More Than Just A Robot
Aug 03, 2009
When we 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. But thats true of many purchases. When you buy an iPod, it just sits there looking sleek, smart and dumb. You need a PC to run the iTunes software, CDs for uploading your favourite sounds, other track and album downloads, a base station with speakers for charging and pumping out music, perhaps some better headphones and an iPod connection for the car.
It doesnt make your initial investment in the player any less worthwhile, it just means there are essential ancillaries needed to store thousands of tracks on the machine and provide you with a flexible, portable, powerful music source.
Much the same is true of an industrial robot. Alone, its a dumb machine, purposeful-looking and beautifully styled, but just standing there. Equipped with the necessary operational, safety and system integration equipment, it becomes a high speed, high precision, flexible automation tool, able to work round the clock relentlessly and reliably. True, the installation might have cost two or three times what you initially thought, but the returns on investment in quality, accuracy and throughput are incontrovertible and, thanks to shrinking capital costs and escalating performance characteristics, the payback period is now much shorter. Besides, whatever machinery youre buying or personnel you are hiring, there are going to be substantial ancillary costs as part of the package - its how these investments perform that matters.
So, to clarify matters, lets look at what extras are typically involved when installing a robot workcell. I have avoided sophistications like vision systems and multiple robots with clash avoidance and focused on a standard flexible workcell, which might pick & place, package and palletise, load or unload, demould, fill or fasten, weld, spray paint, assemble or perform any high speed, precision application for which it has been programmed.
Industrial Robot The heart of any flexible automation workcell is the robot itself, although its cost, performance, payload, kinematics and work envelope, even how it is mounted, will depend upon the application and, to some degree, the robot manufacturer; in straightforward terms, the choice extends from a top-of-the-scale 6-axis Articulated robot, through a high-speed Delta or picker robot, an affordable, workhorse 4-axis SCARA machine, to an inexpensive, yet relatively inflexible Cartesian or gantry type, all of which have optimum applications.
Protective Guarding Robots move at very high speed, and I mean high speed, so they need protecting from unauthorised access, just as people need safeguarding from flying robot arms, and naturally 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 we integrate guarding into the system, employing aluminium profile, stainless steel profiles and shatter-resistant polycarbonate panels.
Safety Interlocks 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 manipulation of the robot in low-speed teach mode, while opto-electronic devices like light curtains and light grids provide hazardous point protection for hands and fingers, without inhibiting production.
End Effector Also known as end of arm tooling, this 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.
Cables & Hoses The high speed movement and inherent flexibility of robots make the management of electrical cables and supply hoses a critical issue and not inconsiderable on-cost; 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 movement, high-speed friction and repetitive movements associated with robot applications, not to mention precise lengths to prevent snagging and stretching.
Ingress Protection Specifying the correct IP rating, or ingress protection, is critical when the robot is operating in a harsh and hostile environment, an explosive atmosphere, a pristine cleanroom or regular, dusty, greasy shopfloor; often its just a question of ticking the option box or specifying a machine thats custom-made for a particular application, like spray painting or foundry work, although sometimes special gaiters, disposable covers or upgraded components are needed, but whatever the solution, enhancing the IP rating inevitably adds to the cost.
Robot Peripherals Its important not to overlook peripheral items like 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 hand-held control and programming units, cost 1k or so, although you dont need one for each robot, but software licenses and plug-in boards for network communications are often needed for every machine, so should be factored into the budget.
Feed Mechanisms Now, with a perimeter-guarded workcell and fully equipped robot, it is necessary to consider feed mechanisms like 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 we 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.
Operator Panel Graphic operator panels, also known as HMI (human machine interface) screens, provide for manual input in the form of operator commands, diagnostics and programming changes and are typically protected for use in hostile environments; touchscreen 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.
Robot Integrator 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, like ourselves perhaps.
As suggested at the beginning, the fact that there is more than just a robot involved in any workcell installation should not affect your ROI calculations, since this has always been the case and industry average payback is now estimated at less than two or three years. Whats more, once your process or production cycle has run its course, the inherent flexibility and programmability of an industrial robot mean it can be reconfigured for other duties, especially as the average working life is more than fifteen years, with minimal downtime and maintenance. Not bad for a dumb machine (beat that iPod).