bridge saw cutter for marble with rotating table

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22 Sep 2023 20:18 #281413 by glct12
Hello
I am working on a project, to convert an old bridge saw cutter for marble with rotating table for the work piece
to a cnc milling machine. My question is how to configure the kinematics of the 4-axis system.The tool is a disk saw (20cm .. 30cm diameter)
that moves in x,y,z axes and at the same time the work piece table can rotate when making curves.
I am going to use servo drives with analog reference inputs and incremental encoders for feedback.
For the logic interface I will use some mesa cards.
Any suggestion for the appropriate cam processor for the gcode generation of dxf files?
I am already familiar with linuxcnc and mesa cards that i have used in the past on other projects.
Thank you in advance.
George

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23 Sep 2023 07:12 #281439 by andypugh
This sounds like a fairly conventional XYZC machine.
Do you need to coordinate the table rotation to the other motion, or us it largely indexing?

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23 Sep 2023 08:15 #281444 by glct12
The axis C is rotating relative to Z axis and coordinated with the other motion.

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23 Sep 2023 08:27 - 23 Sep 2023 08:33 #281445 by Aciera

The tool is a disk saw (20cm .. 30cm diameter)
that moves in x,y,z axes and at the same time the work piece table can rotate when making curves.


I have difficulty picturing this. How are you cutting a curve with a disk saw?


[edit]
Is like at 1:07 in this video (only in your case the work piece rotates)?


If so you don't need any special kinematic in LinuxCNC.
Last edit: 23 Sep 2023 08:33 by Aciera.

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23 Sep 2023 08:39 - 23 Sep 2023 08:51 #281446 by Aciera
If you want to cut noncircular curves or circular ones that have centers that do not coincide with the axis of the rotary c table then you would need a fairly capable CAM. But I don't see how a custom (ie non-trivial) kinematic could be of any use here.

[edit]
Ok, I maybe kind of get it. For the mentioned cases above. You'd want to rotate the C table so the saw remains tangential to the curve and you'd then need the kinematic to adjust the XY-position according to the C axis angle.
For this you could use for example the included XYZAC-trt kinematic and just ignore the A axis.
However you would need a way to calculate C-axis angles depending on the tools position along the arc.
Last edit: 23 Sep 2023 08:51 by Aciera.

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23 Sep 2023 08:51 #281448 by glct12
The machine is similar to the one in the picture.
The table (C axis) is rotating relative to Z axis, which is perpendicular to XY plane.
The disk diameter could be 20cm in minimum.
Attachments:

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23 Sep 2023 08:55 - 23 Sep 2023 09:04 #281449 by Aciera
Like a tangential knife with the C-rotation done by the work piece.

[edit]
Should be possible, I guess. If the calculation of the c-axis angle could be integrated in the XYZC TCP kinematic then you might not even need a CAM. It would just be a regular 3 axis gcode.
I'm not sure I'd want to be the one responsible for writing the c angle calculations though. Just imagine the mayhem if it missed a discontinuity in the math and the resulting angle suddenly changed from positive to negative.
Last edit: 23 Sep 2023 09:04 by Aciera.

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23 Sep 2023 09:10 - 23 Sep 2023 09:24 #281450 by Aciera
Actually SheetCAM seems to offer a ''Dragknife" module that may take care of the angle calculations:

sheetcam.com/Register/purchase

[edit]

seems this user also uses the SheetCAM solution for this.
www.forum.linuxcnc.org/10-advanced-confi...h-xy?start=50#248422
Last edit: 23 Sep 2023 09:24 by Aciera.
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23 Sep 2023 15:45 #281483 by glct12
Regarding the video you attached, the only difference i see is that in my machine,
instead of rotating the disk saw, the table rotates.

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23 Sep 2023 23:54 #281517 by tommylight

The machine is similar to the one in the picture.

Posting a real picture of the actual machine would save us a lot of time trying to guess, so why don't you?
-
The picture you posted, that is not of your machine, i have seen those and have access to if the need arises, but much bigger. Same everything, but bigger, Italian made, NC controlled, etc.
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