Delta printer does not print the full height on the outer edges



  • Hello,
    I have a question about configuring the Duet Ethernet for my mid-sized delta printer.

    The printer has in the middle a print height of exactly 102.4 cm.
    At the outer edge the delta has a height with about 99 cm.

    In the middle he can print up to the top with 102.4 cm.
    Unfortunately, the printer can only print up to 89.9 cm at the outer edge.

    Only a sketch:
    0_1548289925550_Delta.png

    In the picture, the printer is at the maximum height according to the duet. You can see that the delta arm does not go all the way up. It lacks about 9 cm, which are not driven up.

    0_1548290232186_DSC_0328.JPG

    Attached my current configuration:
    config.g
    config-override.g
    homedelta.g

    How do I have to change my configuration that he goes up to the top at the outer edge?

    Thank you.



  • It seems strange that you have that problem, does this effect the level of your bed?



  • Your M665 command is using a value of H1026.4, but according to your drawing is really only 111.4 (102.4+9). My guess is that your smart effector autocalibration routine that you are relying upon to set your endstops might be a little less inaccurate if you used a value that was closer to what the actual value is. I'd change it to H116.4 (based upon your drawing and photo + 5mm) and re-check. Once your calibration is set simply transfer those settings it derived (for M665 and M666) to your config.g



  • Hi,

    I think that your setting for max height is too large.

    Consider the situation when all carriages are at the very top. The nozzle will be centered.

    To move the nozzle to the max radius one or two of the carriages have to drop and in doing so the nozzle will also drop.

    Whatever height the nozzle is at in that condition is going to be appx the max height for your hardware.

    But it's late, I'm tired and could be totally wrong.

    Frederick



  • Thanks for your answers.

    @NOVAprint: The auto leveling works (plus minus 0.3mm). I can compensate this with the H parameter in the leveling routine.

    @ayudtee: The height is not 116mm. The print height is in the center 1024mm.

    @fcwilt: The print height in the center is 1024mm. You are right. If the nozzle move to the outer egde, the nozzle moves a little down to the buttom (so the arm hit not the end stop) . BUT the nozzle should only move about 40mm down (without triggering the end stop). But the nozzle move about 125mm down. There nozzle move 85mm (125mm - 40mm) to much down.
    This waste build volume.



  • @tbs said in Delta printer does not print the full height on the outer edges:

    Thanks for your answers.

    @fcwilt: . BUT the nozzle should only move about 40mm down.

    I don't understand. If the carriage on, say, the X tower is up as high as it goes and you move the other carriages down so the nozzle is at the max radius and is adjacent to the X tower the nozzle is going to be at the max height regardless of how much it has moved down.

    So what do you mean by "should only move about 40mm down".



  • @fcwilt: I will make a video later today in the evening.


  • administrators

    I haven't yet worked out what might be causing that problem. Nobody else has reported it, and I don't see anything similar on my delta.

    What happens when you home the printer? Your homedelta.g file homes the towers, then commands Z to move down by 5mm, then centres the effector. Do the carriages drop by 9cm during this process? If so, at what step?

    Here's the code that limits the height, as at firmware version 2.02:

    const float diagonalSquared = fsquare(coords[X_AXIS]) + fsquare(coords[Y_AXIS]);
    ...
    if (applyM208Limits && coords[Z_AXIS] < reprap.GetPlatform().AxisMinimum(Z_AXIS))
    {
    	coords[Z_AXIS] = reprap.GetPlatform().AxisMinimum(Z_AXIS);
    	limited = true;
    }
    else
    {
    	// Determine the maximum reachable height at this radius, in the worst case when the head is on a radius to a tower
    	const float maxHeight = homedCarriageHeight - sqrtf(D2 - fsquare(radius - sqrtf(diagonalSquared)));
    	if (coords[Z_AXIS] > maxHeight)
    	{
    		coords[Z_AXIS] = maxHeight;
    		limited = true;
    	}
    }
    

    Variable homedCarriageHeight is set to the height at which each carriage triggers the endstop switch, corrected by the M666 endstop adjustments. D2 is the square of the rod length.

    As it happens, I've just replaced that block of code as part of extending the delta kinematics to support up to 6 towers all with different rod lengths. So I can provide a new binary for you to try. But I'd rather find out why the 2.02 firmware isn't working for you first.



  • In the picture you post, is your effector centered while at its maximum height? Both in terms of XY position and real-world position relative to your towers.



  • Here is the announced video:
    https://vimeo.com/313250184

    Process:
    The nozzle is homed with a height of 1024.5mm.
    The nozzle moves in horizontal direction with G1 Y-350.
    Than the printer shows a height of about 899mm.

    But it is from the hardware arms a height of 990mm possible.
    This height is never reached.
    You can see that the arm is about 91mm under the maximum height (end stop).

    Note:
    If I execute G1 X-400 there are about 30mm more possible with the arms.
    If I execute G1 X400 there are about 30mm more possible with the arms.
    If I execute G1 Y400 there are about 5mm more possible with the arms.



  • @fcwilt: After reading the comment from dc42 I understood what you meant.
    This is probably the internal code implementation.

    @dc42: If you have the new implementation for the dynamic height calculation you can send them to me by e-mail to test it.
    But you are right. The I2C error is much more important. I would like to start my 430 hours printjob 😉



  • @tbs said in Delta printer does not print the full height on the outer edges:

    You can see that the arm is about 91mm under the maximum height (end stop).

    What arm does the video show?

    Frederick



  • @fcwilt: The video shows the right arm on the front or the theoretical position is about X500 Y-500.

    The left arm on the front is similar with 91mm.



  • Did you run the autocal feature when the homing file was as you posted?

    Frederick


  • administrators

    I've watched the video.

    1. Can you confirm that when you home the printer, all 3 carriages go right up to the endstop switches, then drop about 5mm?

    2. When you commanded Y to -350, did all 3 carriages drop? The video only shows one of them.



    1. Yes, i can confirm that all three carriage trigger the end stops and move 5mm down.

    2. The video is recorded in the front position.
      The carriage in the front left moves about 91mm down.
      The carriage in the front right moves about 91mm down.
      The carriage in the background middle moves more than 300mm down. But I have not messured the exakt value for the background carriage, yet.



  • Immediately after homing a delta printer, you can't freely move in X/Y without some moves causing a carriage to crash UP into an endstop.

    This move shouldn't produce the behaviour, but perhaps the printer is moving down to a level that allows full X/Y movement without the carriage crashing up.

    EG, if you gave the command G0 Y350, immediately after homing, the carriage would crash. Has the firmware been updated to prevent "illegal" moves of delta kinematics? IE ones that would put the printer at a height where the XY plane is not fully and freely accessible?



  • This may or may not have anything to do with your problem:

    The dimensions given in the M665 in the config-override.g you posted seem odd.

    M665 L1021.500 R527.601 H1030.482 B400.0 X-0.139 Y-0.828 Z0.000

    Specifically, B (printable bed radius) of 400 with a R (Delta radius, measured horizontally, measured "joint center to joint center" of 527, this seems a bit off. The point at which a diagonal arm pivots on the carriage is 157mm beyond the edge of the bed? Normally this is a gap just large enough to run a belt...

    Also, this makes your R (Delta Radius) more than half of your diagonal rod length. This would imply that the rods are at less than a 45 angle when everything is centered. Yet we can see in the video this is not true.

    Again, may or may not be related to the problem...



  • As an aside to this:

    If you have 1021mm arms, it should be easily possible to achieve a print radius of 445mm, Going all the way to 450 causes the rods to be below a 20 degree angle in their "worst case" position.



  • @fcwilt said in Delta printer does not print the full height on the outer edges:

    Did you run the autocal feature when the homing file was as you posted?

    Frederick

    I have run the autoleveling routine and it was the same result.

    @danal said in Delta printer does not print the full height on the outer edges:

    As an aside to this:

    If you have 1021mm arms, it should be easily possible to achieve a print radius of 445mm, Going all the way to 450 causes the rods to be below a 20 degree angle in their "worst case" position.

    I have changed the R parameter to 450, but it is the same result.


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