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issue: October 2004 APPLIANCE Magazine

Production - Commercial Ovens
Automated Thinking


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by Jill Russell, Assistant Editor

With a goal to achieve consistent and increased levels of production, commercial oven producer Ing. Polin & C. implemented an automated flexible sheet metal system.

Maintaining a 15-year relationship with supplier Salvagnini Group (Vicenza, Italy), the decision was easy for the Verona, Italy-based appliance maker. “They were known as the most experienced supplier in the field of flexible automation,” Giovanni Simoni, technical production director of Polin, explains. “For this reason we contacted them. They provide effective and efficient services to support the machinery.” Installing an integrated system comprising a tray store, an S4 punching and shearing center, and an automatic P4 panel bender, Polin says it is able to control several production functions at various rates to accommodate order demand.

A fully automated system from supplier Salvagnini Group (Vicenza, Italy) controls production rates according to order demand with a computer-controlled storage system.

Storage Smarts

The flexible system starts with a shelved “store” where an operator specifies an internal code and quantity for the sheet material and enters the data through a terminal located next to the store. Capable of holding 376 pallets with a maximum capacity of 3,000 kg (approx. 6,600 lbs), the stores can hold material for use on the flexible system in addition to material needed for other production systems.

To ensure an efficient and fluid production run, the store’s Automatic Storage and Retrieval System (ASRS) automatically checks to see if the needed material is available when a production list is loaded into the system. If the material is already in the store, all operations are performed by the automated system. According to Salvagnini, production is interrupted only when the material required on the current production list is not in the store. In this case, the operator can decide to either load a different production list or continue running the initial list, as the required material may have been loaded during the time the warning message was sent. In addition, the control system keeps track of material on multiple levels, including current stored material and material that is available but earmarked for future production. For every batch that is sent to the system, the software displays a table that shows used and available material inventories.

One aspect of the flexible system is that material can be sent to any part of the system at any time. “You need a flexible system in the beginning because you’re starting from the metal sheet, and you have to obtain many kinds of parts,” Nicola Vanzo, project manager for Salvagnini, tells APPLIANCE. “One part can go to the press brake, another is going to go to the welding system, another part to assembly. You have to follow all of your production, which can require a different material.” As a result, Polin has assigned internal codes to different materials. Therefore, once the operator enters a production list, the system automatically reads an ASCII file and sends the pallet to the appropriate designated system area. Unused material is sent back to the store for future use. Machined parts can be stored using the same code system as the sheet material and can later be sent to another system area by the same initial store methods as well.

Ing. Polin & C. (Verona, Italy) produces its commercial ovens on an automated system from Salvagnini Group. The appliance maker says it is planning on installing additional systems from the supplier.

Precise Punching & Systematic Shearing

Equipped with an automatic feed station, the system’s punching center contains a patented head fitted with an independent actuating hydraulic press that comes in contact with every point of the sheet, eliminating any need for rotation. Patented angular sheer-equipped independent blades with an automatic clearance adjustment function can cut the material in any length and in any order according to longitudinal and transverse axes. Polin’s punching and shearing center is equipped with 40 hydraulic presses with a 33-diam maximum punch and four presses with maximum tool dimensions of 90 by 70 mm (3 1/2 by 2 3/4 in). The punching press can also be equipped with additional presses and rotary pressing units to enable embossing.

Polin’s shearing system consists of two fixed 400-mm (15 3/4-in) lower blades that meet to form a point parallel to the axis of the manipulator. Two upper blades feature an inclined cutting edge in respect to the lower blades and are fitted with a blankholder. Incoming blanks can be cut into multiple sheets in various sizes without scrap. The supplier says its punching and shearing system can be used with both magnetic and non-magnetic sheet metal with a maximum thickness of 3.5 mm. Covered with changeable brushes, the work table and conveyer are said to be quiet and help reduce damage to the sheet metal before unloading. This, according to Mr. Vanzo, is a cost savings to Polin. “If you don’t have an automatic store like we have at Polin, you need a main person to take care of that [function],” he says. “Now, the customer is able to follow the feeding of the machine automatically, without an operator.”

Bending Options

Punched parts are inserted into the system’s panel bender by a controlled manipulator, where the blankholder is closed on the bottom blade to lock the part in place. The top blade then moves to perform downward bends, while the bottom blade consequently creates upward bends. Once bending is performed on one side, the manipulator takes the sheet out of the press, rotates it, and inserts the other side. Various bends can be performed, including flattened, radiussed, tubular, and partial.

The supplier says the machine is self-tooling, and complete retooling can be completed within 90 sec. In addition, Polin asked that the bender have the ability to cut during the cycle to produce narrow panels traditionally manufactured on forming machines. To achieve this, the sheet is cut by moving the bottom blade after the top has already bent the sheet, whereas traditionally, the part is bent by moving the top blade. The supplier says the cutting option can cut a solid sheet with a maximum thickness of 2 mm or 1.2 mm for stainless steel.

Hi-Tech Handling

With the flexible system, Polin says the largest benefits of using the supplier’s system is increased productivity and reduced costs and labor. “We reduced costs by increasing productivity,” says Mr. Simoni. “Unmanned production through fully automated solutions cancelled all possible non-value-added work. That is, time and resources spent on areas of the manufacturing process, meaning people moving parts back and forth and feeding or unloading machines.”

The automated handling is integrated into each part of the system. In the store, the production list software initiates the handling of material and moves packs of sheet metal while also preparing and ordering other pallets for upcoming orders. In both the punching and shearing system and the bending system, a universal destacker, capable of feeding sheets ranging from 0.5 and 3.5 mm in thickness, removes the sheets from a pack and feeds the appropriate machines. Magnetic separators or a series of air blasts separate the sheets as six suction cups lift the shorter side of the sheet to the feeder pincher. A safety device checks to ensure that only one sheet has been fed, and the pincher then transfers the sheet to the worktable.

Sheets are centered on the worktable by preset guides and by an optical sensor that detects the end of the sheet as it passes the worktable. Once the sheet is gripped by the manipulator, it is not released until after the designated machine operations are complete. In order to allow all the punches in the head to reach every position on the sheet, one half of the sheet is machined at a time. Scrap is collected from under the machinery and is conveyed to its own container. In addition, exit paths are programmed and a stacker containing two pairs of magnetic belts transfers and places the parts on top of each other. For non-magnetic parts, two sets of rollers, mounted on two oscillating longitudinal beams below the stacker, push the sheets on the belt until the stacker moves the parts.

Parts leaving the bender are stacked and can be programmed to return to the store and can be recalled when requested by a production list. The bender is also equipped with the same centering and unloading stations as the punching and shearing system. Once a part has gone through the bender, a motorized roller table and inclinable rake slide the part to a cushioned stop. From here, the parts are then lifted and stacked.

Challenging Rewards

The completely automated system, according to Polin, has resulted in several benefits since its installation. “Advantages have been numerous,” Mr. Simoni tells APPLIANCE. “From reduction of personnel costs, to increased ability to react to market demands, to increased flexibility allowing smaller stock [leading], to increased production.” The appliance maker says that due to the automated system, both material quality and productivity have increased, as room for error has decreased with fewer workers handling the material.

There were, however, minor challenges associated with the project that both the appliance maker and its supplier worked to overcome. The first involved efficiently fitting the flexible system into Polin’s production facility in Verona. “We had to revise the layout of the system to make it fit exactly in Polin’s plant,” Mr. Vanzo says. “The customer not only asked us to have it fit correctly, but to install the machine following the flow of the material.” This was a challenge, as the facility was older and could not be rebuilt to accommodate the new machinery. The answer, Mr. Vanzo says, was placing the punching and shearing system in line with the panel bender and integrating the two with the automatic store.

In addition, Mr. Simoni of Polin says the conceptual ideas associated with the new system were also a challenge for the company. “We had to conceive products and the production process in a different way,” he says. “We were used to press brakes and other traditional, non-automated machines.”

Even so, the appliance maker says that by using the new system, its final products ended up being produced with fewer parts and screws, and welding was also drastically reduced. “Production has become faster, and the flexibility of the machines allow us to have a much shorter time-to-market. We have increased the range and the number of products we can offer our customers every year,” Mr. Simoni says. “We had to think differently from the way that we were used to. We had to think automated.”

 

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