Mobile robots for cleanroom environments

Driverless transport systems or mobile robots for cleanroom applications still have something of an exotic status. But the market is growing. Whether in semiconductor production, pharmaceuticals or medical technology, mobile robots can revolutionize material transport in sensitive production environments - as the examples here show.

Dust, pollen, suspended matter, aerosols... as many as 10 million foreign particles can be measured in a single cubic meter of healthy and supposedly pure mountain air. By contrast, depending on the ISO cleanroom class, the only particles that will register in a cubic meter of air in a semiconductor or pharmaceutical manufacturing environment will be in the 20-30 µm range. This level of purity is necessary because every single particle can impair the function of a microchip or the effectiveness of a drug – which is not surprising when structures of less than 100 nm in size, approximately one thousandth the diameter of a human hair, are the limit of tolerability in semiconductor production.

The market for numerous products manufactured in cleanroom settings is growing. Take, for example, the wafers and microchips found in every smartphone and car, and nearly every household appliance, often in combination with other sensitive components such as displays or touch screens.

Because cleanliness is so important in this field, even the equipment used for the production of semiconductors itself must be manufactured under cleanroom conditions. And because complete lithography systems for printing wafers, for example, can weigh more than 100 tons, “clean” internal transportation of the system components must also be guaranteed. For this task, Stäubli collaborated with two high-profile manufacturers of semiconductor production equipment to develop heavy-duty mobile robots with load capacities of up to 24 tons.

In cleanrooms, the main reason for using mobile robots differs from automotive and other sectors that already use this technology extensively. It is not about process continuity and automation. Rather, the mobile robot is used to limit contact with personnel, which is always a potential source of contamination in cleanrooms. Because the mobile robot never leaves the production area, it does not introduce even the finest particle containment. Overhead cranes are not an option in cleanroom production either, due to the risk of debris from abrasion. This is why heavy equipment and its components have to be transported along the floor – for example on driverless platform trucks.

Stäubli has set up a dedicated production area for this growing business segment – initially as a simple tent in the production area, now as an independent cleanroom production facility in a separate hall. The creation of this dedicated space was a relatively straightforward, compared to the intensive construction effort involved in the development of cleanroom-compatible mobile robots, including the selection and qualification of suitable materials and components.

“The users of cleanroom mobile robots give us their cleanliness specifications, which are very comprehensive. Many of the required materials have already tested, but there are always some – often plastic – that are not listed in the specifications, which we then have to test extensively,” says Fabian Forster, Project Manager at Stäubli. These tests include outgassing over the entire service lifecycle of the components as well as abrasion caused by operation of the mobile robots. It goes without saying that every test must be documented in detail.

Two examples show how detailed the tests are. Elena Baunoch, Project Manager at Stäubli, explains: “The sheathing of electrical cables must be surface-treated, i.e. annealed or covered, for example by cleanroom-compatible bellows or shrink tubing. And because abrasion can occur when loosening and tightening screw connections, we also have to use approved materials here or carry out extensive testing of each combination of materials.”

These tests and related documentation and coordination work on the first two cleanroom mobile robots projects kept one employee fully occupied for six months. Jan Louwen, Global Head of mobile robot at Stäubli, is convinced that the time and expense will pay off: “We are now so far advanced, in terms of not only production technology but also of organization and expertise, that we are able to handle subsequent projects with much less effort and shorter lead times.”

The staff in the cleanroom production area, separated by a personnel and material lock, have also developed routines for building these sophisticated mobile robots under the very special conditions - wearing cleanroom clothing and using cleanroom-compatible tools.The market for numerous products manufactured in cleanroom settings is growing. Take, for example, the wafers and microchips found in every smartphone and car, and nearly every household appliance, often in combination with other sensitive components such as displays or touch screens.

Because cleanliness is so important in this field, even the equipment used for the production of semiconductors itself must be manufactured under cleanroom conditions. And because complete lithography systems for printing wafers, for example, can weigh more than 100 tons, “clean” internal transportation of the system components must also be guaranteed. For this task, Stäubli collaborated with two high-profile manufacturers of semiconductor production equipment to develop heavy-duty mobile robots with load capacities of up to 24 tons.

In cleanrooms, the main reason for using mobile robots differs from automotive and other sectors that already use this technology extensively. It is not about process continuity and automation. Rather, the mobile robot is used to limit contact with personnel, which is always a potential source of contamination in cleanrooms. Because the mobile robot never leaves the production area, it does not introduce even the finest particle containment. Overhead cranes are not an option in cleanroom production either, due to the risk of debris from abrasion. This is why heavy equipment and its components have to be transported along the floor – for example on driverless platform trucks.

The first two cleanroom mobile robots delivered by Stäubli are used to move equipment components and segments weighing up to 24 tons inside ISO 7-class cleanroom environments and/or transport them from component assembly to final assembly. They do this with a high degree of reliability, no vibration and, above all, without introducing any contaminants. The mobile robots are operated by remote control. One of the first two customers combines the controllers of two mobile robots in master-slave mode so that one vehicle follows the other.

From a user perspective, the new material flow concept brings clear advantages, as is evidenced by the fact that both customers have already ordered additional heavy-duty mobile robots from Stäubli.

Stäubli now plans to open up new fields of application for cleanroom mobile robots in addition to semiconductor production. “We have acquired specialist expertise and a unique market position which we will transfer to other user industries,” said Louwen. The focus this time will be on the pharmaceutical industry. However, in this sector there is more demand for mobile robot fleets providing pallet and container transport than for heavy-duty mobile robots.

Stäubli also has its eye on another, even more demanding application in this industry. The HelMo mobile robot system, for which Stäubli supplies the drive and rotator unit to the Robotics colleagues in Bayreuth, could take over handling tasks in completely different areas of pharmaceutical production. Here too, human-free production avoids unnecessary particle emissions and simplifies the processes in the cleanroom environment. Stäubli will be presenting this concept to the industry. To do this, the HelMo mobile robot needs only to be equipped for cleanroom use, but this is an area of expertise that already exists at Stäubli.

Text: Ralf Högel