Gantry, Cantilever or Moving-Arm? How to Choose a Multi-Axis System
A multi-axis linear system (often called a Cartesian robot) combines two or three linear modules into an XY or XYZ unit. The individual axes matter, but the structure that connects them decides stiffness, working area, accessibility and cost. This guide compares the three common structures – gantry, cantilever and moving-arm – and explains how to choose.
Short answer
- Gantry: the Y axis is supported at both ends by two parallel X axes. Choose it for large working areas, long strokes, heavier loads and the highest stiffness.
- Cantilever: the Y axis is carried by one X axis and overhangs on one side. Choose it for compact cells, open access from three sides and moderate loads.
- Moving-arm: the arm itself extends and retracts across the base axis, and the vertical axis moves as a column. Choose it when the tool has to reach into a machine or fixture from one side while the base stays outside.
Gantry systems
Because the cross beam rests on two base axes, deflection and vibration stay low even with long Y strokes and heavy tooling. Gantries are the standard choice for dispensing, palletising, large-format handling and loading of machine tools.
- Ball screw gantry – e.g. MX-GT3-BS-01: X travel 100–1250 mm, ±0.01 mm repeatability on all axes, up to 1000 mm/s.
- Long-stroke hybrid gantry – e.g. MX-GT3-HB-02: belt-driven base axis with 600–3050 mm travel and 2000 mm/s, combined with ball screw Y and Z axes.
- Dual-X synchronous gantry – e.g. MX-DX2-HB-01: both X axes are driven synchronously, which keeps the beam square at high acceleration.
Points to plan: the footprint is larger, both X axes must be aligned on a flat, parallel base, and with two X motors the drives must be synchronised (electronic gantry function or a mechanical connecting shaft).
Cantilever systems
A cantilever system needs only one base axis, so it is more compact and usually more economical. The working area stays open on three sides, which simplifies manual loading, conveyor integration and maintenance.
- MX-CT3-BS-01: X 100–1250 mm, Y 100–650 mm, Z 100–500 mm, ±0.01 mm repeatability, payload up to 12 kg.
- MX-CT3-IB-01: integrated-guide modules for very compact XYZ units, 50–1100 mm travel, 500 mm/s.
The limit is the overhang: the further the Y axis extends and the heavier the load at its end, the higher the bending moment on the base axis and the larger the deflection at the tool. For long Y strokes or heavy grippers, a gantry is usually the safer choice.
Moving-arm systems
In a moving-arm system the arm module moves as a whole: it extends across the base axis like a telescope, and the Z axis is built as a moving column. The tool can reach into a press, a test fixture or a machine opening while the base and most of the structure stay outside. Example: MX-MA3-BS-01 with ball screw axes on X, Y and Z and ±0.01 mm repeatability.
The reach costs payload: on the MX-MA3-BS-01 the allowable payload falls from 8 kg at 100 mm Y travel to 2 kg at 500 mm. Moving-arm designs therefore suit light tools and moderate speeds; always size them with the payload table for the selected travel.
Comparison
| Gantry | Cantilever | Moving-arm | |
|---|---|---|---|
| Stiffness | Highest | Medium, depends on overhang | Medium, depends on reach |
| Working area | Large, long strokes | Small to medium | Small to medium |
| Access to work area | From the ends | From three sides | Tool reaches in from one side |
| Footprint | Largest | Compact | Compact, base outside the work area |
| Typical tasks | Dispensing, palletising, machine loading, large-format handling | Pick-and-place, testing, screwdriving, compact assembly cells | Loading presses, test fixtures and machines |
Selection checklist
- Working area – required X, Y and Z strokes, plus safety travel at the ends.
- Load and its position – mass of gripper, tool and part, and the distance from the axis (this creates the moment loads that decide between cantilever and gantry).
- Accuracy – ±0.01 mm calls for ball screw axes; for ±0.04 mm a belt-driven base axis can give longer strokes and higher speed.
- Cycle time – travel distances, acceleration and dwell times per cycle.
- Access and integration – where parts enter and leave, where operators and conveyors are, how cables and hoses are routed (energy chains).
- Vertical axis – a ball screw Z axis with motor brake keeps the load safe when power is off.
- Mounting base – a gantry needs two aligned, parallel support surfaces.
For the drive type of each axis, see our guide Ball screw vs. belt drive linear modules.
Frequently asked questions
What is the difference between a Cartesian robot and a gantry robot?
A Cartesian robot is any system of linear axes arranged at right angles (X, Y, Z). A gantry robot is one type of Cartesian robot in which the Y axis is supported on both ends. Cantilever and moving-arm systems are also Cartesian robots.
Can a cantilever system be as accurate as a gantry?
The repeatability of the axes is the same (for example ±0.01 mm with ball screw axes). The difference is deflection under load: with a long overhang or a heavy tool, the position of the tool moves more on a cantilever than on a gantry.
Can the axes be combined freely?
Yes. Many systems use a belt-driven base axis for long, fast travel and ball screw axes for Y and Z where accuracy and holding force matter.
Need a multi-axis system?
Send us the strokes, load, required accuracy, cycle time and a sketch of the cell. We will propose a structure and send a drawing for review. Contact us or see all multi-axis systems.
