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    Community Moderator difalkner's Avatar
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    Default Cuts have steps instead of being smooth

    This is something I have noticed in some jobs but not others; the side wall of the cut should be straight but it has steps in some areas, smooth in others. It doesn't happen on every job I cut and on some it doesn't matter because there are subsequent operations that will remove the steps but it shouldn't be there.

    I'll tell you what I know -
    1) drive belts are tight
    2) the machine is lubed sufficiently
    3) there is no visible change in motion or jerky movement
    4) the simulation in Fusion 360 doesn't show this stepping effect
    5) nothing on the machine appears to be loose
    6) the DC hose is grounded at the DC
    7) there is no audible change when this happens
    8) has happened with both downcut and upcut spiral 1/4" bits
    9) using Mach4 although not the latest release, it's probably 6 months old and I need to update it, and using ESS
    10) the jobs start and finish as designed in Fusion 360, no interruption or appearance of missing steps and being off from that point forward. This one is a 2D Contour profile.
    11) spindle speed is 18,000 and feed is from 100 ipm to 150 ipm with depth of cut 0.125" to 0.150" in hardwood
    12) the bit is tight in the collet and the work piece is well locked down, no movement at all

    This is what I was cutting today, B-52 tails for a trophy shop, 2 up per board of Walnut, cutting time is about 6 minutes, 4 boards and 8 tails total, and the stepped area of cuts is in the same place on each one although more so on the first than the last -
    Cuts have steps instead of being smooth-001-two-tails-jpg

    The red area cuts are very smooth and the green area cuts are stepped -
    Cuts have steps instead of being smooth-002-smooth-walled-cut-1st-tail-jpg

    Cuts have steps instead of being smooth-003-stepped-cut-2nd-tail-jpg

    Right after that I cut the antennas, 10-up, and two of the bases; cuts are smooth except for some fiber tear but that's ok because these get completely rounded over -
    Cuts have steps instead of being smooth-004-antennas-jpg

    Cuts have steps instead of being smooth-005-antennas-one-side-jpg

    Cuts have steps instead of being smooth-006-antennas-2nd-side-jpg

    Here's the finished piece so you'll get an idea what I'm building out -
    Cuts have steps instead of being smooth-028-ready-presentation-blurred-names-jpg

    Here's another example from a couple of week ago, the other side of the letters is very smooth - I believe this is 2D Contour, as well. I don't recall if this has happened on another profile such as Pocket or Adaptive clearing -
    Cuts have steps instead of being smooth-004-steps-jpg

    Ideas?

    Thanks!
    David

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    Last edited by difalkner; 12-01-2017 at 08:21 PM. Reason: Problem solved
    David
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    Member ger21's Avatar
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    Default Re: Cuts have steps instead of being smooth

    My first guess is that this may be caused by CV Mode? Have you set any of the CV angle feedrate settings in Mach4?

    Gerry

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    Community Moderator difalkner's Avatar
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    Default Re: Cuts have steps instead of being smooth

    Quote Originally Posted by ger21 View Post
    My first guess is that this may be caused by CV Mode? Have you set any of the CV angle feedrate settings in Mach4?
    No, Gerry, the only thing I have set on CV is this -
    Cuts have steps instead of being smooth-007-mach4-cv-setting-jpg

    Where would I set the angle feed rate? A quick Google search didn't show me anything...

    I know Fusion 360 has a setting to reduce feed rate at corners, which I have not used, but this issue isn't a corner on the tails. It sort of is on the letters shown earlier.

    David

    David
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    Member ger21's Avatar
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    Default Re: Cuts have steps instead of being smooth

    I don't have Mach4 in front of me, so I'm not sure where? But there's a CV wizard that lets you enter the info.
    Basically, you set a maximum feedrate for each angle change, from 0-180 degrees. I'm not a fan of this method at all, but it's what they have.

    Gerry

    UCCNC 2017 Screenset
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    JointCAM - CNC Dovetails & Box Joints
    [URL]http://www.g-forcecnc.com/jointcam.html[/URL]

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


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    Default Re: Cuts have steps instead of being smooth

    I would probably agree with Gerry. Though I don't use Mach software, can't help with settings.
    Is the cut direction the same? Climb vs Conventional? Is the waste piece on the 'red' image smooth or stepped?

    Just guessing...



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    Default Re: Cuts have steps instead of being smooth

    Ok, found the Wizard but no idea what to set anything on...

    Here are some more photos after taking the tails out of the board -

    Pretty obvious when placed side by side -
    Cuts have steps instead of being smooth-008-green-steps-red-smooth-jpg

    You can see how it's smooth coming down from the top but starts right after the curve of the leading edge of the tail -
    Cuts have steps instead of being smooth-009-starts-near-top-jpg

    Waste side of the good cuts -
    Cuts have steps instead of being smooth-010-waste-side-good-cut-jpg

    Waste side of the stepped cuts -
    Cuts have steps instead of being smooth-011-waste-side-stepped-cut-jpg

    David

    David
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    Member ger21's Avatar
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    Default Re: Cuts have steps instead of being smooth

    I think this is as simple as your spindle being out of tram.

    What led me to the CV was your other pic, with the large steps.

    Gerry

    UCCNC 2017 Screenset
    [URL]http://www.thecncwoodworker.com/2017.html[/URL]

    Mach3 2010 Screenset
    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

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

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


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    Default Re: Cuts have steps instead of being smooth

    I was always told that you should look at the waste piece and if the cut looked cleaner on that piece, than you should switch your toolpath direction. From the pictures, it looks like that is the case, but you didn't answer if the cut direction was the same for both pieces.

    Keep in mind, I am definitely not an expert by any means.

    Dave



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    Community Moderator difalkner's Avatar
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    Default Re: Cuts have steps instead of being smooth

    Quote Originally Posted by ger21 View Post
    I think this is as simple as your spindle being out of tram.

    What led me to the CV was your other pic, with the large steps.
    That, too, was my first thought, Gerry. In checking this past weekend, unless I did something wrong (entirely likely) the spindle checks out. What method do you use or can you point me to a procedure or video showing the best way?

    Quote Originally Posted by beltramidave View Post
    I was always told that you should look at the waste piece and if the cut looked cleaner on that piece, than you should switch your toolpath direction. From the pictures, it looks like that is the case, but you didn't answer if the cut direction was the same for both pieces.

    Keep in mind, I am definitely not an expert by any means.

    Dave
    Sorry, Dave; yes, the cut direction is the same for both pieces, relative to each piece. The direction is opposing relative to the board, though.
    Cuts have steps instead of being smooth-012-cut-direction-jpg

    David

    David
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    Default Re: Cuts have steps instead of being smooth

    This is what I came up with for tram setup since I don't have the double gauge setup. I think it should work ok once I get the glass level. Gotta' work on some songs for Praise Band practice so that's as far as I got but maybe when I get home, or at least first thing in the morning, I'll have a go at this.

    Cuts have steps instead of being smooth-013-tram-setup-jpg

    David

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    Default Re: Cuts have steps instead of being smooth

    David - Here is the . Fast forward to the 7:00 minute mark. I would use a larger diameter bit than they show - maybe a 1-1/4" flat bottom if you have it. Be sure to set your stepover high like they recommend. You can get it very close with this method, probably as close as you're going to get it and certainly close enough to see if that's the problem or not.

    Last edited by difalkner; 11-29-2017 at 10:57 PM.


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    Default Re: Cuts have steps instead of being smooth

    I think it should work ok once I get the glass level.
    The glass being level has nothing to do with the spindle.

    Surface the spoilboard, then just lay the glass right on the spoilboard. You want the spindle perpendicular to the spoilboard, not a shimmed piece of glass.

    Gerry

    UCCNC 2017 Screenset
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    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Community Moderator difalkner's Avatar
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    Default Re: Cuts have steps instead of being smooth

    Well, just thinking out loud, Gerry; if my spindle is off plumb, and I suspect it is, then if I surface the spoilboard it could leave ridges. Albeit light, there would be ridges. But if I get the piece of glass parallel to the X and Y axes and then tram the spindle, when I surface the spoilboard it will be perfect, no ridges, and exactly parallel to the rest of the machine.

    If I surface the spoilboard first, lay the glass on the spoilboard, and then tram the spindle I'll need to surface the spoilboard again to get rid of the ridges - correct? Or am I overthinking this? Clearly I didn't think it through when I set the machine up because I didn't tram the spindle with any degree of accuracy so I don't want to miss it this time.

    Just wanting to understand...

    David

    David
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    Default Re: Cuts have steps instead of being smooth

    David-
    What you're trying to achieve is parallelism between the spindle axis and the Z axis of travel. Once that's achieved, you surface the spoilboard and it will in turn be perpendicular to the Z and parallel to the gantry, X in your case.



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    Default Re: Cuts have steps instead of being smooth

    Surface it with a 1/2" bit, and any ridges should be negligible. And if you then lay the glass, down, it should be in the correct plane, even if it's resting on the ridges.

    Gerry

    UCCNC 2017 Screenset
    [URL]http://www.thecncwoodworker.com/2017.html[/URL]

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

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


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    Community Moderator difalkner's Avatar
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    Default Re: Cuts have steps instead of being smooth

    The really good thing about all this is that I just talked to Nate at FLA and we both realized that when he sent me the upgrades last month he included a tramming mount for the spindle! I just have had zero time to take the machine down so I had not even looked in the box but today I am shutting everything down to install the tramming plate and get this settled so I can move on - got lots of work to do.

    I'll check in later today with photos and updates. Thanks for all the help on this and I sure hope this fixes the problem.

    David

    David
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    Community Moderator difalkner's Avatar
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    Default Re: Cuts have steps instead of being smooth

    Tramming mount installed, spoilboard surfaced, and ready for a test but I don't have anything in the queue for cutting tomorrow. I'll report back next week if I get to cut something that would have had steps before.

    I was able to tram to 0.002" in a 9" circle so that ought to be pretty close to perfect at the spindle. I finally got a good measurement on the previous setup and it was about 0.040" out and that's fairly significant.

    Changing plates -
    Cuts have steps instead of being smooth-015-removing-spindle-mount-jpg

    The geometry of the new plate is different and has the spindle 2" lower than it was in relation to the bearing plate, so I raised the spindle in its mount to compensate.
    Cuts have steps instead of being smooth-016-first-pass-surfacing-tramming-mount-installed

    Surfaced all the way to the note to self at the extreme end of the spoilboard -
    Cuts have steps instead of being smooth-014-spoilboard-surfaced-way-jpg

    David

    David
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    Community Moderator Jim Dawson's Avatar
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    Default Re: Cuts have steps instead of being smooth

    Love your message.

    0.040 is a lot, best of luck.

    Jim Dawson
    Sandy, Oregon, USA


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    Community Moderator difalkner's Avatar
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    Default Update - success!!!

    Quote Originally Posted by Jim Dawson View Post
    Love your message.

    0.040 is a lot, best of luck.
    Yeah, sometimes I crack myself up, Jim - LOL! Thanks, it just seemed like a fitting thing to engrave.

    ++++++++++++++++++++++++++++++++++++++++++++++++

    I found a blank for tails I had glued up earlier so it went on the CNC today and I'm pleased to report that the tramming was successful!!!

    First, I was wrong on the geometry change for the tramming mount vs. the flat plate - the spindle is now 4" lower than it was, not 2" as I previously thought. I don't know if this is going to introduce flex given that the spindle is now sort of cantilevered below the mounting point to the bearings. The spindle mount on the old plate attached to the 4 holes just above the Walnut block. The 3 mounting holes to the ballscrew nut are used in this photo for reference -
    Cuts have steps instead of being smooth-017-tramming-plate-difference-jpg

    Here's the board in the machine -
    Cuts have steps instead of being smooth-018-first-cut-tramming-jpg

    The tail on the left is before the tramming. The two on the right are from this morning and after tramming. Of the two on the right, the left tail is the one that would have had the steps. Both are very smooth and the right one is smoother than the previous 'smooth' cuts.
    Cuts have steps instead of being smooth-019-successful-cuts-right-jpg

    Cuts have steps instead of being smooth-020-successful-cuts-right-jpg

    So, many thanks to all who chimed in with suggestions, videos, and tips - good job, y'all!!!

    David

    David
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