jeremy youngs wrote: > so how far does lcnc actually look ahead????? > One block! It always operates at a speed such that it can come to a full stop on the next G-code block. Some users who do high-speed contouring need more lookahead, and then it becomes arbitrary how far ahead you have to look. I proposed a scheme a long time ago where you would look ahead and mark points where you needed to slow down to avoid exceeding the machine's acceleration limits, then run backward through the program to a point where the slowdown needed to begin. It effectively would add an F word on every block, even when the actual G-code didn't specify one. I also posited that this couldn't be done in real time as the distance back you had to go to begin the slowdown was arbitrary. But, such an operation doesn't sound extremely difficult. Basically, you don't do anything different until you spot a block where the speed needs to be reduced below the commanded feedrate, then you have to run back to put in the lowered speed. Maintaining a queue of past moves that runs back for 100 or so blocks might make it easier to figure out where the slowdown needs to begin.
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