US Patent No. 9,089,914

WIRE ELECTRIC DISCHARGE MACHINE HAVING FUNCTION FOR CONTROLLING MACHINING LIQUID TEMPERATURE


Patent No. 9,089,914
Issue Date July 28, 2015
Title Wire Electric Discharge Machine Having Function For Controlling Machining Liquid Temperature
Inventorship Hiroyuki Furukawa, Yamanashi (JP)
Assignee FANUC CORPORATION, Yamanashi (JP)

Claim of US Patent No. 9,089,914

1. A wire electric discharge machine having a function for controlling a machining liquid temperature, for machining a workpiece
to a desired shape by circulating machining liquid between a machining liquid tank and a machining vessel, generating electric
discharge by applying a voltage across a machining gap between a wire electrode and the workpiece immersed in the machining
liquid stored in the machining vessel while changing a relative position of the wire electrode with respect to the workpiece,
said wire electric discharge machine comprising:
a heater and a cooler configured to regulate the machining liquid temperature of the machining liquid in the machining liquid
tank;

a machining liquid temperature detecting sensor configured to measure the machining liquid temperature;
an ambient temperature detecting sensor configured to measure an ambient temperature around the wire electric discharge machine;
and

a controller coupled to the heater and the cooler, the machining liquid temperature detecting sensor and the ambient temperature
detecting sensor, the controller comprising a processor and a storage memory, the storage memory configured to store data
to control the machining liquid temperature, the data including

an operation beginning time, the operation beginning time being the time at which operation of the wire electric discharge
machine begins; and

a control temperature of the machining liquid at the operation beginning time;
wherein the controller is configured to:
calculate a temperature regulation time period required to regulate the machining liquid temperature
on the basis of a quantity of heat required to cause the temperature of the machining liquid, stored in the machining liquid
tank up to its maximum capacity, to reach the control temperature, and

from the measured machining liquid temperature and the measured ambient temperature around the wire electric discharge machine,
a quantity of heat loss, and a capacity of the heater and the cooler to be used for the temperature regulation, and

calculate a first remaining time period from (i) a time at which the temperature regulation time period is calculated to (ii)
the operation beginning time stored in the storage memory;

wherein the heater and the cooler are configured to start the temperature regulation of the machining liquid temperature when
the calculated temperature regulation time period becomes equal to or exceeds the first remaining time period;

wherein the machining liquid temperature detecting sensor is configured to measure a machining liquid temperature after a
predetermine time elapses since the start of the temperature regulation;

wherein the controller is further configured to:
determine a rate of change of the machining liquid temperature from the machining liquid temperature measured after the predetermine
time elapses since the start of the temperature regulation,

recalculate the temperature regulation time period required to reach the control temperature from the determined rate of change
of the machining liquid temperature, and

calculate a second remaining time period left from (i) a time at which the temperature regulation time period is recalculated
to (ii) the operation beginning time stored in the storage memory; and

wherein, when the recalculated temperature regulation time period is shorter than the second remaining time period, the controller
is further configured to control the heater and the cooler to:

suspend the temperature regulation of the machining liquid temperature for a time period corresponding to a difference between
the second remaining time period and the recalculated temperature regulation time period, and then

resume the temperature regulation of the machining liquid temperature; and
wherein, when the recalculated temperature regulation time period is not shorter than the second remaining time period, the
controller is further configured to control the heater and the cooler to continue the temperature regulation of the machining
liquid temperature.