Robot Selector

How the envelope is calculated

A robot’s rated payload has to cover everything at the end of the arm, not just the part. The tool adds those masses up, then adds a visible planning margin for what is not known yet.

1. Combined carried mass = part mass × parts per grip + gripper or tool mass + other carried equipment
2. Planning payload = combined carried mass × (1 + planning margin)
3. Required reach = the distance you enter, as a minimum

The planning payload is rounded up, never down. The margin is a planning assumption, not a manufacturer selection rule; 20 % is a reasonable starting point while the gripper is not designed yet.

Manufacturers usually state reach to the wrist centre, not to the tool tip. A long tool needs more arm reach than the distance to the part.

Worked example

A cell loads 18 kg steel blanks into a machining centre. The gripper weighs 8 kg and a part-presence sensor with its bracket adds 2 kg. The farthest drop point is 2,100 mm from the robot base, and the robot stands on the floor.

Combined carried mass

18 + 8 + 2 = 28 kg

Planning margin

20 % of 28 kg = 5.6 kg

Planning payload

33.6 kg

Required reach

≥ 2,100 mm, floor mounted

Result: look at robots rated for at least 33.6 kg at a reach of at least 2,100 mm, then check the part’s centre of gravity against each candidate’s load diagram.

How robots are shortlisted

Each catalogued robot variant is checked against the planning payload, the required reach and, when you choose them, the kind of robot, the mounting and the environment. The rules are deterministic and the same for every manufacturer:

• Nominal match: every requirement passes on the manufacturer’s nominal ratings.
• Conditional match: every requirement passes, but at least one only under a documented condition, such as an extended payload rating or a specific variant. The condition is shown.
• Insufficient data: a requirement you set cannot be confirmed from verified evidence, for example an unverified mounting position. Missing evidence is never treated as a pass.
• Not suitable: at least one requirement fails. The closest robots that fail only on payload or reach are shown separately as near misses.

Reach is compared only where the manufacturer’s measure is comparable, and the manufacturer’s own term is shown (DOBOT publishes a working radius, for example). Matches are ordered by your new-or-refurbished preference, the applications the manufacturer lists, and then the smallest payload and reach oversizing. There is no hidden score, and price never affects the order.

The catalog holds 57 exact robot variants (KUKA 8, FANUC 5, ABB 32, DOBOT 7, Universal Robots 5), each with an official manufacturer source and verification date, last updated 2026-10-07. It is a verified seed, not every robot on the market, and it says nothing about stock or availability.

What this tool does not decide

The envelope tells you which size of robot to look at. Choosing the robot also depends on:

• where the centre of gravity sits relative to the flange, and the wrist moments and inertia that creates;
• acceleration, cycle time and duty cycle;
• the orientation of the part and tool during the move;
• process forces from cutting, pressing, inserting or welding;
• the environment, the mounting and the safety concept of the whole cell;
• the accuracy and performance the application needs;
• the manufacturer’s load diagram for each candidate model.

A shortlisted robot deserves investigation; it is not a confirmed fit. The tool does not check load diagrams, reachable poses, cycle time or safety, says nothing about stock, and never quotes a price.