Hand-held Gap&Flush measurement system

The first project of the U-SENSE.IT team consists in the development of a portable device for the measurement of Gap & Flush, designed to perform in-line quality control in the following sectors:

  • automotive
  • house hold appliance
  • aeronautics
  • railways
  • furniture

The first version of the device G3F v1.0 was developed within the framework of the European Project GO0DMAN and has be patented (patent number 102018000003247, filed on 2nd March 2018).

For more information on G3F v1.0 download this paper.

STAY TUNED: a new G3F v2.0 soon to come !!

What the prototype G3F measures

Gap is the measure of the distance between two adjacent panels and Flush is the measure of the step existing between the two panels. 

gap & flush definition

The G3F device

G3F is the instrument developed to measure both the Gap and Flush through an optical measurement method, laser triangulation, and image processing algorithms based on Deep Learning technologies and data collected by other sensors.

Hand-held Gap&Flush measurement system

The key to automate in a reliable way the gap and flush measurement is 3D sensing. The use of a triangulation sensor, through the analysis of the profile of a laser line projected on the target surfaces, provides detailed contours of the interface between adjacent panels, allowing accurate measurement of both the gap and the flush in a single image. Using a proprietary algorithm, the acquired image is processed and the gap and flush values ​​are extracted.

The calibrated device has all the optical components (laser, optics, video camera, electronics, etc.) rigidly mounted inside a compact and lightweight case connected to a mobile phone, in order to reduce the overall dimensions to a minimum. 


  • Allows measurement on different types of surfaces;
  • Security and portability: the solution integrates various safety measures for the operator, turning the laser on and off according to the distance of the measuring instrument with the part to be measured and enabling the measurement only after recognizing the operator;
  • Recognition of individual measurement points, highlighting compliance / not compliance for each measured point;
  • Recognition of the part to be measured;
  • Possibility to operate in contact or at a distance.
  • Automatic storage of collected data;

These features make the instrument usable in different conditions, without the need for set-up operations by specialized personnel.
The device is therefore particularly suitable for the production environment.


  • Easy to use
  • Portability with minimum dimensions
  • Possibility to perform the measurement with or without contact of the surfaces.
  • Possibility to perform the measurement on different types of surfaces (metal, plastics, glasses, ..) having different colours.
  • Uncertainity on gap < 0,15 mm @ 95% confidence level
  • Measurement time: less than 1 s
  • Data transfer via Wi-Fi or Bluetooth


The Gap and Flush measurement  in the automotive sector concerns the control of the assembly operations of the vehicle body and it is a control common to all components (panels, doors, optical groups, aesthetic parts, etc.) and to all production plants. 

Hand-held Gap&Flush measurement system

The G3F instrument has been designed to be used by the operators at the end of the line, where one or more operators must check the correct alignment of the parts in different points of the bodywork. 

In addition to the aesthetic requirements, the non-conformity of these quantities can lead to excessive aerodynamic noise and leakage (water and air infiltrations), with consequent repair and warranty costs.

Traditionally, the Gap and Flush measurements are performed manually with various types of mechanical probes used by operators; in particular, thickness gauges are used for the gap and comparators for the flush.
Typically 50 or more points are checked on each vehicle produced.
Manual measurement has a labor cost and is prone to measurement errors if mechanical probes are not oriented or applied correctly.

To respond to these needs and, in particular, to the need to digitize this control at the end of the production line, the G3F device was developed.

The device is conneted to the server through Wi-Fi or Bluetooth and each measurement is saved in the DataBase. Each device can be programmed in order to check a predefined set of check points using a WEB Portal.