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  1. #1
    Join Date
    Jun 2012
    Posts
    516

    FADAL's Advanced Feed Forward - AFF

    there is a lot about this here already:
    http://www.cnczone.com/forums/fadal/...rking-dnc.html

    I'm trying out AFF for the first time right now, and have it coded into my post processor to turn it on, and choose parameters, etc.

    AFF is actually just making the motion jerky and the toolpaths slower. I'm not sure what to think. It is my understanding that AFF is FADAL's offering for high speed machining. Beyond that vague description, it seems that it really is giving you access to variables that allow you to 'tune' the machine to specific applications.

    This being said, I think it may have been designed with simple toolpaths in mind. Trochoidal paths like trumill / volumill / imachining do a lot of fancy feed rate changes and so on - and the fadal just seems to get slower when running AFF with that kind of path. maybe it will be more beneficial for 3D contouring? I really don't know.

    It seems though, that this is going to be a very long trial and error process, and the conclusion might just be that the machine runs better without AFF anyhow. Good thing I didn't pay a whole lot for the boards (compared to what I can imagine fadal charged for this option). I need to learn how to use it to my advantage. Right now it pretty much sucks.

    Anybody using AFF out there?

    in addition to M94.2 (AFF) I also coded my post to spit out M94.1 (feed rate modifications based on angular change) - this doesn't work at all with toolpaths that change feeds often., and I also set up my most to do M90 thru M93 gain changes based on feed rate. Setting the machine to higher gain just seems to make the motion really jerky and seems very hard on the machine.

    Unfortunately I spent a solid 8 hour day programming these 'advanced' tool sets into my post, and at the end of the day I am shutting all of those features off. wtf.

  2. #2
    Join Date
    Jun 2012
    Posts
    516

    Re: FADAL's Advanced Feed Forward - AFF

    I think I've got this AFF stuff figured out. It doesn't work with G2/G3 at all - you have to export the code HSM style with all small linear moves strung together. Then it works great - the machine can make crazy moves without 'booming' based on the ramp settings. I haven't had any trouble with it not keeping up either so far, and I'm running over DNC.

    This seems to be an advantage vs. the arc moves because the control has to crunch the arc moves and will operate slower. So running the small linear pieces, accompanied by AFF to smooth over the motion seems to be pretty great.

    I talked with David at i-t-s, who worked on AFF during it's development. He explained that AFF basically lets you to control the amount of following error that is allowed - so if you're roughing you can let it have like 0.012" of following error where the control is allowed to 'cut the corner' to that programmable extent. Then during a finishing pass you set the following error much lower, to like 0.0002", and if the control goes into a corner or other big angle change, it will actually make the toolpath wait until the following error tolerance has been achieved - so it won't cut corners.

    without using aff, the control will begin executing the next move maybe ahead of time if you're running a high feedrate and will cut the corner. AFF just provides a way to control the amount of error you can deal with and that may imply faster cycles if the allowed error is big, and it may imply slower cycles for higher accuracies.

    one thing that I don't know about is over-shoot. it seems that AFF assumes that there will be no overshoot, and its basically up to you to choose appropriate gain settings (M90, not associated with AFF), and to choose appropriate ramping (aff accel and decel) parameters to make sure that you don't overshoot.

    so if you can find settings that don't overshoot, you use all G1 moves, and you run with AFF enabled - the machine performs like a champ. It's pretty cool. I'll need to test it out on some mold type surfacing, maybe with and without aff to see if the machine behaves differently in each case - it should where at a high feed rate and no aff, it may overshoot due to lack of ramping control.


    AFF is not: spline interpolation or nurbs interpolation (maybe see fanuc for these $$ and modern options?) - it cannot look ahead and interpolate / fill in more data points to the motion that aren't directly programmed. Haas' high speed machining option does do this - it can make more points out of what you give it, which in theory increases the possible detail. I'm not sure what else the haas software does, but it probably has some kind of look ahead ramping too. But, at least AFF lets you modify how the control deals with high speed machining in the form / level of detail that you feed it.

  3. #3
    Join Date
    Jun 2012
    Posts
    516

    Re: FADAL's Advanced Feed Forward - AFF

    I did a test of a trochoidal toolpath using AFF with all G1 moves vs. not AFF with G2/G3 allowed.

    The toolpath with AFF runs 6% slower than the one with arcs allowed and no AFF.

    That being said, the path using all G1 and AFF is much more smooth, it seems to be under much better motion control. I had to make a LUT of feedrate vs. helical angle / z delta to get my fadal to do the trochoidal paths because if you just let it go as the cam wants to, the fadal gives 'helical ramp too short' errors or something like that - meaning that it cannot interpolate the helix at the high feedrate. So the program will go especially for finishing / rest material paths that it feeds up to the helix at like 150ipm, then I have to instantly program a G9 and an F5, or F2, during a small helix, then reprogram the G8 and F150. I doubt that the control is really able to do this in reality - it probably just doesn't throw an error and the motion probably has a huge error on it. using this method the motion overall isn't quite jerky, but there are plenty of smaller booms still (down from clearly destructive booms and many errors when there is no LUT applied). I've been running like that for about a year. I was also told that G9 doesn't even take effect for something like 0.1" beyond where you program it due to the buffer, and due to high feed rates - so programming the G9, helix and F_low, G8 in reality doesn't do squat. interesting stuff

    with all G1 moves + aff, there is no feedrate LUT, g9/g8, or other post processor nonsense required, the moves are really smooth, and the cycle time isn't much longer (and maybe I can shorten it by changing the aff ramp parameters).

  4. #4
    Join Date
    Aug 2009
    Posts
    12
    Hi

    I have Fadal vmc xt15 year of 1996. I updated hes memory
    To 8mb memory board and same time replaced the software version
    To sys103.5. We use Solidworks for cad and
    Edgecam for cam. We use lot of time high feed milling
    With 7000mm/min speed and many times the machine bumping on
    Corner. And overshoot. We have to create special toolpath to get out
    The bumping. I am interested to put aff board in machine if this silved
    My problem.
    Can we speak about your experience before i buy?
    The aff reduce the speed before the corner and speed up after the corner?
    What is the situation if radius on corner? Same slow down and speed up?
    Works only with G01 code?


    Thanks Tom

    Quote Originally Posted by mflux_gamblej View Post
    I did a test of a trochoidal toolpath using AFF with all G1 moves vs. not AFF with G2/G3 allowed.

    The toolpath with AFF runs 6% slower than the one with arcs allowed and no AFF.

    That being said, the path using all G1 and AFF is much more smooth, it seems to be under much better motion control. I had to make a LUT of feedrate vs. helical angle / z delta to get my fadal to do the trochoidal paths because if you just let it go as the cam wants to, the fadal gives 'helical ramp too short' errors or something like that - meaning that it cannot interpolate the helix at the high feedrate. So the program will go especially for finishing / rest material paths that it feeds up to the helix at like 150ipm, then I have to instantly program a G9 and an F5, or F2, during a small helix, then reprogram the G8 and F150. I doubt that the control is really able to do this in reality - it probably just doesn't throw an error and the motion probably has a huge error on it. using this method the motion overall isn't quite jerky, but there are plenty of smaller booms still (down from clearly destructive booms and many errors when there is no LUT applied). I've been running like that for about a year. I was also told that G9 doesn't even take effect for something like 0.1" beyond where you program it due to the buffer, and due to high feed rates - so programming the G9, helix and F_low, G8 in reality doesn't do squat. interesting stuff

    with all G1 moves + aff, there is no feedrate LUT, g9/g8, or other post processor nonsense required, the moves are really smooth, and the cycle time isn't much longer (and maybe I can shorten it by changing the aff ramp parameters).

  5. #5
    Join Date
    Jun 2012
    Posts
    516

    Re: FADAL's Advanced Feed Forward - AFF

    G8/G9 is bad, just dont even use it. I did a post mod for my solidcam where i would change the ramp mode around, but the fadal control just doesnt work fast enough. I have an AFF board. it sucks. its just too old. the control cannot process enough G1 moves to go faster than about 70 IPM at 0.004" G1 resolution to not overrun the buffer even if running from internal memory.

    i have a lot better luck simply letting your cam output arcs, and don't futs with the G8/G9 thing. just leave it G8 (not absolute stop).

    the other thing that I did do, was my post is modded such that when there is an imachining tool path I have it modify the feed rate output by my cam so to avoid the 'helical ramp too steep' error. thats just trial and error to see what ratio of feedrate, z change, and arc radii the fadal control can handle.

  6. #6
    Join Date
    Jun 2012
    Posts
    516

    Re: FADAL's Advanced Feed Forward - AFF

    also, just use those type of adaptive milling cuts for roughing and leave 0.01" on wall and floor, finish feed at lower rates like 50IPM max.

    also you need to tune your servos, maybe get your machine ball bar checked.

  7. #7
    Join Date
    Aug 2009
    Posts
    12
    Hi

    I got my aff card last week. Working fine when only g1
    Mooves i have. The feed parameter its procent? Example if the high feed milling is 300ipm then feed settings on 50 by offset whats happend?
    I changed the feed but i not realized any different?
    Lookat my videos: its seco 2incs dia high feed cutter run
    300ipm. Gain 100 , accel 200, decel 600, detail .05 (mm)
    Looks sexy moove. Feed settings is not clear for me yet.

    https://vimeo.com/235007887
    Password :7000

    Thanks Tom




    Quote Originally Posted by mflux_gamblej View Post
    also, just use those type of adaptive milling cuts for roughing and leave 0.01" on wall and floor, finish feed at lower rates like 50IPM max.

    also you need to tune your servos, maybe get your machine ball bar checked.

  8. #8
    Join Date
    Jan 2013
    Posts
    24

    Re: FADAL's Advanced Feed Forward - AFF

    Thanks for posting this. It'll be useful to me I think. If I don't fungus it us! lol:cheers:

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