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"Star Peripherals from Heidelberg" Article Series, Part V |
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Less Powder and Lower Dust Levels - the Effective Double Act of the PowderStar AP 500 and CleanStar
The Heidelberger Druckmaschinen AG (Heidelberg) Star System covers the whole system solution incorporating peripherals for Speedmaster presses. The key peripherals are linked to the press via the Prinect CP2000 Center control station by means of a CANopen data bus (CAN = Controller Area Network).
In the first four articles in the series devoted to peripherals, we presented the AirStar 3000 air supply cabinet, the CoatingStar coating supply unit, the InkLine 3000 ink supply system, the DryStar 3000 and DryStar 3000 UV drying systems, and the CombiStar Pro inking unit temperature control and dampening solution supply system. The fifth and final article focuses on the PowderStar AP 500 and the new version of the CleanStar - an effective double act for less powder and efficient process air extraction.
Up to 50 Percent Less Powder
Powder application in sheetfed offset printing is a necessary evil. Very few printshops are able to do without powder altogether, but they all want to minimize the amount they use. The higher the press production speeds, the harder this is to do. Many printshops take no chances and work with high powder settings. Although this prevents ink transfer from one sheet to another, it makes the delivery and the press environment very soiled. If massive amounts of powder are applied, working and turning the sheets and finishing operations also become more difficult.
Conventional powdering systems reach their technical limitations at speeds of 15,000 sheets per hour or less. Only a relatively small proportion of the powder used actually reaches the surface of the print sheet, mainly because of air turbulence in the delivery.
The unique PowderStar AP 500 powdering system from Heidelberg is different. Because the powder is applied to the sheet with significantly greater momentum, the powder jet is much more resistant to air turbulence caused, for example, by sheet travel, the movement of the gripper bars or additional process air extraction. Distribution by up to twenty-four ARS spray nozzles ensures uniform powder application, while powder metering using the tried-and-tested roller metering module pre-meters the powder so precisely that it is applied only to the print sheets and not to the gaps between them.
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"Our visual evaluations of printed sheets reveal that the spray tube of the PowderStar AP 500 applies the powder with unprecedented uniformity and efficiency," comments Claudius Haas, Project Manager responsible for powdering systems at Heidelberg. "This allows printshops to systematically reduce the amount of powder used to a level approaching the minimum required for preventing ink transfer from sheet to sheet - and enables powder levels to be cut by up to 50 percent. At the same time, powder application is up to twice as efficient as with previous high-end powder application systems," he adds.
Less Cleaning and Reliable Compliance with Dust Limits
Despite all the progress made with application processes, a certain amount of powder will inevitably go astray during powdering. To stop this soiling the press environment, being deposited on printing or coating units, or being inhaled by printshop staff, Heidelberg has developed the CleanStar process air extraction system. The new version for the Speedmaster CD 102 and XL 105 is now available.
The new CleanStar collects the stray powder by means of specially arranged extraction devices in the delivery and extracts it via an exhaust air cleaning cabinet. Thanks to optimized exhaust air routing, even thin grammages of less than 70 grams per square meter can be used at a production speed of up to 18,000 sheets per hour on a Speedmaster XL 105 - and this at the maximum extraction power and without impairing sheet travel.
In addition to powder, the CleanStar also extracts paper dust and odors that occur during the drying of inks and coatings, including ammonia vapors and the typical UV odor. The improvement is particularly noticeable at the end face of the delivery. Measurements in accordance with the specifications of the German Institution for Statutory Insurance and Prevention in the Printing and Paper Industry confirm that using the new CleanStar cuts the amount of external dust by over 80 percent. With the Speedmaster XL 105, the level of fine dust emissions is 75 percent below the statutory limit. In addition, eye irritation caused by escaping drying vapors is prevented extremely effectively.
Prevention of powder buildup in the delivery
On average, the delivery is cleaned manually every one to two weeks. The automatic self-cleaning system of the CleanStar has been optimized to lengthen the period between cleaning operations.
Regular blowing of powder and dust from the sheet guide path and delivery air system, in conjunction with dust extraction via the exhaust air cleaning cabinet, prevents clumps of powder building up at critical points in the delivery. This does not result in a "dust-free" delivery. This could hardly be expected, given that several kilograms of powder are used every week. However, it does largely ensure that clumps of powder do not fall unchecked onto the delivery pile. The result is less cleaning and excellent product quality without the inconvenience of powder deposits on the print sheet.
Image 1:
The key to efficient powder application - the spray tube of the PowderStar AP 500 with ARS spray nozzles.
Image 2:
Delivery of the Speedmaster XL 105 with the PowderStar AP 500.
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