Customised solutions for the large range of parts

A coextruded central white guide wedge is aligned in the matching groove of the guide. Permanent magnets secure the steel plates and pull the guide wedge into the guide groove. Fig.: Mulco

“The huge variety of solutions offered by the use of polyurethane timing belts makes them particularly suitable as a universal means of transport for the automation of presses in sheet metal processing. There is no such thing as a standard solution,” the engineer at GPA-Jakob explains. This particularly applies to the transport of sheet metal parts. Detailed, customised solutions are required to meet the very different requirements of a diverse range of sizes, weights and materials.

For the project introduced here, left-hand and right-hand punched sheet steel parts have to be transferred from a stack to a metal forming machine. This requires secure transport and precise positioning of the parts in relation to each other.  “We use BRECO® timing belts for the transport of parts as they can be individually adapted to our particular applications. Hilger u. Kern from Mannheim has been assisting us for many years with ingenious detailed solutions for new transport tasks,” says the GPA engineer.  René Preßler, the customer consultant from Hilger u. Kern, confirms this: “We individually draft several design concepts for each task. In the following consultations with the customer we determine the favoured solution and give technical and commercial support to the customer from the design stage to the launch of the series.

Guide wedges and magnets for precise transport

Transfer point: The steel plates are transferred from the supported belt to the suspended belt. Permanent magnets hold the steel plates securely to the back of the belt. Fig.: Mulco

With a maximum centre-to-centre distance of 8.4 m for the transport conveyor to the metal forming machine, precise guidance of the sheet metal parts and therefore of the belt was particularly important from the beginning. Precise guidance is achieved in the series solution at GPA by a guide wedge extruded in the timing belt. The timing belt wedge is aligned in the matching groove of the plastic guide. Permanent magnets are positioned underneath the guide with precisely coordinated spacing. They generate a force between the back of the belt and the sheet metal parts, and generate a contact pressure for the belts on the guide. “This increases the frictional force between the belt and guide, which affects the drive performance and is decisive for the specification of the drive motors,” says the Hilger u. Kern customer consultant.

The frictional force is influenced by the number, spacing and strength of the magnets. A solution was jointly developed that achieves optimum positioning accuracy with the lowest possible magnetic force. Engineer René Preßler adds: “The guide wedge is simply extruded together with the belt. Wedge guidance of the belt was the ideal solution in this case. Another possibility would have been to use the Conti Synchrodrive N10 variant, a nubbed belt that comes with its own guide system.”

The design engineers from GPA ultimately favoured the 100 mm wide endless joined BRECO timing belt 100 ATK10K13-V.

Suspended transport conveyor

The permanent magnets can be synchronously moved up by a lever mechanism to allow defined discharge of the steel plates. Fig.: Mulco

At the end of the transport conveyor, the sheet metal parts are transferred to a suspended transport unit with 75 mm wide BRECO timing belts.  The necessary holding force of these belts is also generated by permanent magnets, this time together with the weight. The permanent magnets are synchronously lifted for a brief time by a lever mechanism for discharging the sheet metal parts. René Preßler adds: “The possibilities are by no means exhausted”.

Depending on the workpiece weight and shape, a Linatrile backing can protect the back of the belt from the sharp edges of the sheet metal parts and increase its resistance to lubricants. The cutting oil, with which the sheet metal parts are coated, can very rarely lead to the sheet metal parts adhering to the belt during suspended transport after the magnets have been raised or after the electromagnets have been switched off.” The solution: A partial coating of the back of the belt reduces the contact surface and thus the adherence of the parts to the belt.

Last but not least, like TransDev in the UK, Hilger u. Kern, as a member of Mulco-Europe EWIV, is one of the few suppliers who can supply the timing belts in widths larger than 100 mm. If this is not sufficient, timing belts can be joined by a backing to achieve widths of up to 500 mm. Vacuum technology can be used for transporting aluminium sheet metal parts. The specialists in Karlsruhe are unanimous in their choice. “Is there any other machine element apart from the timing belt that can be adapted so flexibly to the different transport tasks?”