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Planning and Design of Multi-layer Shuttle Racking System

Views:242     Author:Site Editor     Publish Time: 2020-12-09      Origin:Site

In recent years, the radio shuttle rack system has been more and more widely used. The storage capacity per unit of this type of shelf is much larger than other types of shelf structure, and it is suitable for the storage of materials with large quantities, small varieties and large flows, such as beverages, dairy products, low-temperature frozen products, home appliances, chemicals, clothing, tobacco, and so on. Shuttle racking is similar to the storage system of traditional drive-in racking, but it is not limited to the depth of the tunnel. The effective space utilization rate can be increased to 90% at most, and the site utilization rate can also reach over 60%, which can realize the maximum loading density. In the shelf structure area, the shuttle trolley is used to complete the cargo handling and storage operations, and the forklift, stacker and other external handling equipment are used at the entrance and exit of the shelf. Radio shuttle racks can also be used in conjunction with a variety of other rack structures to fully meet customer storage requirements.


It is worth noting that the planning and design of the shuttle racking system is limited to the factors of the specification and size of the shuttle trolley, the type of storage items and the unitized size series, the building floor height of the warehouse, the load-bearing of the building ground and the uneven ground settlement requirements, construction cost, forklift lift and storage channels. Therefore, it is particularly important to do a good job in the forward-looking design and planning of the shelf structure. For example, if the unitization of the storage in the warehouse is not done well, it will affect the accuracy and convenience of the operation of the warehouse. If the position of the inner column of the building is unreasonably designed, it will lose a lot of storage space and increase the unnecessary shelf structure layout. Moreover, with the application and development of shuttle racking systems, more and higher requirements have been put forward for the comprehensive application and planning of shuttle racking and other external handling and storage equipment. In view of the improvement of forklift lifting and storage system efficiency, the industry has proposed the planning and design of multi-layer shuttle racking systems that layer the work surface, or use the automatic vertical storage stacker and peripheral equipment to adjust the work surface. Operating mode or structure to better meet customer storage requirements. When planning and designing shuttle racking systems, enterprises should focus on the following aspects:

Radio Shuttle Rack

Unitization of stored goods


The type of goods, specifications and sizes, unit weight, single quantity, shelf life requirements, packaging type, etc. and storage mode play a decisive role in the storage unitization. In order to improve the efficiency of logistics operations in the shuttle rack area, the goods must first be sorted into uniform specifications of goods units with a pallet or pallet structure as the base form. The unitized pallet and pallet structure used in the shuttle rack area must meet the following requirements:


It has a convenient forklift operation space and a static and dynamic load capacity that can carry the weight of the pallet unit. The static and dynamic load capacity of the weight of the pallet unit needs to be combined with the storage form to obtain a good pallet force support mode, so as to facilitate the pallet to have a good dynamic and static structure and force support capacity when stored on the shuttle support rail; also consider during truck operation, the overhanging part of the pallet has good dynamic and static force support capabilities.


The maximum deformation of the pallet is not more than 25mm, so as not to affect the normal operation of the shuttle.


The gap between the pallets and the handling error during the storage of the multi-pallet unit are reasonable. It is even necessary to dynamically analyze the influence of the shuttle's motion curve on the pallet and unit cargo during the handling operation. It also analyzes and verifies the movement performance of the shuttle.


Consider the secondary packaging and reinforcement of the dynamic performance of the stored goods in the handling process. The most typical is flat pallets (including plastic flat pallets, wooden pallets, etc.). Its deformed bodies include column pallets, rack pallets (container racks), cage pallets (warehouse cages), box pallets, collapsible pallets, warehouse cages, etc. It also needs to adapt to the characteristics of the shuttle and the handling mode of the cargo unit.



1. Reasonably analyze and determine the load bearing point of the loading unit with the tray or pallet-like structure as the base form. That is, the support function form on the guide rail and the support function form of the shuttle under the lifting motion of the shuttle, and the simulation calculation or test detection obtains the maximum deformation control amount of the bottom of the loading unit to obtain a loading unit that meets the load-bearing requirements and structure. Interfere with the space movement of the shuttle.


2. The unitization of goods must not only meet the basic requirements of packaging, can effectively protect materials, save space, and facilitate handling, etc.. It must also meet the size requirements that match the unitization. For example, the unitized size must match the size of the standard shuttle car, the size of the standard pallet, and even the width of the shuttle rail and the structure and layout of the shelf. Reasonably analyze and estimate the characteristics of the cargo on the loading unit, and form the cargo into a combination of a certain size and weight to avoid stacking of ultra-wide, ultra-high, and easily bulky cargo. Otherwise, it will affect the choice and optimization of the final functional configuration of the overall system. That is, to meet the final functionality of the system as the planning goal, take the refinement and achievable unit structure as the lead, and combine the assembly test, the shuttle unit combination and the shuttle operation test, or the previous successful experience data as the support, to ensure the unitization of  stored goods is effective and feasible.


3. The unitization of stored goods also forms the basic unit of the basic storage structure and storage cost analysis of this type of shelf. Storage unit and layout size, as shown in Figure 1.

Storage unit and layout size

Figure 1

4. The clearance between the storage cargo unit and the side of the column is 75mm, which determines the width of the aisle of the rack and the specification and size of the shuttle, namely L=W+ 75*2. In Figure 1, L is the clear width of the shelf aisle; W is the width of the pallet (in the direction of the fork); H is the height of the first floor of the shelf: 499 mm; H1 is the height from the top of the goods to the bottom of the upper beam, about 100 mm.


5. The size of the storage cargo unit also determines the calculated length of the shuttle rail and the planned layout size of the shelf structure unit: first in last out = 2A + (n-2) * B + C + n * D; first in first out = 2A + (n-3) * B + 2 * C + n * D.


In the formula: A is the reserved adjustment running distance of the shuttle, about 50mm. Comprehensive processing based on the guide rail hole pitch and adjustment distance. B is the pallet design gap, which is 20mm. Comprehensive consideration based on the test data of pallet manufacturing tolerances and smooth operation. C is the reserved safety distance. It depends on the fork length of the handling equipment and the distance between the first pallet and the second pallet, generally 300mm. D is the depth of the tray. n is the number of pallets.


6. The weight of the storage cargo unit determines the selection and layout of the shelf columns, beams, etc. (theoretical verification and evaluation can be carried out according to the specific conditions of the project, or finite element simulation analysis can be carried out). According to the building height and storage space of the warehouse, the inventory and ground load can also be measured to provide more technical details for the customer's storage plan.


The structure analysis of the shuttle rack system


The shuttle racking system is composed of rack steel structure and its supporting shuttle trolley for pallet unit transportation, forklifts or other transportation systems for the access ports of the rack steel structure system.


Among them, the shuttle rack steel structure can be said to be a good combination structure of the drive-in rack steel structure system and the pallet beam rack steel structure system. That is, the forklift access channel and the forklift operation channel in the steel structure system of the driver's rack are transformed into the operation channel of the shuttle trolley. Forklifts only load and unload goods into the shelf system at the entry and exit ends of the shuttle rack or change the operation channel of the shuttle trolley. It does not need to access the goods in the channel, which improves the safety of operation and the operation efficiency is higher than that of the driver-type rack.


At the same time, the guide rail load-bearing beams of the storage pallet unit in the driver-type rack structure are transformed into the traveling rails of the shuttle trolley and the guide rail load-bearing beams of the storage tray unit. The shuttle trolley transports the pallet unit goods from the inbound end to the corresponding storage location or outbound end. In particular, the cantilever support structure of most guide rail load-bearing beams in the driver-type rack structure is changed to a structural mode in which the pallet beam-type simply supported beam and the cantilever support structure coexist. Improve the structural stability of the shuttle rack system, and also give full play to the storage characteristics of the dense rack.


Shuttle racking is a beam-column structure composed of multi-layer rail load-bearing beams and racking columns, with a special guide rail structure for shuttle trolleys, and a safety protection structure for shuttle trolleys and pallet units. Its components mainly include: shelf columns standing on both sides of the row mouth, track supports, horizontal or back cross tie rods and other safety protection structures (forklift stoppers, protection columns, separate entrance guides, etc.). Among them, the shelf column group is generally composed of shelf columns, horizontal slope compensation, column adjustable feet and other components. The track load-bearing beam is a special support and guide component for shuttle trolley operation that is attached to the main body of the rack beam column structure. Installed vertically on the track support, the pallet unit goods can also be placed directly on the track load beam.

radio shuttle rack system

The track supports are vertically installed on the rack column group, and bear the vertical load from the track load beam. The beam and the column should be connected by plug-in type semi-rigid and semi-hinged to improve the efficiency of assembly and installation. It is advisable to use bolts to fasten the beam and column to ensure the reliability of the structure. The horizontal or back cross rods are used to control the verticality and levelness of the steel structure unit of the shelf to improve the stability of the shelf structure.


The shuttle rails of the radio shuttle racking system have strict requirements on manufacturing and installation, such as: rail straightness: 1.5mm/3m. The overall length is ≤ 5mm, the height difference between the two guide rails in the same tunnel is ≤ 2mm, the guide rail splicing gap is ≤ 3mm, and the net distance between the two guide rails in the same tunnel is 0-2mm. The guide rail has a great influence on the service life of the walking driving wheel (using high-strength polyurethane material), and also has a great influence on the actual operating efficiency of the lithium battery, and will affect the smooth operation of the shuttle trolley and the dynamic load of the overall structure of the shelf.


The structure budget and selection check of the shuttle rack system


In the main structure of the shuttle racking system, the components that must be checked for structural budget and selection include column groups, beam structure components and guide rail components. Considering the flatness of the customer's warehouse floor, it is recommended that the column of the shuttle racking system choose an adjustable foot structure. Taking into account the change in the weight of the storage unit of the goods in the shuttle racking system, it is recommended to do the load checking calculation of the cantilever structure of the shuttle rail support, and to strengthen the column group of the warehouse shuttle racking system through the specification change of the connecting beam in the channel stability constraints, and share part of the perseverance transferred from the guide rail.


The column groups of the pallet shuttle system are mostly cold-formed thin-walled porous steel lattice columns. According to its different loading conditions, the columns must be subjected to theoretical check calculations according to axial compression components and compression bending components. When the column is checked, it is necessary to check the implicit qualitativeness in and out of its own plane as well as the stability of the column in and out of the plane. In the strength check, the effective net section of the column is adopted. In the stability calculation, the net section of the column is used. Since the overall shuttle rack structure is a multi-layer portal steel structure, the load-bearing characteristics and stability of the column group can be checked according to the relevant regulations of calculation and verification of the structure column in the "Cold-formed Thin-walled Steel Structure Technical Specification GB50018-2002".


The column group verification of Weixun’s shuttle rack structure system will be based on the height of the first or second layer of beams, the node pitch of the column group transverse compensation, the position of the center of gravity of the load, the cross-sectional characteristics of the column, the material and the safety design factor calculate the length of the lattice column, the radius of gyration of the section and its slenderness ratio, etc., to check whether the corresponding slenderness ratio meets the degree of section, whether the strength of the column meets the design strength of the material and its axial stability coefficient, etc. . In order to obtain whether the theoretical bearing capacity of the corresponding single column and its column group meets the load requirements of the specific layout structure, it will compare the theoretically calculated bearing capacity with the working condition test, and perform finite element analysis and simulation. The calculation model and shelf lattice column structure are shown in Figure 2.


Calculation model and rack grid hook column structure

Figure 2

The beam group structure of the warehouse radio shuttle racking system generally checks and judges the strength and rigidity index of the beam group according to the simply supported beam and the uniform load form. The cantilever beam structure is used to check the support structure of the guide rail, and the simple beam and the uniform load form are used to check and judge the strength and rigidity index of the guide rail load beam. Considering the operation stability requirements of the shuttle, the deflection control value of the running rail of the shuttle has been appropriately increased (much greater than 1/400 of the distance between the support points of the rail). According to the characteristics of the shelf steel structure, the anti-side movement components of the structure are reasonably arranged, such as the arrangement of the horizontal cross tie rod and the cross tie rod on the back of the structure, to further enhance the stability and carrying capacity of the shelf structure.


For the check of the strength, stiffness, and stability of the shuttle rack structure with uncertain structure, it is recommended to adopt a combination of load-bearing test, theoretical calculation, and assembly and operation simulation. And ensure that there is a full load of 24 hours of operating parameter testing and evaluation results.


Shuttle trolley


The shuttle trolley is mainly composed of two parts: mechanical and electrical. The mechanical part is composed of a shuttle car, a rail system in a shuttle rack structure, and a charging cabinet. The electrical part is composed of a single-machine control system, battery power supply system and dispatch management system.


The body system of the shuttle trolley is mainly composed of a frame body, a traveling drive device, and a decorative cover. The frame body is the main body that carries other components. The walking drive device is mainly composed of a drive shaft, a drive wheel and a motor. The electrical device is composed of PLC, variable frequency drive, photoelectric switch, encoder, barcode recognizer, etc. The shuttle trolley is mainly designed and selected based on its function, size, walking and lifting speed, carrying capacity and battery life, and supporting the design and planning of the steel structure system of the shelf.


The shuttle trolley shall pass the industrial test and intensified test. The overall structure of the trolley shall have sufficient strength. After 1.5 times the rated load overload test, there shall be no permanent deformation or damage. The average trouble-free running time should not be less than 50h, and each unit should be inspected and qualified before leaving the factory.


The shuttle trolley should have the following basic functions: single storage of goods, single/continuous automatic pick-up, automatic pick-up of specified quantity, automatic transfer (tally), manual advance and retreat, lifting, etc., low battery prompt and automatic protection function. It needs to have automatic inventory function, and has an interface for wireless communication with the outside. The interface adopts standard data communication protocol (TC/IP) and can be connected with the warehouse management system to further improve the overall operating efficiency of the shuttle system and the intelligent operation of the system.


Each shuttle trolley must be equipped with a remote control. The remote control must have the following functions:


1. Car-finding function within a radius of 50m.

2. The operating status and fault display of the shuttle trolley, manual forward, backward, continuous picking function, lifting function and emergency stop function, etc.

3. The shuttle trolley must match the shuttle rack structure and storage system, and the maximum deformation of the tray is required to be no more than 45mm.

4. The contact surface with the pallet must be treated with anti-skid treatment, and there is a mechanical anti-skid device at the bottom to prevent the pallet from slipping off the forks during handling.

5. When there is a foreign object in front of it, the shuttle trolley can automatically retract and sound an alarm.

6. Emergency rescue function, etc.


The traveling speed of the shuttle trolley varies according to the specifications, models and load conditions. For example, the normal load speed of a certain shuttle trolley is adjustable from 0.6 to 0.8m/s, and the normal speed of an empty vehicle is 0.7 to 0.9m. /s is adjustable, the slow speed before stopping is adjustable from 0.1 to 0.2m/s, and the manual forward and backward speed is adjustable from 0.1 to 0.2m/s. It takes 93s for the pick-up cycle of approximately 20 board depth (20m); the pick-up cycle for 40 board depth (40m) takes 163s. The maximum tilting load of the trolley is 1500 kg.


pallet shuttle racking

Multi-layer shuttle racking system


The multi-layer shuttle racking system is a brand new cargo storage system. There are many ways to realize the layered storage of goods, which can be the layering of the building structure to form a multi-layer handling operation surface, that is: using the layering principle of the building structure or shelf structure, through the construction of the building or shelf structure, multi-layer and multi-channel working surfaces of various handling equipment such as forklifts or stackers to achieve the maximum storage capacity in a limited space and improve the overall operating efficiency of the warehouse. According to the requirements of operating efficiency, a reasonable number of shuttles are arranged inside the shelves to ensure the efficient and balanced logistics operations inside and outside the shelf area. In the specific implementation case, the multi-layer shuttle racking system has formed different forms such as the rack structure of the forklift multi-layer shuttle operation mode, and the rack structure of the automated stand warehouse and the automatic shuttle warehouse.


The structure and size of multi-layer shuttle racks depend on factors such as storage items, handling equipment and unitized size of pallets. The main structure is mainly in the form of a multi-layer portal frame. Reinforce and adjust the stability of the shelf steel structure system through the local tie rod structure, such as: the top, laneway, back and other diagonal tie rods directly determine the restraint and binding force of the top, middle and end of the shelf column, ensuring the frame structure effectiveness. Because the track support beam is connected with multiple lattice column frames, it balances the frame's resistance to distortion to a certain extent. Especially when there are track support beams on both sides of the lattice column frame, the effect is more obvious.


The construction of a multi-layer radio shuttle racking system is a relatively complex system planning and design process. Many factors must be considered, including: the stability and carrying capacity of the rack steel structure; the intelligent, efficient; the dynamic stability of the shuttle when transporting pallets and the dynamic stability of the shelf steel structure, as well as the operating efficiency and compatibility of supporting forklifts or other handling equipment. All these put forward higher requirements for the design and application of multi-layer warehouse radio shuttle racking system.


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