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issue: March 2006 APPLIANCE Magazine

Production - Assembly and Fastening
Assembly Made Simple

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Specialty HVAC maker Pfannenberg achieved higher productivity with ergonomic workplaces and the EcoFlow linking system from Bosch Rexroth.

Pfannenberg GmbH (Hamburg, Germany) invented the filter fan some 40 years ago and laid the foundations for switch cabinet air-conditioning, and in recent years the increasing demand for cooling units, heat exchangers, heaters, and filter fans for switch cabinet air-conditioning caused the company to take stock of its assembly processes. What it found was time losses caused by incompletely structured processes, insufficient ergonomics at the workplaces and inadequate facilities for deploying extra personnel to meet peak demand.

Frank Sauer, Pfannenberg’s process engineer, summed up the problem: “We had to produce more, yet had no extra reserves to do so. The system before was too complicated in structure, not accurate enough and, in terms of ergonomics, was no longer up-to-date with present-day requirements.”

Pfannenberg turned to Bosch Rexroth AG’s Linear Motion and Assembly Technologies (Main, Germany) for the integration of ergonomic workplaces.

Cooling units of up to 2 m high and weighing 75 kg, such as those Pfannenberg assembles on the line, are not exactly handy. A high degree of creativity was required in the project-planning phase for the new line. Unusual work tables, made from standard components in Rexroth’s manual workplace systems, were developed in cooperation with Pfannenberg.

The table size was selected to accommodate workpiece pallets and had to allow pallets to be turned on the table so parts could be mounted on either side of the cooling units. Recessed ball rollers in the table top made it easy to turn the heavy units.

“This seemingly simple solution takes an enormous strain off assembly personnel, because up to now they had to lift each workpiece to turn it,” Sauer explains.

It is now easy for the employees to set up cooling units of up to 75 kg weight by simply rolling them off the EcoFlow from Bosch Rexroth AG’s Linear Motion and Assembly Technologies (Main, Germany) linking system onto the lowered adjustable table. Pfannenberg GmbH (Hamburg, Germany) registered an increase in productivity just a few months after its new manual assembly line went into operation. The ergonomically designed and linked workplaces made of standard modular components from Rexroth’s manual workplace systems feature a high level of flexibility.

A Table Instead of a Crane

Whereas the cooling units formerly were set up with the help of a crane, the employees now lower the adjustable table, let the cooling unit slide over the EcoFlow rollers and place it at an angle on the workpiece pallet. An additional adjustable table with rollers and centering options is used as a packing workplace.

Before integrating the new system, the height of the cooling units caused assembly issues. Components that had to be mounted in the lower sections of the cooling units forced the employees to their knees. Assembling components in the upper sections sometimes required a ladder.

“Such awkward working positions are now a thing of the past. Thanks to the idea of providing this workplace with a platform on one side of the linking system, assembly operations can now be conveniently carried out either sitting or standing,” Sauer says. “Employees who also prefer standing to sitting when working on the lower part of the cooling unit can turn the unit round and stand on the opposite side.”

The ergonomic nature of the workplaces was designed to reduce work fatigue and thus cut down on errors. The workplaces have lighting systems, shelves and containers for parts, as well as information boards that provide details on the specific operational steps.

An aluminum profile with a sophisticated geometry forms the basis for this profile. Rollers, transverse supports, leg sets, and other components for workplace design can be inserted in the grooves of the profile. The rollers are clipped into a 300 mm-long roller carrier at 50-mm intervals. A plastic guide profile also clips in place to keep the rollers in position. At the same time, the profile is designed to ensure the workpiece pallets are securely guided on the section. As with the grooves in the EcoFlow profile, the T-groove on the workplace provides mounting possibilities almost everywhere and allows for quick modifications.

The Rexroth EcoFlow linking system also allows the use of customized workpiece pallets. Pfannenberg continues to use chip board pallets with specially made cooling unit supports. Plastic corners acting as spacers form part of the EcoFlow range and prevent employees from getting their fingers caught between two workpiece pallets, in addition to helping the workpiece pallet smoothly negotiate curves.

Reduction of Non-Productive Time

Boards with work information explain assembly steps, all the parts required by the operator are within easy reach and tools are ready at hand, all enhancing assembly efficiency. Ball rollers recessed in the table top make it easier to turn the workpiece pallet.

“There are a great many advantages compared with our former assembly line,” reports Frank Sauer. “The workplaces are better illuminated. We have created more working room for the employees and today we have brought the work sequences under far better control.”

For example, in the previous line, tasks were not assigned to a dedicated workplace. This meant that tools were used at different places, could not be fixed as a result, and, therefore, were not always at the employees’ direct disposal. “All this led to non-productive time, which could soon be significantly reduced using the EcoFlow,” Sauer says.

The flexibility, particularly in linking the manual workplaces with EcoFlow, is designed to allow later extensions, and Pfannenberg soon put that feature to the test. Every cooling unit undergoes a 100-percent inspection before leaving the factory, and increasing production rates persuaded Pfannenberg to set up a second workplace with a test station shortly after the project planning phase.

Attaching an additional workplace so quickly, according to Sauer, would have been impossible under the nonflexible structure of the former system. “Extending this line, however, involved no difficulties at all,” he said. “The uniform concept with coordinated and optimally matched components made it possible to install an outfeed section and integrate another test station into the line in no time.”

Should the demand for cooling units continue to rise, the possibility for further modifications is still open.

Suppliers mentioned in this article:
Bosch Rexroth Corp.

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