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Thread: Poalr coordinates

11202017, 09:35 AM #1
POLAR coordinates
Hy
I have come here for asking for some help with polar coordinates.
I have a part witch i must turn. And i must use polar coodinates on secodn spindle. I have swis type lathe. I have two numbers to mil on a face of a bar. I have calcualted number 1 in excel and use one of free converters, it work fine. Then made a 8 and it was great. Then i put all this stuf in the cnc, and i broke a tool. Problem is with F parameter in every block. There is none. So spindle is behaving iradical. So i went back to the table and looked at polar velocity and polar acelaration equation. so,... Now i think that it wopud be best to find some program witch can do this for me. Becose this is a lot of calcualting in excel, ( i can do it but it take time).
My question is. How to get points on the circle of teh center with equal spacing or equal degrees ( here is the firs prorblem you will never get equal of both) or how to calculate F parameter for every move in excel or in some program cad cam or somthing.
What are you using for such programs to do this. I have seen this in esprit program once. There must be other options.
Do you have eny sugestions.
thank you for your answer ant time.
STARODAVNI


11202017, 03:18 PM #2
I don't squat about CNC controllers, gcode, or anything of the sort. However, I do know polar coordinates. It should be super easy to set up a program in excel, mathematica, C, or other program to covert the polar coordinates to cartesian coordinates.
As you know, polar coordinates are written in (radius, angle). Angle can be given in degrees or radians. Conversion to cartesian coordinates (x,y) can be written as (r*cos(angle), r*sin(angle)) where r means radius.
For a more thorough and visual explanation, refer to this link:
Polar coordinate system  Wikipedia

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11202017, 03:33 PM #3
Medsar, he needs the polar coordinates because he is using a rotary axis in substitution for a linear one. A "Y" coordinate does him no good if he has no Y axis.

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11202017, 08:05 PM #4
It's kind of coming out that I know jack squat about CNC....
Thanks Hazzert for explaining that because I just wasn't getting it. If this next attempt isn't helpful, then I'm just going to edit my responses to delete them because I'm not helping the community here...
Could you take an xy cartesian system and wrap it around a cylinder to convert to a polar coordinate system? If I understand it right, the example that is brought up by Starodavni would be a round bar of radius, r, where you are engraving letters or numbers on the surface. And I am assuming the layout/canvas of these numbers are in a cartesian coordinate system? Make the height (or y axis) of your layout/canvas the circumference of the rod and the xaxis however long you want it to be.
For the translation to polar coordinates:
Imagine that we are going to wrap the canvas/layout around the round bar.
For the yaxis:
First we set a zero:
The y axis coordinate gets converted to polar coordinates by setting cartesian y=0 as polar (r,0).
For every other y coordinate, we calculate the angle in polar coordinates by converting the y axis coordinate value to a length on an arc with radius, r (of our round bar), and solving the equation for the angle, theta.
length = (theta/360 degrees)*2*pi*r
y axis coordinate = (theta/360 degrees)*2*pi*r
For the xaxis:
The xaxis now becomes the height the round bar. I'm no CNC guy here....is that the zaxis? Basically, the cartesian x axis now becomes the movement the height (or length depending on how one thinks about it) of the bar/cylinder.
One key distinction that all your units must be the same. i.e. only use mm or inches etc for all the lengths. This, too, can be set up in an Excel program.

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11222017, 10:33 AM #5
Hy
i have onl x axsis and c rotation.
I have put koordinates of leters in excel and calculated points with equal distances. Then i used some free program to convert stuf.
I need F parameter.
N100 X10.0 C=100.0 F10.0
N110 X11.0 C=150.0 F12.0
i need F parameter,every move needs its own f becose of polar velocity and akcelaration vectors. If i put f in the start then spidnle behave iradical.
I need soem equation to calculate polar velocity in excel and poalar axelaration or some program like solid cam or edgecam to do this math for me. But i dont have programs and i dont now, if do i need some post procesor to get out g code in edgecam. In solidcam i now that postprocesro its a must.
I hope i exsplained the problem.
Second problem i did is this. I need a circle. I draw circle in the center of cortazian system and calculated points on the circle. Then i moved this circle to of center of cartezian cooriante system, and do the code. Problem is that this points from center of kortezian koordiante system dont have equal angle from point to point and this is problem. I hopet to get equal distance from point to point and equal angle from point to point in polar system. But this is inposible. So it is a must to have F. I woud need some help with equation for excel spreed sheet. It woud be nice. We can post it on the forum for people to have.
I now for the conversion from polar to kortezian thanks, and back again. I do this in excel. It is equation only one for al 4 quadrants. You make a table nad calcualtes 1000 blocks in a second.
Do enyone now how to calculate point( x and y) on the circle of center with with radius R so that distance betwen points is constant. This is ealy inresting. this woud be realy helpful. s eny matematician here.
Thank you guys for the help and suport.


11222017, 01:53 PM #6
Does your controller support polar interpolation (G112 on a Fanuc). If so, it will be easy to do face milling using X & C.
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