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  1. #1
    Join Date
    Aug 2011
    Posts
    135

    Programming for 4th axis

    I am trying to use my 4th axis with limited success. When trying to cut a 4 axis pocket in something round, my post processor is generating the code and setting the F (feed) to 15 inches per minute (what I have set in my solidcam software).
    This is fine for cuts that dont utilize the A -Axis (moving only in x and Y). Once the cut gets to a rotate command and the A Axis starts spinning, it feeds at what appears to be 15 deg/min (incredibly slow)
    Curious as to how you guys are programming the 4th axis on your machine. Does your post processor/cam software is compensating for the size of the arc created and setting a new Feed on rotate?
    Sorry if this is vague, or hard to understand still trying to wrap my head around 4th axis work myself.

    Thanks
    Here is just a little test part that I am trying to code
    Solidcam starts the tool in the center of the pocket and more or less spirals out. I have a feeling the code would produce the correct part if I gave the machine a month to punch it out. 15 deg/ minute seams to creap along at a snails pace.

  2. #2
    Join Date
    Feb 2006
    Posts
    7063

    Re: Programming for 4th axis

    You'd be much more likely to get the answer you need on a SolidCAM forum than here....

    Regards,
    Ray L.

  3. #3
    Join Date
    Aug 2011
    Posts
    135

    Re: Programming for 4th axis

    Quote Originally Posted by SCzEngrgGroup View Post
    You'd be much more likely to get the answer you need on a SolidCAM forum than here....

    Regards,
    Ray L.
    That's my next stop I was curious as to if this is normal for the cam software to set different feeds for a axis work. I've done some research and it seems as though raise is normal but I don't see how it could be the case

    Sent from my SM-G900V using Tapatalk

  4. #4
    Join Date
    Feb 2006
    Posts
    7063

    Re: Programming for 4th axis

    I've never tried it, but, logically, the CAM would need to know the maximum rotation rate of the A axis, so it does not violate that limit. When doing 4-axis moves, I would expect it to attempt to maintain the specified linear feedrate (which will be a function of the actual part diameter and cut depth), but back off on all axis feeds if that would violate the A axis limit. What happens if you specify a much higher A axis "feed"?

    Regards,
    Ray L.

    - - - Updated - - -

    I've never tried it, but, logically, the CAM would need to know the maximum rotation rate of the A axis, so it does not violate that limit. When doing 4-axis moves, I would expect it to attempt to maintain the specified linear feedrate (which will be a function of the actual part diameter and cut depth), but back off on all axis feeds if that would violate the A axis limit. What happens if you specify a much higher A axis "feed"?

    Regards,
    Ray L.

  5. #5
    Join Date
    Aug 2011
    Posts
    135

    Re: Programming for 4th axis

    Quote Originally Posted by SCzEngrgGroup View Post
    I've never tried it, but, logically, the CAM would need to know the maximum rotation rate of the A axis, so it does not violate that limit. When doing 4-axis moves, I would expect it to attempt to maintain the specified linear feedrate (which will be a function of the actual part diameter and cut depth), but back off on all axis feeds if that would violate the A axis limit. What happens if you specify a much higher A axis "feed"?

    Regards,
    Ray L.

    - - - Updated - - -

    I've never tried it, but, logically, the CAM would need to know the maximum rotation rate of the A axis, so it does not violate that limit. When doing 4-axis moves, I would expect it to attempt to maintain the specified linear feedrate (which will be a function of the actual part diameter and cut depth), but back off on all axis feeds if that would violate the A axis limit. What happens if you specify a much higher A axis "feed"?

    Regards,
    Ray L.
    I totally agree that if i want to maintain 15ipm that it is a function of the diameter of the cut depth. That is about where my research took me.

    I dont understand what you mean by "What happens if you specify a much higher A axis "feed"?"
    In my solidcam software I can specify a feed and of course speed of spindle. It does not (in my limited experience) ask for an A Axis Feed (which would solve all of these issues)

    To give you an example of the code generated

    G1 Y-0.547 Z0.053 F10.
    G1 X5.249 F15.
    G1 Y-0.549 Z0.028 A-87.073


    The Tool Plunges into the material in line 1 at 10 ipm
    The tool makes a small X movement at 15 IPM (from here on in the code feed is not changed)
    The magic starts happening with the A Axis as the tool works out of the center of the pocket. but feed is still set at 15 (which is deg per min I beleive, not IPM)

    - - - Updated - - -

    Quote Originally Posted by SCzEngrgGroup View Post
    I've never tried it, but, logically, the CAM would need to know the maximum rotation rate of the A axis, so it does not violate that limit. When doing 4-axis moves, I would expect it to attempt to maintain the specified linear feedrate (which will be a function of the actual part diameter and cut depth), but back off on all axis feeds if that would violate the A axis limit. What happens if you specify a much higher A axis "feed"?

    Regards,
    Ray L.

    - - - Updated - - -

    I've never tried it, but, logically, the CAM would need to know the maximum rotation rate of the A axis, so it does not violate that limit. When doing 4-axis moves, I would expect it to attempt to maintain the specified linear feedrate (which will be a function of the actual part diameter and cut depth), but back off on all axis feeds if that would violate the A axis limit. What happens if you specify a much higher A axis "feed"?

    Regards,
    Ray L.
    I totally agree that if i want to maintain 15ipm that it is a function of the diameter of the cut depth. That is about where my research took me.

    I dont understand what you mean by "What happens if you specify a much higher A axis "feed"?"
    In my solidcam software I can specify a feed and of course speed of spindle. It does not (in my limited experience) ask for an A Axis Feed (which would solve all of these issues)

    To give you an example of the code generated

    G1 Y-0.547 Z0.053 F10.
    G1 X5.249 F15.
    G1 Y-0.549 Z0.028 A-87.073


    The Tool Plunges into the material in line 1 at 10 ipm
    The tool makes a small X movement at 15 IPM (from here on in the code feed is not changed)
    The magic starts happening with the A Axis as the tool works out of the center of the pocket. but feed is still set at 15 (which is deg per min I beleive, not IPM)

  6. #6
    Join Date
    Jun 2013
    Posts
    1041

    Re: Programming for 4th axis

    He's asking if you can specify a feedrate of 100ipm for the program. Then rerun it dry. If you do this does the a axis go faster then before. If not it would indicate you need to change some settings in relation to the a axis. (gearing, max feedrate etc..)

    Ben

  7. #7
    Join Date
    Aug 2011
    Posts
    135

    Re: Programming for 4th axis

    Quote Originally Posted by bhurts View Post
    He's asking if you can specify a feedrate of 100ipm for the program. Then rerun it dry. If you do this does the a axis go faster then before. If not it would indicate you need to change some settings in relation to the a axis. (gearing, max feedrate etc..)

    Ben

    Yes It does move faster as I ramp up the feeds, but of course this leads to insanely fast lateral moves.
    To be clear, I havent made a chip yet. All of this is air cutting. Trying to work out the bugs without loosing my wits and my endmill stash

    - - - Updated - - -

    Quote Originally Posted by bhurts View Post
    He's asking if you can specify a feedrate of 100ipm for the program. Then rerun it dry. If you do this does the a axis go faster then before. If not it would indicate you need to change some settings in relation to the a axis. (gearing, max feedrate etc..)

    Ben

    Yes It does move faster as I ramp up the feeds, but of course this leads to insanely fast lateral moves.
    To be clear, I havent made a chip yet. All of this is air cutting. Trying to work out the bugs without loosing my wits and my endmill stash

  8. #8
    Join Date
    Feb 2006
    Posts
    7063

    Re: Programming for 4th axis

    There is a fundamental problem with the way it's trying to do the move - X/Y/Z feeds are in inches/min while A feeds are in degrees/min. ANY feed move involving the A axis and any linear axis is going to have the wrong feedrate for one or the other. The only sensible way to do it is to rotate A, then feed in X/Y/Z, lather, rinse, repeat. You definitely need to go to a SolidCAM forum for help. I would expect there is probably a configuration setting that changes the CAM strategy to work better with the 4th axis. Either that, or go very shallow, with a small stepover, so you can safely crank the linear feedrate way up, to get the rotary moves going at a reasonable rate.

    Regards,
    Ray L.

  9. #9
    Join Date
    Aug 2011
    Posts
    135

    Re: Programming for 4th axis

    Quote Originally Posted by SCzEngrgGroup View Post
    There is a fundamental problem with the way it's trying to do the move - X/Y/Z feeds are in inches/min while A feeds are in degrees/min. ANY feed move involving the A axis and any linear axis is going to have the wrong feedrate for one or the other. The only sensible way to do it is to rotate A, then feed in X/Y/Z, lather, rinse, repeat. You definitely need to go to a SolidCAM forum for help. I would expect there is probably a configuration setting that changes the CAM strategy to work better with the 4th axis. Either that, or go very shallow, with a small stepover, so you can safely crank the linear feedrate way up, to get the rotary moves going at a reasonable rate.

    Regards,
    Ray L.
    I agree with what your saying. But what if this wasn't a simple square pocket. What If it where a spiral down the length of the shaft. In that case there would have to be a x movement and a movement at the same time and the feed would have to be calculated in degrees per minute I beleive.

    Sent from my SM-G900V using Tapatalk

  10. #10
    Join Date
    Apr 2013
    Posts
    1788

    Re: Programming for 4th axis

    Others have posted about this sort of problem on the Mach forum but I don’t see any answer that doesn’t require manual intervention. That is, a gcode command to set the radius. See Mach3 Tool Display "squashed" for 4-axis Gcode?? for one discussion.

  11. #11
    Join Date
    Mar 2003
    Posts
    35538

    Re: Programming for 4th axis

    In Mach3, go to Config >Toolpath, and select "Use Diameter for Feedrate".
    Then on the Settings page, there's a setting for Rotation Diameter.
    If Z zero is the center of rotation, enter .001 for the diameter.
    If Z zero is at the surface of the part, enter the RADIUS of the part.

    This should get the tool moving at the correct feedrate on a axis moves.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  12. #12
    Join Date
    Aug 2011
    Posts
    135

    Re: Programming for 4th axis

    Thanks for the replies. I got my post processor to output the correct feed

    Sent from my SM-G900V using Tapatalk

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