CMM Bridge/Gantry Machine Structure: Rigid Framework for Precision Measurement

Product Specifications

Technical details and manufacturing context for Machine Structure (Bridge/Gantry)

Definition

The machine structure, specifically in bridge or gantry configurations, is the core mechanical framework of a Coordinate Measuring Machine (CMM). It consists of a rigid, stable assembly of beams, columns, and rails that defines the machine's working envelope. This structure supports and guides the movement of the probe head (or scanning head) along the X, Y, and Z axes with minimal deflection and vibration. Its primary role is to maintain geometric accuracy and repeatability by ensuring that probe movements are linear, orthogonal, and free from structural deformation under load or during acceleration/deceleration. The design directly influences the CMM's accuracy, speed, and capacity to measure large or heavy workpieces. The structure is typically made from materials such as granite, aluminum alloy (e.g., 6061-T6), cast iron, or carbon fiber reinforced polymer for high-speed models. Key parameters include bridge width (500–3000 mm), bridge length (1000–6000 mm), maximum payload (500–5000 kg), positioning accuracy (±0.001–±0.01 mm per ISO 10360-2), repeatability (±0.0005–±0.005 mm per ISO 10360-2), maximum traverse speed (100–500 mm/s), drive system power (0.1–1.0 kW per axis), operating temperature range (15–30 °C per ISO 10360-2), humidity range (40–60% RH), ingress protection (IP54–IP65 per IEC 60529), material grade (HT250–QT500 per GB/T 9439), and machine weight (2000–20000 kg). These values are reference ranges; actual specifications must be confirmed with the manufacturer for a specific model. The structure's rigidity minimizes dynamic errors during motion, ensuring accurate probe positioning. It is designed to operate within specified environmental conditions to maintain measurement integrity. Regular maintenance includes checking for wear on guideways, verifying alignment, and monitoring temperature stability. Failure modes include structural deformation, bearing wear, and loss of calibration. Selection requires considering workpiece size, weight, required accuracy, and environmental conditions. Verification involves testing per ISO 10360-2 and checking material grades and standards. Always consult the legal manufacturer for model-specific values and compliance.

Working Principle

The structure provides a stable, reference coordinate system. Driven by motors (typically servo or linear motors), the bridge or gantry moves along precision guideways (often air bearings or mechanical bearings on granite surfaces). This movement positions the probe assembly accurately within the 3D measurement volume. The rigidity of the structure minimizes dynamic errors (like bending or twisting) during motion, ensuring that the probe's actual position matches the machine's commanded position, which is critical for high-precision metrology.

Common Materials

Granite, Aluminum alloy (e.g., 6061-T6), Cast iron, Carbon fiber reinforced polymer (for high-speed models)

Technical Parameters

Parameter	Typical range	Notes & selection driver
Bridge Width	500–3000 mm	Determines maximum part width that can be measured.
Bridge Length	1000–6000 mm	Determines maximum part length that can be measured.
Maximum Payload	500–5000 kg	Weight of workpiece plus fixture must not exceed this.
Positioning Accuracy	±0.001–±0.01 mm	Overall volumetric accuracy; tighter is better.ISO 10360-2
Repeatability	±0.0005–±0.005 mm	Scatter of repeated measurements at same point.ISO 10360-2
Maximum Traverse Speed	100–500 mm/s	Higher speed improves throughput but may reduce accuracy.
Drive System	0.1–1.0 kW	Motor power per axis; sufficient for smooth motion.
Operating Temperature Range	15–30 °C	Temperature variation affects accuracy; keep stable.ISO 10360-2
Humidity Range	40–60 % RH	Prevents corrosion and electrical issues.
Ingress Protection	IP54–IP65	Protects against dust and water splashes.IEC 60529
Material Grade	HT250–QT500	Cast iron for stability; ductile iron for higher strength.GB/T 9439
Machine Weight	2000–20000 kg	Affects foundation requirements and shipping cost.

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Components / BOM

Bridge Beam (X-axis)
The main horizontal beam that moves along the machine's X-axis guideways, forming the top of the bridge/gantry.

Material: Granite or aluminum alloy
Carriage (Y-axis)
Moves along the bridge beam (Y-axis) and carries the Z-axis column.

Material: Aluminum alloy
Z-axis Ram/Spindle
The vertical column mounted on the carriage that provides vertical (Z-axis) motion for the probe head.

Material: Aluminum alloy or ceramic
Air Bearing Pads/Mechanical Guideways
Provide frictionless or low-friction linear motion for the bridge and carriage along precision rails.

Material: Porous ceramic (air bearings) or hardened steel (mechanical ways)
Granite Table/Base
The ultra-stable, vibration-damping reference surface on which the workpiece is placed and the bridge/gantry moves over. It is the foundation for the entire structure.

Material: Granite (typically black granite)

Industry Taxonomies & Aliases

Commonly used trade names and technical identifiers for Machine Structure (Bridge/Gantry).

Applied To / Applications

This component is essential for the following industrial systems and equipment:

Coordinate Measuring Machine (CMM)

View system integration details

Manufacturers of Machine Structure (Bridge/Gantry)

Manufacturer profiles associated with Machine Structure (Bridge/Gantry).

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Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review · Page last updated 6 September 2026

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Frequently Asked Questions

What materials are commonly used for the machine structure?

Common materials include granite, aluminum alloy (e.g., 6061-T6), cast iron, and carbon fiber reinforced polymer for high-speed models. Each material offers different stiffness, damping, and thermal stability properties.

How does the structure affect measurement accuracy?

The structure's rigidity and stability minimize deflection and vibration during probe movement, ensuring that the probe's actual position matches the commanded position. This directly impacts the CMM's positioning accuracy and repeatability.

What are typical ranges for bridge width and length?

Bridge width typically ranges from 500 to 3000 mm, and bridge length from 1000 to 6000 mm. These dimensions determine the maximum part size that can be measured.

What environmental conditions are required for optimal operation?

The operating temperature range is typically 15–30 °C, and humidity should be maintained at 40–60% RH. Temperature variations can affect accuracy, so stable conditions are essential.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records.

Preliminary Technical Classification

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pressure:	N/A (structural component, not pressure-rated)
other spec:	Maximum permissible error (MPE): ±(2.5 + L/250) μm, where L is measured length in mm
temperature:	15°C to 25°C (operating), 10°C to 30°C (storage)

Machine Structure (Bridge/Gantry)

Product Specifications

Industry Taxonomies & Aliases

Applied To / Applications

Industrial Ecosystem & Supply Chain Structure

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