Chapter 19: Cylindrical Robots |
19.1 A Short Summary of What This Chapter Covers |
Cylindrical robots are a family of industrial manipulators whose working volume forms a cylinder or a thick cylindrical shell around a central vertical column. They combine two linear motions, usually a vertical lift and a horizontal radial extension, with one rotational motion around the vertical axis. That simple combination gives them a reach that sweeps around a core and moves in and out, up and down, like a human arm reaching across a workbench while the body turns. This chapter explains what cylindrical robots are, how they are built, where they came from, how they differ from other robot geometries, and, most importantly, where they are used in the real world. The emphasis throughout is on practical applications across many industries, including pipe welding, spot welding, machine tool tending, die casting, palletizing, inspection, and more. The chapter is written for a general technical reader, so it avoids heavy mathematics and focuses on clear descriptions, industry stories, and the reasoning behind design choices. |
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19.2 What Makes a Robot Cylindrical |
A cylindrical robot is defined by the shape of the space it can reach, called its work envelope. Imagine a tall post fixed to the floor. A horizontal arm slides up and down this post. The same arm can also slide in and out, changing its distance from the post. Finally, the whole assembly can rotate around the post. If you mark every point the tip of that arm can touch, you get a cylinder. The height of the cylinder is set by the vertical travel. The radius is set by the horizontal stroke. The rotation determines how much of the circle is covered, often a full three hundred and sixty degrees but sometimes less because of cables, hoses, or safety fences. |
This arrangement is called cylindrical because of the shape of the reachable space, not because the robot itself looks like a cylinder, although many do have a cylindrical central column. The three axes are simple: one rotates, two translate. That simplicity is the source of both the strengths and the limits of this design. |
The rotational axis is usually called the theta axis. The vertical axis is often called the Z axis. The radial, or in and out, axis is often called the R axis. Together they form a three degree of freedom manipulator. Some cylindrical robots add a wrist with one, two, or three more axes to orient the tool, but the base machine itself remains a three axis cylindrical arm. When a wrist is added, the robot can tilt and rotate the tool, which turns it into a much more capable machine for welding, spraying, or assembly. |
The work envelope of a cylindrical robot is easy to visualize and easy to fence. It looks like a round column of space. This makes it simpler to guard than a robot with a complex, irregular reach. It also makes it easier to teach a worker where the danger zone is. A painted circle on the floor and a clear height limit often describe the entire risk area. |
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19.3 The Core Mechanical Layout |
Most cylindrical robots share a common mechanical skeleton. At the base there is a rigid frame, often bolted to the floor or to a heavy steel pedestal. Inside the base is the first servo motor, which drives the rotation of the entire upper structure through a gear reducer. Above the base is the vertical column. The column may be a single rigid tube or a machined casting with guide rails running along its length. A carriage rides up and down these rails, driven by a ball screw, a lead screw, or, in some designs, a timing belt or a rack and pinion. The carriage supports the horizontal arm. The horizontal arm slides in and out through the carriage, driven by its own motor and transmission. At the end of the horizontal arm is a mounting flange for a tool or a wrist. |
This layout has several practical consequences. First, the vertical column carries the weight of the arm and the payload, so it must be stiff and strong. Second, the horizontal arm acts like a cantilever beam. When it extends far out, the load creates a bending moment at the carriage. This means the arm must be thick and rigid, and the carriage must be long enough to resist twisting. Third, because the arm moves in and out, the center of gravity of the moving mass changes, which affects the torque needed at the base. Engineers account for this by sizing the base motor and reducer generously and by limiting the payload and speed when the arm is fully extended. |
The drive system is usually electric. Early cylindrical robots sometimes used hydraulic drives, and some heavy duty models still do, but modern machines almost always use alternating current servo motors with precision gearboxes. Ball screws are common for the vertical and radial axes because they convert rotary motion into linear motion with low friction and high accuracy. In some low cost or high speed designs, belts and pulleys are used instead, trading some stiffness for lower cost and less maintenance. |
Sensors are placed on each axis. Rotary encoders on the motors measure position and speed. Sometimes a second encoder is mounted on the output side of the gearbox to correct for backlash. Limit switches or hard stops prevent over travel. In more advanced models, force or torque sensors may be added to detect collisions or to support delicate tasks. |
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19.4 A Brief History |
The cylindrical robot is one of the oldest and most enduring industrial robot designs. Its roots go back to the early days of robotics in the 1950s and 1960s. The first industrial robot, the Unimate, used a polar or spherical coordinate system, but engineers soon realized that a simpler layout with a rotating base and linear axes could be easier to control and cheaper to build. The cylindrical design emerged as a practical compromise between the complex geometry of a fully articulated arm and the limited reach of a simple Cartesian gantry. |
In the 1960s and 1970s, several companies introduced cylindrical robots for machine tool tending. These robots would pick up a raw part, load it into a lathe or milling machine, wait for the machining cycle, and then remove the finished part. This was one of the first truly successful applications of industrial robotics, and it proved that robots could work reliably in harsh factory conditions. |
In the 1980s, the cylindrical robot became a workhorse of the automotive industry. It was used for spot welding, where two metal sheets are joined by a brief pulse of electric current and pressure. The cylindrical arm could reach into a car body, position a welding gun, and repeat the same motion thousands of times per shift. It was also used for pipe welding, where the robot rotates around a pipe or moves along it while keeping the torch at the correct angle. |
In the 1990s and 2000s, the rise of the articulated robot, with its six axes and human like flexibility, pushed the cylindrical robot out of some applications. But the cylindrical design did not disappear. Instead, it found new niches where its simplicity, speed, and low cost were more important than flexibility. Today, cylindrical robots are still built by many manufacturers and are used in electronics, food processing, plastics, metalworking, and many other industries. |
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19.5 Why Choose a Cylindrical Robot |
Engineers choose a cylindrical robot for several reasons. The first is simplicity. With only three axes, the kinematics, which is the mathematics of motion, are easy to solve. This makes the control software simpler and more reliable. It also makes the robot easier to program, because the operator can think in terms of turn, lift, and reach. |
The second reason is cost. Fewer axes mean fewer motors, fewer gearboxes, fewer cables, and a simpler controller. A cylindrical robot is often significantly cheaper than an articulated robot with the same payload and reach. This makes automation affordable for small and medium sized businesses. |
The third reason is speed. Because the axes are linear and rotational, they can be moved very quickly with simple control laws. A cylindrical robot can often beat a more complex robot in cycle time for tasks that only require three degrees of freedom, such as picking a part from a conveyor and placing it on a pallet. |
The fourth reason is rigidity. The vertical column and the linear rails can be made very stiff, which means the robot does not deflect much under load. This is important for tasks like drilling, where the tool must not wander, or for heavy payloads, where a flexible arm would sag. |
The fifth reason is a clean work envelope. The cylindrical shape is easy to fence, easy to model in simulation, and easy to explain to operators. This reduces the cost and complexity of safety systems. |
Of course, the cylindrical robot has limits. It cannot easily reach around obstacles, because it has no elbow or shoulder. It cannot orient the tool in many directions without an added wrist. Its work envelope is a cylinder, which may not match the shape of the task. And its horizontal arm can become very long and heavy if a large reach is needed, which increases cost and reduces accuracy. These limits explain why other geometries, such as the articulated robot, the SCARA robot, and the Cartesian gantry, are also popular. |
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19.6 How Cylindrical Robots Compare to Other Geometries |
To understand the cylindrical robot, it helps to compare it with its relatives. The Cartesian robot, also called a gantry robot, uses three linear axes at right angles. Its work envelope is a rectangular box. It is very stiff and very accurate, but it takes up a lot of floor space and is hard to rotate around a part. The cylindrical robot adds rotation, which makes it more compact and more flexible for tasks that involve turning. |
The polar or spherical robot uses a rotating base, a rotating shoulder, and a linear extension. Its work envelope is a partial sphere. It can reach high and low, but its kinematics are more complex, and its accuracy varies across the workspace. The cylindrical robot is a simplified version of this idea, with the shoulder replaced by a vertical slide. |
The SCARA robot, which stands for Selective Compliance Assembly Robot Arm, uses two rotational axes in a horizontal plane and one vertical linear axis. It is very fast and very good at assembly tasks where the robot needs to be stiff vertically but compliant horizontally. The cylindrical robot is similar in some ways, but its horizontal motion is linear rather than articulated, which gives it a different reach and stiffness profile. |
The articulated robot uses a series of rotary joints, like a human arm. It has a large, complex work envelope and can reach around obstacles. It is the most flexible design, but also the most expensive and the most difficult to control. The cylindrical robot is simpler and cheaper, but less flexible. |
Each geometry has its place. The cylindrical robot is best when the task is repetitive, the part is round or can be presented in a circle, the required motion is mostly turn, lift, and reach, and the budget is limited. |
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19.7 The Work Envelope in Practice |
The work envelope of a cylindrical robot is often described by three numbers: the maximum radius, the minimum radius, and the vertical stroke. The maximum radius is the farthest the tool can reach from the center of rotation. The minimum radius is the closest it can come, which is limited by the length of the carriage and the size of the column. The vertical stroke is the distance the arm can travel up and down. |
Within this envelope, there are regions where the robot is stronger and more accurate. Near the center, the arm is short and stiff, so the robot can carry heavy loads and position them precisely. Far from the center, the arm is extended, so it bends more and vibrates more, which reduces accuracy and payload capacity. Engineers often define a rated payload at a specific distance and a specific speed. If the task requires the robot to work at full extension, the payload must be reduced. |
The rotational axis also has limits. Many cylindrical robots can rotate continuously, which means they can spin without limit. This is useful for tasks like winding, where the robot must follow a rotating part. Other robots have limits because cables and hoses would twist. In that case, the robot may have a mechanical stop or a slip ring to allow continuous rotation without tangling. |
The shape of the work envelope also affects how parts are presented. If the robot is loading a lathe, the lathe chuck is usually placed at a fixed distance from the robot center, so the robot only needs to rotate to the correct angle, extend to the chuck, and lift to the correct height. This is a very efficient use of a cylindrical robot, because the motion is simple and repetitive. |
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19.8 Actuation and Transmission Details |
The motors used in cylindrical robots are usually alternating current servo motors. These motors are compact, powerful, and reliable. They are controlled by servo drives that adjust the current to the motor windings many thousands of times per second. The drive receives a command from the robot controller, compares it with the feedback from the encoder, and adjusts the current to reduce the error. This closed loop control is what allows the robot to move smoothly and accurately. |
The transmission from the motor to the axis can take several forms. For the rotational axis, a planetary gearbox or a harmonic drive is common. A planetary gearbox uses several small gears orbiting around a central sun gear. It is compact and can handle high torque. A harmonic drive uses a flexible metal cup and an oval wave generator to achieve very high gear ratios in a small space. It is often used in the wrist and in the base of small robots. |
For the linear axes, a ball screw is a common choice. A ball screw is a long threaded shaft with a nut that contains recirculating ball bearings. As the shaft turns, the nut moves along it with very little friction. This gives high efficiency and high accuracy. A lead screw is similar but uses sliding contact instead of rolling balls. It is cheaper but less efficient and more prone to wear. A timing belt and pulley system is used in some robots where speed is more important than stiffness. A rack and pinion is used in very long travel axes, such as a gantry, but it is less common in a cylindrical robot. |
The choice of transmission affects the robot's performance. A ball screw gives high accuracy and high stiffness, but it limits the speed because the screw must spin fast. A belt drive allows higher speed but may stretch and lose accuracy over time. A harmonic drive gives high torque and zero backlash, but it is more expensive and can be damaged by shock loads. |
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19.9 Control and Programming |
The controller of a cylindrical robot is a computer that runs the robot's operating system. It reads the program, plans the motion, and sends commands to the servo drives. It also monitors the sensors, handles safety signals, and communicates with other machines. |
Programming a cylindrical robot can be done in several ways. The oldest method is teach pendant programming. The operator holds a handheld device with buttons or a joystick and jogs the robot to each desired position. When the robot is in the right place, the operator presses a button to record the position. The robot then repeats the sequence. This method is simple and does not require a programmer, but it can be slow and imprecise. |
A more modern method is offline programming. The programmer uses a computer aided design, or CAD, model of the part and the robot. The software simulates the robot's motion and generates the program. This allows the programmer to plan the task without stopping production. It also allows the program to be optimized for cycle time and reach. However, offline programming requires an accurate model of the robot and the workcell, and it must be calibrated to match the real world. |
A third method is lead through programming. The operator physically guides the robot arm through the desired motion, and the controller records the path. This is useful for tasks like spray painting, where the motion is smooth and continuous. It requires a robot with backdrivable joints or a special teaching mode. |
The programming language for a cylindrical robot is often a simple text based language or a graphical interface. The program consists of instructions like move to position, wait for input, turn on output, and so on. The controller interprets these instructions and generates the motion. |
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19.10 Safety and Guarding |
Safety is a critical part of any robot installation. A cylindrical robot can move quickly and with great force, so it must be guarded to protect workers. The guard is usually a fence or a light curtain. A fence is a physical barrier that keeps people out of the work envelope. A light curtain is an array of infrared beams that detects when someone reaches into the danger zone. When the beam is broken, the robot stops. |
The cylindrical work envelope makes guarding easier. A simple circular fence around the robot, with a gate for loading and unloading, is often enough. The fence must be tall enough to prevent someone from reaching over it, and it must be strong enough to contain a part if the robot drops it. |
Inside the workcell, there are other safety devices. A safety rated controller monitors the robot's position and speed. If the robot moves outside its allowed area, the controller stops it. An emergency stop button allows the operator to cut power to the motors. A brake on each axis prevents the arm from falling if power is lost. |
Risk assessment is the process of identifying hazards and deciding how to reduce them. For a cylindrical robot, the main hazards are crushing, impact, and trapping. Crushing can happen if the arm moves down onto a person. Impact can happen if the arm swings around and hits someone. Trapping can happen if a person is caught between the arm and a fixed object. The risk assessment must consider all these hazards and choose guards, sensors, and procedures to reduce the risk to an acceptable level. |
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19.11 Maintenance and Reliability |
Cylindrical robots are known for being reliable and easy to maintain. Because they have fewer axes and simpler mechanisms than articulated robots, there are fewer things that can go wrong. The main maintenance tasks are lubrication, inspection, and replacement of wear parts. |
The linear guides and ball screws need regular lubrication. The lubricant reduces friction and prevents wear. It also carries away heat and contamination. The manufacturer specifies the type of lubricant and the interval between applications. In a dirty environment, such as a foundry or a machine shop, the lubricant may need to be applied more often. |
The belts and pulleys, if used, need to be inspected for wear and tension. A loose belt can slip, which causes position errors. A worn belt can break, which stops production. The tension should be checked regularly and adjusted if needed. |
The gearboxes need to be checked for oil leaks and noise. A leaking gearbox can lose lubrication and fail. A noisy gearbox may have worn gears or bearings. The oil should be changed at the recommended interval. |
The motors and drives should be checked for overheating and vibration. Overheating can be caused by a worn bearing, a blocked cooling fan, or an overloaded axis. Vibration can be caused by a loose mounting, a worn coupling, or an unbalanced load. |
The controller and cables should be checked for loose connections and damaged insulation. A loose connection can cause intermittent faults, which are difficult to diagnose. Damaged insulation can cause a short circuit or a safety hazard. |
A good maintenance program includes a schedule, a checklist, and a log. The schedule says when each task should be done. The checklist says what to look for. The log records what was found and what was done. This helps the maintenance team track the condition of the robot and plan for spare parts. |
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19.12 Pipe Welding: A Classic Application |
Pipe welding is one of the most important applications of cylindrical robots. In pipe welding, two sections of pipe are joined end to end, and a weld is made around the circumference. This is a repetitive task that requires a consistent torch angle, a consistent travel speed, and a consistent distance from the pipe. A cylindrical robot is well suited to this task because it can rotate around the pipe while holding the torch at the correct angle. |
There are several ways to use a cylindrical robot for pipe welding. In one setup, the pipe is held stationary, and the robot rotates around it. The robot's rotational axis provides the motion around the pipe. The vertical axis adjusts the height, and the radial axis adjusts the distance from the pipe. The robot can weld a full circle in one smooth motion. This is common for large pipes, such as those used in oil and gas pipelines. |
In another setup, the pipe is rotated by a positioner, and the robot stays in one place. The robot's vertical and radial axes adjust the torch position, while the positioner turns the pipe. This is common for smaller pipes, such as those used in automotive exhaust systems or hydraulic lines. The robot can weld a consistent seam because the pipe rotates at a constant speed. |
In a third setup, the robot is mounted on a track or a carriage, and it moves along the pipe while welding. This is common for very long pipes, such as those used in construction or shipbuilding. The cylindrical robot provides the fine motion for the torch, while the track provides the long travel. |
Pipe welding robots must handle several challenges. The pipe may not be perfectly round, so the robot must adjust the torch distance to follow the surface. The pipe may not be perfectly aligned, so the robot must adjust the torch angle to fill the gap. The weld may require multiple passes, so the robot must change the torch position for each pass. Advanced robots use sensors to measure the joint and adjust the path in real time. This is called seam tracking. A laser sensor or an arc sensor detects the edge of the joint and sends a signal to the controller, which adjusts the robot's motion. |
The benefits of pipe welding robots are significant. They improve weld quality by making consistent, repeatable welds. They increase productivity by welding faster and without breaks. They reduce the risk of injury by keeping the welder away from the heat, fumes, and radiation of the welding arc. They also reduce the cost of rework by catching defects early. |
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19.13 Spot Welding in Automotive Assembly |
Spot welding is another classic application of cylindrical robots. In spot welding, two or more sheets of metal are pressed together between two electrodes, and a large electric current is passed through them. The resistance at the interface between the sheets generates heat, which melts the metal and forms a weld nugget. This is a fast, cheap, and reliable way to join sheet metal, and it is used extensively in the automotive industry. |
A car body is made of hundreds of stamped steel or aluminum panels. These panels are joined by thousands of spot welds. In a typical assembly line, a series of robots perform these welds. Each robot picks up a welding gun, moves it to the correct position, closes the gun to apply pressure, and sends a current pulse. The whole cycle takes only a few seconds. |
A cylindrical robot is well suited to spot welding because the task requires only a few degrees of freedom. The robot needs to reach the weld location, orient the gun perpendicular to the surface, and apply pressure. The cylindrical robot can do this with its three axes plus a simple wrist. The work envelope of the cylindrical robot matches the shape of a car body station, where the robot is surrounded by a ring of weld points. |
In a typical automotive spot welding cell, several cylindrical robots are arranged around a fixture that holds the car body. Each robot has its own set of weld points. The robots work simultaneously, which reduces the cycle time. The fixture rotates or indexes to present different sides of the body to the robots. This is a highly efficient arrangement, and it has been used for decades. |
The challenges of spot welding include electrode wear, which changes the shape of the weld nugget, and shunt current, which occurs when the current takes a path through an already welded area. The robot must be programmed to compensate for these effects. Modern robots use adaptive control, which adjusts the current and time based on the resistance of the joint. They also use sensors to detect the position of the sheets and the condition of the electrodes. |
The benefits of spot welding robots are similar to those of pipe welding robots. They improve quality by making consistent welds. They increase productivity by welding faster and without breaks. They reduce the risk of injury by keeping the worker away from the high current and the sharp metal. They also reduce the cost of tooling, because the same robot can be reprogrammed for different car models. |
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19.14 Machine Tool Tending |
Machine tool tending is one of the oldest applications of cylindrical robots. In machine tool tending, a robot loads a raw part into a machine tool, such as a lathe, a milling machine, or a grinder, and unloads the finished part. This is a repetitive task that requires precision and reliability. A cylindrical robot is well suited to this task because it can reach into the machine, place the part in the chuck or fixture, and withdraw. |
A typical machine tool tending cell consists of one or more machine tools, a robot, and a part storage system. The part storage system may be a conveyor, a pallet, or a bin. The robot picks a raw part from the storage system, moves it to the machine tool, waits for the chuck to open, inserts the part, waits for the chuck to close, and then withdraws. After the machining cycle, the robot removes the finished part and places it on an outgoing conveyor or pallet. |
The cylindrical robot's work envelope is a good match for a lathe or a milling machine. The machine tool is usually placed at a fixed distance from the robot, so the robot only needs to rotate to the correct angle, extend to the chuck, and lift to the correct height. The robot can also rotate to a second machine tool, which allows one robot to serve two or more machines. This is called a robot cell, and it can significantly reduce the cost per part. |
The challenges of machine tool tending include the need for precise alignment between the robot and the chuck, the need to handle chips and coolant, and the need to detect when a part is not properly seated. The robot must be programmed to approach the chuck carefully, to avoid collisions, and to verify that the part is in place. Modern robots use vision systems or force sensors to guide the insertion and to detect errors. |
The benefits of machine tool tending robots are many. They increase machine utilization by reducing the time the machine waits for a part. They improve quality by loading parts consistently. They reduce the risk of injury by keeping the worker away from the moving machine and the sharp edges of the part. They also reduce labor costs by allowing one operator to oversee several machines. |
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19.15 Die Casting and Foundry Work |
Die casting is a process in which molten metal is injected into a steel mold, called a die, at high pressure. The metal fills the die, cools, and solidifies into a part. The die then opens, and the part is ejected. This is a fast, precise, and economical way to make complex metal parts, and it is used extensively in the automotive, aerospace, and consumer goods industries. |
A cylindrical robot is often used in die casting to extract the part from the die and to quench it in a cooling bath. The robot reaches into the die, grasps the part with a gripper, withdraws it, and moves it to the quench tank. It may also apply a release agent to the die, which prevents the part from sticking. This is a harsh environment, with high temperatures, molten metal splashes, and heavy loads. The cylindrical robot is chosen for its rigidity, its simple construction, and its ability to work in a dirty environment. |
In a typical die casting cell, the robot is mounted near the die casting machine. The machine opens the die, and the robot moves in to extract the part. The robot then moves the part to a trim press, where the flash is removed, and then to a quench tank or a conveyor. The robot may also perform other tasks, such as inspecting the part or applying a coating. |
The challenges of die casting robots include the high temperature, which can damage cables and seals, and the heavy payload, which can strain the arm. The robot must be designed with heat resistant materials and with cooling systems for the motors and the controller. The gripper must be able to hold the part securely without damaging it. The robot must also be able to withstand the shock and vibration of the die casting machine. |
The benefits of die casting robots are significant. They increase productivity by reducing the time the die is open. They improve quality by extracting the part consistently. They reduce the risk of injury by keeping the worker away from the molten metal and the moving machine. They also reduce labor costs by allowing one operator to oversee several machines. |
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19.16 Palletizing and Material Handling |
Palletizing is the process of stacking parts or boxes on a pallet for shipping or storage. This is a repetitive task that requires speed, accuracy, and strength. A cylindrical robot is well suited to palletizing because its work envelope is a cylinder, which matches the shape of a pallet load. The robot can rotate to the correct angle, extend to the correct radius, and lift to the correct height. It can place each box in a precise position, building a stable and efficient load. |
In a typical palletizing cell, the robot is mounted at the center of the palletizing area. Conveyors bring boxes to the robot. The robot picks up a box, moves it to the pallet, and places it in the correct position. The robot can build multiple pallets at once, alternating between them to allow the operator to remove a full pallet without stopping the robot. |
The challenges of palletizing include the need to handle different box sizes and weights, the need to build stable loads, and the need to work at high speed. The robot must be programmed to calculate the position of each box, to avoid collisions, and to place the box gently. Modern robots use software that generates the palletizing pattern automatically, based on the box dimensions and the pallet size. They also use sensors to detect the position of the box on the conveyor and to verify that the pallet is in place. |
The benefits of palletizing robots are many. They increase productivity by working faster and without breaks. They improve safety by reducing the risk of injury from lifting heavy boxes. They reduce labor costs by allowing one operator to oversee the cell. They also improve the quality of the pallet load by placing each box consistently. |
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19.17 Inspection and Quality Control |
Cylindrical robots are also used for inspection and quality control. In this application, the robot moves a sensor or a camera around a part to measure its dimensions, detect defects, or verify its surface finish. The robot can reach into tight spaces, follow complex paths, and repeat the same motion thousands of times. This makes it ideal for inspecting parts on a production line. |
In a typical inspection cell, the robot holds a laser scanner or a camera and moves it around the part. The sensor collects data, which is sent to a computer for analysis. The computer compares the data with the design specifications and decides whether the part is acceptable. If the part is not acceptable, the robot can mark it or remove it from the line. |
The challenges of inspection robots include the need for high accuracy, the need for stable motion, and the need to handle different part shapes. The robot must be programmed to follow the correct path, to maintain the correct distance from the part, and to avoid collisions. Modern robots use vision systems to locate the part and to adjust the path in real time. They also use software to analyze the data and to generate reports. |
The benefits of inspection robots are significant. They improve quality by detecting defects that a human might miss. They increase productivity by inspecting faster and without breaks. They reduce the risk of injury by keeping the worker away from sharp edges and hazardous materials. They also reduce the cost of rework by catching defects early. |
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19.18 Electronics and Small Part Assembly |
Cylindrical robots are used in electronics and small part assembly, where they pick up tiny components and place them on a circuit board or in a housing. This is a task that requires high speed, high accuracy, and a gentle touch. A cylindrical robot can be equipped with a vacuum gripper or a small mechanical gripper and can place components with great precision. |
In a typical electronics assembly cell, the robot picks a component from a feeder, moves it to the correct position on the board, and places it. The robot may also apply adhesive, solder, or a screw. The cycle time is often less than a second, so the robot must be very fast. The robot must also be very clean, because dust and debris can damage the components. |
The challenges of electronics assembly include the small size of the components, the need for high accuracy, and the need to avoid electrostatic discharge. The robot must be designed with clean room compatible materials and with grounding to prevent static buildup. The gripper must be able to handle tiny parts without damaging them. The robot must also be able to change grippers quickly, so it can handle different components. |
The benefits of electronics assembly robots are many. They increase productivity by working faster and without breaks. They improve quality by placing components consistently. They reduce the risk of injury by keeping the worker away from repetitive strain and sharp tools. They also reduce labor costs by allowing one operator to oversee several machines. |
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19.19 Food and Beverage Industry |
Cylindrical robots are used in the food and beverage industry for tasks such as picking, packing, and palletizing. In this industry, the robot must be able to withstand frequent washdowns, to handle food safely, and to work in a cold or wet environment. The cylindrical robot is chosen for its simple construction, which is easy to clean, and its ability to work in a dirty environment. |
In a typical food industry cell, the robot picks products from a conveyor and places them in a package or on a tray. The robot may also apply labels, seal packages, or stack trays. The robot must be able to handle different product shapes and sizes, and it must be able to work at high speed. |
The challenges of food industry robots include the need for hygiene, the need for corrosion resistance, and the need for safety. The robot must be made of stainless steel or other food safe materials. It must be sealed to prevent water and bacteria from entering. It must be designed with smooth surfaces and no crevices, so it can be cleaned easily. The robot must also be able to work in a cold environment, such as a freezer, without losing accuracy or speed. |
The benefits of food industry robots are significant. They increase productivity by working faster and without breaks. They improve hygiene by reducing human contact with the food. They reduce the risk of injury by keeping the worker away from sharp blades and hot surfaces. They also reduce labor costs by allowing one operator to oversee several machines. |
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19.20 Plastics and Injection Molding |
Cylindrical robots are used in the plastics industry for injection molding. In injection molding, plastic pellets are melted and injected into a mold. The plastic cools and solidifies into a part. The mold opens, and the part is ejected. A cylindrical robot can reach into the mold, grasp the part, and remove it. It can also place inserts into the mold before the plastic is injected. |
In a typical injection molding cell, the robot is mounted on top of the molding machine or beside it. The robot reaches into the mold, picks up the part, and places it on a conveyor. It may also perform secondary operations, such as trimming, drilling, or assembling. The robot must be able to work quickly, because the molding cycle is often short. It must also be able to withstand the heat of the mold and the noise of the machine. |
The challenges of injection molding robots include the need for high speed, the need for precise positioning, and the need to handle different part shapes. The robot must be programmed to follow the correct path, to avoid collisions with the mold, and to place the part gently. Modern robots use sensors to detect the position of the mold and the part, and to verify that the part is removed. |
The benefits of injection molding robots are many. They increase productivity by reducing the time the mold is open. They improve quality by removing the part consistently. They reduce the risk of injury by keeping the worker away from the moving mold and the hot plastic. They also reduce labor costs by allowing one operator to oversee several machines. |
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19.21 Glass and Ceramics |
Cylindrical robots are used in the glass and ceramics industry for tasks such as handling, dipping, and glazing. In this industry, the robot must be able to handle fragile parts, to work in a dusty environment, and to withstand high temperatures. The cylindrical robot is chosen for its simple construction, which is easy to protect from dust, and its ability to work in a hot environment. |
In a typical glass industry cell, the robot picks up a glass sheet or a bottle and places it on a conveyor or in a rack. The robot may also dip the part into a coating or a glaze. The robot must be able to handle the part gently, because glass is brittle and can break easily. The robot must also be able to work at high speed, because the production line is often fast. |
The challenges of glass and ceramics robots include the need for gentleness, the need for cleanliness, and the need for heat resistance. The robot must be equipped with a soft gripper, such as a vacuum cup or a foam pad, to avoid scratching or breaking the part. The robot must be designed with seals and covers to keep out dust and debris. The robot must also be able to withstand the heat of the furnace or the kiln. |
The benefits of glass and ceramics robots are significant. They increase productivity by working faster and without breaks. They improve quality by handling the part consistently. They reduce the risk of injury by keeping the worker away from sharp edges and hot surfaces. They also reduce labor costs by allowing one operator to oversee several machines. |
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19.22 Aerospace and Defense |
Cylindrical robots are used in the aerospace and defense industries for tasks such as drilling, riveting, and inspection. In this industry, the robot must be able to work with high accuracy, to handle large parts, and to work in a clean environment. The cylindrical robot is chosen for its rigidity, which is important for drilling, and its simple construction, which is easy to clean. |
In a typical aerospace cell, the robot drills holes in a wing or a fuselage, inserts rivets, and inspects the result. The robot must be able to reach the correct position, to apply the correct force, and to measure the result. The robot must also be able to work with different materials, such as aluminum, titanium, and composites. |
The challenges of aerospace robots include the need for high accuracy, the need for high stiffness, and the need for safety. The robot must be designed with high precision gearboxes and encoders. It must be mounted on a rigid foundation to prevent vibration. It must be equipped with sensors to detect the position of the part and the condition of the tool. The robot must also be able to work in a clean room, so it must be designed with materials that do not shed particles. |
The benefits of aerospace robots are many. They increase productivity by working faster and without breaks. They improve quality by drilling and riveting consistently. They reduce the risk of injury by keeping the worker away from sharp tools and heavy parts. They also reduce labor costs by allowing one operator to oversee several machines. |
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19.23 Education and Research |
Cylindrical robots are used in education and research because they are simple, inexpensive, and easy to program. In a university or a technical school, a cylindrical robot can be used to teach the principles of robotics, such as kinematics, control, and programming. Students can learn how to model the robot, how to plan a path, and how to write a program. They can also learn how to integrate sensors and how to design a workcell. |
In research, a cylindrical robot can be used as a testbed for new algorithms and new technologies. Because the robot is simple, it is easy to modify and to instrument. Researchers can add sensors, change the controller, or build a new gripper. They can test new ideas quickly and cheaply. |
The challenges of educational and research robots include the need for safety, the need for documentation, and the need for support. The robot must be designed with guards and emergency stops to protect the students. It must come with a manual and a set of exercises. It must be supported by the manufacturer with spare parts and technical advice. |
The benefits of educational and research robots are many. They help to train the next generation of engineers and technicians. They help to advance the state of the art in robotics. They also help to promote the use of robots in industry by demonstrating their capabilities. |
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19.24 Choosing a Cylindrical Robot for an Application |
When choosing a cylindrical robot for an application, engineers consider several factors. The first is the payload. The robot must be able to lift the part plus the gripper plus any dynamic forces. The payload capacity is usually specified at a specific distance and speed. If the robot will work at full extension, the payload must be reduced. |
The second factor is the reach. The robot must be able to reach every point in the work envelope. The maximum radius must be greater than the farthest point. The minimum radius must be less than the closest point. The vertical stroke must be greater than the height difference. |
The third factor is the speed. The robot must be able to complete the task in the required cycle time. The speed is specified for each axis, and the actual speed depends on the path and the payload. Engineers use simulation to estimate the cycle time. |
The fourth factor is the accuracy. The robot must be able to position the tool within the required tolerance. The accuracy is affected by the stiffness of the arm, the resolution of the encoders, and the backlash in the gearboxes. Engineers often choose a robot with a higher accuracy than needed to allow for wear and other factors. |
The fifth factor is the environment. The robot must be able to work in the temperature, humidity, dust, and vibration of the workplace. It must be protected from water, chemicals, and other hazards. It must be designed with the right materials and seals. |
The sixth factor is the cost. The robot must fit the budget. The cost includes the robot, the controller, the gripper, the sensors, the guarding, and the installation. It also includes the cost of programming, training, and maintenance. Engineers often compare the cost of the robot with the cost of manual labor and with the benefits of improved quality and productivity. |
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19.25 Installation and Commissioning |
Installing a cylindrical robot is a process that involves several steps. The first step is to prepare the site. The floor must be level and strong enough to support the robot and its foundation. The power and air supplies must be available. The safety fence must be built. |
The second step is to mount the robot. The robot is usually bolted to a steel plate or a concrete pad. The mounting surface must be flat and clean. The bolts must be tightened to the correct torque. The robot must be leveled and aligned. |
The third step is to connect the cables and hoses. The power cables, the encoder cables, the communication cables, and the air hoses must be routed and connected. The cables must be protected from damage and from electromagnetic interference. |
The fourth step is to configure the controller. The controller must be set up with the correct parameters for the robot, the tools, and the workcell. The safety devices must be tested. The communication with other machines must be established. |
The fifth step is to program the robot. The program must be written, tested, and optimized. The robot must be taught the correct positions and the correct paths. The program must be verified to ensure that it is safe and effective. |
The sixth step is to train the operators. The operators must learn how to start, stop, and monitor the robot. They must learn how to handle faults and how to perform basic maintenance. They must learn how to work safely around the robot. |
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19.26 Common Faults and Troubleshooting |
Cylindrical robots can experience several common faults. One is a position error, which occurs when the robot does not reach the commanded position. This can be caused by a loose belt, a worn gearbox, a faulty encoder, or a collision. The troubleshooting process involves checking each axis, measuring the error, and replacing the faulty component. |
Another fault is a servo alarm, which occurs when the servo drive detects an overload, an over speed, or a feedback error. This can be caused by a mechanical jam, a short circuit, or a parameter error. The troubleshooting process involves reading the alarm code, checking the motor and the drive, and clearing the fault. |
A third fault is a communication error, which occurs when the controller cannot communicate with the robot or with other machines. This can be caused by a loose cable, a faulty connector, or a software problem. The troubleshooting process involves checking the cables, the connectors, and the software settings. |
A fourth fault is a programming error, which occurs when the robot does not follow the intended path. This can be caused by a wrong position, a wrong instruction, or a wrong parameter. The troubleshooting process involves reviewing the program, checking the positions, and testing the robot in slow speed. |
A good troubleshooting process includes a systematic approach, a good documentation, and a spare parts inventory. The technician should start with the simplest possible cause and work toward the more complex. The technician should also consult the manual and the manufacturer's support. |
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19.27 The Future of Cylindrical Robots |
The future of cylindrical robots is likely to be shaped by several trends. One trend is the increasing use of collaborative robots, which are designed to work safely alongside humans. A cylindrical robot can be made collaborative by adding force sensors and by limiting the speed and force of the axes. This would allow the robot to work without a fence, which would save space and improve flexibility. |
Another trend is the increasing use of vision systems and artificial intelligence. A cylindrical robot with a camera and a learning algorithm could recognize parts, plan paths, and adapt to changes. This would make the robot easier to program and more versatile. |
A third trend is the increasing use of modular designs. A cylindrical robot could be built from standard modules, such as a base, a column, an arm, and a wrist. This would allow the robot to be customized for a specific application and to be repaired quickly. |
A fourth trend is the increasing use of energy efficient drives and lightweight materials. A cylindrical robot with a lightweight arm and an efficient motor would use less power and would be cheaper to operate. This would make automation more accessible to small and medium sized businesses. |
A fifth trend is the increasing use of digital twins, which are computer models of the robot and the workcell. A digital twin can be used to simulate the robot, to optimize the program, and to predict maintenance. This would reduce the time and cost of installation and improve the reliability of the robot. |
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19.28 A Detailed Summary of Cylindrical Robots |
Cylindrical robots are three axis manipulators with a cylindrical work envelope. They combine two linear axes, usually a vertical lift and a radial extension, with one rotational axis around a vertical column. This simple arrangement gives them a unique set of strengths and weaknesses. They are simple, inexpensive, fast, and rigid. They are easy to program, easy to guard, and easy to maintain. But they are less flexible than articulated robots, and their work envelope may not match the shape of every task. |
The chapter began with a short summary, then explained what makes a robot cylindrical, described the core mechanical layout, and traced the history of the design. It compared cylindrical robots with Cartesian, polar, SCARA, and articulated robots, and explained why an engineer might choose one over the others. It described the work envelope, the actuation and transmission, the control and programming, the safety and guarding, and the maintenance and reliability. |
The heart of the chapter was the application examples. Cylindrical robots are used in pipe welding, where they rotate around a pipe and hold a torch at the correct angle. They are used in spot welding, where they position a welding gun and apply pressure to join sheet metal. They are used in machine tool tending, where they load and unload lathes, milling machines, and grinders. They are used in die casting, where they extract parts from a hot mold and quench them. They are used in palletizing, where they stack boxes on a pallet. They are used in inspection, where they move a sensor around a part. They are used in electronics assembly, where they place tiny components on a circuit board. They are used in the food and beverage industry, where they pick, pack, and palletize products. They are used in plastics and injection molding, where they remove parts from a mold. They are used in glass and ceramics, where they handle fragile parts. They are used in aerospace and defense, where they drill and rivet large parts. They are used in education and research, where they teach and test new ideas. |
For each application, the chapter described the task, the setup, the challenges, and the benefits. It explained how the cylindrical robot's work envelope matches the shape of the task, how its simple construction makes it reliable, and how its low cost makes it accessible. It also explained the limits of the design and the situations where another geometry might be better. |
The chapter concluded with a discussion of how to choose a cylindrical robot, how to install and commission it, how to troubleshoot common faults, and what the future might hold. The key message is that the cylindrical robot is not a obsolete design. It is a mature, proven, and versatile machine that continues to play an important role in modern manufacturing. Its simplicity is its strength, and its applications are limited only by the imagination of the engineers who use it. |
cs@easiersoft.com