Casting machine control

A control system for a dual drive casting machine having a master roll driven by a master motor, a slave roll driven by a slave motor, means for feeding molten metal into the nip of the rolls and means for withdrawing cast sheet from between the rolls, the control system comprising:

• means for setting a desired rotational speed of the master motor;
• means for controlling rotation of the slave motor at a selected offset from the master motor;
• first means for decreasing speed of the master roll when a change in torque exceeds a selected high limit;
• band pass means for excluding changes in torque at a rate greater than a given higher frequency and lower than a given lower frequency and passing changes in torque between the lower and higher frequencies;
• and
• second means for decreasing speed of the master roll when the rate of change of the torque passed by the band pass means is greater than a selected magnitude.

A control system for a dual drive casting machine having a master roll driven by a master motor, a slave roll driven by a slave motor, means for feeding molten metal into the nip of the rolls and means for withdrawing cast sheet from between the rolls, the control system comprising:

• means for setting a desired rotational speed of the master motor;
• means for controlling the current of the slave motor at a selected offset from the current of the master motor;
• comparator means for comparing the current for driving the master roll with a selected current;
• means connected to the comparator means for decreasing speed of the master roll when the magnitude of change in compared current exceeds a selected high limit;
• band pass means connected to the comparator means for excluding changes in current at a rate greater than a given higher frequency and lower than a given lower frequency and passing changes in current between the lower and higher frequencies;
• and
• second means for decreasing speed of the master roll when the current passed by the band pass means is greater than a selected magnitude.

A dual drive roll casting machine comprising:

• a master roll;
• a master motor coupled to the master roll for rotating the master roll at a selected speed;
• a slave roll;
• a slave motor coupled to the slave roll for rotating the slave roll;
• means for introducing molten metal into the nip between the rolls;
• means for withdrawing cast sheet from between the rolls;
• and
• an adjustable offset servo system connected to the slave motor and including feedback from the slave motor for controlling rotation of the slave motor at a selected offset from the master motor.

A control system for a dual drive casting machine having a master roll driven by a master motor, a slave roll driven by a slave motor, means for feeding molten metal into the nip of the rolls and means for withdrawing cast sheet from between the rolls, the control system comprising:

• means for setting a desired rotational speed of the master motor;
• means for controlling rotation of the slave motor at a selected offset from the master motor;
• means for sensing the current for driving the master roll;
• first means for decreasing speed of the master roll when a change in current exceeds a selected high limit;
• band pass means for excluding changes in current at a rate greater than a given higher frequency and lower than a given lower frequency and passing changes in current between the lower and higher frequencies;
• and
• second means for decreasing speed of the master roll when change in current passed by the band pass means is greater than a selected magnitude.

A method for controlling a dual drive casting machine having a master roll driven by a master motor, a slave roll driven by a slave motor, means for feeding molten metal into the nip of the rolls and means for withdrawng cast sheet from between the rolls, the method comprising the steps of:

• setting a desired rotational speed of the master motor;
• controlling rotation of the slave motor at a selected offset from the master motor;
• sensing torque driving the master roll;
• decreasing speed of the master roll when a change in torque exceeds a selected high limit;
• sensing changes in torque at a rate between a given higher frequency and a given lower frequency;
• and
• decreasing speed of the master roll when the rate of change of the torque between the lower and higher frequencies is greater than a selected magnitude.