Collaborative robots are increasingly used for end-of-line palletising, and they run into the same wall almost immediately: a cobot's vertical reach is shorter than a full pallet stack. The solution is a vertical axis under the robot. Getting that axis wrong is expensive, because the failure mode is not a stall — it is wobble, and wobble in a palletising cell means dropped cartons and misaligned stacks.

Competitor coverage of this topic is thin. LINAK markets a cobot-palletiser lifting column solution, and Firgelli publishes a load-focused sizing article, but neither addresses the parameter that actually governs the design: overturning moment.

Quick answer Stroke comes from pallet height minus the robot's own reach. Load is rarely the constraint. Moment is. Specify a guided telescoping column, not a bare actuator rod, and confirm the holding behaviour between layers.

Why a Cobot Palletizer Needs a Vertical Axis at All

A typical palletising cell stacks to somewhere between 1.5 m and 2.2 m. A cobot bolted to a fixed pedestal can comfortably reach the lower layers, but as the stack grows the arm approaches the limits of its working envelope — where it loses payload capacity, loses precision, and adopts awkward joint configurations near singularities.

Adding a vertical axis solves it: the robot works within its optimal envelope at every layer, and the column simply repositions the whole robot upward as the stack grows. This is often called a seventh axis.

The alternative — buying a physically larger industrial robot — costs far more and usually forfeits the collaborative safety characteristics that made a cobot attractive.

How Do You Calculate the Required Stroke for a Palletizing Column?

Work backwards from the finished pallet:

Stroke=H_stack​+H_{pallet base​}+H_clearance​−R_{robot vertical}

Where:

• $H_{\text{stack}}$  = maximum product stack height
• $H_{\text{pallet base}}$  = pallet thickness (a standard timber pallet is around 150 mm; confirm yours)
• $H_{\text{clearance}}$  = gripper height plus the carton height plus safe approach clearance
• $R_{\text{robot vertical}}$ = the vertical span the robot can cover while staying within its good working envelope, which is less than its catalogue maximum reach

​Worked example: Stack 1,800 mm, pallet base 150 mm, gripper plus carton plus approach clearance 400 mm. Robot comfortably covers 900 mm of vertical span from a fixed base.

1800+150+400−900=1450 mm of stroke

Two practical notes:

• Do not use the robot's catalogue maximum reach in this formula. Payload capacity falls off near full extension, and a palletising gripper plus carton is a meaningful payload.
• Add margin for future product changes. A cell built for exactly today's stack height becomes obsolete the moment marketing changes the carton size.

Stroke on our lifting column and industrial ranges is built to order — a column page such as the FY018C states customised stroke configurations, and the FY018D publishes a segmented extension design in 2–3 sections. Segmented designs matter here: they achieve long extension from a shorter retracted height, which is what lets a tall-stroke column fit under a robot without raising the base excessively.

Load Is Not the Hard Part — Overturning Moment Is

Here is the calculation people skip.

A cobot rated for, say, 20 kg payload, weighing perhaps 30 kg itself, plus a gripper — call the total vertical load on the column roughly 60 kg, or under 600 N. Against our published column capacities that is unremarkable: the FY018C publishes 8,000 N and the FY018D publishes 6,000 N load capacity in its body specification.

But vertical load is not the design driver. When the robot extends horizontally to place a carton at the far corner of the pallet, it creates a bending moment at the column:

M=F_{horizontal offset}​×d

A 25 kg combined arm-and-payload mass extended 1.2 m from the column centreline generates roughly:

25×9.81×1.2≈294 N⋅m

...applied as a static bending moment, plus a dynamic component every time the robot accelerates or decelerates its arm. That is the load case that determines whether the column is stiff enough.

Consequences for specification:

👉 This is the number to send us. When you enquire, give us the maximum horizontal offset and the mass at that offset, not just the robot payload rating. Deflection performance is application-specific and we will confirm it against your figures.

Lifting Column vs Rod Actuator: Which Belongs on a Palletizer?

There is a valid hybrid: a rod actuator driving a separately guided vertical carriage on linear rails. Here the rails carry the moment and the actuator provides only axial force. That works well and can be cheaper, at the cost of a bulkier frame and more assembly. It is the same principle as the diverter side-load rule in our conveyor diverter guide — never let an actuator rod act as a structural guide.

Speed, Cycle Rate and Where the Duty Limit Bites

Palletising is the friendliest duty profile in this whole content cluster, and for a pleasant reason: the column moves once per layer, not once per carton.

A typical layer of 6–10 cartons might take one to three minutes to build. During that entire period the column is stationary. Then it repositions by one carton height — perhaps 200–300 mm — and stops again.

So the constraint flips. Where a diverter is limited by cycles per hour, a palletising column is limited by whether it must stay energised while stationary.

If the drive holds mechanically, the duty consumption is trivial. If it holds by remaining powered, then an axis that is stationary for 90% of the shift is drawing power and generating heat for 90% of the shift — which no 10% duty rating survives. Every model in our industrial series publishes 10% duty as 2 min on / 18 min off, so this question must be settled before selection. See the arithmetic in duty cycle for 24/7 warehouse actuators.

Our published column pages do not state holding or self-locking behaviour, so confirm it with us for your model and load.

Integration: Control, Feedback and Safety

Position feedback. The robot controller needs to know the column height to compute placement coordinates. Feedback options stated on our pages include feedback sensors and signal-sending limit switches on the FY020 and FY015, and optional Hall sensors on the FY011E. Confirm the exact feedback type available for a column configuration.

Coordination. Two workable architectures: index the column between layers while the robot pauses (simple, safe, slightly slower), or move the column while the robot repositions (faster, requires proper interlocking). Most cells use the first.

Safety. The column is part of your machine's safety story, not a self-contained safe component. ISO 13849-1:2023 governs the design of safety-related parts of control systems, with its scope covering "the design and integration of safety-related parts of control systems (SRP/CS) that perform safety functions" (ISO). A vertical axis carrying a robot introduces a potential falling hazard, so the risk assessment for the cell must address descent under fault. We cover the buyer-side view of what to request in actuator compliance for material handling machinery.

Environment. Most palletising is dry indoor duty; IP65-class protection is generally appropriate. Food-adjacent lines with wash-down require IP67 — see the warehouse IP rating guide. Note that our published lifting column pages state IP43 on the FY018C and IP20 on the FY018D, so tell us your environment and we will confirm which configuration is suitable.

Specification Checklist for a Palletizing Column

Robot model and mass: ____ kg Maximum gripper + carton payload: ____ kg Maximum horizontal reach in use: ____ mm ← drives the moment Max stack height: ____ mm Pallet base height: ____ mm Robot's usable vertical span from base: ____ mm Required column stroke (calculated): ____ mm Retracted height available: ____ mm ← often the binding constraint Layers per pallet: ____ Time stationary per layer: ____ min Acceptable deflection at full extension: ____ mm Environment: dry indoor / food wash-down / cold


The two lines that most enquiries omit — maximum horizontal reach and acceptable deflection — are precisely the two that determine whether the cell will stack accurately.

Frequently Asked Questions

What stroke does a cobot palletizer column need? 

Stack height plus pallet base plus gripper clearance, minus the robot's usable vertical span. A 1,800 mm stack commonly lands around 1,400–1,500 mm of stroke.

Why a lifting column instead of a linear actuator? 

Because the robot applies a bending moment, not just weight. A guided telescoping column carries that moment; a bare rod is not designed to.

How fast does the column need to move? 

Slowly. It repositions once per layer, not per carton — force and stiffness matter far more than speed.

Does the column hold the robot between layers? 

Yes, for most of the cycle. Confirm whether it holds mechanically or under power; the latter consumes duty allowance continuously.

What load capacity do I need? 

Vertical load is usually modest — a cobot plus gripper is often under 1,000 N, against published column capacities of 6,000–8,000 N. Specify against moment and deflection instead.

Can I use a rod actuator with external rails? 

Yes. If the rails carry the moment, a rod actuator can provide the axial force. It is a valid, often cheaper approach with a bulkier frame.

Talk to Us About Your Palletizing Cell

Send robot model, maximum horizontal reach in use, stack height and available retracted height, and we will come back with a column configuration, stroke and the load/moment behaviour you can expect.

Discuss your palletizing cell → · Lifting column series → · Back to the material handling guide →