- Vision systems
The performance of part and component traceability solutions are determined by the quality of the OCR characters or Datamatrix code, but also by the quality of the vision system and associated real-time communications. The aim of these vision systems consist of enhancing the readability of the mark allowing the part recognition. These systems are comprised of lighting apparatus and camera systems.
VIN Marking and vision equipment
VIN marking is a packag consisting of:
- A scribing machine e8 i 113s
- A PC, a vision decoder, the SIC VIN software
- A “standard” camera
The principle to validate that the VIN has correctly been engraved by:
- Validating that there is loss of pitch on the i113s.
- Checking if number of “high position” stylus is detected
- Validating placement of the last character read (generally the logo) with camera
Premium VIN marking with OCR ( Optical Character Recognition)
The premium VIN system is based on the same mechanics as the previous one. Main differences are in the vision system. This high-end vision equipment requires OCR technology.
To optimize reading of Datamatrix codes, four main image treatment functions are used:
- DILATE: this method increases the size of cleared cells (used for a white code on black background)
- ERODE: this function increases the size of dark cells (used for a black code on white background)
- OPEN: cancel the white numerical noise on the dark cells
- CLOSE: cancel the black numerical noise on clear cells
- Lighting systems
ISO 15415 recommends four light sources for a vision system, arranged in a concentric circle to the inspection area.The height of lighting system should be adapted in a way that centers beam on the code. The optimal angle is 45° between the light and the code surface, but it could differ from 30° to 90° in specific applications.
- DOAL (Diffused On-Axis Light): The rays of light are transmitted through a diffuser, reflected on a two-way mirror, then shined directly on the part. The camera is often adjusted at right angles to the light source
- Dark-field illumination or horizontal light: This lighting system is used for irregular surfaces, as impurities reflect light toward the camera (fixed vertically). LEDs are mounted in a circular ring form.
- Back light: This lighting apparatus is placed under the part you want to observe. It reveals either a part outline, or a mark for a translucent part.
- Dome light or Continuous Diffused Illumination: This type of lighting is used for mirror surfaces. Most cylindrical or spherical parts require this type of light equipment.
- Here is a short list of common lighting systems
Dot peen marking custom adjustments
- “Bright field” or direct lighting: It could fit with the use of 120° stylus, mainly on finished or smooth parts but not on a 90° stylus (mainly rough parts) where the contrast will be too weak.
- “Dark-field” or indirect lighting: the use of leaning lighting requires image processing to enhance the complete image of the Datamatrix cells. The external lighting gives images of clear cells on dark background. It is used when:
.Using a 90° stylus (rough or raw part), we suggest inclination of lighting apparatus in order to obtain reflected light by the half surface of dots.
.Using a 120° stylus, we suggest an inclination of lighting apparatus and reading system of 30°.
The function of cameras is only reading codes (Datamatrix particularly), even if they are more and more equipped with communication features.
OCR means Optical Character Recognition. The process is to read basic text marked on a part, and change it as a machine-encoded content. Our team program the reading equipment to help recognize one or several characters. These intelligent systems can read easily specific fonts OCR -A and OCR-B that are included in all our marking equipment.
Main application in automotive is VIN marking, VIN for Vehicle Identification Number.
Datamatrix codes can be detected thanks to a camera (flash + photo) and a software able to read and decode the data. Datamatrix codes need to be marked with high-end machines, and SIC Marking is renown as a world leader in this activity.