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There is more to an industrial robot workcell than the machine itself, according to Stirling Paatz of robot integrator Barr and Paatz.

When the company provides a quote for a fully functioning robot workcell, customers are sometimes surprised that there are costs and items of equipment other than the industrial robot itself.

This is the case with many purchases; for instance, when a customer buys an Ipod, he or she will need a PC to run the Itunes software, CDs for uploading sounds, other track and album downloads, a base station with speakers for charging and listening to music, perhaps some better headphones and an Ipod connection for the car.

It does not make the initial investment in the player any less worthwhile; it just means that there are essential ancillaries needed to store thousands of tracks on the machine and provide the user with a flexible and portable music source.

Much the same is true of an industrial robot.

Equipped with the necessary operational, safety and system integration equipment, it becomes a high-speed, high-precision, flexible automation tool that is able to work round the clock reliably.

It is true that the installation might have cost two or three times what the customer initially thought, but the returns on investment in quality, accuracy and throughput are indisputable and, thanks to shrinking capital costs and escalating performance characteristics, the payback period is now much shorter.

Whatever machinery a customer is buying or whatever personnel he or she is hiring, there are going to be substantial ancillary costs as part of the ‘package’.

The heart of any flexible automation workcell is the robot itself, although its cost, performance, payload, kinematics, work envelope and even how it is mounted will depend upon the application and, to some degree, the robot manufacturer.

The choice includes a six-axis articulated robot, a high-speed Delta or picker robot, an affordable workhorse four-axis SCARA machine and an inexpensive yet relatively inflexible Cartesian or gantry type, all of which have optimum applications.

Robots move at very high speed, so they need protecting from unauthorised access, just as people need safeguarding from flying robot arms.

There is strict safety legislation and a series of machinery directives.

Hard guarding typically comprises modular wire mesh panels, aluminium supports and access doors of a compliant height, which cannot be removed without tools, even using force, although for smaller cells guarding can be integrated into the system, employing aluminium profiles, stainless-steel profiles and shatter-resistant polycarbonate panels.

Having provided the perimeter security, there needs to be electronic provision for safe, authorised access for personnel, without interrupting the robot work cycle, and unfettered ingress for feed mechanisms and workpieces.

This is achieved through a system of safety interlocks and electro-mechanical guard door switches, with a bypass to enable the manipulation of the robot in low-speed teach mode, while opto-electronic devices such as light curtains and light grids provide hazardous point protection for hands and fingers, without inhibiting production.

The end effector, also known as end-of-arm tooling, is the most essential robot peripheral, either for gripping tools or workpieces or functioning as the tool itself, such as welding and spray guns.

The most common end effector is the gripper, which activates jaws or fingers to hold or manipulate parts, usually pneumatically but also electrically or hydraulically, although there are also vacuum cups for flat or moulded sheet material and electromagnetic pick-ups for parts with a ferrous content, the correct specification of which is critical to the accuracy and repeatability of any robot process.

The high-speed movement and inherent flexibility of robots make the management of electrical cables and supply hoses a critical issue.

Although standard cabling and process hoses are often channelled internally through the robot body and arm, some will need to be mounted externally and special high-flex cable and flexible carriers are required to withstand the twisting movements, high-speed friction and repetitive movements associated with robot applications, in addition to precise lengths to prevent snagging and stretching.

Specifying the correct ingress protection (IP) rating is critical when the robot is operating in a harsh and hostile environment, an explosive atmosphere, a pristine cleanroom or a regular, dusty or greasy shop floor.

Often, it is just a question of ticking the option box or specifying a machine that is custom made for a particular application, such as spray painting or foundry work.

Sometimes, however, special gaiters, disposable covers or upgraded components are needed but, whatever the solution, enhancing the IP rating inevitably adds to the cost.

It is important not to overlook peripheral items such as teach pendants, interface boards, communications cables and software licences, which are often not included in the machine purchase price, yet are essential for operation.

Teach pendants, which are handheld control and programming units, cost approximately GBP1,000.

Although a teach pendant is not needed for each robot, software licences and plug-in boards for network communications are often needed for every machine, so should be factored into the budget.

Now, with a perimeter-guarded workcell and a fully equipped robot, it is necessary to consider feed mechanisms such as conveyors, which enter and exit the cell through light curtain-protected access points and deliver workpieces to the robot.

Their specification is largely determined by the size and nature of the product and customers employ proprietary conveyor belts, powered rollers, vibratory and vacuum feeders and other transfer systems, often modified with custom-made pallets and tooling to carry items at the required orientation and frequency.

Graphic operator panels, also known as human-machine-interface (HMI) screens, provide for manual input in the form of operator commands, diagnostics and programming changes and are typically protected for use in hostile environments.

Touch-screen panels, with pressure switch electronics covered by a protective screen, provide user-friendly operation and graphically convey information to the operator, while multi-layered protocols permit varying levels of access to software menus and connectivity with the robot controller.

Responsible for the design, fabrication, integration and programming of a robot workcell for a particular application, the robot integrator is a key ‘component’ and should be brought in at the earliest possible stage.

In addition to specifying and sourcing the optimum robot and peripherals, the integrator will document details of the proposed workcell and produce a 3D animated solution, using high-end simulation software, to prove the solution works and should be selected on the basis of experience, technical know-how and the ability to manage a total project.

The fact that there is ‘more than just a robot’ involved in any workcell installation should not affect a customer’s return-on-investment calculations, since this has always been the case and industry average payback is now estimated at less than two or three years.

Once a process or production cycle has run its course, the inherent flexibility and programmability of an industrial robot mean that the machine can be reconfigured for other duties, especially as the average working life is more than 15 years, with minimal downtime and maintenance.

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