Lathe with Live tooling

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29 Apr 2011 15:26 #9512 by brianm
I have built a lathe that I would like to add live tooling to. Basically the lathe design has a 3HP AC Motor driven by a motor controller for turning operations. (This is fairly simple to setup in EMC). However, I also have a stepper motor that can be engaged to the spindle. So basically, I want to use the lathe for turning and then enter some M code and the stepper motor will engage and I can do live tooling operations. (Controlling the spindle via the stepper motor instead of the Main drive motor). I am unsure how to start doing this. Can someone sort of point me in the right direction....

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29 Apr 2011 22:12 #9517 by Rick G
Replied by Rick G on topic Re:Lathe with Live tooling
Hello,

You might look for some ideas here...
www.linuxcnc.org/component/option,com_ku...imitstart,0/lang,pl/

Rick G

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30 Apr 2011 22:15 #9523 by brianm
Replied by brianm on topic Re:Lathe with Live tooling
Thanks for the reply,

I read through that post a bit, but not sure if it is what I am trying to do....

I have been trying to read and understand the kinematics in order to translate a C-Axis (spindle, which i think would be joint 5?), the X-Axis (tool parallel to Z-Axis on the center line Which I think would be joint 1?), The Z-Axis (Parallel with the centerline of the spindle and tool) would be joint 2?) into a XYZ plane with the 0 in the center of the spindle. I have programmed on HAAS machines before and they call it cartesian polar transformation.

Here is how the HAAS manual describes it:
Cartesian to Polar coordinate programming that converts X,Y position com-
mands into rotary C-axis and linear X-axis moves. Cartesian to Polar coordi-
nate programming greatly reduces the amount of code required to command
complex moves. Normally a straight line would require many points to define
the path, however, in Cartesian, only end points are necessary. This feature al-
lows face machining programming in the Cartesian coordinate system

I have read the section in the manual a few times, and the wiki and looked at the source files for some of the kinematics. I feel like I am starting to understand it, but still am very foggy on the subject.

I tried to put the rotatekins in the stepper_inch example configuration just to see how it worked (instead of loadrt trivkins I put loadrt rotatekins in the hal file). (My computer is not hooked up to any machine). When I load the program I see Joint 0,1,2 on the jog screen. (I am assuming that would be the actual motors). Then when I go to MDI mode, I thought that if I did a command like G1 X10. Y10. F10. that I could look at the motor-pos-command for 0 and 1 and see them both moving... (Which in my mind would be like the C axis and X axis motors moving). However, I get a joint following error.... Not sure why. Can someone explain what I am missing or where I can get some good examples....

My ultimate goal that I have in my mind (not sure if it is the best or possible). Is to create my own kinematics file and have a hal pin that is controlled by a Gcode (G112 in the HAAS control). By default it uses the trivkins for normal lathe cutting. However, when the G-Code is implemented it changes to something similar to the rotatekins and allows me to program the live tooling in XYZ coordinates. Does this seem to be possible or does someone have a better way or method?

Thanks
Brian

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01 May 2011 10:51 #9525 by Rick G
Replied by Rick G on topic Re:Lathe with Live tooling
O.K. you might want to start with experimenting with the 9 axis sim and the GEOMETRY statement to get an idea how the axis can work together.
Could what you are describing be similar to a mill with a rotary table under the spindle?

Rick G

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01 May 2011 14:19 #9526 by brianm
Replied by brianm on topic Re:Lathe with Live tooling
Ok, I will play with that a bit. I also am looking at the tripod configuration.

Yes, Basically what I am describing would be a mill with a rotary table sitting flat on the table (center of rotation parallel to Z Axis). Then remove the Y Axis. So you have a X axis and Rotary Axis to make your X Y paths.

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01 May 2011 18:37 #9528 by cncbasher
to be able to use live tooling which for example is to engrave or mill around the spindle axis or to drill perhaps holes around a pcd on the fact of the part , you can as you suggest switch between motors using a macro , however also take into concideration the spindle will need to also have an encoder so that positional and index information is always available to emc2 , the majority of major machines use a heavy servo motor as the spindle motor is standard in this situation and not a usual lathe motor along with shaft encoder , so no switching of motors is required .

most software these days can output the correct gcode , mastercam , solidcam etc .

and is simply shown in gcode as C30.0 ( as an angle ) , and always programmed in G97 mode (r/min) & feedrate in units of time (in/min)

this is possible via a script or macro

here's a simple c code example
/* PROG.TO CONVERT CARTESIAN COORDINATES(X,Y)
INTO POLAR COORDINATES(ARG,ANG)*/

#include<stdio.h>
#include<math.h>
#include<conio.h>
main()
{
float x,y,r,theta;
clrscr();
printf("enter cartesian coordinates");
scanf("%fOlof',&x,&y);

/* conversion */
r=sqrt(x*x + y*y);
theta=atan(y/x); /* angle in radian */
theta=theta*180/3.14; /* angle in degrees*/
printf("\n polar coordinates are argument=%f and angle=%f' ,r,theta);
getch();
}

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01 May 2011 20:03 #9529 by Rick G
Replied by Rick G on topic Re:Lathe with Live tooling
Brian,

Have you looked here...
linuxcnc.org/docs/html/man/man9/kins.9.html

maxkins might be worth looking at.

Rick G

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