Synchronised multi-axis motion control

Filling Machines and Production Line

Advanced production line in most industries involve many different processes. For instance, yogurt filling machines involves feeding pot material from a coil into a press machine mounted with die. Finished part out of the press and die is empty pots ready for the next stage. Next stage might involve wrapping pots with labels printed with product details or it might involve another press and die arrangement to craft product details on empty pots. Empty pots  then pass through section of production line containing large containers filled with yogurt contents ready to pour yogurt and fruit into empty pots through nozzles. Once all bottles are filled, production line pushes them to next section where pots are sealed. All pots also have to go through foreign particle analysis via advanced X-Ray scanning machines. Pots then go through sorting sections where series of delta robots hovering over conveyor starts to sort pots in order and arrange them in groups of 12 bottles in a tray. These robots are all pre-programmed and know location of each pot and for a multi-flavoured production run where adjacent pots contain different fruit filling, sophisticated delta robots pick and place to achieve combination of yogurt flavours programmed in production run recipe. Conveyor pushes pot trays into a wrapping machine that feeds web to wrap around the trays. Another pick and place robot picks up packages and place on a  pallete that awaits until programmed numbers of packages are loaded. Pallets are then pushed onto a vertical elevator that transports fresh yogurt packages into environmentally controlled store rooms.

Motion Synchronisation

It is worth mentioning different sections automatically get notifications when previous section has finished the process. Messaging between section is tightly synchronised to ensure maximum production rate is achieved. Feed forward controls coupled with transducers analogue data as well as programmed motion profile works all in synchronisation to ensure nozzles are dipped down to fill trays as soon as trays are parked right underneath filling nozzles. All processes are further layered with safety devices which are scanned continuously in real time to ensure processes work in harmony and there is no danger to the environment as well as operators, technicians, engineers working around the machinery. From first press machines to film wrapper machine and finally to packaging pallet loaded with layers of packages, every stage of motion on the production line is synchronised and aware of motion in neighbouring section. Typically, such manufacturing line contain over 500 servo motors driven by servo drives and advanced motion controller. Looking within electrical cabinets of these production lines, we often find all those drives are linked together in a sort of daisy-chain arrangement. It is fascinating to see such complex processes simplified so elegantly and maintained by few engineers who design, install and code these production lines. I have had opportunity to work a bit on these production lines and I was amazed to see level of details involved to achieve confidence that everything is right and production line is ready to hand over to shift operators. I think it is a very serious job considering the sheer size of these machines as well as mighty motion performed by different sections. When I first saw a production line, it was shut down  with some sections even missing essential components that monitored and controlled synchronisation such as light curtains, profibus network nodes, festo valves, HMI stations, proximity sensors even motion axis motors and measuring systems were missing. I ended up working within a team of very talented and experienced engineers. Amongst the jobs we divided between us included:

  • Completing Electrical Schematics for control cabinets
  • Completing profibus network for production line
  • Installation and commissioning festo valves
  • Installing sensors and motors that were missing
  • Completing all I/O checks prior establishing power
  • Ensuring all network nodes were connected to line PLC and motion controller
  • Commissioning of electrical cabinets step by step switching on MCB circuit breakers
  • Calibrating and commissioning individual motion axis and measurement systems
  • Instrumentation and calibration
  • Machine safety software development and commissioning
  • Programming Super Visory Control and Data Acquisition SCADA software
  • Production line commissioning, initial runs and hand over to operators

Above are only few of the jobs that I remember. I particularly enjoyed calibrating motion axis and establishing network communication between axis for synchronisation. I remember I forgot to tune some servo drives and when I enabled motor motion, it tripped prompting error on display to complete tuning. Overall, memorable experience..