Rivas Robotics: excellence in robotic palletizing
Bag palletizing robot
Bag palletizing robot
Specialists in bag palletizing
The bag has to be worked on before it is palletized
A bag is filled standing up. That means that by the time it reaches the end of the line, all the product has settled to the bottom and the bag has an irregular shape: fat at the bottom, slack at the top. Palletized like that, every bag sits differently, the layer does not come out flat, and the pallet ends up skewed, unstable, or bursting in transit.
That is why, in bag palletizing, the important work happens before the robot ever handles the bag. What determines final stability is not the robot: it is the compaction and the gripper.
Compaction: the critical point
It is the system that comes before the pick point, and it is what separates a pallet that holds from one that does not. The bag passes over square-roller conveyors, with a top roller that presses it and evens it out: this corrects the deformation caused by filling and distributes the product along the whole length of the bag.
The result is a bag with a regular, repeatable shape. And a regular bag stacks flat, layer on layer, with no gaps or unevenness accumulating towards the top. Without compaction, every bag introduces its own error and the pallet adds them all up.
Of all the bags, the one that gives the most trouble is not a particular material: it is the one with a lot of excess film. The surplus packaging moves around and the evening-out behaves differently.
One gripper for all your formats
The gripper is a fork type: its forks enter between the rollers at the pick point, immediately after the compaction system. It weighs between 60 and 70 kg, a little more when it also has to handle the empty pallet or insert slip sheets, because that adds components.
And here is the thing almost nobody asks about and everybody cares about: it is always the same gripper. A single gripper covers multiple bag formats and sizes — 10 kg, 25 kg and up to 50 kg — so if you produce in several formats there is no gripper change and no line stop to do it. Flexibility is not paid for in changeover time.
Which bags, and which weights
All the usual packaging is palletizable: paper, raffia, polypropylene and plastic, both valve bags and open-mouth bags. You do not have to choose the bag with the robot in mind.
On weight, the normal range today is 10 to 25 kg. The 50 kg bag is still used in some countries but is falling out of use for occupational health reasons. Big bags are out of scope: they are not palletized with a robot, they are handled a different way.
As for product, bag palletizing covers practically everything packed that way: chemicals, pet food, aggregates, stone, salt, animal feed, PET. If your product goes in a box, the box palletizing page explains the gripper and the throughput for that format.
The pattern and the pallet
The pattern is defined by the customer, and it tends to be fairly standard: three by two solves most cases. The installation adapts to whatever pallet size you use, not just the Euro pallet or the American pallet — some countries work with their own dimensions and that does not constrain the project.
As far as you want to automate
The level of automation is your call, and it can be extended later. At the most basic level, the robot palletizes and feeds the empty pallets itself. From there you can add an automatic pallet dispenser, slip sheets between layers and an automatic stretch wrapper at the end of the line.
Each plant goes as far as makes sense for it: the cell does not force you to buy everything up front.
Tell us what bag you produce, in which formats and at what throughput, and we will size the cell around your real product. The design is done on your bag, not on a generic one.
Bag palletizing: what we can do
| Throughput achieved | Up to 15 bags/min |
| Installation in production | Salt bag palletizing with 2 infeed lines at 15 bags/min |
| Payload | Up to 1,000 kg, gripper included |
| Palletizing height | Up to 2,700 mm |
| Reach | Up to 3,300 mm |
| Robots integrated | Yaskawa, KUKA, FANUC, ABB |
Why is a bag harder to palletize than a box?
Because a bag is filled standing up. By the time it reaches the end of the line, the product has settled to the bottom and the bag is left with an irregular shape: fat at the bottom, slack at the top. If you pick it up like that and set it on the pallet, every bag sits differently, the layer does not come out flat, and the pallet ends up skewed, unstable, or bursting in transit.
So with bags, what decides pallet stability happens before the robot gets to it: at the compaction stage. The bag passes over square-roller conveyors with a top roller that presses it, corrects the deformation from filling and distributes the product along the whole bag. A regular bag stacks flat; an uncompacted one puts its own error into every layer, and the pallet adds them up.
I produce several bag formats. Do I need a gripper for each one?
No. The gripper is designed for the range of bags you produce, and one gripper covers several formats and weights — 10, 25 and up to 50 kg — with no tooling change and no line stop.
When the bags are very different from each other, what we do is customise the gripper so it can pick them all, rather than build several. It is a fork gripper, and the forks enter between the rollers at the pick point, immediately after compaction.
I palletize salt, flour or chemicals. Will the robot cope with that environment?
Yes, but the cell is designed for that environment from the start. There are three typical situations:
Explosive atmospheres. In areas with explosive atmospheres — flour dust, animal feed, chemicals — the installation is executed in accordance with the ATEX directive, and is delivered with its certificate of conformity issued by an external, independent certification body. It is not a self-declaration: the installed cell is verified and certified by an accredited third party. For the customer that means the palletizing cell arrives ready to work in its classified zone, with the documentation a buyer in sectors such as flour or chemicals is going to require.
Corrosive environments. With salt, and with aggressive chemicals in the air, components have to be stainless. Salt eats anything that is not.
Dust. The robot is protected with covers, from a fabric cover that isolates it from dust through to specific covers depending on what is in the room.
Tell us what you pack and what condition the room is in, and the cell is sized for that.
How many bags per minute can be palletized?
Working bag by bag, the reference is 15 bags/min. That is the practical ceiling for that method.
If you need more, you change method, not robot:
- Two at a time. The robot handles two bags per movement. The cycle slows slightly, but since it moves twice as much, throughput goes up.
- By complete layers. Less common, but it is the answer when the required throughput is genuinely high.
One of our installations in production palletizes salt with two infeed lines at 15 bags/min.
For bags, is a robot better than a gantry palletizer?
With bags, the gantry is the most common solution on the market, so it is a fair comparison and worth making with real arguments.
What the robot brings is flexibility, and it shows in three things:
- Maintenance, which is easier to sustain over time.
- Adapting to several lines: one robot can serve more than one bagging machine.
- The type of installation, which is not tied to a rigid layout and accepts changes of format and pattern.
If your plant is always going to make the same thing, in a single format and on a single line, the gantry is a reasonable option. As soon as there are several formats, several lines or any expectation of change, the robot comes out better.
Can one robot serve two bagging lines?
Yes, and it is very common. It is one of the reasons to choose a robot over a gantry: the same equipment serves two lines if the throughput allows it.
From there, what you automate around it is up to you. Slip sheets — at the base, between layers or on top — are fitted or not according to each customer’s palletizing system. And the stretch wrapper at the end of the line is added according to the level of automation you want. The cell does not force you to buy everything up front, and it can be extended later.
How much does a bag palletizer cost?
The price does not depend on the format, but on the production speed and the degree of automation of the line. The three brackets, with what each one includes, are on our palletizing robot price ranges.
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