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  1. #21
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    Quote Originally Posted by rockaukum View Post
    Thanks for sticking with me guys,
    This morning I disconnected the Shields on all cables that I had previously attached. I ran the same cut and the results were a bit improved.
    Cable shielding should be done at the source or head end only, and left floating and not attached on the field side. Also, keep your DC return path (negative) and your AC equipment ground isolated.



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    Default Re: Missing steps or something else?

    Ger21,
    The sample cuts were done in two passes, 1/8" each, same as the other cuts. I feel the same way about it being on the second pass that is why I question the rapids... Could it be that the when doing a rapid it is loosing steps there due to the acceleration / deceleration being too much over a long travel? That was my thought when I was changing the acceleration in motor tuning.
    GF357,
    Yes thanks for that. That is how I had it set and that is when all the problems evolved. Now in the process of backtracking to resolve the issue of lost steps (?).
    I will visit the shop later and copy the g-code for posting...
    Thanks again!
    ra
    edit: Added g-code for "it works" pocket operation and the two alignment tests.
    interesting note.... I did a simple cut for my daughter today. Went well. Seems to work as long as the cut can be done in one pass....

    Attached Files Attached Files
    Last edited by rockaukum; 06-30-2017 at 08:14 PM.


  3. #23
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    Default Re: Missing steps or something else?

    Earlier you said you set the acceleration to 10?
    Try it at 5.
    Could it be that the when doing a rapid it is loosing steps there due to the acceleration / deceleration being too much over a long travel?
    Over a long distance the machine should only be accelerating briefly at the start. So distance of rapids shouldn't be an issue, unless it's not reaching top speed.




    4.Checked for the pulse width in motor tuning and could not find it.... Read to try to set it at 15?
    Bottom of the screen, "Step Pulse 1-5us". Type in 15.


    For the itworks code, try changing the G0 in line 5600 to G1, and see if it makes a difference? That seems to be where it's losing position.

    Gerry

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    Default Re: Missing steps or something else?

    ger21,
    Went to the shop this morning.
    1. Changed line 5600 as suggested and ran the code. Came up with the same results as before.
    2. Changed the step pulse to 15 (for some reason when I originally looked at that, it thought that it was a 1 - 5 value only) and ran the code. PERFECT! Cut came out spot on even with go to zero after the cut.
    3. Changed line 5600 back and ran the code. Came out PERFECT again.
    This stuff is way over my head but I still try to learn and I give my thanks to you and the others for your patients and help! Much appreciated....
    I have enclosed several photos and one from the driver spec on the step pulse info.
    SO.... From here.... Re-establish the shields or leave it alone with out them?
    Leave the step pulse at 15 or adjust? should direction be set as well?
    AGAIN, many thanks for all the input....
    ra
    go to zero after cut

    cut after changing step pulse to 15 with line 5600 changed

    after cut step pulse at 15 and change line 5600 back to original setting


    Attached Thumbnails Attached Thumbnails Missing steps or something else?-img_4848-jpg   Missing steps or something else?-img_4850-jpg   Missing steps or something else?-img_4851-jpg   Missing steps or something else?-screen-shot-2017-07-01-8-01-a  



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    Default Re: Missing steps or something else?

    So, the problem seems to be that your drives needed a longer pulse with, as their manual states. Most decent drives work fine with 2us or less. Yours need more than 5us.

    Gerry

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    Default Re: Missing steps or something else?

    That router bit looks like it's spinning too fast, or you're cutting too slow. Cleaning it with a bit cleaner or oven cleaner will help to keep it sharp longer.

    Gerry

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    Default Re: Missing steps or something else?

    Thanks for the tip on the cleaning of the bit. I was at 14000 rpm (i think) and 80ipm. It seams that no matter what speed or feed with mdf that it does not produce chips. I did a cut later in the afternoon on poplar with the same feed and speed and the bit was producing chips with that cut. I will be looking into feed and speed calculators soon to get that dialed in. Any suggestions for these calculators?
    As for the steps pulse, If i'm reading that correctly, it requires five or more. Should I dial it back down to 5 and do a sample cut and keep increasing until I get the desired results, or just leave it at 15?
    Also with the shields, should I re-connect them? If the problem comes back then i'll know to leave them off?
    Thanks for all the help, learning every day which I feel is the correct direction....
    rockaukum



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    Default Re: Missing steps or something else?

    Quote Originally Posted by rockaukum View Post
    Why is that bit black? Looks like it is badly burned. Also, are you using down cutter? Why? A down cutter means that the chips are pushed in under the cutter (which explains why the tip is burned). Up-cutters have a natural chip cleaning, it makes more mess but does a better job in my opinion.

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    Default Re: Missing steps or something else?

    I thought that I was upcutting...
    based on this diagram, It would appear to me that I am upcutting? Also, this bit was used quite a bit when I was set up with a router that had a fixed rpm of 28000. Could this explain the burnt tip, spinning too fast for the feed rate as when I started out I was cutting at 40ipm.
    Missing steps or something else?-screen-shot-2017-07-02-11-14-a



  10. #30
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    Default Re: Missing steps or something else?

    What your diagram is showing is more commonly called Conventional (Up Milling) and Climb (Down Milling) Cutting.
    And has nothing to do with the type of tool you are using, which is what he was referring to. You are using a downcut spiral bit, which cuts with a downward shear cut, vs an upcut spiral, which cuts with an upward shear cut.

    There's nothing wrong with using downcut spirals, which are often preferable when cutting wood and wood products. Just ramp in, rather than plunging.
    I program and run an industrial router in my day job, and we buy about $1000 in bits a year, and spend probably twice that in sharpening costs. I haven't used an upcut spiral bit in about 5 years.

    Gerry

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  11. #31
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    Default Re: Missing steps or something else?

    If you want chips from particle board or MDF, up the feedrate to 500ipm.

    I will be looking into feed and speed calculators soon to get that dialed in. Any suggestions for these calculators?
    Most feed and speed charts/calculators are designed to give maximum tool life. This is often not possible on hobby machines, due to a lack of power and rigidity.

    12,000-14,000 rpm and 100 ipm is a good starting point. If the machine is OK with that, increase the feedrate as much as you want, as long as the cut quality doesn't suffer. In moist cases, cut quality will be more important than chip load.
    Fwiw, at 14,000 rpm, you can easily push a 1/4" cutter at over 300ipm, if your machine is up to it.

    Gerry

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    Default Re: Missing steps or something else?

    Thanks for the explanation gerry, Time to put on my running shoes and see how quick it ca run....
    I have not been using the ramp feature but will be giving that a go next time.
    Thoughts on the shield connection again and adjusting the step pulse numbers?
    ra



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    Default Re: Missing steps or something else?

    I'd probably set the pulse width to 10, ans see if it runs OK there.

    As for the shields... I guess hook them back up, and see if anything changes.
    Be sure to only change one thing at a time.

    Gerry

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    JointCAM - CNC Dovetails & Box Joints
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    Default Re: Missing steps or something else?

    Quote Originally Posted by ger21 View Post
    There's nothing wrong with using downcut spirals, which are often preferable when cutting wood and wood products. Just ramp in, rather than plunging.
    Is there any advantage/differences in results? I thought they were designed for hand routers to help holding down the material to counteract the pulling forces. OK, the problem may be the same with large wooden sheet material in CNC, but is there a general advantage in using them other than this?

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    Default Re: Missing steps or something else?

    They give a much better finish on the corner of the face/cut than an upcut. This is very important with plywoods and sheets with other finish surfaces, like melamine. And when routing solid woods, downcuts tear out much less than upcut bits.
    The downside is that they will leave a poor edge finish on the bottom of parts, when cutting through.

    Upcuts do have their place. They are good for deep pockets, as they pull the chips out of the cut. And they are good for joinery, like box joints, and tenons, where you are cutting the end of the boards, rather than the face.

    As an alternative to using a compression bit, is to make one pass with a downcut, for a clean top edge, followed by a final pass with an upcut, for a clean bottom edge. This can work well if you're machine isn't capable of deep single pass cuts, which is what compression bits are designed for.

    Gerry

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    JointCAM - CNC Dovetails & Box Joints
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  16. #36
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    Default Re: Missing steps or something else?

    Thanks for the very good explanation. I have never done anything in wood yet, except surfacing MDF a few times but that doesn't count.

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    Default Re: Missing steps or something else?

    Quote Originally Posted by ger21 View Post
    They give a much better finish on the corner of the face/cut than an upcut. This is very important with plywoods and sheets with other finish surfaces, like melamine. And when routing solid woods, downcuts tear out much less than upcut bits.
    The downside is that they will leave a poor edge finish on the bottom of parts, when cutting through.

    Upcuts do have their place. They are good for deep pockets, as they pull the chips out of the cut. And they are good for joinery, like box joints, and tenons, where you are cutting the end of the boards, rather than the face.

    As an alternative to using a compression bit, is to make one pass with a downcut, for a clean top edge, followed by a final pass with an upcut, for a clean bottom edge. This can work well if you're machine isn't capable of deep single pass cuts, which is what compression bits are designed for.
    Another option is a mortise compression spiral, which has a shorter up-cut section; thus the same tool could be used for both passes.

    Quote Originally Posted by A-Camera
    Is there any advantage/differences in results? I thought they were designed for hand routers to help holding down the material to counteract the pulling forces. OK, the problem may be the same with large wooden sheet material in CNC, but is there a general advantage in using them other than this?
    Actually, using a down-cut spiral on a hand-held router poses some risks as you'd require extra force on your part to hold the router down, and potentially as you push the router, as the router would tend to lift. Also a reason why you wouldn't use a down-cut spiral inverted in a router table - this would tend to lift the work as you guide it along the fence. For a similar reason you wouldn't want to climb-cut manually, at least unless you have a lot of experience with hand-held routers, and then, only very carefully, as the router would want to get pulled along the cut.



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Missing steps or something else?

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