How clean is my robot?
As cleanroom applications grow in manufacturing, finding the right fit is important
The past decade has changed our daily activities in such a way that we cannot imagine a life without the convenience of an iPhone, DVR, digital camera or our other favorite electronic gadgets. All the images, music and video created by and stored on these gadgets generate tremendous demand for data storage.
Studies show that with the increased speed and convenience of file transfer, the average consumer stores these memory intensive files in at least two locations demanding even greater capacity. Industry data also suggests that consumers will purchase at least two hard drives in 10 years, so demand for manufacturing storage devices and memory is growing exponentially.
So, what do you need to know about cleanroom robots and equipment to service this market? How are they different from traditional robots? What about certification, maintenance and those pesky particles?
As the name implies, cleanrooms control the level of particle contamination present that can potentially degrade the products being manufactured. Cleanrooms are classified according to the number and size of the particles permitted per volume of air.
For example, a Class 10 cleanroom denotes that no more than ten particles of 0.5 µm or larger and zero particles of 5.0 or larger are permitted per square foot of air. Contaminants can be generated by people, process, facilities and equipment. In order to control contaminants that are invisible to the human eye, the manufacturing cell and in many cases the entire room must be controlled. Robots used in this environment must meet stringent clean room certification requirements to prevent them for acting as a source of contamination.
Sealing the robot
How do cleanroom robots differ from their standard counterparts? Much of the hardware used in a cleanroom robot is the same as any other robot with the important exception of a combination of sealed covers to prevent particles from escaping the robot, stainless steel hardware, proper non-gassing lubricants and vacuum to evacuate any internally generated particles.
“Robots designed for clean room processes have special considerations for harnesses. From a design standpoint the harness can be a serious particulate generator and a major design challenge for clean applications,” said Scott Klimczak president of CHAD Industries, a pioneer in the area of wafer and substrate handling WLP I (Wafer Level Packaging) applications. “Understanding the harness requirements and how the robot design will integrate a harness should always be stressed in the robot selection.”
As a matter of practice, materials prone to particle generation are substituted or coated to eliminate the potential for contamination of the manufacturing area and ultimately the components being processed. Depending on your application, cleanroom robots can be linear, SCARA, six-Axis or delta type robots but they all must meet strict cleanroom certifications.
Certification is done by counting the particles generated when the robot is in motion. The industry uses particle counters which have to be calibrated to meet or exceed the standards set by the National Institute of Standards and Technology. In addition to NIST traceable practices, other standards of particle counter calibration include Japanese Industrial Standard (JIS) B 9921, Light Scattering Automatic Particle Counter, and ASTM F 328-98, Standard Practice for Calibration of an Airborne Particle Counter Using Monodisperse Particles.
The particle counters are placed in various locations from where particles can enter the environment from the robot to determine the cleanroom class. Adept Technology, Inc. a leading manufacturer of cleanroom robots tests robots both internally and through third party testing and certification to ensure integrators and end-users deploy their equipment appropriately to meet manufacturing cleanliness requirements.
Such robots are designed for high speed, precision applications frequently involving vision guidance. The challenge with this market segment is that it demands careful consideration of not only the components used to develop a highly robust manufacturing process but the manner in which they are integrated has significant impact on the ultimate cleanliness of the cell. The success of an installation is heavily dependent on tightly integrating engineering and sales teams.
The right fit
Manufacturers with a cleanroom application have numerous options when considering how to manipulate parts and automate their processes. What should you consider when choosing the right robot? Because each company has unique requirements the best approach is to begin by determining answers to the following questions and work directly with the robot manufacturer to select the optimal robot configuration.
What is the cleanroom specification?
There are two accepted clean room specifications, the ISO 14644-1 spec and the Fed 209E spec. Confusion and the improper clean specification will greatly impact the design and the cost of the machine.
Following is a table that correlates the two:
· What is the required cycle time?
· What are the work envelope requirements and associated interferences?
· What is the tolerance stack-up for the process and ultimate repeatability requirement for the robot?
· Does your robot partner maintain experience in deploying cleanroom robots to help guide you in integrating a clean solution?
· Does the robot company have service engineers in the area to support them?
The cell geometry and the cleanliness requirements are important to define before selecting a robot. Depending on the cell design and the robot style selected, a lower class robot may be able to be used and still meet the overall system requirements if the system is designed appropriately.
For example if you are handling a semiconductor wafer, a robot that can operate under the wafer with a vertical laminar flow of clean air present sweeping the particles away from the product, the ultimate requirement for the robot may be less stringent.
Once you’ve determined which robot best fits your application, installing the cleanroom robot requires additional attention to cleanliness. This is where your robot manufacturer and system integrator must be capable of providing direction to ensure a successful installation. The following are a few examples of how deploying a clean robot differs from that of cells in an ambient environment.
“Robots built for Class 1 environments are wrapped in several layers to protect them as they are shipped to the site,” said Kevin Lonie, application sales manager for Clear Automation, a Connecticut-based automation integrator specializing in the design, engineering, fabrication and installation of integrated robotic and machine vision systems. “Then at the site the equipment is moved through progressively cleaner spaces as the wrapping is wiped down and finally removed before entering its ultimate clean room destination.”
To avoid spreading particles during installation, the robots and all other accessories should be wiped with cleanroom wipes to remove any foreign particles. Once this is done, it is a good practice to connect the robot to the plant’s vacuum system and evacuate the robot for several hours to make sure all particles are purged completely. In the semiconductor and hard-disk drive industries, it is difficult to avoid having people working in a cleanroom because of monitoring tasks, non-robotic material handling steps, etc. But minimizing the number of people working within the cleanroom environment allows a manufacturer to better maintain a clean environment. So it’s fortunate that today’s highly reliable servo-driven robots require minimal maintenance. Industrial robots are being implemented increasingly in cleanrooms due to their exceptional meantime between failure when compared to conventional equipment
As the need for products manufactured in a clean environment increases, manufacturers will be looking to automation to increase production, reduce cycle times and decrease costs all documented benefits of robotic automation. Value exists in fully understanding how to deploy robotics and related technologies in cleanroom environments in advance of commissioning to ensure a successful and clean process.
Rush LaSelle is director of worldwide sales and marketing for Adept Technologies and has more than 20 years of experience with advanced robotics and automation systems. He has worked extensively to expand the reach of robotics into markets and industries traditionally underserved by flexible automation technology. Prior to joining Adept Technology, he served as a General Manager for FANUC Robotics America, Inc. He holds a BS in Mechanical Engineering from Santa Clara University and an MBA from UC Berkeley's Haas School of Business.