It started with the need to cut tapered polycarbonate panels for conservatory roofs. In the past this was done with saws, but Polycut of Hull developed the technology to cut the panels accurately using knives. This built up their expertise in using X-Y motion control. Together with drives and a control system from Lenze, Polycut have now produced a unique machine to create accurate holes in insulated cladding boards for buildings.The machine was designed and developed in record time, based around concepts of economy in construction and operation.
Polycut was established in 2001 as part of Clearview (Yorkshire) Limited in Hull. Clearview supply conservatory roofs and their initial requirement was to cut panels in multiwall polycarbonate which is constructed with boxed sections to provide insulation. This material is a hollow structured polycarbonate extrusion and can be up to 35mm thick. Traditionally "wall-saws" have been used where the panel is placed on a near vertical bed and a gantry with a rotating saw cuts in vertical and horizontal directions. Of course these wall-saws can only cut 90° angles unless the board is repositioned. The Polycut machines use 3-axis motion control and knives instead of saws which allows the cutting of the tapers found in conservatory roofs, and also optimisation of the sheet material.
There are further advantages of using knives. Compared to saws there is no dust created, and dust is a major nuisance in production as it gets into the boxed channels and static makes it very difficult to clean. With the Polycut machine "all you have to do is cut, pack and wrap" says their Managing Director Mark Robinson. With saw cut machines it is common for more time to be spent cleaning the material than cutting.
Polycut have successfully diversified into other designs as special purpose machinery based around their skills of X-Y positioning. Examples are punching holes in aluminium glazing bars and their X-Y-Eazy for fast measurement of railtrack and railway station platform dimensions. They are capable of a flexible, fast and economic response to customer needs. Their latest machine for building cladding leaders Kingspan however, reverts back to their experience with the cutting of panels. Affectionately known as the "dibbler" this new design accurately positions holes into composite cladding boards with dimensions up to 8 x 4.5m.
Kingspan manufacture these composite panes as efficient and economic insulation cladding for buildings. A layer of fire-proof hardboard is fixed onto a steel frame. Then a layer of foam insulation up to 200mm thick is glued into place. Brackets to hang cladding onto the face of the panels are needed to be fixed from the foam side and it is necessary to drill through the foam and hardboard, then tap into the ribs of the steel frame. This was a difficult measurement task done by hand with resulting quality and scrap problems. Kingspan specified in their requirements a machine that would automatically create the holes in exactly the right location ± 1mm, ready for pins and brackets to be fitted.
Polycut began with a roller in-feed bed, then an operational section to punch the holes and finally a roll off bed all inclined at 10° so that the weight of the panels (up to 300Kg) holds their position. In the operational centre section a gantry with Lenze drives for X-Y motion control moves a punch head to the required positions, up to 120 holes per panel. The horizontal and vertical speed of the head is 1.7m/s. The head is fitted with a pneumatic punch and the height above the panel is controlled by distance sensor and geared motor to a constant distance. The punch penetrates up to 200mm into the foam with a spring damper absorbing the force when it reaches the panel. Kingspan specified a 3 minute production cycle for a panel with 60 punch holes and in the Polycut machine achieves this including the in-feed and out-feed times.
The machine design emphasised economic and efficient construction. Lenze worked closely with Polycut in this area. The machine control and visualisation was done in a single device – the EL110 HMI with PLC – an economic and compact solution that comes complete with Windows, PLC software and Visualisation software. The range has touchscreens available from 5" to 12", in this case the 10" screen was used. The drive requirements were assessed by Lenze and they established that inverters were capable of the speeds and accuracy giving a lower cost alternative to servo drives. In another case of a single device doing two functions, the Lenze 8400 Highline inverters were specified and they do both the driving and positioning functionality on the X-Y axes. The two axes geared motors are Lenze helical type GST which has a two stage gearbox with 96% efficiency. The motors are fitted with a HTL encoder for position feedback to the inverters.
Polycut are able to meet a very tight 12 week schedule specified by Kingspan for the design and construction of the machine. This would not have been possible without the close teamwork from Lenze who became a single source of responsibility for the drives and control. Lenze supplied the panel which was manufactured at their Systems Division in St Helens. Also they wrote the software for the visualisation and PLC control which included a RS232 barcode reader and communication with the factory control system by Ethernet. The PLC communicates with the 8400 Highline inverter drives using the CANbus which is integrated on both these Lenze L-force products and the drives handle the motion profiles, plus giving a signal when the target position is reached.
Polycut made the machine adaptable to suit different widths of panel by using split roller beds. As the operator loads a panel, he can move the load bed to the correct width position so that the panel is properly supported. The operator then scans a barcode on the panel and starts the machine from the touchscreen. Working from the barcode, the PLC accesses the appropriate DXF file from the factory network, and powered rollers then drive the panel to a stop in the central operating section. As the panel moves from section to section the bed width is automatically adjusted to the incoming panel. The punching process begins and visualisation of the panel for the operator is available at the touchscreen. At the end of the process powered rollers drive the board to the roll-off section where the operator unloads it. Each of the three sections of machine can handle a different width of board at one time giving maximum production flexibility for Kingspan.
The project including design, source and machine build was done successfully in a remarkably short 12 week period at the end of 2008. Polycut used their expertise in X-Y positioning together with a strong innovative approach to the specification. Lenze worked closely with Polycut giving a fast response and proposing products that are efficient and economic. The panel was designed and built in a very short period. New software was written, for example the barcode scanning and the optimisation of paths to minimise the head travel. Mark Robinson comments "Polycut and Lenze have formed a responsive team. The design and right technology all worked well from day one".