Method and device for detecting tool abnormality in machine tools

In a method for detecting tool abnormalities in numerically controlled machine tools wherein machine tool data values are determined from and are a function of the operating conditions of the machine tool, and involving the comparing of said machine tool data values to a threshold data value selected from a plurality of threshold data values according to numerical control data prior to making the comparisons, comprising the steps of:

• (a) sequentially storing in a memory means a plurality of said threshold data values which correspond to different positions along the machining path determined according to said numerical control data;
• (b) determining, at different positions along the machining path specified by said numerical control data, the actual machine tool data values;
• and
• (c) controlling the machine tool in response to a comparison of the determined machine tool data value and the threshold data value stored in the memory means for the position, selected according to the numerical control data, at which the corresponding actual machine tool data is determined.

A device for detecting tool abnormalities in numerically controlled machine tools wherein machine tool data values are determined from and are a function of the operating conditions of the machine tool, and wherein a tool abnormality is detected by comparing said machine tool data values to a threshold data value selected from a plurality of threshold data values, comprising:

• (a) a machine tool control unit for outputting numerical control data, for determining and outputting machine tool data values and for terminating machining in response to receipt of a stop-machining signal;
• (b) a threshold setting switch;
• and
• (c) an abnormality detection unit connected to the machine tool control unit and the threshold setting switch for (i) performing a first operation if the switch is determined to be on, said first operation including determining and automatically setting a threshold data value according to machine tool data values received from the machine tool control unit under the control of the numerical control data, and (ii) performing a second operation if the switch is determined to be on, said second operation including selecting a set threshold data value and comparing said threshold data value to machine tool data values received from the machine tool control unit according to the numerical control data and outputting a stop-machining signal to the machine tool control unit if a comparison indicates a machine tool abnormality.

A device for detecting tool abnormalities in numerically controlled machine tools wherein machine tool data values are determined from and are a function of the operating conditions of the machine tool, and wherein a tool abnormality is detected by comparing said machine tool data values to a threshold data value selected from a plurality of threshold data values, comprising:

• (a) a machine tool control unit for outputting first numerical control data and second numerical control data, for determining and outputting machine tool data values, and for terminating machining in response to receipt of a stop-machining signal;
• (b) a threshold setting switch;
• and
• (c) an abnormality detection unit connected to the machine tool control unit and the threshold setting switch for (i) performing no operations if no first numerical control data is received from the machine tool control unit, (ii) performing a first operation if first numerical control data is received from the machine tool control unit simultaneous with the switch being on, said first operation including the determining and automatically setting a threshold device value according to machine tool data values received from the machine tool control unit under the control of the second numerical control data, and (iii) performing a second operation if the first numerical control data is received from the machine tool control unit simultaneous with the switch being off, said second operation including the selecting of a set threshold data value and comparing said threshold data value to machine tool data values received from the machine tool control unit according to the first numerical control data and outputting a stop-machining signal to the machine tool control unit if a comparison indicates a machine tool abnormality.

A method for detecting tool abnormalities in a numerically controlled machine tool of the type which performs a sequence of operations to carry out a machining procedure, and in which tool abnormality detection is carried out only during certain of said operations, comprising:

• providing a data set specifying during which operations in said sequence tool abnormality detection is to be carried out,
• storing a set of tool abnormality threshold parameters for utilization during respective ones of said operations, and
• detecting, during performance of an operation in said sequence for which said data set specifies that tool abnormality detection is to be carried out, the actual tool performance values and comparing these with the stored abnormality threshold parameters for the respective operation;
• and
• controlling the operation of said machine tool in response to such comparison.