Multi-Axis Sensor Assembly

The multi-Axis sensor consists of a hexapod truss structure arranged between two plates without additional joints. The sensor is (usually) manufactured from a single piece of high-strength aluminum (3.1354) or high-strength ferritic stainless steel (1.4542).

For the sensor to function correctly, it is crucial that the end faces are not locally deformed.

A local deformation is caused, for example, if a point force Fz were applied at the center of the sensor.

The force is applied across the entire surface of the circular ring between the inner centering collar and the outer diameter. The force is also applied to the trapezoidal segments of the circular ring. The recesses between the segments are not subjected to any load.

Besides the force transmission on the circular ring, the flatness and stiffness of the connecting flange are important parameters. High-strength aluminum or tempered tool steel 24CrMo4 or C60, or high-strength stainless steel 1.4542, should be used as the material. 3D-printed plastic flanges are unsuitable!

A loose screw can cause measurement errors on the order of 10% or more.

The tolerance for the flatness of the flanges is 0.02mm.

Table 1 provides guidelines for the thickness of the connection flanges and the recommended tightening torque. If the recommended tightening torque exceeds the sensor’s rated torque, no torque should be applied through the sensor. Instead, the counter-torque should be applied directly to the flange.

The screws should have a minimum strength class of 8.8. Screws with a strength class of 10.9 are recommended for torques above 100 Nm.

Symmetry of the Flange

When designing the flange, care should be taken to ensure that local weak points do not cause asymmetrical deformation of the surface of the force sensor.

Isolated outbreaks, such as those shown in the adjacent figure, should be avoided.

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Flange Assembly

Mounting all components from one side is often only possible by designing a two-part flange.

Example for 6A110:

Adapter for Comau SMART-5 NJ-60:

Flange for K6D80:

Force/Moment Introduction

When applying forces and moments, care must be taken to ensure that the flange plates of the 6A sensor are not deformed. In particular, when applying moments, the application should be central and symmetrical.

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Flatness of the Flange Plate

The image shows a local deformation of the flange plate due to an asymmetrical introduction of a moment.

Symmetrical Introduction

The figure shows a flange for the (largely) symmetrical introduction of moments for the 6A225 sensor.

Rules for the Installation of 6A Sensors

  • High rigidity of the flange plate,
  • Good symmetry in the load/force transmission via the flange plate,
  • Minimal deformation within the sensor mounting surface <<10µm,
  • If these points cannot be achieved, then calibration of the sensor with the accessories is recommended.
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Centering

  • The multi-axis force sensors feature a centering collar (inner diameter with 0…+0.1mm oversize, 1…3mm depth).
  • Additionally, two pin bores with clearance fit E7/m6 are provided.
  • To ensure the angular position is correct, one of the following options is recommended (depending on manufacturing tolerances):
  • Use of the centering collar to secure the centering plus 1 centering pin to secure the angular position in a slotted hole
  • Use of 2 centering pins: in a bore E7 to ensure centering, and in a slotted hole to ensure angular position
  • Use of 2 centering pins in two bores E7 to ensure centering and angular position (“double fit”)
  • Use of the centering collar and use of 2 centering pins in two E7 bores (“triple fit”)
  • If double or triple fits are used, it is recommended to use DIN 7979 centering pins with internal threads if they are to be disassembled.

Materials

  • Where possible, the flange should be made of the same material as the sensor: aluminum sensors with an aluminum flange (approx. 23 µm/m/°C), steel sensors with a steel flange (approx. 12 µm/m/°C). Otherwise, the temperature-related drift of the sensor can be negatively affected by the introduction of temperature-induced stresses.

Installation Position

  • The sensors can be mounted in any orientation. As with any force sensor, care must be taken to ensure that the connecting cable is attached to the fixed surface (the stationary flange). Otherwise, forces will be transmitted to the sensor via the connecting cable.

Flange Plates and Tightening Torques

The table provides guidelines for the material thickness of the flange plates and for the tightening torques for mounting the sensors.

  • Sensor
  • 6ADF45
  • 6A27
  • 6A40
  • 6A40
  • 6A55ri
  • 6A55ri
  • 6A68
  • 6A68
  • 6A80
  • 6A80
  • 6A110
  • 6A110
  • 6A130
  • 6A130
  • 6A150
  • 6A154
  • 6A154
  • 6A175
  • 6A225
  • Variant
  • 20N/1Nm
  • 50N/1Nm
  • 50N/5Nm-100N/5Nm
  • 200N/5Nm-500N/20Nm
  • 50N/5Nm-100N/10Nm
  • 200N/20Nm-1kN/40Nm
  • 1kN/20Nm-2kN/50Nm
  • 5kN/50Nm-10kN/500Nm
  • 200N/20Nm-1kN/50Nm
  • 2kN/100Nm-5kN/250Nm
  • 1kN/100Nm-8kN/500Nm
  • 10kN/750Nm
  • 1kN/200Nm-5kN/500Nm
  • 15kN/1.2kNm
  • 2kN/200Nm-10kN/1kNm
  • 50N/5Nm-100N/10Nm
  • 200N/20Nm-500N/50Nm
  • 10kN/1kNm-50kN/5kNm
  • 50kN/10kNm-200kN/5kNm
  • Material Thickness(mm)
  • (3.0)
  • (3.0)
  • (5.0)
  • (6.0)
  • (5.0)
  • (8.0)
  • (10.0)
  • (12.0)
  • (8.0)
  • (10.0)
  • (14.0)
  • (14.0)
  • (16.0)
  • (18.0)
  • (20.0)
  • (10.0)
  • (10.0)
  • (28.0)
  • (40.0)
  • Thread
  • M3
  • M2
  • M5
  • M5
  • M5
  • M5
  • M10
  • M10
  • M8
  • M8
  • M10
  • M10
  • M12
  • M12
  • M12
  • M6
  • M6
  • M16
  • M20
  • Tightening Torque(Nm)
  • (1.3)
  • (0.4)
  • (6)
  • (6)
  • (6)
  • (6)
  • (40)
  • (60)
  • (20)
  • (30)
  • (50)
  • (70)
  • (80)
  • (120)
  • (100)
  • (10)
  • (14)
  • (250)
  • (500)
  • Screw-In Depth(mm)
  • (5)
  • (4)
  • (6)
  • (6)
  • (6)
  • (6)
  • (12)
  • (12)
  • (9)
  • (9)
  • (10)
  • (10)
  • (14)
  • (14)
  • (14)
  • (8)
  • (8)
  • (24)
  • (23)