After carrying out routine maintenance and rectifying a number of breakdowns on the main production line at Hambleside Danelaw, we were requested to inspect a system which had been installed as a retro-fit addition, but had never been operational.
The system is located in an enclosure, housing saws for trimming the edges of GRP roofing products and is designed to chop up off-cuts, enabling them to be dropped into bins and preventing the waste product from accumulating in the enclosure.
The operation of this system was intended to be automatic, with the chopper adjusting its operation speed to match that of the main production line. The system had been designed, built and installed by a Dutch company, and although the mechanical process of the system was sound, the control system simply did not work.
Without the use of this guillotine system, the production line operatives were required to manually remove the waste product from the enclosure, resulting in a large build up of waste prior to removal and a very dangerous trip hazard.
As with a number of previous projects, the electrical schematic drawings had not been translated into English and alterations made to the control system had not been noted.
The control system supplied was basic, poorly designed and built with very poor quality control gear and inverted drives not capable of performing the required function.
The panel itself was very crowded, housing a number of contactors and relays, two inverters, a PLC and various other components in an enclosure that was too small and not ventilated.
The method of monitoring and controlling position implemented within this system proved to be one of the main problems. Attached to the drive roller of the product line was a 10,000 ppr encoder and installed on the chopper was a crudely fabricated rotating arm which passed a proximity sensor.
The result of this was that, when the movement of the guillotine bed was going against the movement of the production line, the guillotine blade would often be down, causing the waste material to be pushed up the line. This often resulted in trimming saws being knocked out of place and waste material to back up over the product itself, rendering affected sheets useless.
Although the input for line speed was accurate and reliable, the proximity sensor mounted on the guillotine system did not allow accurate positional fine tuning.
The decision was therefore taken to replace the un-operational control system with a bespoke automatic control system catering for all the clients’ requirements.
After spending a considerable amount of time inspecting and attempting to set up and operate the original guillotine control system without success, it was requested that we design, supply and install a new system of control.
Due to the difficulties encountered trying to get accurate positional control and synchronisation of the movement of the guillotine moving bed with the production line, the use of high spec inverters was required.
Normally, for such accurate positional control, servo motors would be used, but since all hardware such as motors, gear boxes and framework was present and suitable it was requested we design a control system to control the existing items of hardware.
The proximity sensors and arms were removed and high precision encoders were retro-fitted to the guillotine motors, allowing fine tuning and easy synchronisation with motion inputs of both the production line and guillotine systems being very accurate.
The instillation of this new control system has now allowed the client to use the guillotine system, resulting in a much safer and less laborious process of managing the waste product produced by the production line.