Method of revising NC program for four-axis lathes

A method of preventing interference between tools in an NC machine tool controlled by first and second NC programs which control the movement of first and second tool rests, respectively, to machine a workpiece, comprising the steps of:

• (a) reading the first and second NC programs one block at a time in successive fashion and executing interpolative simulations on the first and second NC programs while displaying the first and second tool rests;
• (b) determining whether the tools on the first and second tool rests interfere with each other during the interpolative simulations executed in said step (a);
• (c) suspending execution of the interpolative simulations of said step (a) when it is determined in said step (b) that there is interference between the tools, and returning the displayed first and second tool rests to a position corresponding to the beginning of the blocks of the first and second programs in which interference occurred;
• (d) executing interpolative simulation according to one of the first and second NC programs to move the display of the first tool rest in accordance with the corresponding block of the first NC program, while maintaining the interpolative simulation according to the second NC program in a suspended state;
• (e) determining whether the tools on the first and second tool rests interfere with each other during said step (d);
• (f) storing sequence numbers corresponding to the blocks of the first and second programs in which the interference occurred in said step (b) when it is determined that there is no interference in said step (e);
• (g) returning to said step (a) after said step (f) has been completed;
• and
• (h) automatically revising the first and second NC programs after interpolative simulation has been executed for all of the first and second NC programs, by inserting a wait command in front and each block of the second NC program having a stored sequence number corresponding to the second NC program being suspended in said step (d), and inserting a wait command after each block of the first NC program corresponding to a stored sequence number for the first NC program for which interpolative simulation was executed in said step (d).

A method of revising NC programs for a four-axis lathe in which there are provided first and second NC programs corresponding to first and second tools rests, respectively, the first and second NC programs each having wait commands, wherein a workpiece is machined by controlling movement of the first and second tool rests independently in accordance with the first and second NC programs, respectively, while synchronization is achieved by the wait commands, said method comprising the steps of:

• (a) executing interpolative simulations one block at a time in successive fashion based on the first and second NC programs when an interference check is made, said step (a) including storing several items of latest NC data in the first and second NC programs for which the interpolative simulations are executed in a memory;
• (b) checking whether tools on the first and second tool rests interfere with each other during said step (a);
• (c) when it is determined in said step (b) that there is interference, halting the interpolative simulations and moving the tool rests back to the beginning of blocks in which the interference occurred, said step (c) including reading out starting positions of the blocks in which interference occurred from the memory and moving both of the tool rests back to the starting points of the blocks;
• (d) holding the interpolative simulation according to one of the first and second NC programs in the halted state and executing the interpolative simulation according to the other of the first and second NC programs to move solely the corresponding tool rest along a path in the block in which the interference occurred while checking for interference;
• (e) when no interference is found when moving solely the one tool rest in said step (d), storing sequence numbers of the first and second programs which prevailed when interference occurred;
• and
• (f) revising the NC programs after the interference check by inserting a wait command ahead of the sequence number of the NC program for which the interpolative simulation was halted in said step (d), and inserting a wait command after the sequence number of the NC program for which the interpolative simulation was executed in said step (d).