KEVOS® MAKEOS · Pneumatics
Vacuum Gripper Sizing (Cups, Diameter, Holding and Evacuation Time)
Will these suction cups hold the part through the move, what cup size or count would, and how quickly does the system pull down to working vacuum?
Sizing of a vacuum gripper: holding force per cup and in total, the force needed with acceleration, orientation and safety factor (as the vacuum cup tool), the cup diameter needed at the cup count and the cup count needed at the cup diameter, and the time to evacuate the cups and lines to the working vacuum at the pump or ejector flow, against your cycle allowance.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Cup diameter | mm | Effective diameter of each cup. |
| Number of cups | Number of cups. | |
| Working vacuum | kPa | Vacuum below atmospheric that the system holds. |
| Part mass | kg | Mass of the part. |
| Acceleration of the move | m/s² | Largest acceleration during the move. |
| Cup orientation | choice | Whether the cups face down (lifting) or sideways (holding by friction). |
| Friction coefficient (cup to part) | Friction between cup and part for vertical cups. | |
| Safety factor | Safety factor you require (often 2 horizontal, 4 vertical). | |
| Volume of cups and lines | L | Internal volume of the cups, hoses and manifold to evacuate. |
| Vacuum generator suction flow | L/min | Suction flow of the pump or ejector at free air. |
| Evacuation time allowed | s | Time you allow to reach working vacuum. |
Method and formulas
- Force per cup = vacuum × π D² ÷ 4; force needed = m (g + a) × SF, divided by μ for vertical cups (as the vacuum cup tool).
- Cup diameter needed = √[4 F ÷ (π × vacuum × n)]; cups needed = F ÷ force per cup (rounded up).
- Evacuation time ≈ V ÷ Q × ln[p_atm ÷ (p_atm − vacuum)].
- Example: 4 cups of 40 mm hold 301.59 N against 148.07 N; the system pulls down in 0.26906 s.
Limitations
- Flat, sealed surfaces; porous or curved parts leak and need larger flow.
- Ideal pump-down at constant flow; real generators lose flow as vacuum rises.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Design a gripper for sheet, cartons or panels
- Check a gripper for faster robot moves
- Size the vacuum generator for the cycle time
Who it is for
- Automation engineers
- Machine designers
- Robotics engineers
What you get
- Holding force and force needed
- Cup diameter and count needed
- Evacuation time
Interpreting the result
- Vertical cups need about twice the holding force of horizontal ones for the same part.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3032–3041. Topic reference; no source tables or recommended settings are reproduced.
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Open the Vacuum Gripper Sizing (Cups, Diameter, Holding and Evacuation Time) calculator
