5-Axis Load Cells 101

A 5-axis load cell is a multi-axis sensor designed to resolve complex multi-directional loading into three orthogonal forces and two bending moments. By combining multiple sensing elements into one precisely machined structure, a 5-axis load cell provides comprehensive measurement of complex loading conditions that conventional single-axis load cells cannot accurately capture.

Interface 5-Axis Multi-Axis Sensors are designed for testing and measurement analysis in robotics, aerospace, automotive testing, biomechanics, material testing, and industrial research where multiple forces and moments act on a structure simultaneously.

The sensor is machined from a single monolithic spring element, typically using high-strength alloy steel, stainless steel, or aluminum. Machining the entire sensing body from a single structure eliminates mechanical hysteresis, joint shifting, friction interfaces, and thermal expansion discrepancies that occur when joining multiple single-axis sensors into a single test apparatus.

The structure incorporates internal flexures engineered using finite element analysis to isolate directional deflections. The flexures deform elastically under specific force and moment vectors while maintaining high overall structural rigidity. Strain gages are bonded to the flexure surfaces and wired into five independent Wheatstone bridge circuits.

The five measurement channels correspond directly to the Cartesian coordinate system:

1. Fx bridge detects orthogonal shear strain parallel to the X-axis.
2. Fy bridge detects orthogonal shear strain parallel to the Y-axis.
3. Fz bridge monitors tensile or compressive strain along the primary vertical Z-axis.
4. Mx bridge is wired across opposing flexure elements to isolate differential strain resulting from bending moments applied about the X-axis.
5. My bridge operates on the perpendicular plane to measure bending moments applied about the Y-axis.

When an external load acts on the transducer, the engineered flexures undergo microscopic elastic deformation within their proportional limits. This deformation alters the electrical resistance of the bonded strain gages, unbalancing the Wheatstone bridges and producing differential millivolt-per-volt output signals proportional to each applied component.

Because complex multi-axial loads generate distributed stress fields across a continuous metal body, mechanical flexure isolation cannot eliminate secondary strain on adjacent channels. This parasitic response is known as crosstalk. To resolve this, multi-axis measurement combines mechanical geometry optimization with a factory-calibrated mathematical decoupling matrix to cancel cross-axis sensitivity and deliver independent channel data.

TIP: Refer to our Multi-Axis Fundamentals Guide for technical information about this type of measurement device.

5-Axis Mechanical Design

Unlike a standard single-axis load cell, a 5-axis load cell features a sophisticated flexure design that isolates deformation for each measurement axis while maintaining structural rigidity. The Interface 5AR70 5-Axis Force/Torque Load Cells and 5AR110 5-Axis Force/Torque Load Cells construction includes:

• One-piece monolithic sensing element
• Multiple precision-machined flexure beams
• Independent strain gage bridge circuits
• Temperature compensation
• Environmental sealing
• Shielded multi-conductor cable or connector
• Precision mounting surfaces to maintain calibration integrity

Unlike a 6-axis load cell, a 5-axis sensor does not measure the torsional moment about the Z-axis (Mz). This makes it ideal for applications where rotational torque around the primary axis is negligible or not required.

Installation and Signal Processing Criteria

Achieving specified sensor accuracy requires precise mechanical mounting and synchronous signal conditioning.

Mounting surfaces on the host structure must be precision-ground, rigid, and clean. Surface flatness deviations exceeding 0.012 mm introduce mechanical pre-stresses in the sensor body when you secure the mounting hardware. This uneven clamping force causes zero-balance offsets, increases nonlinearity, and degrades channel decoupling. Use high-strength, calibrated bolts and tighten them incrementally in a cross pattern to the specified torque values.

Mechanical alignment relative to the coordinate system is critical. Angular misalignment during installation introduces mathematical transformation errors, causing true Fx loads to register partially on the Fy channel and true Mx moments to register on My. Use machined pilot registers, dowel pin holes, or keyways to align the sensor coordinate axes with the machine datum.

Instrumentation must provide simultaneous, synchronized analog-to-digital conversion across all five bridge channels to capture transient events without phase distortion. High-precision data acquisition software uses a 5×5 calibration matrix, multiplying the five raw voltage outputs by the sensor calibration coefficients to output decoupled engineering units for each force and moment channel in real time. Check out the 5-Axis Load Cell in our 5AR-BX6-ETH/CAN Complete System.

Typical Applications for 5-Axis Load Cells

Because mechanical systems rarely encounter loads along a single axis, 5-axis load cells are used where multi-directional forces and off-center bending moments occur simultaneously. At the same time, axial torsion is constrained or unnecessary. Common use cases include:

• Robotic End-of-Arm Tooling: Measuring contact forces and tool-offset tipping moments during automated grinding, deburring, polishing, and heavy part transfer.
• Aerospace Structural and Aerodynamic Testing: Capturing lift, drag, side loads, and pitch-roll moments on scale models in wind tunnels and during control-surface fatigue testing.
• Automotive Suspension and Chassis Development: Monitoring multi-axis spindle and subframe reaction loads, steering linkage inputs, and component durability during road-load simulations.
• Biomechanics and Orthopedic Research: Evaluating kinematics, wear patterns, and multi-directional joint forces in hip, knee, and spinal implant simulators.
• Prosthetics Evaluation: Measuring ground reaction shear, vertical compression, and resulting socket bending stresses during dynamic gait testing.
• Material and Structural Testing Systems: Subjecting anisotropic materials, structural composites, and mechanical fasteners to combined tension, shear, and off-axis bending loads.
• Industrial Automation and Assembly: Monitoring insertion forces, press-fit alignment, and side-loading moments in high-precision automated assembly machines.
• Machine Tool and Process Monitoring: Tracking tool-deflection forces and tilting moments in multi-axis milling, friction-stir welding, and metal forming operations.
• Friction, Wear, and Tribology Test Rigs: Measuring normal loads, dual-axis friction forces, and specimen tilt to maintain alignment and verify friction coefficients.
• Research and Academic Test Laboratories: Providing synchronized multi-axis load data for advanced structural dynamics, kinematics research, and mechanical validation test stands.

Multi-Axis Architecture Comparison

Selecting the correct multi-component sensor depends on the active degrees of freedom and the mechanical constraints of the test setup:

• A 3-axis load cell measures only the orthogonal forces Fx, Fy, and Fz. Use it when applied loads act directly through the sensor’s geometric center, or when external structural bearings fully react to any extraneous tipping moments. Reference: 3-Axis Load Cells 101
• A 5-axis load cell measures Fx, Fy, Fz, Mx, and My. Select it when multi-directional loads act at a distance from the sensor surface, generating significant tipping moments. At the same time, torsional rotation about the primary Z-axis is mechanically constrained, eliminated by free-rotating bearings, or negligible.
• A 6-axis load cell measures all six spatial degrees of freedom: Fx, Fy, Fz, Mx, My, and Mz. This design is needed when you must record pure torsion about the axial centerline, along with forces and bending moments, in fully unconstrained kinematic systems. Reference 6-Axis Load Cells 101

Use the Interface Multi-Axis Sensor Selection Guide to find the right load cell for your specific requirements.

A 5-axis load cell provides significant performance and integration advantages over assemblies constructed from multiple individual sensors. By measuring five independent loading components simultaneously from a shared reference origin, the single-body design delivers synchronized force and moment data while eliminating the mechanical alignment errors inherent in multi-sensor fixtures.

Additionally, the compact, space-saving footprint simplifies mechanical installation, reduces cable management to a single interface, and streamlines calibration procedures without compromising overall measurement accuracy.