Automated storage and retrieval system
A storage and retrieval machine (SRM ) (English stacker crane (STC ) or storage and retrieval machine - S / R machine ) is a rail-mounted, single-track vehicle for operating the goods in a high-bay warehouse. The height of a RBG starts at about 6 feet and goes up to a maximum height of 46 meters. There are RBG that can serve the entire camp on a switch system ( curve- RBG for lower benefits ), or with a converter to change the lane and those that operate in only one passage ( aisle -bound RBG for high powers ). The level of automation ranges depending on the application of automated to fully manual.
The motion of a RBG takes place in the following three axes:
- X = pass longitudinal direction ( driving unit )
- Y = vertical direction ( stroke unit )
- Z = Gangquerrichung ( load-bearing unit )
- 3.1 Performance of a RBG
- 3.2 Optimum speed ratio
- 3.3 Periods 3.3.1 Mean Time
- 3.3.2 Single Game
- 3.3.3 combined game
- 4.1 Manual Control
- 4.2 Semi-automatic control
- 4.3 Automatic Control
History and Development
With the advent of mass production in industry, the demands on the internal material flow and thus to the warehouse equipment is getting bigger. The requirement to be able to store in a small area, more and more, the block storage emerged in the 50s. The block bearings were operated with stacker cranes, which already required much less space for the streets and reached heights that were not possible with a forklift or reach truck.
In the 60s came the first stacker cranes, which were gas -bound, in contrast to the stacking cranes and thus did not need a portal for traversing the entire hall. This not only increased the storage capacity through increased use of space, but also the performance, there was available for each lane a separate RBG now. At first drove the RBG as small gantry cranes at the ceiling and were led on the ground. But it soon went on to initiate the force is not on the shelf or the hall ceiling, but on the hall floor, as this was mechanically much easier to control. The one lane at the bottom moving RBG could now provide increasingly higher performance.
Were the RBG still operated by hand until now by a driver, enabled the development of information technology in the 80 's, the degree of automation of the stacker cranes.
This led to a strong growth of the industry from the 90s. In the following years, the development of the software should ( LSR ( warehouse control unit ) and LVR ( warehouse management system ), see high-bay warehouse ) gain an ever increasing importance. Mechanical RBG were demanded by the ever-increasing performance, but the basic concept remained until today.
Mechanical Configuration of an RBG
The stacker crane is not a combination of truck and hoist, but because of the guidance above and below a typical hoist which moves itself in the direction of travel (X -axis) and the lifting in the stroke direction (Y -axis). The stacker crane never occurs alone, but always in combination with a so-called load-carrying agent which manipulates the load directly or the so-called loading equipment, which act as carriers of cargo ( in Z direction).
Typically, a storage and retrieval machine for each aisle is installed. The change of the aisle would require a much more complex structure and greatly increase the access times to a shelf; nevertheless they are made (usually referred to as ' sideflexing ' RBG). If inputs and paging paged separately, even pairs of stacker cranes for each aisle are obvious. Not only the desired operating time determines the choice of solutions, but also payloads, building heights, storage strategies, etc.
Landing gear
The single-track chassis connects the two wheels with the mast or the frame. The wheels are guided on rails and are rotatably mounted in curved RBG. Depending on the type of rail ( hot-rolled sections such as U-sections, I-sections and railroad tracks ) and wheel load of steel, plastic or Vulkollan wheels ( steel hub with molded elastomer tread ) can be used in single or Doppelradkästen. Depending on the power requirements of one or both wheels are driven.
Mast
The mast ( pillar) connects the chassis with the top crosshead. Depending on the application, one- or two- pole versions ( frame units ) is possible. Along the mast of the lifting carriage is guided. However, the mast contains other components such as the hoist to the rope or chain drive, the main cabinet, platforms and ladders with the personal protective equipment (PPE), current leads to the main cabinet and the lifting of slip lines or cable chains.
Lifting
The lifting carriage carries primarily the load to be carried and equipped with means for receiving and discharging the load, the so-called load-receiving means.
In automatic RBG can be found on the lifting usually a Notsteuerstand ( for troubleshooting ). For manual RBG a cabin with more or less extensive equipment (PPE, seat, shelves, PC, scanner, fire extinguisher ... ) is often attached. An important issue here is the design of the escape route.
The lifting movement is via a rope, belt or chain drive. Thus, the lifting movement is switched off automatically at a mechanical blockage of the lifting devices, safety switches are mounted to detect slack rope or overload in the suspensions. On lifting equipment to prevent a crash when using rope or chain breakage are present. This safety device is especially important when people can travel with the RBG.
Top crosshead
The head traverse contains the upper chassis and possibly connects the two towers. The upper chassis is composed of guide rollers in a rail on Regaljoch (upper connecting structure of the shelf rows) are conducted. For non- curve- Einmastgeräten the top crosshead can even be omitted.
The head Traverse is particularly important when multiple curve- RBG are in a rail system. In this case, a collision must be prevented. The means for anti- collision are incorporated in the head cross-member, this also serves as a buffer.
Drive and performance
The travel and hoist drives today are predominantly variable-speed electric motors, wherein the driving performance is always higher to lower access times and increase system performance. Hydraulic drives are due to the high risk of contamination, especially for the goods, hardly used.
Performance of a RBG
Typical performance of a RBG for Euro pallets with 1000 kg payload, Ly = 30 meters and a total weight of 20,000 pounds are summarized in the following table:
These values vary greatly with the parameters RBG height and payload. A RBG in a small parts storage can reach due to the much lower mass acceleration values of 3-4 m / s ².
Optimum speed ratio
The velocities in the x and y directions are directly related to the stock dimensions. The optimum speed ratio is when simultaneous lift and travel movement simultaneously arrives from point x0/y0 the lifting point in Lx / Ly, in other words, the velocity ratio vx / vy corresponds to the aspect ratio Lx / Ly. The optimal length of the aisle (Lx ) for the example in the table above, according to this condition:
Lx = Ly * ( vx / vy ) = 30 * (225 /90) = 75 meters
Seasons
When play time is the sum of all times that are needed for a given motion of the RBG in a high- bay warehouse. It corresponds to the response time of a control system or the access time of a hard disk drive. You can draw conclusions on the handling capacity (number of import, export and / or rearrangements per unit time ) of a high -bay warehouse. These seasons can after implementation of the project be measured directly and are thus part of the loss; while deviations of 6 % is permitted. In our example from above, for example, 85 singles matches ( outsourcing ) and 50 double cycles ( storage and retrieval ) can be achieved per hour.
Mean Time
When one speaks of seasons, the middle seasons are always meant. This is a statistical mean under the assumption that all subjects be approached uniformly in a given period. The exact calculation is very complicated and impractical. For this reason, an average duty cycle is defined and the points P ( range space ), A ( Auslagerpunkt ) and E ( pre-storage ) determined depending on the dimensions of the actual stock. There are six different cases are distinguished ( see more details in the FEM 9.851 ) depending on the location of A and E in the camp.
Single game
A single play of a RBG consists of the sum of all time for a storage or retrieval including all driving, positioning, control and fork seasons. A single match for the swap therefore describes the path A → P → A, a single match for the storage E → P → E.
Combined game
A combined game ( or duplicity ) of RBG consists of the sum of all time for a storage and retrieval including all driving, positioning, control and fork seasons. One such game describes the path E → P1E → P2A → A
Types of control
Manual control
In manual control all movement axes are controlled by the ride- operator via the joystick or button. In this control in normal operation shall be prevented by logical and electrical interlocks that all movements are possible at any time. Due to the ever-increasing degree of automation manually operated RBG not play a significant role anymore. But especially for commission works man -operated devices are still used.
Semi-automatic control
In this control certain movements are automated. Very useful, for example, the so-called fork cycle in which the operator is visited by the specialist in question and with one keystroke following cycle starts:
Telescopic fork extend → telescopic fork lift fork retract →
Automatic control
In the automatic control all the movements of RBG be controlled autonomously and monitored on storage and retrieval system. The movement is coordinated by the warehouse management system by the application data. The data transmission between the functional units can be carried out eg via cable, fiber routes ( infra-red) or by radio.
A manual movement of each RBG is possible via a Notsteuerstand with which to connect to the warehouse management system can be overridden.
Displacement measurements
In order to determine the position in the x- direction, mainly incremental or absolute working laser metrology or rotary encoders are used.
Investments
The cost of a RBG depend heavily on the degree of automation, the dimensions, number of pieces and the performance data from. A smaller automatic RBG is in the range of 100,000 euros, for a RBG as in the example above are investments in the range of 300,000 euros.
Relevant standards
- EN 528 storage and retrieval equipment - Safety
- FEM 9.001 terminology / dictionary storage and retrieval machines
- FEM 9.101 Terminology / stacker cranes definitions
- FEM 9.221 Grading for RBG / reliability, availability
- FEM 9.311 calculation bases for RBG structures
- FEM 9,512 bases of calculations RBG engines
- FEM 9753 Safety rules for storage and retrieval machines
- FEM 9.851 Grading for storage and retrieval systems - Showtimes
- FEM 9.831 calculation bases for RBG in HRL area: Tolerances, deformations, clearances in the high -bay warehouse
- FEM 9.832 calculation bases for RBG in the MLS area: Tolerances, deformations, clearances in automated small parts warehouse