HMI and PLC Control Systems

Most programmable logic controllers (PLC) are equipped with a touch screen. Touch screens are available in several sizes and this will depend on the furnace and application.

These control systems display several pages for parameters setting, live graphical trending and alarm information. The HMI display is linked to the temperature controller(s) and a PLC (programmable logic control) to provide a fully integrated and sophisticated control system. All parameters required for operation are accessed via the HMI touch screen.

Examples of parameter settings available:

• Temperature
• Flow rate
• Pressure
• Circulation fan speed
• Cooling fan speed
• Damper valve positioning

These control systems can be connected to computer systems via communication links which can be:

• RS232 or RS485
• Ethernet
• Data logging access via Ethernet or USB memory stick
• Remote display of the control system to a PC or handheld device via an internet accessed webpage

Based on a SIEMENS S7-300 the TP1900 and WinCC PLC controller are available for all standard vacuum chamber furnaces.

With the TP 1900 (19” display), 20 unique heat treatment programs can be stored with a maximum of 25 different segments. The furnace is operated by automated programming via a touch panel interface with logging of all process and operational data. Generation of a CSV file is possible for further analysis and evaluation. Remote maintenance is optional.

With the WinCC control unit, 50 unique heat treatment programs can be stored with each program consisting of a maximum of 30 different segments. The furnace is operated by automated programming via a touch panel interface with logging of all process and operational data. Generation of a CSV file is possible for further analysis and evaluation. Remote maintenance is optional. A complete PC is included with the WinCC control unit, which provides more flexibility compared with the TP 1900 option. A TeamViewer program can be installed into additional PCs for additional personnel to access the furnace.

For reactive gases, such as hydrogen, a safety PLC is used in vacuum chamber furnaces.

With the more simple Eurotherm Mini 8 controller, 12 unique heat programs can be stored with a maximum of 16 different segments. A segment can consist of a temperature increase, decrease, dwell time, or ramp time. Pumps, mass flow controllers, and valves can be adjusted by the controller. Remote operation and programming is an available option. The Mini 8 controller is available with a colour display touch screen panel in sizes of: 4.3” or 7.5”.

With a PLC all the necessary PID temperature controls can be programmed individually. Multiple cascade controls in a single furnace are also possible.