Positioning Equipment


Positioning equipment is used to handle material at a single location. It can be used at a workplace to feed, orient, load/unload, or otherwise manipulate materials so that are in the correct position for subsequent handling, machining, transport, or storage. In many cases, positioning equipment is required for and can be justified by the ergonomic requirements of a task. As compared to manual handling, the use of positioning equipment can provide the following benefits:

  • raise the productivity of each worker when the frequency of handling is high,
  • improve product quality and limit damage to materials and equipment when the item
  • handled is heavy or awkward to hold and damage is likely through human error or
    inattention, and
  • reduce fatigue and injuries when the environment is hazardous or inaccessible.

1. Manual (no equipment)

  • Under ideal circumstances, maximum recommended weight for manual lifting to avoid back injuries is 51 lbs.
  • Recommendation based on NIOSH (National Institute for Occupational Safety and Health) 1991
  • Lifting Equation, which uses six multipliers to reduce maximum recommended weight for less than ideal lifting tasks

2. Lift/ Tilt / Turn Table

  • Used when positioning involves the lifting, tilting, or turning of a load.
  • Can be used to reduce or limit a worker’s lifting and/or reaching motions.
  • Pallet load levelers are lift and turn tables used in manual palletizing to reduce the amount of bending and stooping involved with manually loading a pallet by combining a lifting and turning mechanism with a device that lowers the table as each layer is completed so that loading always takes place at the optimal height of 30 in.

3. Dock Leveler

  • Used at loading docks to compensate for height differences between a truck bed and the dock

4. Ball Transfer Table

  • Used in conveyor systems to permit manual transfer to and from machines and conveyors and between different sections of conveyors
  • Since loads are pushed on the table, ball friction limits the maximum load weight to 600 lbs.

5. Rotary Index Table

  • Used for the synchronous transfer of small parts from station to station in a single work center
  • Circular table rotates in discrete intermittent steps to advance parts between stations located along its perimeter
  • Since each part moves between stations at the same time, it is difficult to put buffers between stations
  • Different from conveyors used as in-line indexing machines, where linear transfers can take place between multiple workcenters separated by long distances, since a rotary index table is restricted to circular transfers with a single compact work center

6. Parts Feeder

  • Used for feeding and orienting small identical parts, particularly in automatic assembly operations [Boothroyd]
  • Motion of parts in a random pile channeled so that each part automatically assumes a specified orientation, where the symmetries of a part define its possible orientations
  • Motion can be imparted through vibration, gravity, centrifugal force, tumbling, or air pressure
  • In a vibratory bowl feeder, the most versatile type of parts feeder, parts are dumped into a bowl and then move vibrate uphill along a track towards an outlet, where rejected parts fall off the track and are recycled
  • Parts feeders can be used to provide inspection capabilities with respect to the shape and weight of parts (e.g., the coin feeder of a vending machine)

7. Air Film Device

  • Used to enable precision positioning of heavy loads
  • Sometimes referred to as “air pallets”
  • Can be used in place of cranes and hoists
  • Thin film of compressed (10–50 psi) air used to float loads of up to 300,000 lbs. so that a horizontal push of 1 lb. can move 1000 lb. load; floating action enables load to rotated or translated in any direction in the horizontal plane
  • Requires a smooth floor surface against which air streams underneath the device can push
  • Can be used in warehousing as the mechanism to convert stationary racks into sliding racks

8. Hoist

  • Used for vertical translation (i.e., lifting and lowering) of loads
  • Frequently attached to cranes and monorails to provide vertical translation capability
  • Can be operated manually, electrically, or pneumatically
  • Uses chain or wire rope as its lifting medium
  • Requires a smooth floor surface against which air streams underneath the device can push
  • Hoists are categorized into duty classes: H1—infrequent, standby duty use (1 or 2 lifts per month); H2—light duty (avg. 75 start/stops per hour); H3— medium (max. 250 start/stops per hour); H4—heavy, and H5—severe duty

9. Balancer

  • Mechanism used to support and control loads so that an operator need only guide a balanced (“weightless”) load, thus providing precision positioning
  • Frequently attached to cranes and monorails to provide vertical translation capability
  • Can be used to support hand tools to reduce changeover time
  • Can also be attached to hoists and manipulators

10. Manipulator

  • Used for vertical and horizontal translation and rotation of loads
  • Acting as “muscle multipliers,” manipulators counterbalance the weight of a load so that an operator lifts a small portion (1%) of the load’s weight
  • Can be powered manually, electrically, or pneumatically
  • Manipulator’s end-effector can be equipped with mechanical grippers, vacuum grippers, electromechanical grippers, or other tooling
  • Manipulators fill the gap between hoists and industrial robots: they can be used for a wider range of positioning tasks than hoists and are more flexible than industrial robots due to their use of manual control

  • (a) Rigid-link Manipulator
    • Although similar in construction, a rigid-link manipulator is distinguished from an industrial robot by the use of an operator for control as opposed to automatic computer control

    (b) Articulated Jib Crane Manipulator
    • Extends a jib crane’s reaching capability in a work area through the use of additional links or “arms”

(c) Vacuum Manipulator
  • Provides increased flexibility because rigid links are not used (vacuum, rigid-link, and articulated jib crane manipulators can all use vacuum gripper end-effectors)

11. Industrial Robot

  • Used in positioning to provide variable programmed motions of loads
  • “Intelligent” industrial robots utilize sensory information for complex control actions, as opposed to simple repetitive “pick-and-place” motions
  • Industrial robots also used for parts fabrication, inspection, and assembly tasks
  • Consists of a chain of several rigid links connected in series by revolute or prismatic joints with one end of the chain attached to a supporting base and the other end free and equipped with an end-effector
  • Robot’s end-effector can be equipped with mechanical grippers, vacuum grippers, electromechanical grippers, welding heads, paint spray heads, or any other tooling
  • Although similar in construction, an industrial robot is distinguished from a manipulator by the use of programmed control logic as opposed manual control
  • Pick-and-place industrial robots can be used as automatic palletizers
  • Mobile robots similar in construction to free-ranging AGVs
  • Can be powered manually, electrically, or pneumatically