vending machines. Until recently, the machines were manually moved along on gravity roller conveyor from one assembly station to the next through production.
The process was labor-intensive, and given the weight of the machines (up to 800 lbs.), it raised ergonomic concerns as well. In addition, the Snack machine line capacity was limited to 50 machines per shift, which was insufficient to keep pace with increasing demand. Clearly, CNV needed to find a way to increase line capacity and also address its ergonomic concerns.
“Most of the assembly work in the final assembly area of the plant takes place on conveyors,” explains Manufacturing Engineer Bill Ellis. “Given the kind of products we manufacture, a conveyor-based system makes sense, but we needed to overcome the limitations that were inherent in our original approach to materials handling.”
After reviewing several alternatives, Ellis and the other members of the company’s project team met with their local Hytrol Conveyor distributor, Munroe Material Handling, to design a cost-effective solution.Continued reliance on gravity conveyors in the final assembly area was ruled out; instead, the company would switch to powered roller conveyors. Working with sales engineers from Munroe Material Handling, the project team laid out a Hytrol conveyor system that would carry machines through the assembly process, while also accumulating and staging them as required
An Assembly Operation That Flows
The assembly operation at the Bridgeton plant begins when empty machine cabinets are brought from the facility’s painting operation. The cabinets are loaded onto six parallel rows of powered roller conveyor. After each cabinet is loaded, an employee uses a push button to start the system. The conveyor accumulates and stages the cabinets for delivery to the assembly line.
All of the rollers in this segment of the system are plastisol-coated in order to prevent any scratching of the bottoms of the machines. At the end of this section of conveyors, a transfer car picks up and carries cabinets from the end of each conveyor line to a single main assembly conveyor. The transfer car can be operated under either manual or automatic control.
Once it has been transferred to the main assembly conveyor, the cabinet is carried to an accumulation zone where an employee, using a lift and tilt fixture, installs its legs and positions it onto a pallet. From this point, the cabinet travels along through a series of workstations. If a parts shortage or some other factor delays the completion of a machine, the unit is transferred at a right angle by a chain transfer to a parallel staging conveyor. Cabinets proceed from the first main assembly area to a second main assembly area via a chain transfer. The layout of this second area closely resembles that of the first. An off-line horseshoe-shaped sub-assembly area feeds product tray assemblies to the main assembly line.
After all of the assembly steps have been completed, the machine is ready to undergo testing. The machines are transferred into and out of the test stations using right-angle chain transfers. The test stations consist of gravity conveyors with chain transfers mounted in them.
There are a total of 8 test stations. As each machine reaches the beginning of the test section, it will move into the first available test station. After a machine passes the testing procedure, it is transferred back to the main conveyor for transport to accumulation, packaging, and shipping. At the discharge end of the system, machines are conveyed onto a special pneumatic lift table. The table takes machines from the 12-in. top-of-roller elevation down to a 6-in. top-of-roller elevation of an already existing gravity conveyor.
Another customized feature is a pneumatic lift table from Hytrol that transfers cases from a conveyor line with a 13-inch clearance to one with an eight-inch clearance. That lower clearance is required for certain assembly tasks that could be performed more safely and comfortably with the lower clearance.
Picking The Right Components
According to Bill Ellis, selecting the right components was a key to success of the project. “Munroe Material Handling and the Hytrol design engineers steered us away from custom-designed components that required long lead times,” Ellis notes. “With the exceptions of the transfer car and the pneumatic lift table, every component we used was a catalog item. Even the chain transfers are right out of the catalog. Our use of off-the-shelf items really cut the lead time dramatically.”
National Vendor’s timing for the project proved to be fortuitous. As the installation and start-up of the new conveyors neared completion, the company received a special order that required a 20% increase in production of Snack machines. The investment in the new production system paid off: the required ramp-up in production was met without a hitch.
A Snapshot Of The Upgraded Assembly Line
|Company: Crane National Vendors
Facility: Merchandising Machines Manufacturer
Location: Bridgeton, Missouri
Size: 500,000 Square Feet
Employees: Over 500
Product Handled: Snack Machines
Number of feet of powered conveyor: 750
Number of feet of gravity conveyor: 250
Permanent Workstations: 7
Flexible-Position Workstations: 27
Test Stations: 8
Conveyor supplier: Hytrol Conveyor Company, Inc.
Equipment distributor: Munroe Material Handling Company, Inc.