Tote that barge! Lift that bale! Assemblers-like the riverboat men of old-know all too well the challenges of gravity.
Imagine, though, that one day your operators show up for work with the strength to effortlessly pick up an engine block or a box weighing hundreds of pounds-with one hand. Then again, and more to the point for all too many production workers, imagine an operator lifting moderate loads dozens or even hundreds of times without having to worry about feeling sore at the end of the day.
Traditionally, assemblers have had to rely on cumbersome chain pulls or hard-to-fine-tune, "jerky," power winches to manipulate parts and product as they make their way to, from and along an assembly line. However, thanks to advances in sensor technology and electronic controls, today's intelligent material handling devices truly function as an extension of an operator's arms and hands.
Obviously, there is still a place for basic lifting devices. But, in those applications where cycle times are critical, or where delicate, cumbersome objects need to be carefully positioned as part of the assembly process, spending the extra money to increase throughput and cut down on ergonomic dangers is often a good idea. And, the equation looks even better when you factor in the various safety and process control features available with some of today's models.
Pick Your Positioner
As is the case with power tools, which can run on compressed air or with the help of electric motors, there's more than one way to move stuff around. For example, an assembler can go with a fully electric system, like the G-Force line from Gorbel Inc. (Fishers, NY) and the Cobotics Line from Stanley Assembly Technologies (Cleveland). These systems feature digital, electronic control and servo drives akin to those used in the robotics industry to lift and manipulate bulky or heavy items.Another option is comprised of systems that incorporate the same kind electronic control, but rely on more traditional pneumatic lift systems, like the Intelift Control System line from Ingersoll-Rand Co. (Annandale, NJ). According to John Perkins, engineering manager for material handling at Ingersoll-Rand, his company chose the "air-over-electric" approach for a very good reason: the standard pneumatic balancer technology that provides the muscle for the Intelift line-which has now been on the market for more than half a decade-is both robust and well-proven.
No matter what the drive system, the key to any intelligent assist device (IAD), or intelligent lifting system, is its digital controller, which uses algorithms and sensors to transmit an operator's "intent" to the motor doing the actual lifting. In the case of Stanley Assembly Technologies' Cobotics iLift lifters, these "brains" are housed both within the lifter itself and a programmable "hub" that is an integral part of the in-line control handle. This hub, which functions as a mini-PLC, includes a system start-and-stop button; status lights; a serial programming port; an auxiliary button that can be programmed to provide custom functionalities; and configurable I/O for use with end effectors or tooling.
Lifters in Gorbel's G-Force line, which is comprised of the advanced BXi series and more basic BX series, also rely on a controller that is an integral part of the control handle. The controller in an Intelift system is housed alongside the pneumatic motor, although the control handle still includes a similar number of control buttons.
Whatever the configuration, each IAD depends on an integrated load cell, which enables the unit to operate in "float mode" by monitoring the weight of the payload, its inertia and any up or down force being applied by the operator. This feature makes it possible for an operator to manipulate an object by holding onto the object itself, without pushing any buttons or having to touch any part of the actual lifting system.
Obviously, this streamlines the material handling process substantially, because the operator can concentrate on positioning the part or subcomponents being moved, as opposed to the lifting system. It also allows the operator to use both hands to control part orientation, as opposed to having one hand on the part and the other on a control handle.
According to Perkins, this kind of performance becomes especially important during final positioning of a larger component prior to installing it on a product. As an example, he cites an application in which an assembler implemented an intelligent lifting system with a spindle end effector to install truck tires. By harnessing the system's fine-motion control, operators are spared the chore of having to muscle the heavy tires around themselves. It is also much easier to line up the wheels with the lugs.
Perkins notes that in many cases, the size and weight of a component or assembly is not the only consideration. Cycles times and throughput also make a difference. Lifting and then installing, say, a 30-pound subassembly just one time certainly shouldn't break an operator's back. But, require an operator to do that same task dozens of times in the course of a single day, and the situation changes completely.
Stephen Klostermeyer, global product manager for Stanley Assembly Technologies' Cobotics line, adds that given the trend toward working with larger and larger subassemblies in product final assembly-especially in the automobile industry-this ability to manipulate heavy items is becoming increasingly important. The alternative is slower cycle times, worker injuries and expensive, accidental product damage.
Beyond the basic float feature, having an onboard computer in charge opens up an entire world of possibilities in terms of performance and system integration. For example, an assembler can program a system to incorporate reduce-speed points and travel-distance limits to avoid collisions. Systems can also keep track of preventative maintenance schedules and communicate with plantwide information systems via an Ethernet interface.
In addition, IADs have the capability to ensure a part is being securely gripped before they will allow an operator to carry it away. Similarly, systems can be programmed with an interlock to ensure an item is not released until the end effector is no longer under load. This prevents an operator from inadvertently dropping an item. Systems can even be programmed to automatically release a load once its weight is being fully supported to help reduce cycle times.
Perhaps most impressive is the load cell's ability to make the lifting system a part of an assembler's quality assurance system. Specifically, because it is carefully weighing each item as it is being moved, the system serves as a kind of a go, no-go parts presence device. Let's say a company is assembling small diesel engines and an operator forgets to fill one of the engines with oil. Because that engine will register on the lifter as being too light, the lifter will notify operators that something is wrong before that engine can be removed from the line.
Beyond the Z-Axis
Of course, IADs do not just move up and down. In many ways, the true power of an intelligent assist system lies in its ability to help operators move horizontally, in the X and Y axes.According to Klostermeyer, ergonomic lifters have gone a long way toward eliminating the lower-back injuries associated with heavy lifting. But, operators are still vulnerable to injuries to the shoulder and upper back resulting from repeatedly having to muscle loads around once they're airborne. He remembers this as being a major concern back in the late 1990s, when IADs were first being introduced to the automotive sector. "They would say, ‘This is great, but do you have X and Y?'" Klostermeyer recalls.
To solve these problems, assemblers can implement intelligent assist in an overhead rail system using servo-driven end trucks and bridge cranes like those found in Stanley Assembly Technologies' iTrolleys line. Like their iLift counterparts, these components employ multiple intent sensors and processing algorithms that allow an operator to move a heavy load, without having to push any buttons or even touch the material handling system.
For example, Stanley Assembly Technologies manufactures a proprietary noncontact cable-angle sensor that measures minute deflections of an iLift lifting cable as an operator begins pushing on a suspended load. The result is a system that masks the inertia of the overhead crane, an increasing source of repetitive motion injuries in today's high-paced assembly environment.
Stanley Assembly Technologies also offers a multipurpose iGrip handle equipped with load sensors that allow an operator to rotate a load around the Z axis as well move along X and Y. This approach becomes necessary when using multiaxis, rigid arm systems in which the Z axis consists of a pneumatic or servo-controlled column, as opposed to a wire. Like the in-line iLift handle, the iGrip system includes a digital hub for programming system parameters such as speed and acceleration. It can also include controls for manipulating the end effecter to change roll and pitch.
One of the advantages of this kind of "rigid" approach is that an operator can program "virtual limits," or stopping points, to define a working envelope in 3D space. This feature serves as a valuable tool for preventing collisions and product damage. It also serves to pare down cycles times by guiding a subassembly or component to where they belong.
For example, Klostermeyer cites an application in which an assembler implemented a multiaxis system for installing dashboards on an automotive assembly line. By setting up the system's virtual surfaces so that they "funneled" the dashboard in through the door opening, the operator could install it much more quickly. With collisions no longer a problem, the operator could concentrate on the fine-tune movements required to correctly seat the assembly.
Another feature that can increase throughputs is a programmed auto-return. Obviously, this is not a new concept. Balancers and reels have been set to return to a given vertical position for some time. However, with digital 3D control, an IAD system can follow a long and complex path to a preset loading position, freeing up an operator to spend that much more time adding value.
Finally, as is the case with lifters working exclusively in the Z axis, multiaxis systems can be fully integrated into a plant's information systems to provide production data, keep track of preventative maintenance needs and alert operators in the event of an operational problem.
They can also provide error-proofing performance by monitoring weight and position in 3D space. This, in turn, ensures that an operator is picking up the correct part, securing it in the correct position and, in those cases where there is a preset sequence of tasks, performing multiple operations in the correct order.
According to Klostermeyer, this is where IAD technology becomes especially powerful, when it becomes an integral part of the overall production process.
