Selecting the right stacker crane system starts with accurate pallet dimensions, load data, storage targets, and operating conditions. UNISTAR helps purchasing teams compare crane capacity, rack configuration, aisle requirements, safety functions, and total operating cost before approving an automated storage and retrieval system.
Do not select a crane from the nominal pallet label alone. Measure the complete load unit that will enter the rack, including the pallet, product overhang, wrapping, straps, labels, and any attached containers.
Measure pallet length from the front edge to the rear edge.
Measure pallet width from the left edge to the right edge.
Measure the total loaded height from the floor contact point to the highest product point.
Record any load overhang on each side.
Check whether pallets are damaged, warped, or inconsistent in size.
Identify whether the pallet is a standard wood pallet, plastic pallet, steel pallet, or custom carrier.
A pallet listed as 1200 x 1000 mm may require a larger storage position if the product extends beyond the pallet or if the rack needs additional side clearance. The final storage position must be based on the largest practical load unit, not the average unit.
The crane must be sized for the maximum operating load, not only the normal load. Include the weight of the pallet, product, packaging, separators, and any reusable transport container.
Empty pallet weight.
Average product weight.
Maximum product weight.
Packaging and wrapping weight.
Weight variation between product types.
Any future increase in product density or pallet weight.
For procurement, create a load profile with the minimum, average, maximum, and expected future weight. This prevents a system from being designed only for today's average load.
Load weight alone does not determine whether a stacker crane can handle a pallet safely. A tall, flexible, uneven, or liquid-filled load may require a different fork design, slower acceleration, or additional load stabilization.
Confirm whether the load is centered on the pallet.
Check whether the product can shift during acceleration or braking.
Identify cartons that can collapse under pressure.
Measure the center of gravity where possible.
Record whether the load is wrapped, strapped, banded, or uncovered.
Determine whether the load requires a clamp, fork extension, telescopic fork, or special carrier.
Determine how many pallet positions the warehouse must hold at one time. Separate active stock, reserve stock, quarantine stock, returned goods, damaged goods, and empty pallet positions.
List the number of pallet positions currently required.
Add seasonal inventory peaks.
Add the expected growth for the next three to five years.
Reserve locations for quality inspection, damaged products, and incomplete loads.
Define the percentage of empty locations required for operational flexibility.
A high-density system may reduce floor area, but excessive utilization can make replenishment difficult. Purchasing teams should compare nominal capacity with the practical capacity available during peak operations.
Throughput is the number of pallet movements the system must complete within a defined period. Specify inbound storage, outbound retrieval, relocation, inventory checking, and emergency movements separately.
Inbound pallets per hour.
Outbound pallets per hour.
Combined storage and retrieval cycles per hour.
Peak hourly demand.
Average daily movements.
Number of shifts per day.
Required operating days per week.
Maximum acceptable waiting time at the input and output stations.
Do not size the crane using the daily average if the warehouse has short periods of intense activity. Peak demand determines the required speed, number of cranes, number of stations, and control strategy.
Purchasers should specify how the system must perform during normal operation and how quickly it must recover from a fault.
Required operating hours.
Target system availability.
Maximum acceptable recovery time.
Required spare parts availability.
Remote support requirements.
Local maintenance capability.
Manual recovery procedures.
The rack position must provide enough clearance for the pallet, load, crane forks, rack beams, neighboring loads, and installation tolerances. A position that is too tight can cause collisions, product damage, and repeated equipment faults.
Use the following design sequence:
Start with the maximum pallet length and width.
Add the largest product overhang allowed by the operation.
Add side clearance between the load and rack components.
Add clearance between adjacent loads.
Add front and rear insertion clearance for the fork mechanism.
Confirm the final position size with the rack manufacturer and crane supplier.
Clearance values depend on pallet quality, load stability, crane accuracy, rack tolerance, and operating speed. Do not use a generic clearance value without confirming it with a complete layout and load test.
Single-deep storage is often easier to access and control. Double-deep or multi-deep storage can increase density but may reduce selectivity and require special telescopic forks or load handling devices.
Use single-deep storage when every pallet requires direct access.
Consider double-deep storage for stable products with predictable stock rotation.
Confirm that the fork stroke reaches the rear pallet position.
Check whether the rear pallet can be retrieved without moving the front pallet.
Verify that load deflection does not interfere with neighboring positions.
Confirm fire protection and inspection access requirements.
The available building envelope determines the mast height and the number of storage levels. The floor must also support the rack and crane loads without excessive settlement or vibration.
Measure clear building height below beams, lights, sprinklers, ducts, and other obstructions.
Check floor flatness and levelness along the complete crane rail path.
Confirm concrete strength and anchor capacity.
Check seismic, wind, and local building code requirements.
Allow space for maintenance access and emergency evacuation.
Identify temperature-controlled, dusty, humid, or corrosive areas.
The rated capacity must cover the complete load unit under the most demanding operating condition. It should also consider the height of the load, the reach of the forks, acceleration, braking, and future changes in the product mix.
Compare suppliers using these capacity questions:
What is the maximum rated load per pallet position?
Does the rating include the pallet weight?
Does the rating change at greater lifting heights?
Does the rating change for double-deep storage?
What load center is used for the capacity rating?
What happens if the load is not perfectly centered?
What overload detection and prevention functions are included?
A capacity margin should be agreed with the supplier after reviewing actual load data. A large unused capacity can increase equipment cost, while insufficient capacity creates safety and reliability risks.
Single-column cranes may suit lighter loads and lower heights. Double-column designs are commonly selected for heavier loads, taller racks, greater rigidity, or demanding throughput.
Single-column design: suitable for lighter loads and compact applications.
Double-column design: suitable for higher loads, taller storage, and increased structural stability.
High-speed design: suitable for short cycle times and high throughput.
Special temperature design: suitable for cold storage or freezer environments.
Explosion-protected design: suitable for regulated hazardous areas when properly certified.
The final choice should be based on load weight, mast height, cycle time, building conditions, maintenance access, and total cost rather than equipment appearance.
The load handling device must support the pallet without bending, slipping, or damaging the product. It must also match the storage depth and pallet entry direction.
Standard forks for common single-deep pallet storage.
Telescopic forks for double-deep or multi-deep storage.
Wide forks for large or unstable loads.
Special forks for non-standard pallet openings.
Clamps for loads that cannot be handled with standard forks.
Custom carriers for drums, coils, bins, or irregular products.
Ask the supplier to confirm fork opening dimensions, fork length, allowable load center, minimum pallet quality, and the required position accuracy.
Input and output stations affect travel distance, labor requirements, and system throughput. The station should match the pallet flow, operator workflow, and surrounding conveyor or transport equipment.
Floor-level stations for simple pallet transfer.
Elevated stations for direct connection to production lines.
Separate inbound and outbound stations for high-volume operations.
Combined stations for lower-volume facilities.
Buffer conveyors for peak arrival and dispatch periods.
Inspection stations for barcode, weight, and load quality checks.
Each station should include a method for detecting pallet presence, verifying pallet identity, checking load height, and preventing damaged or oversized pallets from entering the rack.
A stacker crane system depends on coordinated mechanical, electrical, and software controls. The warehouse management system should know the location and status of every pallet.
Confirm the following functions:
Barcode, RFID, or other pallet identification.
Automatic location assignment.
Inventory status management.
Batch, lot, expiry, and first-in-first-out control.
Automatic error messages and alarm history.
Manual recovery mode.
Warehouse management system interface.
Warehouse control system communication.
Data backup and user permission management.
Performance reporting and cycle history.
Safety requirements should be included in the technical specification instead of added after equipment selection.
Fenced access areas.
Interlocked safety doors.
Emergency stop circuits.
Light curtains or scanning devices.
Overspeed and position monitoring.
Load presence and load overhang detection.
Anti-collision control.
Safe maintenance access.
Emergency lowering or recovery procedures.
Compliance with applicable local standards.
Prepare one controlled document containing the pallet dimensions, load dimensions, maximum weight, load center, pallet type, product stability, and allowable variation.
Include photographs or drawings of the smallest, largest, tallest, and most unstable loads. This gives each supplier the same information and makes quotations easier to compare.
Survey the proposed installation area before requesting a final design. Record clear height, floor condition, columns, doors, sprinklers, lighting, utility lines, and maintenance access routes.
Use a current building drawing and verify critical dimensions on site. Old drawings can omit structural changes or installed equipment that affect crane placement.
Convert business requirements into measurable engineering values.
Calculate total pallet positions.
Calculate average and peak inbound movements.
Calculate average and peak outbound movements.
Add relocation, inventory check, and exception movements.
Define the required cycle time.
Define the operating schedule and future growth factor.
Request that suppliers show how their proposed number of cranes and storage lanes meet the peak cycle requirement.
Compare single-deep, double-deep, and multi-deep layouts according to product rotation and access requirements. Calculate the tradeoff between storage density, retrieval selectivity, crane complexity, and potential product blocking.
Match the crane capacity, mast height, travel speed, lift speed, fork stroke, and control functions to the load and layout. Confirm that the proposed crane can handle the heaviest and largest approved load at the highest storage level.
Review conveyor height, pallet transfer direction, barcode position, electrical supply, network connection, fire systems, drainage, temperature, and access for installation.
Identify which tasks are included in the supplier scope and which tasks remain with the buyer. This may include foundation work, rack installation, electrical cabling, network connection, software integration, testing, and operator training.
Do not compare only the purchase price. Use a common comparison sheet that includes:
Storage capacity.
Maximum load capacity.
Cycle performance.
Energy consumption.
Software functions.
Safety equipment.
Installation and commissioning.
Training and documentation.
Warranty period.
Preventive maintenance.
Spare parts cost and delivery time.
Expected service life.
Require a design review using real load samples or accurate load replicas. Test pallet entry, fork engagement, load stability, position accuracy, barcode reading, emergency stops, and recovery procedures.
Ask for acceptance criteria that clearly define the required number of successful cycles, maximum errors, system availability, and response time for faults.
Steel tape measure for pallet and building dimensions.
Laser distance meter for aisle length and building height.
Calibrated floor level or digital level.
Industrial weighing scale or verified weight records.
Calipers for pallet opening and fork entry measurements.
Camera for documenting load condition and obstructions.
Barcode scanner or RFID reader for identification testing.
Moisture, temperature, or dust measurement tools when environmental conditions require them.
Current warehouse layout drawing.
Pallet dimension and weight matrix.
Product and load photographs.
Inventory and throughput history.
Peak season demand data.
Building and floor specifications.
Electrical and network requirements.
Fire and safety requirements.
Required software interface description.
Supplier quotation comparison sheet.
Factory acceptance and site acceptance test plan.
The best system is compatible with the complete range of pallet sizes and loads that the warehouse will handle. A low-price system that cannot reliably process the largest load will create operational restrictions and manual workarounds.
Maximum pallet size.
Minimum pallet size.
Maximum load height.
Maximum load weight.
Allowable load overhang.
Fork opening requirements.
Load center limits.
Pallet quality requirements.
High density is valuable when land or building space is expensive. Direct access is valuable when products have high turnover, strict expiry control, or many stock keeping units.
Choose higher density for reserve storage and stable product groups.
Choose higher selectivity for fast-moving or expiry-controlled products.
Use zoning to combine dense storage with fast-access locations.
Consider product compatibility before placing different goods in the same deep lane.
Calculate the complete cost over the expected service life rather than comparing the initial equipment price alone.
Equipment purchase cost.
Rack and conveyor cost.
Building preparation cost.
Installation and commissioning cost.
Software integration cost.
Energy consumption.
Routine maintenance.
Replacement parts.
Downtime risk.
Labor savings.
Future expansion cost.
Using average dimensions and average weight can result in unsafe handling of oversized or overweight pallets. Design the system using the maximum approved operating values and define how exceptions will be rejected.
Broken boards, missing blocks, bent plastic pallets, and uneven loads can prevent safe fork engagement. Establish pallet inspection rules and include reject handling at the input station.
A rack position that matches the pallet footprint may not provide enough space for product overhang, pallet variation, crane tolerance, and load movement. Require a complete clearance calculation.
Daily totals hide short periods of high demand. Use hourly and shift-level data to identify peak cycles and queue formation at the input and output stations.
New packaging, heavier products, different pallet types, and increased inventory can make an otherwise suitable crane unusable. Include an approved future load range and expansion plan in the specification.
A low quotation may exclude software integration, rack protection, site preparation, commissioning, training, spare parts, or performance testing. Compare identical supply boundaries before selecting a supplier.
Pallet tracking errors can create inventory losses even when the mechanical equipment operates correctly. Confirm identification, location management, error recovery, reporting, and system integration before purchase approval.
Ask how technicians will access the crane, retrieve a pallet after a fault, replace critical components, and restore the system after a power or communication failure.
Maximum pallet length and width are documented.
Maximum loaded height is documented.
Maximum total load weight includes the pallet.
Load center and overhang limits are defined.
Rack position dimensions are confirmed.
Storage height and aisle dimensions are confirmed.
Required input and output throughput is guaranteed.
Fork type and reach are specified.
Environmental conditions are accepted by the supplier.
Supply scope is clearly listed.
Delivery schedule is realistic.
Installation responsibilities are assigned.
Factory and site acceptance tests are defined.
Warranty coverage is documented.
Preventive maintenance frequency is specified.
Critical spare parts are identified.
Training is included.
Software updates and technical support are explained.
Expansion options are documented.
The final approval should follow a review of the complete layout, actual pallet samples, operating cycle calculations, safety assessment, software interface, and maintenance plan. This approach reduces the risk of purchasing a crane that fits the rack but does not fit the real operation.
The correct stacker crane system is selected by connecting pallet dimensions, maximum load, load stability, storage density, throughput, building conditions, software, safety, and lifecycle cost. A structured step-by-step review gives purchasing teams clear evidence for comparing suppliers and prevents expensive changes after installation.
For pallet measurements, load capacity review, rack layout, and automated storage planning, contact UNISTAR through the provided contact channel and request a solution based on your actual pallet and load data. A properly specified stacker crane system can improve storage density, reduce manual handling, and provide reliable pallet movement as your operation grows.
