Kategorien: Application News (english) News vom 15.04.2005

KUKA Roboter GmbH - Linear Robots versus six-axis Robots for Handling of Injection Molded Parts

For the automation of an existing injection-molding machine customer Burk intended to adopt a solution using a three-axis linear robot. As the ceiling of the existing production shop was too low, however, a special design would have been necessary. In vie

For the automation of an existing injection-molding machine customer Burk intended to adopt a solution using a three-axis linear robot. As the ceiling of the existing production shop was too low, however, a special design would have been necessary. In view of this the company began to look for new solutions.

Starting Point / Task definition

Ing. Klaus Burk GmbH produces plastic injection-molded parts which are used, for example, for winding, packaging and transportation of high-quality foils and ultra-thin films. One of the company’s injection molding machines, with a clamping force of 1,500 tonnes, produces five different end plates used to package hanging rolls of foil and paper. Daily output is between 800 and 1,000 units.

The task requirement was for the automation of the unloading of this injection molding machine. The quality of the recycled thermoplastics used by Burk as raw materials had been improved, thus eliminating one obstacle to automation. Higher-quality plastics eliminated the need for visual inspection, which automation would clearly have made difficult.

Implementation

In the search for an automation solution, the si6-axis robot proved to be a better alternative than a linear unit. Due to its free motion possibilities in space, the si6-axis robot is ideally suited for lateral unloading of parts from an injection molding machine.

In terms of cost-effectiveness too, the special-construction linear unit’s price/performance ratio could not compete with that of jointed-arm robots, whose sale prices have dropped significantly in recent years due to series production. And given that si6-axis robots are, in any case, much more flexible than linear units with regard to possible changes in their applications, the company management decided to make an investment in the future.

The jointed-arm robot uses its vacuum gripper to remove the respective end plate from the mold. It then stacks the plastic part on a conveyor belt leading out of the cell, and deposits the sprue in a container provided for that purpose. The sprue is subsequently recycled and therefore remains in the production cycle.

System components / Scope of supply

The automation solution comprises a KUKA KR 125 robot with a PC-based robot controller including the Control Panel with a familiar Windows interface. The robot is additionally equipped with a pneumatic suction gripper.

The scope of supply also included the conveyor system, the safeguards, the robot enclosure, the programming, the assembly and the commissioning. The supplier was KUKA system partner ASS Maschinenbau GmbH, Overath, Germany.

Results / Benefits

Increase in productivity

Use of the robot has enabled the user to achieve absolutely uniform cycle times. This was not the case with manual unloading, which was associated with fluctuations in quality and lower output. The KR 125 has boosted productivity of the system by about 20 percent.

Reserve capacity

In addition to improving performance, the KR 125 also has significant reserve capacity, while the injection molding machine is operating almost at its limit. It was therefore possible to adjust the speed of the robot in order to minimize wear.

Ergonomic benefits

The end plates weigh twelve kilograms each, and manual handling was ergonomically inconvenient and thus very tiring. Installation of the robotic cell meant that manual handing was no longer necessary, resulting in improved working conditions for the employees. Previously, the operator had to reach a long way into the injection molding machine each time and, in this awkward position, lift a relatively heavy part – a very strenuous activity, which made it necessary to relieve the operator at regular intervals.

Operating convenience

If Burk wishes to change the injection molding machine over to another product, all the operator has to do is select the appropriate program, which is stored in the robot controller. The gripper does not have to be exchanged, since the center point of the plastic parts being handled is always in the same position. If Burk wishes to change the injection molding machine over to another product, all the operator has to do is select the appropriate program, which is stored in the robot controller. The gripper does not have to be exchanged, since the center point of the plastic parts being handled is always in the same position.

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Pictures: KUKA Roboter GmbH

Contact:
KUKA Roboter GmbH, Hery-Park 3000, D-86368 Gersthofen
Herr Rüdiger Sonntag, Tel.: (+49) 0821/4533-3456, Fax: (+49) 0821/4533-2934
e-mail: ruedigersonntag @ kuka-roboter.de Website: www.kuka-roboter.de

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