What is a cobot?

Picture two people at a market stall. One folds shirts and the other slides them into bags, and they share one table. Neither needs a cage around them, because each can see the other, and both slow their hands when they reach for the same shirt.

Now swap one of them for a machine, and that machine is a cobot. The word is short for collaborative robot, and it means a robot arm designed to work beside a person rather than behind a fence.

An ordinary factory arm cannot do this, because it swings fast and heavy, and it has no idea you walked in. However, a cobot is built the other way round. It moves gently, it feels contact, and it stops.

What makes a robot collaborative

Four design choices do most of the work.

• Limited force. The motors are sized so the arm cannot hit hard, and the joints sense resistance and give way.
• Gentle speed. It runs at a walking pace when a person is near.
• A smooth body. Rounded edges and covered joints, so nothing pinches a finger or catches a sleeve.
• Easy teaching. You take the arm by the wrist, move it where you want, and press save.

That last one changed who can use a robot. Older arms needed a trained programmer and a keyboard. However, a cobot can be taught a simple pick and place job in an afternoon, by the person who already does that job.

The four ways a robot may share your space

International safety standards set out four ways, and any real installation uses one or a mix of them.

1. Monitored stop. The arm halts while you are inside its area, and carries on when you leave.
2. Hand guiding. You move the arm yourself, using a handle with a switch, and it does nothing on its own.
3. Speed and separation. Sensors watch the gap, and the arm slows as you come closer and stops when you are close.
4. Power and force limiting. Contact is allowed, and the force it may apply is capped low enough to avoid injury.

The fourth mode is the one people mean when they picture a cobot. A technical specification known as ISO/TS 15066 goes into detail here. It sets limits on how hard a robot may press on different parts of the body. Those limits are why a cobot feels slow. Speed and force are the same problem wearing two hats.

Why the robot alone is not safe

This is the part that gets skipped, and it is the part that matters. THE JOB IS SAFE, NOT THE ROBOT.

Ask what the arm is holding. A soft rubber gripper on a light box is one thing. A knife, a hot glue gun, a spinning drill or a sheet of glass with sharp edges is quite another. The arm may be gentle and the tool is not.

Ask what else is in the space. Perhaps a part sticks out at eye height, or perhaps a hand can be pressed against a table edge. Speed limits do not help if a person can be trapped between the arm and a wall.

Therefore, the law and the standards ask for a risk assessment of the whole job, not just the machine. Buying a cobot does not remove the fence by itself, but it makes a fence unnecessary in many jobs, once somebody has checked the job.

What a cobot is good at

Feeding machines is the most common use anywhere. A cobot loads a blank into a machine, waits, takes the finished part out, and starts again. That job is dull for a person and simple for an arm.

Packing and palletising come next. So does putting in screws, applying glue in a line, testing buttons on a device, and moving samples around a laboratory bench.

Small workshops gain the most. A cobot suits short runs and frequent changes, since it can be retaught in an hour and moved to another bench on a trolley. Fenced arms are cheaper for each part when the run is very long, but they are also slow to change and costly to install.

There is a quieter gain as well. A cobot can hold a part steady at the right height while a skilled worker does the fiddly bit. The person keeps the judgement and the machine takes the strain.

What a cobot is bad at

Speed is the first limit. A caged arm can move much faster. Therefore, it wins where cycle time decides the price of each part.

Weight is the second, and most cobots carry a few kilograms. Remember to count the gripper, because it eats part of the load. A heavy gripper on a light arm leaves nothing for the part.

Reach is the third. These arms are usually sized for a bench, so a large pallet may need a lift or a rail.

The last limit is the one people find hardest to accept. A cobot is an arm, and it has no legs, no map and no plan of its own. Put one on a wheeled base and it must also work out where it is, which is the job described in SLAM.

How to tell a cobot from other robots

Question	Cobot	Industrial arm	Humanoid
Where does it work?	Beside a person	Inside a fence	In human spaces
How fast is it?	Walking pace	Very fast	Slow
What does it carry?	A light load	A heavy load	A light load
Who sets it up?	The operator	A programmer	A specialist team
How mature is it?	Sold and working	Sold for decades	Mostly early

A humanoid robot is a different bet altogether, because it aims to move around the whole building. A cobot stays at one bench and earns its keep there today. Both belong to the wider field of robotics, and they solve different problems.

What to check before you buy one

Work through six questions with the supplier, and write the answers down.

• How heavy is the part, with the gripper included?
• How many seconds may one cycle take?
• Is the tool sharp, hot or spinning?
• Can a person be trapped between the arm and anything solid?
• Who does the risk assessment, and when?
• Who reteaches it when the product changes?

Then run a trial for a week on the real line, with the real parts, including the dented and dirty ones. Count how often a person has to step in. Some jobs also need the arm to feel its way into a tight fitting. That skill is often trained with reinforcement learning rather than written by hand. Ask whether your job is one of those, because the answer changes the price.

Just Out Tech explains new research in plain language. This article was drafted with AI assistance and checked by a human against the original source.