Flexo Technology
Sleeve inspection systems on flexographic plate mounters
F
lexographic photopolymer plate sleeves in fl exo printing must be in good condition to ensure consistent print quality. Any damage or wear to the sleeves that results in round,
high or low dots aff ects the printing and therefore the quality of the print.
Sleeve scanning systems are being incorporated by manufacturers of printing plate mounters. These sleeve scanning systems are precision scanning systems for checking, recording and tracking the TIR (Total Indicated Runout), or the total indicated runout of the sleeves, and in addition also with laser systems, the surface of the sleeve.
HOW ARE THEY USED AND WHY USE SCANNING SYSTEMS?
Scanning sleeves provide an important control over print quality. A regular scanning programme means that damaged or out-of-specifi cation sleeves do not enter the production process, helping to maximise production effi ciency. The tracking system is a predictive maintenance tool that allows the life of a sleeve to be predicted so it can be replaced before it goes out of specifi cation. In addition, these inspection systems can be used for quality control of the current sleeve supplier, or to evaluate new suppliers.
Sleeve inspection systems can measure to an accuracy of up to +/- 5 microns and can be either contact or laser systems. The inspection criteria are defi ned by the user via the assembler interface, allowing operators to set tolerance limits and the number of measurement points across the width of the sleeve. The operator also enters information such as sleeve identifi cation, width and print repeat into the system.
WHAT ARE THE DIFFERENT TYPES OF SCANNING SYSTEMS AND HOW DO THEY VARY?
The sleeve inspection systems are generally available on semi-automatic and automatic plate mounters, as long as the cameras and mandrel are motorised with an encoder. Dedicated stand-alone scanning systems are also available.
Here we explore the three most common scanning systems:
1. SLEEVE TIR MEASUREMENT - CONTACT SENSOR
A high precision contact sensor measures radial scan points (circumference) at user-defi ned points across the width of the sleeve, typically 5+ but this may
depend on the width of the sleeve. A linear or axial plot is available that indicates in TIR for any band (measurement) across the width of the sleeve. The measurement time of a sleeve is approximately 60 seconds. Used for polymer or aluminium mandrels and sleeves, it is the most common and most economical system. As it uses a contact sensor, it cannot be used with Twinlock sleeves.
2. TIR MEASUREMENT SLEEVES - LASER SENSOR Uses a non-contact triangular displacement laser sensor, with higher repeatability accuracy and also with a linear or axial pattern. The measurement time of a sleeve is approximately 120 seconds. This system can be three times the price of the sensor, as it uses a laser for measurement, but as well as mandrels, polymer and aluminium sleeves, it can also measure Twinlock sleeves.
3. SLEEVE SURFACE SCANNING - LASER This system can scan sleeves in widths from 40mm to 100mm and generates a contour map of the sleeve surface allowing identifi cation of high and low spots, or cut damage. An axial map is also available which indicates TIR for any band measured across the width of the sleeve. The system can be tailor-made to suit the customer’s needs, from quick passes with several measurements to a deep surface measurement.
Measurement accuracy is +/- 25 microns and the average measurement time will depend on how much of the sleeve is inspected and at what sizes, but typically around 180 seconds. This system does allow a contour map of the sleeve surface and can be used for mandrels, polymer and aluminium sleeves, but not Twinlock sleeves.
Sleeve inspection systems are already available on the market, and therefore off er not only added value to the plate mounter, but are an important tool in quality control within the fl exographic process. Although it is generally specifi ed when investing in a new plate mounter, it is possible, depending on the manufacturer and model, to upgrade the existing mounter with sleeve inspection systems. Dedicated stand-alone systems are also available. This technology will allow printers to have much better quality control and minimise possible printer downtime, thus saving time and costs.
22
June 2024
www.convertermag.com
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