Robots can carry out pharmaceutical manufacturing tasks faster, more consistently and more cost-effectively than manual labour. As significant as these benefits are, however, they are far outweighed by the fact that every activity that a robot performs is verifiable. Not only does the robot perform its tasks exactly as it is told to, everything it does can be thoroughly documented. When a human technician places a drug sample into an oven, sets the oven’s temperature to a particular temperature, sets a timer for so many minutes, then removes the sample, questions can always remain: Was the temperature correctly set? Was the timer correctly set? Was the sample actually removed at the specified time? With a robot, not only are such tasks carried out with an extremely high degree of repeatability, but every parameter in the process can be automatically monitored, recorded and verified.
Choosing the right equipment
The success of any automation project depends first of all on choosing the right equipment. There are three types of industrial robots most commonly used in pharmaceutical manufacturing — cartesian, SCARA and articulated.
Cartesian robots: In their simplest form, cartesian robots consist of two linear slides placed at 90-degree angles to each other, with a motorised unit that moves horizontally along the slides in the x- and y-axes. A metal rod called a quill can be added as a third axis (z), which moves up and down in the vertical plane. The quill holds the robot’s end-effector, such as a gripper. A fourth axis (t, or theta) allows the quill to rotate in the horizontal plane.
The chief advantage of cartesian robots is their low cost, although their restricted range of motion limits their usage. They are often incorporated into automation subsystems or machines dedicated to a single purpose, such as assay testing.
SCARA robots: SCARA stands for “selective compliance articulated robot arm.” This refers to the fact that a SCARA’s arm segments, or links are “compliant,” that is, they can move freely, but only in a single geometrical plane. Most SCARAs have four axes. Even though three- and five-axis SCARAs are also found, the terms “SCARA” and “four-axis robot” are often used interchangeably to refer to a four-axis SCARA.
Articulated robots: Articulated robots not only have more joints than SCARAs, they have both horizontal and vertical joints, giving them increased freedom of movement. Whereas a Cartesian robot has a cube-shaped work envelope and a SCARA has a cylindrically shaped one, the work envelope of an articulated robot is spherical. With their greater flexibility of movement, articulated robots can perform almost any task that can be performed by a human arm and hand.
The most common articulated robots have six axes. The first link rotates in the horizontal plane like a SCARA, while the second two links rotate in the vertical plane. In addition, six-axis articulated robots have a vertically rotating “forearm” and two vertically rotating “wrist” joints, which let them perform many of the same types of movements as a human forearm and wrist.
Determining the type of robot needed
The first step in automating a process with a robot is to establish the process parameters, including (1) the required type and size of end-effector, or end-of-arm tooling (EOAT), (2) cycle time, (3) repeatability, (4) reach and (5) payload capacity. Taken together, these will usually determine whether a cartesian, SCARA or articulated robot is necessary. Another essential consideration is the environment in which the robot will be operating. Robot models are available for use in cleanrooms, and in applications where bio-contamination control is required, aseptic models have special seals, outer coatings and other construction features that allow them to be cleaned with hydrogen peroxide.
After a robot is selected, it needs to be integrated into the process. Robots are usually mounted in an enclosed automation work cell. The robot and any other associated equipment are bolted to the cell’s steel base or, in the case of an overhead mounting, from a steel superstructure. The upper walls of the cell are generally made of aluminium-framed, shatter-proof clear plastic or see-through, metal-mesh screening. This keeps operators safely separated from the robot, while still allowing them to observe the cell’s activity.
As a safety precaution, opening the cell’s access door automatically stops all robot motion. In cases where the robot is not enclosed in a cell, light curtains or pressure-sensitive floor mats can also provide automatic safety shutoff. The robot’s computerised controller, which contains the electronic circuits that run the robot and interfaces to external equipment through a variety of network inputs and outputs, is usually situated on a platform underneath the cell. Programming the robot is accomplished by means of either a teaching pendant—a handheld interface device that communicates with the controller—or by a computer. Most robot manufacturers offer user-friendly programming software that does not require specialised engineering skills. Some robot controllers can also interface with third-party software, such as National Instruments LabVIEW, which allows the user to program the robot without having to learn a new programming language.
The teaching pendant allows an operator to move the robot from one point to another and instruct it what to do at each location, thus, “teaching” it the desired routine. With available software, robots can also be programmed offline on a remote computer, saving development time. A virtual, simulated 3-D environment lets the user configure the robot and any peripheral devices without having to actually operate them.
Ten things to consider when choosing a robot
Experience and reputation of the manufacturer: Look for a manufacturer who has established itself as an industry leader and whose robots have stood the test of time.
Documented MTBF: Robots, which are often required to operate two or three shifts per day, every day of the year, must above all be reliable. Manufacturers who stand behind their robots’ reliability will be happy to furnish documentation of their mean time between failures (MTBF).
High maximum allowable moment of inertia: Look for a robot with a high maximum allowable moment of inertia, a measure of how much force it can exert. The higher the maximum allowable moment of inertia, the more easily the robot can lift and move a given size of payload, putting less strain on the robot’s motors and resulting in a longer working life.
Continuous-duty cycle time: When comparing robot cycle times, be sure to ask whether the figures given are for continuous duty or only shorter bursts of an hour or less. If the latter, the robot will have to operate at a slower speed in normal operation.
Compact, efficient robot design: A compact robot design with slim arms and a small footprint makes integration easier and saves valuable factory floor space. In addition, designs with concealed air and electrical lines keep the lines from interfering with other equipment, as well as protecting them from wear and damage, thus, reducing overall costs.
Robot controller features: Desirable features to look for in robot controllers include compact size and light weight; fast processing speed; modular expandability, to accommodate additional peripheral equipment without having to purchase a new controller; ease of integration with a vision system, PLC or other devices; and ease of servicing.
Affordable offline programming software: Be sure that the offline programming software being offered does not include expensive, advanced features that are unnecessary for your needs.
Low energy consumption: Ask about the robot’s energy consumption. Efficiently designed, slim and lightweight robot arms require less power, so their motors draw less electrical current. This can result in significant long-term cost-savings.
Safety codes: To protect employees and limit your company’s liability, verify that the robot meets or exceeds all current safety codes.
Short training: Ask about the length of required training. Unnecessarily long training can result in excessive unproductive employee time and travel costs.