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Technical Articles
Home >> Technical Articles >>Extrusion System with Facility to Change Pipe Dimensions and Enhance Productivity
Extrusion System with Facility to Change Pipe Dimensions and Enhance Productivity
Time: 2008-11-27
QuickSwitch system, when attached to the conventional extrusion system can change pipe dimension by pressing a button and without stopping the line. This system offers flexibility and cost savings within the designated diameter range - without stopping the production line. As a result, capacity utilization and productivity surge.
QuickSwitch can be used flexibly in the production of both single and multi-layer polyolefin pipes within the designated diameter range. The PVC QuickSwitch system can process all available PVC dryblends and C-PVC and covers the 90-60mm diameter range. QuickSwitch is offered either as a complete automated extrusion line or as an upgrade package for already-installed conventional lines. The focus of development at present is to make QuickSwitch available for more dimensions and other raw materials.
Conventional dimension change is a time and labour-intensive procedure and as such it is a significant cost factor. Reducing this cost was the motivation for QuickSwitch. The new system was developed by Krauss-Maffei, in cooperation with Egeplast Werner Strumann GmbH. With QuickSwitch, dimension change is easier and faster. A QuickSwitch dimension change is highly automated - initiated at the touch of a button - and steplessly adjustable. The line does not stop; instead the changeover is a continuous process. It takes only a matter of minutes before the line is again producing perfect pipe - in the new dimension. Productivity jumps, while the number of manhours calculated for operating the line drops significantly. In addition, the volume of production waste is reduced to an absolute minimum, because the line is not run down and restarted. For the first time, producers can supply pipe that is produced to order just in time in the required dimensions. The cost of stockpiling pipe can be eliminated or substantially reduced.
QuickSwitch automated dimension change 'on the fly' has been achieved by means of a number of technical innovations in the pipehead itself and on downstream units. The decisive feature of the new pipehead is the adjustable die gap. Die and mandrel are conically shaped. Changing the axial position of the mandrel allows a smaller or larger gap to be produced. The position and hence the die gap width, can be precisely adjusted from the control system. This allows close control over both the wall thickness and the diameter of the extruded pipe. This type of mandrel adjustment can be used for monoextrusion and coextrusion. The suction bell is located between the pipehead and the calibrating unit and is sealed by these two components on the delivery and outlet sides. It stretches open the parison as it exits the pipehead if the requisite parison diameter is greater than the maximum adjustable die diameter. The core component of the QuickSwitch equipment is an adjustable calibrating basket. It performs the shaping tasks of a standard calibrating unit but can be altered seamlessly across the line's full diameter range. The calibration basket consists of several hundred movable segments. The individual segment surfaces together form a smooth pipe bore that is perfectly circular. The inner radius of this flexible cylinder can be infinitely adjusted with high precision by turning an external wheel. The inlet and outlet of the vacuum tank have to be sealed in order that a vacuum may build up. For the inlet, this is done by the calibrating unit. For the outlet, it is done by a vacuum tank end seal. The end seal employs individual segments which are located in a plane and spring loaded around the pipe circumference. The side facing the pipe is rounded. This prevents unwanted indentations in the form of grooves. The pipe has to be guided through the vacuum tank and the spray baths.
The QuickSwitch dimension change unit provides support in the tanks by means of so-called combination rolls.
These rolls are spring loaded and adjust automatically to the diameter of the produced pipe. The spring hardness is matched to the dimension range and thus to the associated meter weight. The necessary support is provided by an arrangement of alternating different roll geometries in the tanks. The haul-off for the dimension change has its own diameter recognition and adjustment system as well as a fully automatic pressure and counter-pressure mechanism. The diameter is adjusted while the line is running. Separate shut-downs and start-ups are not required. Dimension change occurs in-line.
The saw also has its own diameter recognition and adjusting system. It can therefore automatically adjust to changed pipe diameters and separate them while the line is running. A variable clamp system ensures that there is no longer any need for separate changing the saw. The key component for the fully automated QuickSwitch change is the QuickSwitch control. It stores production parameters for all the pipe dimensions in the range. These are – the position of the pin, the diameter of the calibration basket and its speed of rotation, the vacuum in the suction bell, the position of the vacuum tank and the vacuum, the meterweight of the pipe, the extruder throughput rate, the haul-off speed and the contact pressure and counter-pressure of the haul-off tracks. When a dimension change is initiated, the operator has to select the parameter set for the desired pipe dimension. The parameters are transmitted to the control system. The operator can make final adjustments before pressing "the start button" to confirm the parameters and activate the dimension change.
QuickSwitch is less labour intensive than a conventional system so that fewer operators are needed to run the line. Changing dimension on a conventional line uses about nine manhours. With QuickSwitch, by contrast, one operator presses one button (maximum changeover time 20 minutes). The saving is around 1300 manhours a year. To this can be added around 350 hours normally taken up with cleaning components taken out of service.
On a conventional system, the pipe produced during set-up after a dimension change is reject product because it is not up to specifications, eg, for wall thickness. This reject product is usually recycled in-house. The regrind is added in defined proportions to virgin material. QuickSwitch virtually eliminates the cost of producing and recycling reject product. On the conventional line as described above, production waste totals about 110 tpa. On a QuickSwitch system, this drops to only 14.4 tpa, because the line does not have to be stopped and restarted.
QuickSwitch enables pipe producers to respond far more flexibly to customer orders. Even without a huge inventory, they can offer customers fast delivery, knowing that they can switch production easily and quickly to produce batches of different dimensions. The cost and the risk of a big inventory is substantially reduced and less capital is tied up in as yet unsold pipe.
Today there are only two decisive factors in the market for selling standard PE pipes: Price and Delivery time.
With QuickSwitch you also can achieve a short delivery time by utilizing a just-in-time production. Due to the variety of articles, it is impossible to have all pipes in stock. Often, orders are obtained only because time requirements can be met. The shorter the delivery time one can offer, the better the price which can be realized. QuickSwitch also allows an economical production of small lots, which are often demanded by customers.
Another benefit with QuickSwitch is less maintenance. QuickSwitch allows a production without interruption. Almost no cleaning of the melt-outlet of the pipe head is necessary. There is no possibility of making errors when setting-up the lines in comparison to traditional production lines (wrong or damaged calibration equipment, gaskets, supporting discs etc.)
A further benefit is, that every dimension exactly to customer requirements can be produced. All non-standard dimensions are possible to produce, no additional tools or equipment is necessary. Therefore there is a market opportunity for "CLOSE-FIT RELINING" systems within the QuickSwitch dimension range.
Krauss-Maffei currently offers its KM-QS QuickSwitch extrusion lines in three sizes. For pipe diameters from 32 to 63 mm, diameters from 75 to 160 mm and diameters from 160 to 250 mm for single layer and multi-layer pipes.
Krauss-Maffei also offers QuickSwitch upgrade packages, for the above diameter ranges, for retrofitting already installed production lines as well as complete new QuickSwitch lines.
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