Proxima is the result of the development of a of precision, fully automated system for monitoring each phase of the banknote production process. These systems will assess the printing quality of banknotes at each production step in real time. The extremely high resolution and precision of the inspection and measurement tools will detect and identify not only defects, but also drifts or trends away from the specification during the printing process, before they reach the stage that could generate spoilage at final sorting.
Along the printing process priority is given to very high resolution measurements, versus 100% on line inspection, which instead becomes important towards the end of the production line, at finishing.
By means of Statistical Process Control methodology the systems will analyse the assembled data and will extract meaningful information for the operator, to enable him to retain control and monitor the particular process for maximum effectiveness. Within the system are integrated automatic calibrations and reference targets, usable at any time and in a fully automatic way, to guarantee the precision, accuracy, repeatability and reliability of the measurements.
Detailed reports will certify the quality of each inspected sheet and also entire production batches.

 

System structure

PROXIMA is based on advanced HW and SW technologies integrated into a reliable and robust system. The main system features are:

 

1. Gearless paper transport based on direct drive motors on each cylinder
2. Air grippers used to hold a sheet and to transfer it from one cylinder to the other
3. Single camera system for maximum precision and repeatability
4. Highly reflective "flat" mirrors creating optimum optical viewing conditions in confined spaces
5. Integrated and always available calibration and reference targets

 

How the system works

• A series of sheets is withdraw from a printing press and placed on the input plate
• Single sheets are then automatically fed into the system from the input plate, to initiate the inspection process.
• During the first revolution of the main cylinder the image on the front of the sheet is acquired.
• The IR illuminator is then initiated and a second pass is performed to acquire the transparent image.
• The sheet is then transferred to the front/back rotator before being represented again to the main cylinder.
• The main cylinder rotation is reversed and the back side of the sheet is viewed by the camera to acquire the verso image.
• Finally, the sheet is released from the main cylinder and deposited into the output pile via the front/back rotator.
• All these operations are performed in 90 seconds.
• The system can be recalibrated at any time by cross-referencing the calibration targets located on the main cylinder. This operation can be automatically initiated before the system measurements are conducted.
• A moving rail may be optionally used to carry and position special sensors (e.g. a high resolution array camera)
• The combination of the main cylinder rotation with the linear motion of this rail provides a mechanism to measure any point on the front or back of the sheet.
• When all the required measurements have been taken, the system automatically updates the manual display for the operator as well as the production database and graphical display.

 

System characteristics

Paper transport

 

• Both manually controlled and automatic single sheet feeding available
• Automatic back/front and transparency sheet examination
• Extremely accurate transport systems, suitable for high-resolution image capture
• User friendly feeder and delivery system
• Sheet tracking via bar code reading

Image acquisition

• Front, back and transparency images acquired with a single camera system
• High resolution (85 micron/pixel) colour line scan camera
• Full colour RGB reflective images
• Near IR transparency images
• High quality optics for optimal geometry and colour analysis
• Ultra high-resolution array camera (8-4 micron/pixel) for detailed analysis

Light source

• Homogeneous and consistent light source
• Visible and near IR illumination
• Light spectrum suitable for colour analysis
• Long life lamps

Processing

• 600 Mb of data per sheet
• 90 seconds per sheet
• Powerful, off the shelf multiprocessor system

Operation

• User-friendly graphical Interface
• Easy system set up and training
• SPC reporting for timely detection of process deviations
• Report generation by batch to certify quality measurements

Calibration

• Automatic and online system check and calibrations
• Geometric calibrations
• Light and color calibration
• Certified calibration targets
• High accuracy measurements guaranteed for every sampled sheet

Reference targets are integrated on the system main cylinder and are available at any time for performing functional checks and calibrations. For achieving the highest reliability and efficiency their positioning in front of the camera is performed in a fully way.
Room has been foreseen for installation of reference targets concerning other special sensors.

The use of certified calibration targets and the level of automation built in the system guarantee that taken measurements are accurate and effectively usable for process appraisal.

 

Inspection Capabilities

The front, back and transparency of sample sheets is inspected to provide the following measurements:

 

Offset printing quality

• Plate to plate register
• Front to back register
• Colour and density
• Perceptive colour analysis
• Perceptive integrity analysis
• Fine line and micro-printings check
• Machine Readable Features control

Substrate

• Colour and density measures
• Opacity check
• Integrity check
• Substrate security features to offset print register

Substrate security features

• Watermarks
• Security threads 1D and 2D
• OVD stripes
• Iridescent features

 

Detection of process deviations

PROXIMA evaluates sampled sheets and analyses the collected data to create reports and alerts the operator to any necessary intervention
This is achieved by means of a process defined as "measures aggregation".
Measurements are combined in line with criteria that can prompt the operator to adjust the critical element of the printing press.

 

Typical aggregation criteria are related to space, time and press multiplicities, e.g.:

• Defects occurring every three sheets may be associated to blankets
• Defects occurring on every sheet may be due to printing plates
• Vertical inking variation on banknotes may be associated to inking fountains adjustments.
• Horizontal inking variation may be due to mechanical problems with inking cylinders.

 

Operator Communication

A synoptic screen is used as an operator interface to provide continual system updates and to promptly indicate any potential process variations.

 

Indicated process or raw materials variations may include:

Substrate

• Dimensional stability (squareness, tears, folds)
• Positions of all features (watermarks, threads, stripes)
• Integrity of substrate features and colour

Plate to plate register

• Front/back register
• Plate damage or wear
• Debris or contamination

Blankets

• Damaged blankets
• Contamination

Inks and inking fountains

• Colour variation
• Over/under inking
• Inking fountains (horizontal inking variations)
• Printing cylinders (vertical variation)

 

System technical specifications