Application

Six hundred 25-kilogram sacks a shift – stacked by hand

A sack of cement weighs 25 kilograms, a sack of compound feed 40. Individually that is unremarkable. Six hundred times a shift it is fifteen tonnes – moved by two people, bent over, from a height nobody chose.

Component: Valve or pillow sack
Weight: 15 to 50 kg
Cycle: 6 to 12 sacks a minute
Frequency: 400 to 900 per shift
Movement: pick up, turn, place in pattern
Environment: dusty, pallet height up to 1.80 m

01 — The task

Fifteen tonnes a day, sack by sack, with the back.

The sack leaves the scale on a short belt, has to be picked up, turned and placed on the pallet in pattern – layer by layer, every second one offset by 90 degrees. The bottom layer sits at knee height, the top one above shoulder height: both are critical under the key indicator method, and there are fourteen layers in between. The sack itself is the real opponent. It has no fixed shape, its contents shift as it is lifted and it slips out of any grip that holds it in one place only. A rigid form gripper closes on nothing, and a vacuum cup finds no sealed surface on woven polypropylene.

What the solution has to do

The gripper has to hold the soft sack securely even as the contents shift during lifting.
Placing must follow the pattern – a skewed stack topples in transit.
Around 1.4 metres of lift separate the belt from the top layer.
Dust and paper abrasion rule out sensitive guides and exposed electronics.
With feed and food, no lubricant may run across the pallet.

02 — The solution

How we solve it

The gripper decides, not the unit

Two approaches hold up in service with a soft sack. A clamp gripper takes the sack across its full width between two jaws and compresses it slightly – the contents can shift without the grip easing. A needle gripper pierces the fabric with fine needles and carries on them; it is faster but leaves puncture marks and is ruled out wherever the sack has to stay sealed. For paper valve sacks the clamp gripper is the safe choice, for woven PP sacks both are common. That decision comes before choosing the unit, not after.

A rope unit is enough – if the pattern works

Unlike joining, no appreciable lateral forces occur here: the sack is placed, not pressed. That makes an articulated-arm rope unit or a balancer on a rail system the more economical answer – it carries the load in suspension and follows the hand without resistance. What matters is area, not reach: bagging point, two pallet positions and the change between them add up to a rectangle of roughly four by three metres. An area rail system covers that completely, a column unit only a circle within it.

Grip height is the real strain

In an assessment under the key indicator method it is not weight alone that counts but posture. Serving the bottom pallet layer from standing means bending the trunk more than 60 degrees; the top layer means working above shoulder height. Both disappear once the unit takes the lift and the operator only guides. Where a pallet changer with a lowering table can also be planned in, the strain drops a second time – working height then stays the same across all fourteen layers.

03 — What changes

At the workstation afterwards

25 kilograms of lifting load become a few newtons of guiding force.
One person stacks the pallet instead of two.
Trunk bending and overhead work disappear – the assessment improves in force and posture.
The stacking pattern stays even because placing is no longer done on the swing.
Changing to another sack format costs a jaw setting, not a conversion.

04 — Matching equipment

What we build it from

Lifting equipment · Balancers

Skyline Rope Balancer

Weightless handling – floating instead of lifting.

View device Lifting equipment · Balancers

Articulated Rope Unit

Articulated reach meets weightless floating.

View device Lifting equipment · Conveyor systems

Rail System

The whole area covered – in X and Y.

View device

Frequently asked questions

Clamp gripper or needle gripper for sacks?

The clamp gripper holds across the surface and damages nothing – it is the default for paper valve sacks and for anything that has to stay sealed. The needle gripper is faster and more forgiving on approach, but leaves punctures in the fabric. Both are common in feed and building materials; in food filling it is almost always the clamp gripper.

Is this worth it compared with a palletising robot?

From around 1,200 sacks a shift with a stable format the robot wins. Below that – and wherever formats, pallet sizes or stacking patterns change daily – the hand-guided unit is more economical: no enclosure, no programming, commissioning in days rather than months.

Does this work in the dust of a bagging line?

Yes, with the right design. We use encapsulated guides, bellows on the cylinders and pneumatic control without exposed electronics in the dust zone. Maintenance is then limited to visual checks and the annual statutory inspection.

Matching services

Industries

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