The challenge
Fresh, washed, and packaged salad tubs are a staple of modern grocery retail, and the volumes behind them are relentless. Our customer was running a packaging line where sealed salad tubs had to move from the filling station into shipping cases, two at a time, on a robot arm that had very little payload headroom left.
Two constraints defined the problem. The gripper had to lift two full tubs per cycle without pushing the arm past its rated payload, and every surface touching the package had to be appropriate for a food environment. A machined aluminium gripper of the required footprint would have consumed most of the available payload before a single tub was picked.
Manual handling was the alternative, and it carried its own cost. Every human touch on a sealed food package is a contamination risk and a throughput ceiling.
Our solution
Our engineering team designed a vacuum gripper in Nylon PA12 and produced it by selective laser sintering on an EOS P396. Additive manufacturing let us treat the whole tool as one continuous structure rather than a stack of brackets, plates, and fasteners.
Topography optimization drove the geometry
Instead of starting from a solid block and removing material, we defined the load paths between the tool flange and each suction cup position, then let the structure follow those paths. Material sits only where force travels. The finished tool weighs 1.2 kg and assembles from three components.
Food-grade suction cups handle the contact
Cup selection was matched to the film lid of the salad tub, which is thin, slightly flexible, and easy to deform under too much vacuum. The cups seal against the film without collapsing it, so the package arrives in the case looking the way it left the filler.
Vapour polishing seals the surface
Black dye vapour polishing closes the porosity naturally present in a sintered nylon part. The result is a smooth surface that wipes down cleanly and does not trap product residue between shifts.
Full specifications
| Material | Nylon PA12 |
|---|---|
| Machine | EOS P396 |
| Layer thickness | 120 microns |
| Build time | 18 hours |
| Post processing | Black dye vapour polishing |
| Number of components in the assembly | 3 |
| Tool weight | 1.2 kg |
| Units per cycle | 2 sealed salad tubs |
| Gripping method | Vacuum, food-grade suction cups |
Results
The line runs at the robot pace rather than an operator pace, and the arm no longer slows down to protect a payload margin.
No human hand touches the sealed package between the filler and the shipping case.
At 1.2 kg the tool leaves the arm with capacity in reserve for heavier products later.
Frequently asked questions
Can a 3D printed gripper be used in a food packaging environment?
Yes, when the material and the finish are chosen for it. This tool is printed in Nylon PA12 and vapour polished, which seals the surface porosity that raw sintered nylon has. The suction cups that make direct contact with the package are food-grade components. For washdown or direct unpackaged food contact we review the specific requirement before specifying materials.
How much lighter is a printed gripper than a machined one?
Weight reductions of 40 to 60 percent against a machined aluminium equivalent are typical, because topography optimization removes material that a subtractive process would have to leave behind. This tool is 1.2 kg.
Will suction cups damage a sealed film lid?
Not when the cup and the vacuum level are matched to the film. Cup diameter, bellows profile, and applied vacuum are all selected against the specific package. Over specifying vacuum is the usual cause of deformed lids, and it is avoidable.
Can this gripper be adapted to a different tub size?
Yes. Because the tool is printed rather than tooled, changing the cup pitch or the number of pick positions is a design revision, not a retooling cost.
Which robot arms is it compatible with?
Any industrial robot or collaborative robot. We design the mounting flange to the robot interface, or to a tool changer if the cell runs multiple tools.
Have a similar application?
Send us the part, the payload, and the cycle time. Our engineering team will scope the tool with you and tell you honestly whether additive manufacturing is the right answer for it.