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  1. #1
    Registered
    Join Date
    Feb 2012
    Posts
    52

    Look Ahead During DNC/Drip Feed

    My shop has a 1994 VF3. I was reading in the book that during drip feed there is no look ahead. Maybe I misread that... does that seem right to you? I ask because I am looking into 3rd party USB-RS232 devices to get past our 1MB memory limitation, mostly for 3D type surfacing work, but having 0 look ahead is probably going in the opposite direction. Thoughts?

  2. #2
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    Join Date
    Nov 2006
    Posts
    487

    Re: Look Ahead During DNC/Drip Feed

    Well, those older controllers are pretty slow compared to the newer ones when the HSM option became available. I would say they do have lookahead but it's probably limited to just one line at a time. The bigger problem I encounter with drip-feeding large programs is starving the memory buffer, so you have to run the RS232 relatively high baud, while also not trying to push through a bajillion line segments per second. It works but all depends on the feedrate and how tightly-packed the lines are.

  3. #3
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    Join Date
    Aug 2015
    Posts
    93

    Re: Look Ahead During DNC/Drip Feed

    You don't have 0 look ahead. I forget the exact amount but I believe pre-1999 its around 30 lines or something like that.

    For drip feeding if you keep your feedrates at or below 100 ipm you should be fine. Over 100ipm the control starts to have problems.

    I second the high baud rate. On our VF-4 we are running a baud rate of 38400 and we do a lot of surfacing and high speed machining on it. Also, Xmodem works better than Xon\Xoff.

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