Medical Device Link.

Originally Published EMDM May/June 2004

ENGINEERING INSIGHT

A robot developed for cleanroom use is an integral part of a turnkey automation system designed by Geiger Handling Systems for a pharmaceuticals company.

IInjection moulding technology has made great strides in recent years, specifically in terms of shot weight and consistency. To reap the full benefit of these advances, however, users must have a reliable and uninterrupted supply of raw material and be able to closely control cycle times. Furthermore, small or medium-sized parts made with multicavity moulds must be rapidly and carefully removed from the tool. When producing parts for the healthcare sector, some of these operations have to be done in a cleanroom setting, creating yet another set of requirements.

While injection moulding machines are routinely fitted with parts-handling devices, the add-ons are not always designed for cleanroom use. Geiger Handling Systems AG (Schwarzenburg, Switzerland) was recently approached by a multinational pharmaceuticals firm that was sourcing an automated system to mould and join two plastic parts—a container and lid—in a Class 100 (ISO Class 5) cleanroom. The automation specialist developed a turnkey system comprising two injection moulding machines in a parallel configuration paired with industrial robots. The installation eliminated contamination concerns while optimizing throughput.

Handling Challenges

While Geiger Handling Systems has broad expertise in developing handling systems, designing a turnkey automation system that operated partly within a Class 100 cleanroom posed some unique challenges.

It was clear from the outset that conventional handling equipment would not meet the strict cleanliness requirements. In addition, the dissimilar plastic parts had to be moulded simultaneously, removed, and assembled within a short cycle time. To satisfy these demands, Geiger Handling Systems paired each injection moulding machine with a dedicated robot and gripping mechanism. Although the firm builds a range of linear handling equipment, it opted for an industrial RX 130 robot manufactured by Stäubli (Horgen, Switzerland), which was specifically designed for cleanroom applications. A material feeder was added to the front end to complete a fully automated system that could operate in multiple shifts.

Two four-cavity moulds were used during the pilot phase. For serial production, a 32-cavity mould for the containers and 64-cavity mould for the lids were built. They achieved respective cycle times of 13 and 23 seconds. That left a 2-second window during which the moulded parts had to be removed from the tooling. This is accomplished in a single step by robots fitted with vacuum grippers, which remove and place the parts in the centre of the cell, where they are assembled. A robot then puts the assembled products on a conveyor system that carries them to a Class 1000 (ISO Class 6) cleanroom for further processing.

To prevent contamination of the parts during moulding, the clamps are positioned inside the Class 100 cleanroom. The machines are mounted on rails to allow technicians to slide them into the adjacent Class 1000 cleanroom for servicing. Following maintenance or a tooling change, the injection moulding machines are pushed back and the clamps are secured in their operational position.

Unlike the moulding equipment, the robots are permanently mounted on a stainless-steel base inside the Class 100 cleanroom. A laser system is used to automatically adjust and calibrate the robots, and the control terminals are located outside of the Class 100 area, again to minimize contamination risks. Maintenance and observation windows around the perimeter of the cleanroom allow personnel to clean the grippers without having to go inside. Defective parts are evacuated via chutes that are constructed directly under the windows.

The stainless-steel vacuum grippers are designed to be lightweight and durable. Because of process consistency achieved by the use of robotic technology, the grippers are able to rapidly and precisely enter and exit the mould without docking. Vacuum switches verify part presence, while photoelectric cells monitor the performance of the grippers. Each robot is equipped with its own vacuum supply system and vacuum pumps that consume minimal energy.

Geiger Handling Systems attributes the success of this project to its single-minded focus on customer satisfaction. Although it has many years of experience developing handling systems in-house, the company recognized that this particular application would best be served by the use of a robot built by Stäubli. It is but one example, says the firm, of its commitment to tailoring automation systems to precisely meet customer needs. n

To learn more about Geiger Handling Systems AG, select #7 on the reader service card or go to RequestLink at www.devicelink.com/emdm.  For more information about Stäubli, select #8.

Copyright ©2003 European Medical Device Manufacturer