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  1. #1
    Join Date
    Jan 2013

    Slow feedrate into/out of corners

    We have a Streamline Automation CNC that was designed for cutting large EPS blocks of foam. We also use this machine to cut flat sheet stock like wood and plastic. Because this machine has such a large Z Axis the router is mounted very high off the surface. This results in shaking of the mount when a dramatic change in the tool path occurs. Its like driving a car into a sharp corner and not letting off the gas or braking, the machine just goes in full throttle, whatever the feed rate is set at.
    The lead into a tight corner cuts pretty smooth but with the sudden change in direction to get out of the corner cut there is a shake that occurs and makes a scalloped cut coming out due to the shaking. This is sometimes accompanied with a bang or hit sound because the change in direction is so forceful on the machine.

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    Is there a way to slow the feed rate coming into a tight corner and then slowly ramp back up to speed once you come out of the cut? I'm familiar with the Motion Delays in FlashCut but that just seems to force the machine to a dead stop (resulting in shaking) then it immediately accelerates back to the feed rate resulting in shaking coming out of the corner.

    We've tuned the servos and tightened everything up which resulted in much better machine operation but that does not address the high mount design that will shake. Lowering overall feed rate helps but then we have to deal with slow cut times and some materials require higher feed rates.
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  2. #2
    Join Date
    Dec 2012

    Re: Slow feedrate into/out of corners


    While I´m not familiar with your particular machine I believe there should be some parameter in your configuration table that must allow to reduce speed when approaching any corner. It might be labeled as APPROXIMATION or something like that. The number refers to the distance from the corner at which the axis movement is to start reducing speed so that it reaches zero at the end of the segment.

    Another approach might be to add a dwell time at the end of every corner. In the language of my machines it would be something like the following:

    REM: Horizontal line to 20.0 mm right.
    LIN: 200, 0
    REM: 500mS dwell.
    DWELL: 500
    REM: Vertical line to 20.0 mm up.
    LIN: 200, 200

    The DWELL line is a must have in the program listings of my machines as that triggers the approximation sequence. If I discard it in the program above the machine does not change speed at all doing precisely what you mentioned in yours. Even a DWELL:0 will do the trick.

    I hope this helps.


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