Application 1
Application 1
Application No.1 - Rotational Moulding Machine
Application No.1 - Rotational Moulding Machine
Embedded Files
This application deals with the control of a Carousel Rotational Moulding Machine. The project involved panel design, plc and hmi application software, testing at the customer's works, and on site commissioning.
This was, without doubt, one of the top 5 most demanding projects we have undertaken. The complexity of the cycle, and the mathematics involved in the speed and pressure control were quite a challenge.
Key components:- Mitsubishi Q series PLC, Beijers E1151 hmi, ethernet, CC-Link, Inverters
Key software issues:- CC-Link communications, PID temperature control, Inverter control and diagnostics via an E1000 hmi.
Please scroll down to see more detail of the application
The above drawing shows the configuration of the system.
The central part of the system is a Mitsubishi Q series plc, communicating with a Mitsubishi colour, touch screen hmi. The Inverters are controlled over CC-Link, along with the majority of the I/O. Data is logged to a red lion data station, communicating with the plc and hmi on ethernet. All manual control is carried out via the hmi.
What the plant does
Rotational Moulding machines are used in the plastics industry; used in the manufacture of items such as oil/water tanks, bottle banks, water floats, and numerous other items. This project was for the design of a control system for a standard machine, but covering numerous "options".
The machine comprises four arms, which index through five stations to complete a cycle. Each arm can be set (via a recipe) to rotate clockwise and anti-clockwise at varying speeds for varying times throughout the cycle. At the end of the arm is a plate which rotates in the opposite plane to the arm. This too can be set (via the recipe) to rotate clockwise and anti-clockwise at varying speeds for varying times throughout the cycle. The rotation of the arm has a direct effect on the rotation of the plate, which has to be taken into account when calculating the inverter speeds required for the plate drive. At times, it can even be necessary to run the plate in the opposite direction to achieve the correct speed and direction.
The oven stage requires both controlled oven movement, and PID temperature control to maintain the temperature setpoints set up in the recipe. Depending on the type of burner, the PID loop either controls a modulating or on/off gas valve
The cooler is enclosed, with an entry and exit roller door, cooling fans, extraction fans, and water sprays. These, again, are all controlled according to the recipe.
Air injection can be applied in the oven and cooler stages, set in the recipe as set times and set pressures. Pressures are adjusted and monitored via CC-Link to air modulating valves.
The system consisted of 7 control panels, all communicating on CC-Link. Although PJC Systems designed the system, and all the panels, the panels themselves were manufactured by others. The main control panel housed the power distribution, the Mitsubishi Q series plc, and the Beijers E1151 15" hmi. The other six panels all housed starters, inverters, and remote (CC-Link) i/o associated with a specific part of the machine: the oven, the cooler, and each of the 4 arms. Because all but the main panel are inaccessible whilst the machine is in operation, all status flags are communicated over the network to the plc/hmi, giving a great deal of diagnostics at the main control panel.
Although, in this case, PJC Systems did not manufacture the control panels, we produced all the engineering drawings.
PJC Systems generated these drawings:
Externals - showing how all the external wiring connects to the system
Internal wiring diagrams - showing all internal panel wiring.
When required, we can also produce:
External Layout - showing the layout of the outside of the panel, particularly the door
Internal Layout - showing the backplate layout
The slideshow above shows photographs of the plant that PJC Systems controlled.
The machine is a Rotational Moulding Machine, used to make such items as oil tanks, floats, etc etc. Powdered plastic is put into the mould, and the lid put on and clamped. The arm is then moved to each station in turn (oven, sinter, and cooler), where the appropriate heating/cooling is applied whilst the mould is rotated at the required speed and orientation. When the full rotation of the machine is complete, the lid is taken off and the properly formed product is removed.
The slideshow above shows the hmi screens that PJC Systems designed for this project. The system was designed as a standard control system to cover a number of machines, so among the 98 pages of graphics, PJC Systems developed pages to depict the machine under several different configurations: rotating clockwise or anti-clockwise, fitted with 3 arms or 4, and with several cooling configurations. There are numerous diagnostic pages covering the i/o, and comms, including communicating with the inverters on CC-Link. Manual control is also via the hmi
Page updated
Google Sites
Report abuse