This document is a rough overview of what happens once the Start button is pressed on a Nebitype Model NTC.
The machine should be left to heat up, and an hour is a reasonable amount of time to allow for this to occur.
This is a good time to do some oiling (see Nebitype Lubrication) and cleaning.
After an hour the molten type metal should be very gently stirred to ensure the type metal is mixed and that any trapped impurities in the metal
will come to the surface.
(Type metal is a eutectic alloy of Tin, Antimony and Lead and needs to be heated to the correct temperature to ensure the alloy is completely
amalgamated. Whilst the metal will be fluid in less than an hour, it's good practice to let it stabilise then stir it.)
Once stirred, any dross on the surface of the type metal should be skimmed off, leaving a clean, shiny surface.
The two heating systems operate independantly of each other and are set to slightly different temperatures.
The mouthpiece heater is cooler as its purpose is to keep the type metal flowing during the casting process,
and is set by the dial on the panel beside the Start/Stop switches.
The Pot heaters are set via a couple of dials on the temperature guage on the door at the bottom right
hand side of the machine.
When the Start button is pressed the motor is started via a contactor. The Start switch appears to have two functions with the
motor, one of which is momentarty and appears to engage the start capacitor/winding, the other that engages the contactor to run the motor
until the end of cycle.
When the motor starts the water pump, which is connected to the drive shaft via a v-belt, will start pumping coolant from the tank to the
mould, via the T-block and Water Control (bypass) valve.
The elevator will rise, first pulling the stick holder forward, then clamping the stick-holder, stick and mould up against the mouthpiece. The full clamping pressure is provided by the forks at the top of the machine, however the stickholder is initially pushed forward into place by the Elevator Slide Bell Crank, actuated by the elevator.
When the Stickholder, Stick, Mould and Mouthpiece are correctly clamped together the pins in the stick will depress the microswitches in the stick holder's microswitch assembly which will enable casting. (There are three microswitches in the microswitch assembly, all of which must be closed to enable casting.)
The machine will continue its cycle and if the microswitches are all engaged the plunger will depress, delivering molten type metal to the mouthpiece. The metal will pass through the mouthpiece, through the mould and into the cavities of the matrices. The molten metal will chill through it's solidification point and harden. Note that the machine will maintain pressure to the plunger whilst the type metal is cooling to prevent shrinkage in hardening. (Even though the constituent metals are designed to limit shrinkage, this method ensures a clean and solid slug).
The machine will continue to run, raising the plunger, and the elevator will retract downwards, pulling the stick holder and stick away from the mould and mouthpiece. The mould will return to its start position where the trimming knife will run left to right along the back of the mould, trimming the back of the slug and brushing the cuttings into the collection tray. The same lever that advances the knife also wipes the mouthpiece with an oil impregnated felt wiper and wipes the shavings from behind the mould with a small leather wiper. If fitted and enabled, the metal feeder will have engaged to lower a type metal ingot into the pot. Most metal feeders are a solenoid based system, however my NTC is a very early model which has a mechanical arm running inside the metal feeder support post, actuated by the plunger mechanism.
Now the slug has been trimmed, an ejector blade will emerge from behind the resting position of the mould, pushing the slug out into the jaws of the slug gripper. The slug gripper, which operates along the same arm as the knife and mouthpiece wiper, will retract as the trimming knife retracts (right to left), pulling the slug back to the slug tray and releasing it.
The machine will complete its cycle, the end-of-cycle point being triggered by the cycle-end microswitch (#E10086) in the base of the machine, and the machine will stop - unless the continuous casting switch (#E10009) is on, in which case the cycle will repeat casting until the Stop switch is pressed or the continuous casting switch is turned off and the machine completes its cycle.