. .
Page 25 of 33 FirstFirst ... 152324252627 ... LastLast
  1. #241
    Hi Bert,

    Sounds like it is working for you, fantastic. What laser and camera are you using? Are you sure of the units, i.e. did you set the um per pixel?

    I'm assuming you moved the machine frame to meet the laser plane to get the corners so close, adjustable feet?

    My 6 inch concrete slab also looks like jelly with this system.

    Joe

  2. #242
    Quote Originally Posted by devmonkey View Post
    Hi Bert,

    Sounds like it is working for you, fantastic. What laser and camera are you using? Are you sure of the units, i.e. did you set the um per pixel?

    I'm assuming you moved the machine frame to meet the laser plane to get the corners so close, adjustable feet?

    My 6 inch concrete slab also looks like jelly with this system.

    Joe
    Today i got to some measuring again.

    About my setup.

    I have a cheap bosch crosshair laser which I now know is not up to this task.

    The webcam is a 1920x1080 6.2 ish by 3mm sensor... so +/- 3um.

    Yes i have m12 adjustable bolts in the feet.
    10 deg of turning on the feet is clearly visible in the software.

    About the units i am sure it is still on defaults so 1um, need to check.
    Yes my measurements in the earlier post are off by factor 3.
    Not yet that important since i was testing the setup and finding out the sop.

    ### about The laser.
    The selflevelling seems to be spot on.
    The optics are not.
    I found out today.
    Moving towards and from the laser the light is straight (light travels in a straight line) moving along the projected line gives false readings. +/- 60 um / 80 cm at about 3meters distance so only a few degrees

    Now i know this, it is okay the way it is.
    Just make sure you move in a straight line from and to the lightsource.

    I have to put the laser a bit further away to get into the better sensitivity range of the camera. It all helps.

    Actionplan:
    * Input the correct units in the software
    * Use a tripod laserplatform
    * Put the tabel diagonals in plum.
    * Check the 2 long axis.
    * Check the short axis for horizontal variations.
    * Check the short axis at lowest point and highest point to check top and bottom rail for allignment.

    I have not thought of a way to check the spindle for misalignment by webcam/laser without trusting the optics.

    But maybe a conventional plumbline and a light source (is that the right English word?) can do the job.


    Grtz Bert.

    Verstuurd vanaf mijn SM-A320FL met Tapatalk

  3. #243
    Really useful details, thanks Bert.

    When you see the error from moving along the projected line, is it random noise or is it like the line is bent up or down in the middle, like your gantry measurement ?

    I think I have seen the line bent like this. I did a little experiment with a dot laser and a glass cylinder (wine glass stem). When the laser passes through the cylinder at 90 degrees you get a straight line projected, when you angle the glass a lot you get a visibly bent line either up or down depending which way to hold the angle.

    Maybe this is a common problem with the line optics, and maybe we could calibrate it out by taking two sets of measurements along a straight edge with the laser flipped 180 axially for each set. Will have to think on this, any thoughts welcome...

    Although it would not be easy to flip your laser as it is on a pendulum.

  4. #244
    Quote Originally Posted by devmonkey View Post
    Really useful details, thanks Bert.

    When you see the error from moving along the projected line, is it random noise or is it like the line is bent up or down in the middle, like your gantry measurement ?
    Hi devmonkey,

    Yes it was like you described with the laser vs wineglass stem.



    The noise was within 5 orso units.
    when measure is pushed several times in 60 sec... maybe +/- 1 or 2 units.




    Grtz Bert.






    Verstuurd vanaf mijn SM-A320FL met Tapatalk

  5. #245
    Hi Bert,

    I have had an idea of how to create a tool to check whether the rails are planar that doesn't matter if the laser line is bent.

    It is effectively a large scale repeat-o-meter using the laser rather than DTI and thereby avoiding a very long infinitely stiff top bar:
    Click image for larger version. 

Name:	repeat-o-meter.jpg 
Views:	151 
Size:	22.1 KB 
ID:	27444

    The setup would consist of 4 spherical feet arranged in a square. 3 of these feet would be rigidly mounted on a triangular frame, the fourth foot would float on an arm that can pivot up and down on a hinge at the centre of the square. The camera would be fixed above this forth foot and the laser fixed to the triangular frame diagonally opposite. None of this would need to be high precision, the only requirement is that the triangle be stiff.

    To calibrate the tool you could use any reasonably flat surface, it doesn't have to be a perfect plane but shouldn't be pitted.

    Lay the tool on the surface and mark where the 4 feet touch as accurately as you can. Take a height reading of the laser on the sensor. Now lift the tool and rotate it 90 degrees such that the feet sit back on the 4 marks made and take another height reading. I think that the middle of the two height readings will be the point where all 4 feet are in plane, so we zero the tool to this mid point.

    If this is a new machine then you would level the master rail bed in isolation using the laser projecting along it.

    Now place the new calibrated tool on the machine frame such that two feet of the triangle rest on the master rail bed and the other two on the slave rail bed. Now adjust the slave rail bed under the floating foot until you read zero. These four points on the machine are now in plane. You can check the tool is still calibrated by rotating it 90 degrees on the machine frame and checking for zero.

    We now have two points on the slave rail bed that are planar with the master so the slave rail bed can now be levelled in isolation to a line passing through these two points.

    Click image for larger version. 

Name:	IMG_20200225_091309 (Large).jpg 
Views:	130 
Size:	72.5 KB 
ID:	27445

    I think this a similar approach to using two crossed wires between 4 points to check for plane when the wires just touch, but this should be much more accurate.

    If you had a machine where the two rail beams are adjustable at the ends then this would be an extremely simple way to bring them into plane.

    Cheers, Joe
    Last edited by devmonkey; 25-02-2020 at 11:03 AM.

  6. #246
    Quote Originally Posted by devmonkey View Post
    Hi Bert,

    I have had an idea of how to create a tool to check whether the rails are planar that doesn't matter if the laser line is bent.

    It is effectively a large scale repeat-o-meter using the laser rather than DTI and thereby avoiding a very long infinitely stiff top bar:
    Click image for larger version. 

Name:	repeat-o-meter.jpg 
Views:	151 
Size:	22.1 KB 
ID:	27444

    The setup would consist of 4 spherical feet arranged in a square. 3 of these feet would be rigidly mounted on a triangular frame, the fourth foot would float on an arm that can pivot up and down on a hinge at the centre of the square. The camera would be fixed above this forth foot and the laser fixed to the triangular frame diagonally opposite. None of this would need to be high precision, the only requirement is that the triangle be stiff.

    To calibrate the tool you could use any reasonably flat surface, it doesn't have to be a perfect plane but shouldn't be pitted.

    Lay the tool on the surface and mark where the 4 feet touch as accurately as you can. Take a height reading of the laser on the sensor. Now lift the tool and rotate it 90 degrees such that the feet sit back on the 4 marks made and take another height reading. I think that the middle of the two height readings will be the point where all 4 feet are in plane, so we zero the tool to this mid point.

    If this is a new machine then you would level the master rail bed in isolation using the laser projecting along it.

    Now place the new calibrated tool on the machine frame such that two feet of the triangle rest on the master rail bed and the other two on the slave rail bed. Now adjust the slave rail bed under the floating foot until you read zero. These four points on the machine are now in plane. You can check the tool is still calibrated by rotating it 90 degrees on the machine frame and checking for zero.

    We now have two points on the slave rail bed that are planar with the master so the slave rail bed can now be levelled in isolation to a line passing through these two points.

    Click image for larger version. 

Name:	IMG_20200225_091309 (Large).jpg 
Views:	130 
Size:	72.5 KB 
ID:	27445

    I think this a similar approach to using two crossed wires between 4 points to check for plane when the wires just touch, but this should be much more accurate.

    If you had a machine where the two rail beams are adjustable at the ends then this would be an extremely simple way to bring them into plane.

    Cheers, Joe
    Hi Joe,

    I am not sure i understand correctly.
    Does this device need to be at the exact centre of diagonals?

    Doesnt the mentioned reference flat surface have to be in the same paralel plane as the rails then?



    Grtz Bert.

    Verstuurd vanaf mijn SM-A320FL met Tapatalk

  7. #247
    Hi Bert,

    No nothing needs to be centred on the diagonals, the only restriction is that the device can only check a square not a rectangle, but this doesn't matter as we can always define a square ontop of the rectangle formed by our pair of rail beds.

    The reference surface doesn't really exist. What we are doing is defining a square as four points on the device, call them A, B, C, and X:

    AB
    XC

    With [A,B,C] fixed in relation to each other and X able to move up and down. Since [A,B,C] are fixed relatively to each other (in a triangle) they form a plane. The laser is fixed to this plane on the device near B pointing towards X. The camera is fixed to X.

    Now define a square the same size on a table top or the machine frame or whatever, label the corners of this square 1, 2, 3, 4:

    12
    43

    Place the device over this square such that A==1, B==2, C==3, X==4. Measure the laser height on the sensor at X. Now rotate the device 90 degrees so that say A==2, B==3, C==4 and X==1 and measure the new laser height at X which will have changed because your surface defined by [1,2,3,4] you drew on your table is not a perfect plane.

    Now if you were to move X up or down so that the laser measured height is half way between the two heights measured then I think that X will be planar with A,B,C. So zero the software at the mid height between the two X heights measured and you now have a calibrated device which will read zero when placed on a true plane and a signed error when placed on an untrue plane. In other words [A,B,C,X] will be planar when the newly zero'd X is at zero. You can use this to check a machine is in plane and adjust the machine as required until it reads zero.

    I haven't tested this only thought about it, I might be missing something, will draw it in CAD and check the theory is correct.

    Cheers, Joe
    Last edited by devmonkey; 27-02-2020 at 01:11 AM.

  8. #248
    Hi Bert and everyone,

    Here are some renderings of the laser-plano-meter I've been trying to describe.
    Click image for larger version. 

Name:	LASER_PLANE_1.jpg 
Views:	176 
Size:	1.02 MB 
ID:	27468 Click image for larger version. 

Name:	LASER_PLANE_2.jpg 
Views:	163 
Size:	1.43 MB 
ID:	27469

    It consists of a square device sat on 4 spherical feet at the corners. 3 corners of the square are rigidly connected to form a triangle (orange part) with laser attached. The forth corner is attached by the green arms to the triangle with flexures that allow it to pivot up and down with respect to the triangular plane, effectively the square is allowed to fold along its diagonal. The camera sensor is attached to the forth corner.
    Click image for larger version. 

Name:	LASER_PLANE_3.jpg 
Views:	145 
Size:	466.4 KB 
ID:	27470

    The laser will project a line on the sensor, the height of this line is related to the angle of the fold. The goal is to find the sensor reading where ALL 4 feet are in the same plane thereby providing a method of measuring the error of any surface from a plane. We will call this sensor reading ZERO.

    To find ZERO we place the device on any surface, doesn't need to be a plane. We then take the laser height measurement H1 in this position. Now rotate the device 90 degrees about the Z axis and replace it on to the same surface so that each foot is in the same place as its predecessor was in the first position. Now measure laser height H2.

    With both H1 and H2 we can calibrate the device. ZERO is the mid point between H1 and H2.

    Now place the device on the surface to be measured, e.g. the pair of X rail beds of the CNC frame. The deviation from ZERO will tell you how much to adjust the frame under the 4th foot in order to bring the surface into plane.

    An alternative way to think of it is if you just placed the non-zero'd device on the machine frame and take the laser height measurement, then rotate 90 degrees and repeat, if the heights are different you need to adjust the frame. Make the adjustment, rotate the device back to its original position and repeat until the height readings match.

    EDIT
    Should be noted that this device could be constructed with a DTI instead of a laser as per a normal repeat-o-meter. In this case you would have just the orange triangle and replace the laser with a long arm with the DTI on the end. The problem of course would be that the error due to the long arm flexing due to its own weight and the pressure from the DTI spring would far exceed the resolution of the DTI. This is not a problem with the laser beam as it wont bend no matter how long it is.

    Cheers, Joe
    Last edited by devmonkey; 02-03-2020 at 06:51 PM.

  9. The Following User Says Thank You to devmonkey For This Useful Post:


  10. #249
    Quote Originally Posted by devmonkey View Post
    Hi Bert and everyone,

    Here are some renderings of the laser-plano-meter I've been trying to describe.
    Click image for larger version. 

Name:	LASER_PLANE_1.jpg 
Views:	176 
Size:	1.02 MB 
ID:	27468 Click image for larger version. 

Name:	LASER_PLANE_2.jpg 
Views:	163 
Size:	1.43 MB 
ID:	27469

    It consists of a square device sat on 4 spherical feet at the corners. 3 corners of the square are rigidly connected to form a triangle (orange part) with laser attached. The forth corner is attached by the green arms to the triangle with flexures that allow it to pivot up and down with respect to the triangular plane, effectively the square is allowed to fold along its diagonal. The camera sensor is attached to the forth corner.
    Click image for larger version. 

Name:	LASER_PLANE_3.jpg 
Views:	145 
Size:	466.4 KB 
ID:	27470

    The laser will project a line on the sensor, the height of this line is related to the angle of the fold. The goal is to find the sensor reading where ALL 4 feet are in the same plane thereby providing a method of measuring the error of any surface from a plane. We will call this sensor reading ZERO.

    To find ZERO we place the device on any surface, doesn't need to be a plane. We then take the laser height measurement H1 in this position. Now rotate the device 90 degrees about the Z axis and replace it on to the same surface so that each foot is in the same place as its predecessor was in the first position. Now measure laser height H2.

    With both H1 and H2 we can calibrate the device. ZERO is the mid point between H1 and H2.

    Now place the device on the surface to be measured, e.g. the pair of X rail beds of the CNC frame. The deviation from ZERO will tell you how much to adjust the frame under the 4th foot in order to bring the surface into plane.

    An alternative way to think of it is if you just placed the non-zero'd device on the machine frame and take the laser height measurement, then rotate 90 degrees and repeat, if the heights are different you need to adjust the frame. Make the adjustment, rotate the device back to its original position and repeat until the height readings match.

    EDIT
    Should be noted that this device could be constructed with a DTI instead of a laser as per a normal repeat-o-meter. In this case you would have just the orange triangle and replace the laser with a long arm with the DTI on the end. The problem of course would be that the error due to the long arm flexing due to its own weight and the pressure from the DTI spring would far exceed the resolution of the DTI. This is not a problem with the laser beam as it wont bend no matter how long it is.

    Cheers, Joe
    Yes, that really helped.

    This is a clever design.

    I will try this later. I think a simple laserpointer will do i guess in this scenario.


    Thnx Grtz Bert.



    Verstuurd vanaf mijn SM-A320FL met Tapatalk

  11. #250
    Afternoon all.

    I've finally got back to my machine project. I gave up with trying to create a planar surface in one shot and as the weather had warmed up I poured epoxy, this looks like it has worked well and made a very close surface for final levelling using the laser and shimming if required.

    Anyway the purpose of this post is to describe a new app I put together today for laying the master rail straight. I decided it would be easier to use a taut wire rather than the laser for this and a cheap USB microscope.

    So armed with some 0.28mm black fishing line I found in the garage and a club hammer I tensioned a wire parallel to where the master rail will sit. I used some white insulation tape on the machine frame below the wire to provide good contrast for the software and the wire runs over a couple of bolts that run through angle iron supports clamped to the ends of the machine frame. The wire is anchored at one end and the club hammer suspended from the other, the fishing line stretches out quite a bit and you can see the nylon flowing under the microscope, I waited for it to stop flowing before doing anything else.

    The microscope is attached to a hiwin carriage and the new app accurately locates the wire allowing you to zero the tool then reports the error as you slide the carriage back and forth. A 3D printed clamp allows the microscope to the rigidly attached to the magnetic base.

    Nothing new in the process that other people have performed other than the app that lets you achieve excellent accuracy with little effort. The resolution is roughly 3um per pixel repeatable down to less than 1um (relative to the straightness of the taut wire obviously).

    The wire locating algo is quite different from the laser gausian model and seems extremely robust. For those interested it locates the two edges of the wire using a median gradient threshold down each column of pixels, regresses lines down these edges and auto tunes the threshold until it has exactly two lines that completely cross the image from left->right. It then bisects the two edge lines to locate the wire centre. This removes any error from tapering of the wire due to stretching under tension. You hit zero then the app will will show you the relative error to this point as you move the rail and/or carriage about.

    Anyway I captured this video showing the app working on the machine frame:


    I will use this tool to set the master rail over the next day or so.

    Cheers, Joe

  12. The Following User Says Thank You to devmonkey For This Useful Post:


Page 25 of 33 FirstFirst ... 152324252627 ... LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. WANTED: K40 laser
    By dfox1787 in forum Items Wanted
    Replies: 0
    Last Post: 23-10-2018, 08:34 PM
  2. Newbie - Help With Laser Cutting Speed And Power - 60W Laser
    By nickpscott in forum Laser Machines & Building
    Replies: 2
    Last Post: 11-11-2015, 10:07 PM
  3. FOR SALE: K40 laser not working (laser fires)
    By calida in forum Items For Sale
    Replies: 0
    Last Post: 31-03-2015, 08:45 PM
  4. WANTED: GCc Laser Pro or Epilog Laser Cutter Machine
    By Brownhills school in forum Items Wanted
    Replies: 1
    Last Post: 10-05-2012, 04:30 PM
  5. help with cnc laser
    By swinds in forum Laser Machines & Building
    Replies: 11
    Last Post: 09-01-2012, 10:15 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •