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Thread: Saturn 2 4x4 - Nema 23

  1. #49
    Community Moderator ger21's Avatar
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    Default Re: Saturn 2 4x4 - Nema 23

    The part I don't understand is how adjusting the sensors helps to make the gantry square.
    Say one sensor sticks out 1" farther than the other. When you home the gantry, one side will move 1" farther than the other. To get it square, you move the sensor.

    Gerry

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    Default Re: Saturn 2 4x4 - Nema 23

    Where did you get the heat sinks if I may ask?
    Well, I got those from a heatsink scrap bin at the place I used to work at.
    Mostly point of sale (POS) machine heatsinks. I had to drill and tap four holes in these to attached the Gecko drives.

    Some POS heatsinks are like a work of art because they are custom mfg'ed for each model. Just search around for used POS, Surepos or ThinkCentre heatsinks.
    They can be had pretty cheap.

    Thanks.
    Jack



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    Default Re: Saturn 2 4x4 - Nema 23

    Quote Originally Posted by ger21 View Post
    Say one sensor sticks out 1" farther than the other. When you home the gantry, one side will move 1" farther than the other. To get it square, you move the sensor.
    Hi Gerry. Two things.
    1- Can I assume those two sensor blocks are exactly aligned with each other?
    2- I have been homing to the right back of the machine. Just noticed there is only one side (left) with a block on it back there!! The front of the machine has a block on each side.
    Don't tell me my gantry is on backwards! That would be an issue at this point to say the least.

    Thanks.

    Edit. that can't be right. The rack and pinion drives would not work if that was the case. ??



  4. #52
    Community Moderator ger21's Avatar
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    Default Re: Saturn 2 4x4 - Nema 23

    1) Never assume.

    2) I can't answer that, as I'm not familiar with the layout of that machine.

    Gerry

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  5. #53
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    Default Re: Saturn 2 4x4 - Nema 23

    Mine is NEMA 34 but it Homes left front which is pretty much standard. My indexing blocks can not be adjusted as mounted. The Proximity switches are mounted on top of the Gantry. Spring tension, do not get too tight. Mine is about 1 1/16 inch from the top of the black bracket to the top of the washer on top of the spring.

    Attached Thumbnails Attached Thumbnails Saturn 2 4x4 - Nema 23-right-jpg   Saturn 2 4x4 - Nema 23-left-jpg  
    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router


  6. #54
    Community Moderator ger21's Avatar
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    Default Re: Saturn 2 4x4 - Nema 23

    Looking at those pics, it looks like the sensor position can NOT be adjusted?
    Sorry, I thought that they were setup like the CNCRP machines.

    Gerry

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


  7. #55
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    Default Re: Saturn 2 4x4 - Nema 23

    Quote Originally Posted by wmgeorge View Post
    Mine is NEMA 34 but it Homes left front which is pretty much standard. My indexing blocks can not be adjusted as mounted. The Proximity switches are mounted on top of the Gantry. Spring tension, do not get too tight. Mine is about 1 1/16 inch from the top of the black bracket to the top of the washer on top of the spring.
    My machine does have the two in the front of the machine. I'm just homing off my Y limit sensor I guess. Will look into changing that. I know Mach3 is set for just the one Y sensor at the moment.

    Thanks.
    Jack

    - - - Updated - - -

    Quote Originally Posted by ger21 View Post
    Looking at those pics, it looks like the sensor position can NOT be adjusted?
    Sorry, I thought that they were setup like the CNCRP machines.
    No worries fancy pants.



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    Default Re: Saturn 2 4x4 - Nema 23

    The only adjustment on the sensor is up and down. It picks up the block from the side. The block could be adjusted IF it was mounted correctly.. That would involve drilling and tapping another hole for the flat head allen screw. Frankly I do not know if its Metric or Imperial, I have taps for both but right not I do not need to adjust. My gantry as near as I can tell is within .020 or so square using the end plates as reference. I was waiting until my spoil board to come in and I would cut a large rectangle with a very light cut and check.

    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router


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    Default Re: Platform Leveling

    Quote Originally Posted by PLJack View Post

    I've heard that before. The part I don't understand is how adjusting the sensors helps to make the gantry square. I definitely plan to do that once I know it is square. Then turn on the dual sensor Y axis homing.
    That way it will self square each time I home it.
    This requires that you adjust the sensors very carefully so that they both turn on at the same time when the gantry is square. I haven't done this, so I'm not sure if this would work, but here is how I would approach it:

    1) Home the gantry to one sensor (let's call this the primary side).
    2) Adjust the secondary sensor so that it just barely turns on when the gantry is homed to the primary. In theory, this will have both sensors turn on at about the same time.
    3) Make sure that your system is calibrated correctly (i.e. linear moves only in X, Y, and Z are accurate)
    4) Run a program where you can cut a square or rectangle and measure the diagonals. (or use my pin method from above).
    5) Use you're measurements to create an accurate sketch in your favorite CAD program, representing your slightly not square rectangle.
    6) Use this sketch to figure out the linear distance that you need to adjust your gantry. Remember that the rectangle you cut is smaller than the distance between your sensors, so you will need to take that into account.
    7) Your sensors will be threaded on a consistent pitch (usually 1 mm for the sensors Fineline provides). This means that the sensor will move by 1 mm (0.03937 inches) for every turn on the nut. If you mark one flat on one of the nuts and rotate it proportionally (e.g. 1/2 turn of the nut is 0.5mm), you can move the sensor in a very controlled manner, adjusting it by a few thousandths of an inch if needed. Be sure to snug up the sensor carefully each time you adjust it, making sure that you don't rotate it or the nut you just adjusted.
    8) Adjust the secondary sensor, loosen the gantry, leaving one screw on each side slightly snug, then re-home the gantry. Alternately, you can loosen all the screws, but you need to make sure that you push both sides of the gantry in the same direction (e.g. towards the front of the machine) when you tighten everything up each time. The play in the holes is enough to allow the gantry to be out of square. All of this is to try to be as consistent as possible in your adjustments so that you aren't chasing square back and forth forever.
    9) Machine another test rectangle, measure and repeat. If you calculate the adjustment needed correctly, and adjust carefully, you should only need a few iterations to get the diagonals pretty close. In your CAD model you can figure out how close your diagonals need to be to each other to have the gantry square to your desired accuracy. The first iteration might make things worse, depending on how well you adjusted the secondary sensor the first time and how the gantry was biases on its holes, but after that, it should get better each iteration.

    Once you have the gantry square, you can turn off the secondary sensor, but I would leave it in place and don't change the adjustment. If the gantry ever goes out of square, you just have to loosen the bolts, re-home, tighten and check for square. It should be pretty close.

    Again, I haven't tried this, so if anyone else has an easier or more efficient method, I'd love to hear about it. I'm an engineer, so I tend to take an analytical approach. The machinists I know often have some pretty cool techniques that they have learned/developed that are way faster and more accurate than what I come up with. On my machine, I basically kept nudging it as carefully as I could until it was close. It took alot of tries, and I eventually gave up trying to make it better.

    -Robert



  10. #58
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    Default Re: Saturn 2 4x4 - Nema 23

    Or make your rectangle cut on the board, lay a square on it see which sensor Block you need to move and do it. But I do not think that will work with the welded gantry unless you unbolt from the linear bearing block. Yes you need both the Y and Slave (B) sensor in operation in case something goes wrong.
    See the pictures I posted above for why you can not adjust the sensor.

    Attached Thumbnails Attached Thumbnails Saturn 2 4x4 - Nema 23-block-jpg  
    Last edited by wmgeorge; 08-24-2018 at 08:48 AM.
    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router


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    Default Re: Saturn 2 4x4 - Nema 23

    See my post #19 in David Falkner's "Calibration Question" thread for a discussion of an alternate method for determining whether your gantry is perpendicular to the Y axis, and if it's out, quantifying exactly how much adjustment is needed. It's called the 5 Cut Method. It is a bit time consuming, but works better than any other method I've found. On the Saturn 2, you'll have to be able to adjust the sensor blocks. You'll also need to loosen the gantry and move it the amount necessary to correct the error. I can say from experience that having to loosen both sides of the gantry to adjust it makes the whole process very fussy. Leaving one bolt snug as a pivot point helps but it's not perfect when trying to achieve movements in the thousands of an inch range. Having a very stiff machine is both a blessing and curse. It's great for cutting, but a bear for adjusting making adjustments. With extrusion-based machines, forcing the gantry into square works OK. Not so much for machines with linear rails where binding can be a problem.

    Gary




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    Default Re: Saturn 2 4x4 - Nema 23

    I have no plans of incorporating that method. I am making money when my machine is running and .030 inch in 48 inches is all I need. If I wanted or needed milling machine accuracy I would buy one.

    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router


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