The all new DDC disctrete digital control system is operated from a single control panel that controls all electrical furnctions of the furnace. The control system has six basic functional groups: Energize Lamps, Power, Temperature, Transport, Calibrate/Test and Statuus. On LA-series furnaces the process Gas Flow Control flowmeters are located on the control console. On larger furnaces the flowmeters are located on a panel below the control console.
Using ENERGIZE LAMPS switches for Zones 1, 2 and 3 TOP and BOTTOM lamps user selects which bank of lamps is on in each zone and thereby controls whether the furnace is operated as a radiant, conduction or mixed mode IR furnace.
The furnace can be operated in a number of different modes to model the behavior of a radiant, convection and/or conduction furnace making it an ideal all-around furnace for production or laboratory applications.
HIGH TEMPERATURE FURNACE. By enabling any combination of top and bottom lamps, the furnace can be operated in mixed mode combining characteristics of convection, conduction and radiant heat. Enable all lamps to achieve highest temperatures (800-1000°C) to benefit from both the fast response of an infrared furnace and stable operation of a convection furnace.
INFRARED FURNACE. The furnace can be operated in radiant mode by only enabling top lamps. This mode emphasized fast response characteristics of radiant furnaces and de-emphasizes conduction characteristics. This mode is often selected for dryer and infrared curing applications.
CONDUCTION FURNACE. Furnace can be operated using only the bottom lamps which emphasizes conduction and convection characteristics of the oven.
MAIN POWER light (white lamp) is always lit when power is applied from the facility circuit breaker.
CONTROLS light is lit when power is applied to the furnace systems. Operator presses green CONTROLS ON pushputton to start belt motor controller, cabinet and cooling system fans, furnace zone temperature controllers and any optional equipmenet. Operator pressess red CONTROLS OFF pushbutton to turn off the furnace. Furnace will complete shutdown immediately after the COOL DOWN sequence is completed.
LAMPS light is lit when the lamps have been turned on. Operator presses green LAMPS ON button to applies line voltage to lamps. Lamps selected by the TOP LAMPS and BOTTOM LAMPS are energized, others remain off. Operator presses the LAMPS OFF pushbutton to de-energize all lamps immediately.
COOL DOWN light (blue lamp) is lit during furnace cool down cycle. COOL DOWN START pushbutton immediately de-energizes the lamps, but allows delayed shutdown of the control system while the belt, cabinet and cooling system fans remain on until the zones cool. Cooldown is maintained until all zones are below 100°C for 60 seconds. After this time if the operator had pressed the Controls OFF button, the rest of the furnace will shutdown. Only the gas flow to the furnace remains for the opertor to shut down.
Temperatures in each zone are controlled by independent PID controllers, one per zone. Type K thermocouples provide zone temperature feedback shown on the 2-color display to making it easy to compare setpoint and measured temparatures. The controllers feature 2 alarm relays that can be configured to sound a buzzer and light on temperature deviation. For Overtemperature, if temperature reaches a high-high setpoint, Overtemperature condition causes lamps to shutoff, sounds buzzer and a light appears on the control panel.
The motor speed is controlled by manually adjusting the ADJUST SPEED knob clockwise to increase speed, counter-clockwise to decrease speed. A digital meter displays the motor revolutions scaled to belt speed in any units desired. Once the speed is set, the PLC controller locks in the belt speed and maintains the speed, even with fluctuating temperature and voltage conditions.
On new LCI furnaces the belt speed transport system uses the same motor and control system found on most high-end LCI and RTC Radiant Technology furnaces. With this high quality motor/controller configuration, the furnace can operated at extremely low belt speeds up to the furnace top speed with better than 20:1 turndown ratio.
On LCI refurbished RTC LA-309P furnaces the transport drive is RTC's standard Bodine shunt wired motor with a new controller and encoder for belt speed control and feedback.
Standard belt speed ranges are 13-250 mm/min (0.5-10 ipm), 25-500 mm/min (1-20 ipm), and 50-1000 mm/min (2-40 ipm). Range can be configured for units of mm/min, cm/min or inches/minute. Other furnace speeds can be ordered and alternate units can be configured for your application.
The ALARM displays four critical conditions:
When the SILENCE pushputton is pressed, the audible buzzer is silenced, but the alarm light remains ON
until the conditon is remedied.
The CLEAR pushbutton shuts of the buzzer and resets the silence latch.
By pressing the CALIBRATE LAMPS button, operators can check top and bottom lamps by zone to verify lamp condition. During calibration, alarm functions remain active.
LAMP ELEMENT MONITOR. The element monitor furnction detects failed lamp strings (lamp or number of lamps wired in series). Since the hermetic design of the furnace chambers require the ends of the lamps to be enclosed, individual lamp string failures may be difficult to detect visually. Pressing the TEST LAMPS button applies 50% power to the top and bottom lamps in each zone, selected using the TOP and BOTTOM LAMPS ENERGIZE LAMPS switches. An array of twelve (12-14) lamps will indicate which lamp strings have failed, if any. Zone temparature and alarm functions remain active during this test. Once pressed, the selected lamps will remain energized for 2 minutes.
POWER. During normal operation, the TOP and BOTTOM LAMP STRING indicator lamps light indicating when and where heating power is being applied.