CRT displaying method in numerical control devices

A CRT displaying method for use in a numerical control device for controlling a machining apparatus which is provided with a machining tool to machine a workpiece, for example a wire electric discharge machining apparatus. When an error condition occurs, an alarm code number corresponding to the error condition is displayed together with an alarm message corresponding to the alarm code number. Further, a manner how to escape from the error condition is obtained based on the alarm code number and an operational program so that an operator can move the machining tool easily to escape from the error condition according to the manner which is displayed on the CRT graphical and literally.

BACKGROUND OF THE INVENTION 
The present invention relates to numerical control (NC) devices, and more 
particularly, to a method for displaying not only a code number and a 
message indicative of an alarm or an error condition which may occur 
during an operation of an apparatus controlled by the NC device but a 
manner how to escape from the alarm or error conditions on a CRT display 
for a numerical control device. 
FIG. 1 is a schematic diagram showing an NC system including a CRT 9 and a 
numerical control device 8 controlling the CRT 9. The numerical control 
device includes a keyboard 10 for inputting data and instructions and a 
paper tape reader 11 for reading an operation program and data from an NC 
tape. 
FIG. 2 is a diagram showing an example of display image which displays a 
code number indicative of an alarm, an alarm message and the like in 
conventional NC system. 
The conventional CRT displaying method in the numerical control device will 
be described hereinafter with reference to FIGS. 1 and 2. Assuming that an 
electric discharge machining apparatus is controlled by the numerical 
control device 8, the numerical control device 8 first analyzes an NC 
program prepared by an operator, which is read out from the NC tape by the 
paper tape reader 11. The electric discharge machining apparatus performs 
the machining operation to obtain the programmed machining shape. When, 
for example, an alarm indicating an H/W stroke end where the machine is 
cut out of machining area limit occurs during the machining operation, the 
machining operation is stopped immediately, and an alarm code number 
corresponding to the alarm is set in an alarm code number area of a 
memory. 
When the operator selects such a display as shown in FIG. 2. The content of 
the alarm is displayed according to the following manner on the CRT 9. The 
corresponding alarm message is searched based on the alarm code number to 
display on the CRT, the alarm code number in an alarm code number 
displaying area 12 and the alarm message in an alarm message displaying 
area 13 thereof, respectively. 
The conventional CRT displaying method of numerical control devices is 
disadvantageous in that it takes long time to escape from an alarm or 
error condition because an operator's escaping operation is not performed 
until analyzing messages displayed on the CRT 9 or reading an instruction 
manual. 
SUMMARY OF THE INVENTION 
The present invention is made to solve the above-mentioned problem. It is 
an object of the invention to provide a CRT displaying method in numerical 
control devices. In the method, it is easy to escape from the alarm or 
error conditions because the operator is informed of an occurrence alarm 
or error conditions together with an escaping manner from that conditions 
during the numerically controlled machining operation by both graphical 
and literal representations. 
The above, and other object of the present invention are accomplished by a 
CRT displaying method for use in a numerical control device for 
controlling a machining apparatus which has a machining tool to machine a 
workpiece, said displaying method comprising the steps of detecting an 
occurrence of an error condition during an operation of said machining 
apparatus, displaying an alarm code number assigned in advance to said 
error condition, said alarm code number being displayed in an alarm code 
number area on said CRT, displaying an alarm message corresponding to said 
alarm code number in an alarm message displaying area on said CRT, 
graphically displaying an manner how to escape from said error condition 
which is calculated based on said alarm code number and an operational 
program for said numerical control device, literally displaying said 
manner.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the figures, an embodiment of the invention will be described 
below. FIG. 3 is a schematic diagram showing an example of a display on a 
CRT 9 according to the present invention. When a tool arrives at a stroke 
end beyond which an apparatus is out of a machining area limit, occurs in 
the wire cut electric discharge machining apparatus. There are provided an 
alarm code number area 1, an alarm message area 2, and an area 7 for 
displaying a message as to the how to escape from the stroke end. In the 
display, a table stroke frame 3 indicates the possible machining area, a 
line 4 indicates a machining locus 4, a position 5 indicates a tool stop 
point at the stroke end, and an arrow 6 indicates a direction in which the 
tool is allowed to escape. 
The operation will be described hereinafter. 
When an alarm indicative of an H/W stroke end occurs during a machining 
operation, the machining is stopped immediately and an alarm code number 
is set in the alarm number area of a memory. 
Referring to the flow chart in FIG. 4, it will be explained how to display 
a picture image shown in FIG. 3 on the CRT 9 after an operator's selection 
for the image. 
When the operator selects the image of FIG. 3, the alarm code number is 
displayed in the alarm code number area 1 as shown in a step S1 of FIG. 4. 
Then, the alarm message corresponding to the alarm code number is searched 
to be displayed in the alarm message displaying area 2 as shown in a step 
S2. 
Then, as shown in a step S3, the possible range of machining of the 
electric discharge machining apparatus is obtained by an analysis of a 
machining program or the like, so that the possible range, i.e., a table 
stroke frame is graphically displayed on the CRT 9. Then, as shown in a 
step S4, the machining locus is displayed graphically from the start point 
of machining to stop point. Then, as shown in a step S5, the position 
where the machining tool is prevented from advancing at the stroke end is 
displayed graphically. Then, as shown in a step S6, a direction in which 
the tool can be allowed to escape, is computed through the analysis of the 
stroke end position and the machining program to be displayed on the CRT 
9. Finally, as in a step S7, the manner how to escape from the stroke end 
position is obtained based on the analysis of the alarm number, the stroke 
end position and the machining program, so as to be literally displayed in 
the escaping manner displaying area 7. 
To this end, the operator can be notified of the occurrence of the error 
condition and/or the alarm therefor by manner of both the literal 
representation of the steps S1 and S2 and the graphical representation of 
the steps from S3 to S5; and the operator can be also notified of the 
escape manner by both the literal representation of the step S7 and the 
graphical representation of the step S6. 
Because it is possible to display the escaping manner in the graphical 
representation and the literal representation simultaneously even if the 
alarm or error occurs during the numeral controlled machining operation, 
the present invention is advantageous in that it is easy to escape from 
the alarm or error conditions. 
Though the above embodiment is directed to the escape from the error of a 
stroke end, it is clear that other embodiments for different alarms and 
errors is possible and have the same effect as the above embodiment has. 
That is, many different modifications of the present invention may be 
possible without departing from the spirit and scope of the present 
invention. It should be understood that the present invention is not 
limited to the specific embodiment described in the specification.