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IndustryArena Forum > CAM Software > Autodesk CAM > Lower spindle rpm when feed rate decreases
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  1. #1
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    Lower spindle rpm when feed rate decreases

    I have this problem of now knowing how to lower the rpm of the spindle when the toolpath slows down (ex corners)
    I need this feature because as i cut aluminium composit panel, when the feed rate gets lower (like in corners), the spindle keeps the same high rpm and the plastic mets, leaving me with lots of parts cleaning afterwards.
    If I decrease the rpm in general, on the straight line the spindle makes unproper cuts, if i lower the general feed rate the machine time increases a lot (i run at 20m/min)
    My question is how would be best to approache the problem. My thoughts are that this can be achieves through a CAM software (maybe fusion 360) and not through the cnc controller(delta nc300) parameters.

    If you know fusion 360 doing this, or other CAM software i am considering buying it as it will help me a lot in cutting production tines

    Thank you
    Marius

  2. #2
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    Re: Lower spindle rpm when feed rate decreases

    Quote Originally Posted by nicubila View Post
    I have this problem of now knowing how to lower the rpm of the spindle when the toolpath slows down (ex corners)
    I need this feature because as i cut aluminium composit panel, when the feed rate gets lower (like in corners), the spindle keeps the same high rpm and the plastic mets, leaving me with lots of parts cleaning afterwards.
    If I decrease the rpm in general, on the straight line the spindle makes unproper cuts, if i lower the general feed rate the machine time increases a lot (i run at 20m/min)
    My question is how would be best to approache the problem. My thoughts are that this can be achieves through a CAM software (maybe fusion 360) and not through the cnc controller(delta nc300) parameters.

    If you know fusion 360 doing this, or other CAM software i am considering buying it as it will help me a lot in cutting production tines

    Thank you
    Marius
    Is the feed rate decreasing automatically by the machine control or is it in the program
    Mactec54

  3. #3
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    Re: Lower spindle rpm when feed rate decreases

    Quote Originally Posted by nicubila View Post
    I have this problem of now knowing how to lower the rpm of the spindle when the toolpath slows down (ex corners)
    I need this feature because as i cut aluminium composit panel, when the feed rate gets lower (like in corners), the spindle keeps the same high rpm and the plastic mets, leaving me with lots of parts cleaning afterwards.
    If I decrease the rpm in general, on the straight line the spindle makes unproper cuts, if i lower the general feed rate the machine time increases a lot (i run at 20m/min)
    My question is how would be best to approache the problem. My thoughts are that this can be achieves through a CAM software (maybe fusion 360) and not through the cnc controller(delta nc300) parameters.

    If you know fusion 360 doing this, or other CAM software i am considering buying it as it will help me a lot in cutting production tines

    Thank you
    Marius
    Why does it slow the feed around corners?.
    Anyway. It's swings and roundabouts afaic. If you put a S code at a corner the machine is likely to:
    Arrive at corner - stop for a second - adjust rpm's - cut around corner - stop - adjust rpm's - carry on to next corner.
    Where it stops you'll likely still get either a burn or a burr.

  4. #4
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    Re: Lower spindle rpm when feed rate decreases

    @mactec54 curently the spindle works at program S speed irrelevant if the feed rate is full or decreased. I am looking for a solution to obtain a reduction of the spindle rpm when the feedrate is lower due to corners. Either controller or program, it does not matter how i obtain this. But as @dazp1976 says, the S will not change on the fly, and the axes will stop to adjust for the S, which makes the situation worst.
    Ideally what I need is a way to have lets say
    10m/min feed rate and S 20.000rpm wehen in straight line
    and
    S 8000rpm when feed rate goes down to 4m/min as it goes through a curve and axes need to slow down.
    And if the corner and precision requirement are tight and feed rate must go lower, the S should not go below 5000rpm.

    I am a bit surprise to find such little info about this option in online sourced. It goes along the concept of constant removal rate, and should be easily achieveble as an interpolation of spindle with the other axes.
    As I said when I cut plastic I see that higher rpm makes nice cuts on straight line cut burrs in corners, lower rpm nice corners but spindle is struggling in straight line.

  5. #5
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    Re: Lower spindle rpm when feed rate decreases

    Quote Originally Posted by nicubila View Post
    @mactec54 curently the spindle works at program S speed irrelevant if the feed rate is full or decreased. I am looking for a solution to obtain a reduction of the spindle rpm when the feedrate is lower due to corners. Either controller or program, it does not matter how i obtain this. But as @dazp1976 says, the S will not change on the fly, and the axes will stop to adjust for the S, which makes the situation worst.
    Ideally what I need is a way to have lets say
    10m/min feed rate and S 20.000rpm wehen in straight line
    and
    S 8000rpm when feed rate goes down to 4m/min as it goes through a curve and axes need to slow down.
    And if the corner and precision requirement are tight and feed rate must go lower, the S should not go below 5000rpm.

    I am a bit surprise to find such little info about this option in online sourced. It goes along the concept of constant removal rate, and should be easily achieveble as an interpolation of spindle with the other axes.
    As I said when I cut plastic I see that higher rpm makes nice cuts on straight line cut burrs in corners, lower rpm nice corners but spindle is struggling in straight line.
    Can you just cut it 'normal' or faster but this time leaving say 0.2mm+ on the stock (roughing).
    Then run a 'slower' pass all around it at full depth right at the end to remove the left on material. (finishing).
    That will prob work.

  6. #6
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    Quote Originally Posted by dazp1976 View Post
    Can you just cut it 'normal' or faster but this time leaving say 0.2mm+ on the stock (roughing).
    Then run a 'slower' pass all around it at full depth right at the end to remove the left on material. (finishing).
    That will prob work.
    Both sides of the cut are active parts, so i need then both. I use the suggested technique in other cuts, but here is not feasible

  7. #7
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    Re: Lower spindle rpm when feed rate decreases

    Is it reasonable to think your computer processor that drives the control may not be able to keep up in the corners? Or that your axis motors may need to have their parameters adjusted to more closely match each other for speed and acceleration? If you're programs are using center point control and the cutter is relatively small in diameter, I can't imagine the feed speed around corners should change all that much that it would require a rotational spindle speed change.

  8. #8
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    Re: Lower spindle rpm when feed rate decreases

    Quote Originally Posted by nicubila View Post
    @mactec54 curently the spindle works at program S speed irrelevant if the feed rate is full or decreased. I am looking for a solution to obtain a reduction of the spindle rpm when the feedrate is lower due to corners. Either controller or program, it does not matter how i obtain this. But as @dazp1976 says, the S will not change on the fly, and the axes will stop to adjust for the S, which makes the situation worst.
    Ideally what I need is a way to have lets say
    10m/min feed rate and S 20.000rpm wehen in straight line
    and
    S 8000rpm when feed rate goes down to 4m/min as it goes through a curve and axes need to slow down.
    And if the corner and precision requirement are tight and feed rate must go lower, the S should not go below 5000rpm.

    I am a bit surprise to find such little info about this option in online sourced. It goes along the concept of constant removal rate, and should be easily achieveble as an interpolation of spindle with the other axes.
    As I said when I cut plastic I see that higher rpm makes nice cuts on straight line cut burrs in corners, lower rpm nice corners but spindle is struggling in straight line.
    What dazp1976 has said is incorrect, the machine will not stop to change speeds or feeds you can not use the ( S ) by it's self it has to be M3S--------

    You have not said what control you are using as some controls already have this, they will slow down at a corner automatically, but don't normally change the spindle speed

    You can do all of this in your program at the end of the straight cut M3S8000 and then at the next move add the Feed move, this will change on the fly so at your G2 or G3 line just add the Feed Rate F-----

    You may need to have a Braking Resistor if you don't have one, for a rapid slow down of your spindle, or the VFD Drive may shut down

    The Spindle speed change needs to be on it's own line M3S8000 and the Feed on the line of the move
    Mactec54

  9. #9
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    Re: Lower spindle rpm when feed rate decreases

    Quote Originally Posted by MARV View Post
    Is it reasonable to think your computer processor that drives the control may not be able to keep up in the corners? Or that your axis motors may need to have their parameters adjusted to more closely match each other for speed and acceleration? If you're programs are using center point control and the cutter is relatively small in diameter, I can't imagine the feed speed around corners should change all that much that it would require a rotational spindle speed change.
    This is a normal thing to do, some quality controls will slow the feed rate for going around a corner by a % that you can set in the control
    Mactec54

  10. #10
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    Re: Lower spindle rpm when feed rate decreases

    Quote Originally Posted by mactec54 View Post
    What dazp1976 has said is incorrect, the machine will not stop to change speeds or feeds you can not use the ( S ) by it's self it has to be M3S--------
    You have not said what control you are using as some controls already have this, they will slow down at a corner automatically, but don't normally change the spindle speed
    You can do all of this in your program at the end of the straight cut M3S8000 and then at the next move add the Feed move, this will change on the fly so at your G2 or G3 line just add the Feed Rate F-----
    You may need to have a Braking Resistor if you don't have one, for a rapid slow down of your spindle, or the VFD Drive may shut down
    The Spindle speed change needs to be on it's own line M3S8000 and the Feed on the line of the move
    Learn something new everyday.
    That might be useful when milling a block of ally.
    Sometims tend to go too big a woc when rounding off an edge.
    The slow down could be benificial for the first few passes.

  11. #11
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    Re: Lower spindle rpm when feed rate decreases

    I see now what you mean, and frankly i did not try this option. But I should try it then with an M3 and proper S.

    I use a Delta NC300 controller, but could not find yet a parameter that would do this. That is why i was thinking of options to do this in CAM toolpath. doing this by hand is out of the question, there are thousands of corners in each model I make. Any change would require manual change again.

    My best bet is for now is a very sharp tool with lots of clearance (so far Datron are very good), allow for the highest tolerance i can afford in the corners (so feed rate remains high), compromise on the highest feed rate, and find a sweet spot between the straight line feed rate and corner feed rate.

  12. #12
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    Re: Lower spindle rpm when feed rate decreases

    Quote Originally Posted by nicubila View Post
    I see now what you mean, and frankly i did not try this option. But I should try it then with an M3 and proper S.

    I use a Delta NC300 controller, but could not find yet a parameter that would do this. That is why i was thinking of options to do this in CAM toolpath. doing this by hand is out of the question, there are thousands of corners in each model I make. Any change would require manual change again.

    My best bet is for now is a very sharp tool with lots of clearance (so far Datron are very good), allow for the highest tolerance i can afford in the corners (so feed rate remains high), compromise on the highest feed rate, and find a sweet spot between the straight line feed rate and corner feed rate.
    This software can change the feed rate on the fly while it is cutting the part running VoluMill

    https://www.3dsystems.com/software/gibbscam/volumill
    Mactec54

  13. #13
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    Quote Originally Posted by mactec54 View Post
    This software can change the feed rate on the fly while it is cutting the part running VoluMill

    https://www.3dsystems.com/software/gibbscam/volumill
    That sounds good, it is worth trying, thank you

  14. #14

    Re: Lower spindle rpm when feed rate decreases

    I think you've misunderstood how modern adaptive toolpaths work, such as the ones in Fusion. Consequently, I suspect you are overthinking this. They change the feedrate as they change direction in order to keep the spindle / tool load constant - that's the whole point of them. If you start changing the spindle speed partway along a toolpath, you are most likely going to be compensating for a problem that doesn't exist.

    May be worth reading up on HSMworks and the Fusion CAM toolpaths (they are the same product) to understand what is happening, instead of looking for a special solution you almost certainly don't need. These modern toolpaths have transformed how machines operate (even old ones!). You don't need to limit the feedrate to the worst case anywhere on the path and cause the rest of the path to be painfully slow.

  15. #15
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    Re: Lower spindle rpm when feed rate decreases

    Quote Originally Posted by Muzzer View Post
    I think you've misunderstood how modern adaptive toolpaths work, such as the ones in Fusion. Consequently, I suspect you are overthinking this. They change the feedrate as they change direction in order to keep the spindle / tool load constant - that's the whole point of them. If you start changing the spindle speed partway along a toolpath, you are most likely going to be compensating for a problem that doesn't exist.

    May be worth reading up on HSMworks and the Fusion CAM toolpaths (they are the same product) to understand what is happening, instead of looking for a special solution you almost certainly don't need. These modern toolpaths have transformed how machines operate (even old ones!). You don't need to limit the feedrate to the worst case anywhere on the path and cause the rest of the path to be painfully slow.
    That is what I already posted with the software link, HSM or Fusion does not come close to what I posted VoluMill is the real deal
    Mactec54

  16. #16
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    Quote Originally Posted by Muzzer View Post
    I think you've misunderstood how modern adaptive toolpaths work, such as the ones in Fusion. Consequently, I suspect you are overthinking this. They change the feedrate as they change direction in order to keep the spindle / tool load constant - that's the whole point of them. If you start changing the spindle speed partway along a toolpath, you are most likely going to be compensating for a problem that doesn't exist.

    May be worth reading up on HSMworks and the Fusion CAM toolpaths (they are the same product) to understand what is happening, instead of looking for a special solution you almost certainly don't need. These modern toolpaths have transformed how machines operate (even old ones!). You don't need to limit the feedrate to the worst case anywhere on the path and cause the rest of the path to be painfully slow.
    The work i need this feature is 2.5D, or rather 2D.it cuts contours in Dibond type material. I do not see how a cutting strategy can achieve optimal toolpath and finish withoit slowing down the spindle in corners.
    I agree that in complex parts there are lots of opportunities to improve on these 2 variables (feed rate and finish), but it is not the case here.

  17. #17

    Re: Lower spindle rpm when feed rate decreases

    Well Fusion and most modern HSM toolpaths manage it - by changing the feedrate and the width of cut. It's called "adaptive". They don't change the spindle speed.

    Keep working at it and perhaps you will understand how they manage it. Or if you really think you have something that the entire industry has overlooked, think about patenting it!

  18. #18
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    Re: Lower spindle rpm when feed rate decreases

    Quote Originally Posted by Muzzer View Post
    Well Fusion and most modern HSM toolpaths manage it - by changing the feedrate and the width of cut. It's called "adaptive". They don't change the spindle speed.

    Keep working at it and perhaps you will understand how they manage it. Or if you really think you have something that the entire industry has overlooked, think about patenting it!
    No you are not understanding what his needs are which is totally different to what you are talking about, the adaptive tool path would not work for him at all
    Mactec54

  19. #19
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    Re: Lower spindle rpm when feed rate decreases

    I'm not sure you'll be easily able to achieve this in CAM.

    The problem you are dealing with is deceleration into the corner and acceleration out of the corner.

    The sharper (smaller radius) the corner, the slower the feed rate will be at the corner.

    Most CAM is not aware of / accounting for acceleration speed. Acceleration varies a lot across different machines and sometime different axes on the same machine.

    For pockets a good solution is to use a smaller cutter so that it sweeps around the corner (rather than stopping).

    Difficult to solve if you need both sides of the cut unchanged. (I.e. you have two profiles that can't be altered).

    .

    Posting a picture of parts may help
    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)

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