Depalletizing cartons: how the 3D camera runs the robot cell
Depalletizing is the reverse palletizing process: a robot takes cartons off a pallet and hands them over to a line or a warehouse system. Unlike palletizing, the system does not know the position of the cartons, because no two stacks are alike. That is exactly why a depalletizing cell needs a 3D camera. This article explains how object detection works, what the cell consists of and when automation pays off.
Reading time approx. 7 minutes
Why depalletizing is harder than palletizing
In palletizing, the robot builds the stack itself. The position and orientation of every carton are known to the controller, because they follow from the pallet pattern. In depalletizing, the stack arrives from the warehouse or from a supplier. The system knows neither the exact position of the cartons nor their dimensions with certainty.
4 deviations make depalletizing more demanding:
- Leaning stacks. Cartons shift during transport. A layer image defined in a pattern editor only roughly matches the real situation.
- Changing carton formats. Changing suppliers and products bring different dimensions onto one pallet or from pallet to pallet.
- Slip sheets. Cardboard or plastic sheets between the layers have to be detected and set aside separately. Otherwise the robot picks the slip sheet instead of the carton.
- Unknown remaining heights. After partial removal or restacking, the information about the real height of the remaining stack is missing.
A rigidly programmed cell fails on these deviations. It misses the pick, pulls in slip sheets or causes stops that an operator has to clear by hand. Without machine vision, the robot stays limited to uniform pallets with a known layer image. Everything else remains manual work with heavy lifting and time pressure.
What the 3D camera does in the depalletizing process
The 3D camera is the sensor that turns an unknown stack into concrete pick points. It captures the pallet surface as a depth image. From it, the controller gets position, orientation and footprint of every visible carton of the top layer. The robot plans its grip from this data instead of a taught pattern.
3 figures show what current systems deliver:
- Recognition rate. The vision manufacturer Mech-Mind states a recognition rate above 99 % for its depalletizing solutions, with a position accuracy of ±5 mm.
- Detection speed. The PALLOC 3D vision system from SICK detects up to 2,000 cartons per hour according to the manufacturer.
- Format flexibility. Camera-based object detection handles changing carton formats without anyone reprogramming the cell.
The camera placement follows 2 designs. An overhead camera captures the complete layer in one image and delivers the pick points of all visible cartons. A camera on the robot arm captures the layer from a scan position that the robot has to approach before every image cycle. That costs cycle time but saves the camera gantry above the pallet and fits into tight cells. The MalocherBot data sheets list both variants as vision options.
Without a 3D camera, a robot depalletizes only stacks whose build is exactly known. With a 3D camera, the cell handles leaning layers, changing formats and slip sheets, because it plans every grip from the current depth image.
The 4 components of a depalletizing cell
A depalletizing cell consists of 4 components that have to be matched to each other:
1. The robot. Reach and payload determine which pallet heights and carton weights the cell covers. At InfectoPharm, a NACHI MZ25 industrial robot moves packaged pharmaceutical cartons up to 20 kg. For lower heights and weights, cobots are an option too.
2. The 3D camera. It delivers the pick points that a programmed cell does not have. The range includes the Mech-Mind series and PALLOC from SICK. PALLOC is designed specifically for depalletizing; Mech-Mind provides a solution of 3D camera and software. Camera systems in the marketplace.
3. The gripper. Vacuum area grippers (foam grippers) are common in depalletizing cartons, because they cover different carton sizes with one tool. The KENOS area gripper from Piab is a typical representative. The limits and sizing of vacuum grippers on changing cartons are covered in the post on misgrips after a carton change.
4. Pallet lift and software. A pallet lift raises the stack to a constant working height. The robot saves travel distance, and the cycle time can drop. The software connects camera, robot and gripper into one process and lets the operator add new carton types as a parameter set, without programming.
The throughput of the cell results from the interaction of all 4 components, not from the camera alone. How cycle time, gripper and pallet changeover determine real throughput is calculated in the post on the throughput of palletizing robots.
Field example: depalletizing at InfectoPharm
InfectoPharm, a pharmaceutical company based in Heppenheim, depalletizes packaged medicines fully automatically and hands them over to an automated warehouse system. The cell is a MalocherBot M, configured as a depalletizing cell with the 4 components from above: NACHI MZ25 industrial robot and Mech-Mind 3D camera system. The KENOS area gripper from Piab, a pallet lift and the LUNA OS software complete the setup. Commissioning took place in 2025.
The Mech-Mind camera detects the position and orientation of the cartons on the pallet automatically. The robot removes the packages and places them in pairs on trays that are handed directly to the warehouse system. An integrated pallet lift reduces the robot movements and enables short cycle times with high process stability.
At InfectoPharm, camera-based object detection handles changing carton formats without intervention in the controller. In regulated pharmaceutical production, that is an advantage with every product change. A second feature is parallel operation: the system stands directly in front of the line. Manual depalletizing with a Schmalz vacuum lifting system remains possible. Automation and manual work can thus be combined. The full configuration with specifications is in the InfectoPharm case study.
When automated depalletizing pays off
Whether the investment in a depalletizing cell pays off for you depends on 3 levers:
- Staff. Manual depalletizing is heavy, monotonous work. The cell takes over the physically demanding part; your staff takes over inspection and replenishment tasks. InfectoPharm uses the freed-up capacity for higher-value activities.
- Process reliability. The cell works reproducibly and independently of the staffing situation. The material flow towards the warehouse system stays constant, even during sick leave or holiday periods.
- Flexibility. Where carton formats change frequently, camera-based detection saves the changeover times that a rigid cell would need for every change.
As a rule of thumb: more pallets per shift and heavier cartons accelerate the payback. Frequent format changes additionally argue for the camera instead of a rigid cell. A concrete calculation with your own figures is provided by the ROI calculator.
Automated depalletizing pays off when stacks arrive with an unknown build, formats change and the process has to run constantly. The 3D camera is the component that makes automation possible in the first place.
Frequently asked questions
The 6 most frequent questions about automated depalletizing.
What is the difference between palletizing and depalletizing?
In palletizing, the robot stacks cartons onto a pallet following a known pattern. In depalletizing, it removes cartons from a stack whose exact build is unknown to the system. Depalletizing therefore needs machine vision that captures the position and orientation of every carton before the pick.
Why does a depalletizing cell need a 3D camera?
Because the stack arrives from the warehouse or from a supplier and the system does not know the position of the cartons. The 3D camera creates a depth image of the pallet surface and delivers pick points, orientation and footprint of the top layer. Without a camera, the robot can only work off stacks that are exactly known.
What happens to slip sheets in automated depalletizing?
Slip sheets made of cardboard or plastic have to be detected by the camera system and set aside separately by the robot. Otherwise the robot picks the slip sheet instead of the carton. Whether a system detects slip sheets reliably belongs in the pick test with real pallets.
Can a depalletizing cell handle changing carton formats?
Yes, if it works with camera-based object detection. The camera measures every carton in the depth image, and reprogramming for format changes is not needed. The operator adds new carton types in the software without programming effort. At InfectoPharm, this works in daily operation with changing formats.
How fast does a robot depalletize?
Throughput depends on cycle time, gripper, stack format and pallet changeover, not on the camera alone. For the detection itself, SICK states a high reserve: the PALLOC 3D vision system detects up to 2,000 cartons per hour according to the manufacturer.
Can automated and manual depalletizing be combined?
Yes. The cell at InfectoPharm is positioned directly in front of the line, and manual work with a vacuum lifting system remains possible in parallel. This constellation suits sites that want to absorb peaks or introduce automation step by step.