Robot Troubleshooting 331

5 Whys Technique

A troubleshooting process where operators ask a series of "why" questions, usually five, in order to isolate the root cause of a problem. The 5 Whys Technique is also a useful starting point for other troubleshooting methods.

alignment

The accurate positioning of parts in a mechanical system in relation to one another. Alignment needs to be checked regularly because components can shift during operation.

alphanumeric

Containing letters and numbers. Alphanumeric words are usually used as shorthand for issues explained in detail in accompanying manuals.

arms

A long appendage that allows a mechanical device to reach for parts and other components. An arm on a robot can be a set of rigid sections connected by articulated joints or a single, long bar.

automated

Performed without human intervention or involvement. Automated manufacturing systems make use of computer systems to control various machine tools and manufacturing components.

backlash

Unwanted motion caused by gaps between components that transmit motion, such as two gears or a leadscrew and a nut. Backlash occurs upon a reversal of motion, or if an excessive force is applied in the direction of motion that causes a snatching action.

ballscrews

A threaded device that rotates to provide precise linear motion. Ballscrews are often powered by servomotors and require proper lubrication and cleanliness to function properly.

bearings

A device that allows one moving part to glide past another moving part with reduced wear and friction. Bearings that are loose can lead to overshoot while worn bearings can lead to undershoot.

belt

A band of flexible material that is looped around two or more pulleys to transmit motion. Belts are used to transfer the motion of the motor to the robot in order to perform a task.

brake

A component that slows or halts motion. Brakes may be present in the joints and end effectors of a robot and can be mechanical or electronic.

cable testers

An electronic device that assesses the level of data flow, or signal strength, through a cable or from a wireless router. Cable testers are used to ensure that information is being properly exchanged between the robot and the machine interface.

catastrophic failure

The sudden and complete breakdown of a machine or part. Catastrophic failure can be hazardous to workers as it often involves flying debris and unexpected and fast machine movement.

check sheets

An information-gathering tool used to collect data in real time. On check sheets, tick marks are put into different cells of a table to create a graphical representation of numerical data, such as the number of times a robot halts unexpectedly in an hour.

condensate traps

A device that removes the unwanted moisture that often occurs in pneumatic systems. Condensate traps are connected between the compressor and the inlet to the pneumatic system and often operate by draining automatically.

condense

Become concentrated. Water can condense in a humid environment and cause damage to mechanical components.

contamination

The presence of unwanted foreign matter. Contamination in fluid systems can cause damage to fluid hoses, seals, or valves.

continuity testing

Assessing the presence and quality of current flow in a circuit. Continuity testing determines if there is an unwanted break or other malfunction in the circuit that prevents it from functioning properly.

control program

A set of symbols and rules used to represent information and directions to a control device so that it can apply instructions. Control programs for robots or control systems will typically be explained in the robot manufacturer's manual.

coolant line

A hollow tube that conveys a specialized, heat-reducing fluid to specific parts of a machine. Coolant lines are especially common on welding robots.

corrective action

A solution implemented to resolve a manufacturing or robotic issue. Corrective actions include repairing a broken part, renewing a worn part, cleaning a sensor, cleaning the robot, adjusting the computer programming for a machine, or checking the quality of the incoming parts.

corrective actions

A solution implemented to resolve a manufacturing or robotic issue. Corrective actions include repairing a broken part, renewing a worn part, cleaning a sensor, cleaning the robot, adjusting the computer programming for a machine, or checking the quality of the incoming parts.

couplings

A component that connects two objects in a fluid system. Couplings are prone to leaking because they create breaks in a uniform shaft or tube.

debris

Unwanted loose fragments. Debris is a common byproduct of manufacturing operations.

defective

Damaged or not up to specifications. Defective parts must be discarded or reworked and represent a loss to the manufacturing operation.

defective

Not meeting required quality and performance specifications. Defective parts are usually scrapped, discarded, or reworked.

dehumidifier

A device that removes excess moisture from the air. Dehumidifiers can be used to keep a work area dry and prevent water-related damage to machine components.

delta robot

A special type of robot that has three sets of connected arms that work in conjunction to move one end effector. Delta robots are most commonly used in packaging or assembly processes.

division charts

An organizational tool that breaks down a mechanical component into small, discrete components. Division charts for robotic grippers might include servomotors, sensors, and the actual grippers or mechanical fingers.

electric motor

A device that uses electrical power to create rotary motion. Electric motors for robots are typically servomotors or stepper motors.

encoder

A device that translates rotary or linear motion into a digital signal. Encoders can become loose or get dirty, leading to malfunctions that cause machine positioning issues.

end effectors

The component of the robot that interacts with a part or object. End effectors perform the actual task the robot is designed to perform, such as welding, moving, assembling, or sensing.

engineers

A person who is responsible for ensuring a manufacturing machine or process runs efficiently and safely. Engineers are generally in charge of any troubleshooting and repair operations.

error codes

An alphanumeric word that references a specific cause of malfunction. Error codes appear on the robot machine interface and are cross-referenced in the manual.

exploded views

A diagram that shows all the components of an assembly by picturing them all separately in the order they fit together. An exploded view of an assembly helps operators see where various components in a part are supposed to go.

fabrication

A process that involves joining components or material together. Fabrication processes include riveting, fastening, gluing, and soldering.

feedback

A return signal that confirms the position of the robot. Feedback devices include proximity sensors and encoders.

filler metal

Metal deposited into the weld that adds strength and mass to the welded joint. Filler metal is often delivered to the weld in the form of the consumable wire electrode.

finger

A gripper appendage with its own set of flexible joints. Fingers on a robot can move with accuracy and dexterity similar to a human finger.

fishbone diagrams

An organizational chart that lists every possible cause for each effect. Fishbone diagrams have the effects as the main categories, with a series of lines coming off of them similar to the bones of a fish.

flow chart

An organizational tool that diagrams a specific process step by step with branches depending on the particular issues that arise. Flow charts ask "yes" or "no" questions in order to guide an operator to the probable solution for a problem.

fluid hoses

A hollow tube, which may be rigid or flexible, that is used to convey fluid in a fluid system. Fluid hoses, particularly flexible ones, may wear over time and leak, often around the connection joint or where scuffing takes place, causing the fluid system to malfunction.

fluid systems

A power transmission system that uses the energy of flowing liquids and gases to transmit power. Fluid system robots have additional components that can malfunction, such as hoses and valves.

fork vehicle

A mobile robot that uses a set of prongs that slide under a load in order to lift and transport it. Fork vehicles usually move pallets from one area of a work space to another.

friction

A force that resists motion between two components that are moving while in contact with each other. Excessive friction generates excessive heat and can lead to premature wear and other damage of machine components.

fuse

A safety device that detects excessive electrical current in a system. Fuses often have components that melt in the presence of excess current to open a circuit.

gear

A circular, toothed machine component that engages, rotates, and transmits power to another circular, toothed machine component when rotated. Gears are usually used in pairs to transmit energy and motion.

grid

A bounded area. A grid in robotics can refer to a narrow area of movement or performance around a set baseline or home position.

grid shift

A positioning error that leads a robot to move in a predictably incorrect fashion or create parts that will be predictably out of tolerance. Grid shift occurs when a robot jumps to a new and unwanted baseline home position but then functions normally.

gripper

A dexterous material-handling component that properly holds a component without slippage in order to move it from one place to another or manipulate it with a given path of motion. Grippers allow robots to hold components in order to perform complex tasks, such as handling small parts or assembling components precisely.

home position

The central point from which a mechanism begins an operation. The home position, or machine zero point, has a value of zero in the programming language of the mechanism.

home switch

A component that provides a reference point for encoders. Without a home switch, encoders are unable to assess how they have moved in relation to a set point.

humid

An atmosphere containing a large amount of moisture. A humid work environment can cause issues if electrical components become too damp.

hydraulic

Power created by the controlled motion of a liquid. Hydraulic systems are often used with robots that must lift heavy loads.

joint

A connecting component on a robot that can move with an angular motion about the connecting center as well as, sometimes, rotate on an axis perpendicular to the centerline of the arm. Joints on a robot mimic the movement on human joints, such as an elbow, with the additional ability to sometimes rotate.

joint bearing

A structural component in a robotic arm that allows for rotational movement. Joint bearings consist of cylindrical pieces of metal connected to the robot by spherical components that allow free range of motion.

kinks

An unwanted bend in a flexible, linear object, such as wire or a power cable. Kinks often prevent an object from performing its function correctly.

lasers

A device that generates a coherent and narrow beam of light that can be precisely aimed and controlled. Lasers can be used to assess component alignment.

liner

A hollow sheath set inside a welding torch to facilitate the movement of the wire. Liners can tear or become cluttered with debris and cause the wire to pass through the torch or robot incorrectly.

lubrication

A substance that reduces friction in moving machine components. Adding lubrication is a common preventive maintenance task that prevents issues such as premature component wear or one-off pulses.

machine

To shape a workpiece into a part using a cutting tool, such as a mill, drill, or other material-removal tool. Robots may machine workpieces or parts by removing material or feeding parts into a machining process.

machine interfaces

The control system on a manufacturing machine that operators use to interact with the machine. Machine interfaces may be complex, such as computer touchscreens, or simple, such as control panels with just a few buttons.

machine zero point

The central point from which a mechanism begins an operation. The machine zero point, or home position, has a value of zero in the programming language of the mechanism.

machining

The process of removing material to create an object. Machining can be used to remove materials such as plastic, metal, ceramic, and wood and includes traditional methods, such as milling, drilling, and grinding, and unconventional methods that use electricity, lasers, or ultrasound.

maintenance personnel

A person who is responsible for repairing a machine and performing scheduled upkeep procedures, such as adding lubrication. Maintenance personnel generally help implement the corrective action decided on by the engineer.

material-handling

The process of loading, unloading, placing, or manipulating objects or materials. Types of material handling include machine tending, part transfer, packaging, and palletizing.

material-removal tools

A device that separates excess substance from an object. Material-removal tools include drills, mills, burrs, coated abrasive belts, and sometimes lasers.

metal cutting

A machining process that uses a tool to remove metal from a workpiece. Metal-cutting processes performed by robots include grinding, milling, and drilling.

misaligned

Positioned incorrectly. Misaligned parts are often a result of incorrect robot motion, slippage within a gripper, sensor errors, poor placement prior to gripping, worn robot components, dirt, excessive loading, or programming errors.

mobile robot

An automated machine that can move around a space and perform a task without operator intervention. Mobile robots, sometimes called automated guided vehicles (AGVs), include tow vehicles, unit load carriers, and cart vehicles, among others.

movable axis

A connecting component on a robot that can rotate and move up and down. The movable axis, or joint, mimics the movement of human joints, such as the elbow joint; however, those movements might also include a rotational axis perpendicular to the centerline of the arm.

multimeters

A device that is used to asses the quality and functionality of electrical connections. Multimeters combine the functions of an ammeter, voltmeter, and ohmmeter.

one-off pulse

A robot motion error where the robot occasionally moves incorrectly or occasionally creates parts out of tolerance before returning to normal motion. One-off pulses generally occur as the result of an intermittent mechanical issue, such as inconsistent lubrication.

operators

A person who is responsible for running a manufacturing machine or process. Operators assist with troubleshooting when issues arise on a production line.

organizational tools

An implement or document that helps an operator streamline and categorize data or information. Organizational tools include check sheets, fishbone diagrams, and flow charts.

overshoot

To exceed a set value. Overshoot in robots refers to a robot always moving past a desired location.

peak efficiency

The maximum level of productivity possible for an operation or machine. Peak efficiency is rare to achieve in real-world conditions but serves as a good benchmark for gauging the effectiveness of an operation or machine.

permanent solutions

A corrective action that provides a stable, durable, and complete solution to a root cause. Permanent solutions, such as correcting the control program or swapping a damaged part for a new identical replacement, allow the robot to return to previous efficiency, precision, and safety levels.

pinhole leaks

The loss of hydraulic or pneumatic fluid through a small hole in the fluid system. Pinhole leaks, particularly those in pneumatic systems, may require the use of specialized equipment, such as an ultrasonic leak detector, to detect them.

pneumatic

Power created by the controlled motion of gas, usually air, under pressure. Pneumatic systems are often used to power robotic grippers, simple pick-and-place devices, and robots where electric motors might pose a hazard.

production rates

The speed at which a manufacturing operation produces products. Production rates can slow due to worn, dirty, broken, or malfunctioning machines or processes.

programming parameters

A set of rules, limits, or physical properties that determine the characteristics and allowable actions and movements of a machine. Programming parameters for robots include speed of movement, positional coordinates (linear, angular, and spacial), and sensor interfaces, which all become part of the program that controls the entire robot function.

proximity sensor

A device that uses an electronic sensing field to detect the presence of an object. Proximity sensors can be used in conjunction with robots to help position the robot in space relative to other objects.

recalibrated

Reset or reconfigured in order to more accurately measure a quantifiable subject, such as motion. Feedback devices need to be recalibrated if they begin to measure movement or numbers incorrectly.

reference

To set a consistent baseline point to measure against. Operators need to reference some encoders to a home switch for them to be able to accurately measure their motion.

reworked

Subjected to further manufacturing procedures, such as rewelding, remachining, or reassembly. Defective parts can be reworked to save material and reduce the cost of scrapping.

robots

A machine, often with articulated joints and gripping capabilities, that can be programmed to precisely perform a variety of complicated, repetitive tasks. Robots are used to assemble parts, weld joints, and position components, among many other manufacturing tasks.

root cause

The underlying issue that leads to a problem. A root cause is the fundamental problem, such as a leaking coolant line, that causes the symptoms of machine malfunction, such as a prematurely wearing motor.

scrapped

Discarded, recycled, or otherwise destroyed. Parts must be scrapped if they do not meet official part specifications.

seals

A device used to contain pressure and prevent leakage in a fluid system. Seals include mechanical devices and rubber and polymeric rings, as well as other configurations of material that can be applied to a fluid system connection.

sensors

A device that detects the presence or absence of an object, or specific properties of that object, and provides feedback to the robot control system. Sensors allow robots to interact with their environment.

servomotor

A small motor used in robots to allow for precise movement. Servomotors are often used in several places in a robotic arm, including the elbow joint and the gripper.

signal strength

The data power output from a network connection cable or a wireless router. Signal strength can be measured using a cable tester.

software

The coded instructions, formulas, and operations that structure the actions of a computer. Software includes any program added to the physical computer, or hardware, to enable it to perform specific tasks, such as controlling a robot.

spring

A flexible device made of coiled material that yields under force and returns to its original shape once the force is removed. Springs are used to connect the arms of delta robots.

step lists

An organizational tool where operators list every possible step in a manufacturing process. Step lists help operators assess what specific parts of the manufacturing process they must monitor to determine the root cause.

suction cup

A rubber or plastic device, usually shaped like a disc, that sticks to smooth, nonporous surfaces. Suction cup size may determine the strength of a robot's grip.

teach pendants

A hand-held device that can be used to program a robot and control its movements. Teach pendants will display error codes when a robot malfunctions.

temporary solution

A corrective action used as a stopgap until a more permanent and complete corrective action can be implemented. Temporary solutions, such as adding lubrication to a joint rather than replacing a worn coolant line, are not optimal because they reduce both robot and production efficiency and potentially compromise operator safety.

tolerance

An acceptable deviation from a desired dimension that meets specifications. Parts outside of a required tolerance must be discarded or reworked.

troubleshooting

An organized protocol for finding the root cause of a manufacturing problem. Troubleshooting often involves a logical process of elimination to identify the root cause of a problem.

troubleshooting manual

A document that outlines common issues that arise in manufacturing operations along with corrective actions. Troubleshooting manuals streamline the troubleshooting process and are sometimes provided by the equipment manufacturer.

undershoot

To fall short of or below a set value. Undershoot in a robot refers to a robot consistently and repeatedly not moving far enough to reach a desired location.

valve

A mechanical device by which the flow of liquid or gas may be regulated by movable parts that open, close, or obstruct one or more openings or passageways. Valves can break or leak and lead to a malfunction of the fluid system.

wear

The gradual removal or decay of material caused by contact, corrosion, and friction. Wear can occur on many parts of the robot, such as the sensors, gears, and end effectors, and cause the robot to malfunction.

weld pool

The area of molten metal that is created by the heat of the welding torch. The weld pool solidifies and forms the weld when the heat is removed.

welding

A joining process that permanently bonds two or more separate components. Welding can use heat, pressure, or both and is often performed by industrial robots.

welding arc

The area in which electricity transfers from the wire electrode to the workpiece. The heat generated by the arc melts the base metals and filler metal during welding.

welding robots

An automated machine that can permanently join materials together through the use of heat, often transmitted through a consumable wire electrode. Welding robots usually need troubleshooting when they suffer from poor wire feeding, inconsistent or off-location welds, and premature consumable failure, among other issues.

welding torch

A welding instrument that conducts electricity, guides the wire electrode, and, in some cases, releases protective shielding gas. Welding torches are the end effectors of welding robots.

welds

A mix of metals that joins at least two separate parts. Welds can be produced by applying heat, pressure, or both heat and pressure, and they may or may not use a filler metal in addition to the workpieces.

wire

A thin, flexible, elongated piece of metal. Wire in welding refers to the consumable metal fed through the welding machine to create the mass of the actual weld.

wire feeder

The device connected to or built on the welding machine that dispenses the welding filler metal. Wire feeders should be cleaned of dust regularly to prevent malfunctions.

wiring diagrams

An illustrated version of an electrical circuit. Wiring diagrams indicate the connections of the components in electrical or electronic circuits.

workholding devices

A component used to support, locate, and hold a workpiece. Workholding devices include clamps, vises, and collets.

working backward

A troubleshooting process where operators reverse a manufacturing process to assess each step for potential root causes. Working backward helps organize the troubleshooting process and ensures operators check each possible root cause.

wrist joint

The joint that connects the gripper or other end effector of the robot to the robot arm. Wrist joints have a number of components to allow full rotational movement for the gripper or other end effector.