Method and apparatus for optimal feedrate control on wire-cutting electric discharging machine (WEDM)
AssigneeIndustrial Technology Research Institute
InventorsHsi-Pin Li, Hsin-Jung Chuang, Tsuen-Pann Shieh
Life of this patent
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Abstract
Disclosed is a feedrate controlling method and apparatus for controlling a wire-cutting electric discharging machine (WEDM) to operate at optimal feedrate. In the apparatus, a discharge frequency counter is used to count the frequency of normal discharge and the frequency of abnormal discharge, from which two performance indexes: stability percent (STB) and efficiency percent (EFF) are obtained. These two performance indexes allow the apparatus to use a decision table to obtain an optimal feedrate variation used to change the current feedrate so as to operate the WEDM with maximum stability and efficiency.
Claims6
A method of controlling feedrate for a wire-cutting electric discharging machine, comprising the following steps of:
- (1) counting frequency of normal discharge (f.sub.normal) and frequency of abnormal discharge (f.sub.abnormal);
- (2) calculating the value of stability percent (STB) according to the following equation:
- ##EQU7## wherein k! denotes the (k)th sampling, and ##EQU8## but if STB<0, STB=0 is used;
- (3) calculating the value of efficiency percent (EFF) according to the following equation:
- ##EQU9## wherein t.sub.off =idle period during normal discharge (unit:
- us),
- t.sub.ab-off =idle period during abnormal discharge (unit:
- us),
- .tau.=sampling period (unit:
- sec),
- and 0<t.ltoreq.2;
- (4) obtaining a value of feedrate variation .DELTA.F% selected from a decision table of predetermined values mapped by the STB and EFF values;
- and
- (5) adjusting current feedrate of the WEDM by a variation equal to the selected value of .DELTA.F%.
An apparatus for controlling feedrate for a wire-cutting electric discharging machine, comprising:
- (1) means for counting frequency of normal discharge (f.sub.normal) and frequency of abnormal discharge (f.sub.abnormal);
- (2) first arithmetic means for calculating for the value of stability percent (STB) in accordance with the following equation:
- ##EQU10## wherein k! denotes the (k)th sampling, and ##EQU11## (3) second arithmetic means for calculating the value of efficiency percent (EFF) in accordance with the following equation:
- ##EQU12## wherein t.sub.off =idle period during normal discharge (unit:
- us),
- t.sub.ab-off =idle period during abnormal discharge (unit:
- us),
- .tau.=sampling period (unit:
- see), and
- <
- t.ltoreq.2;
- (4) third arithmetic means for obtaining a value of feedrate variation .DELTA.F% selected from a decision table of predetermined values mapped by a combination of the STB and EFF values;
- and
- (5) means for adjusting current feedrate of the WEDM by a variation equal to the selected value of .DELTA.F%.
Dependencies are inferred from the claim text.