Include rotation from A in G0

andypugh
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6 years 10 months ago #152181 by andypugh

Replied by andypugh on topic Include rotation from A in G0

anpoit00 wrote: I doubt that it is work because unknowing angle for the next movement (for G1 yes but G2, G3 ..)

It isn't very hard if you run through the G-code line-by-line in an input filter.
Basically before every G1 put in a G0 to the tangent of the G1 section.
Additionally, for a G2 or G3 append an A move to the new angle.

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Badger
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6 years 10 months ago #152184 by Badger

Replied by Badger on topic Include rotation from A in G0

I did a quick test with gcodetools using the tangent knife tool and it may do what you need. This is using the settings from my Rugbot which of course will be different from you machine.

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andypugh
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6 years 10 months ago #152275 by andypugh

Replied by andypugh on topic Include rotation from A in G0

Here is a partial solution. It is an input filter that converts this input:

Code:

(dragknife test)
G21
G0 X10 Y10
F10
G91.1
G1 X10 Y -10
G1 X-10 Y-10
G1 X-10 Y10
G1 X10 Y10
G3 X10 Y -10 J-10
G3 X-10 Y-10 R10
G90.1
G3 X-10 Y10 I-10 J0
G2 X10 Y10 R20
M2

To this output

Which almost, but not quite, does what is needed.

The problem I am seeing is that whilst he angles of the starts and ends of arcs are correct, the tool won't necessarily turn the right direction to cut properly.

But I am going away for a week, so thought that it might be best to hand it over, in case you want to try to make the required changes.

It uses the normal atan2 convention where the +X direction is 0, +Y = 90, -X = 180/-180 and -Y = -90. Your A axis would need t change that.
A variable defined near the top allows for changing to use C for the tool rotation.

Edit the INI file [FILTER] section:

Code:

[FILTER]
PROGRAM_EXTENSION = .ngc G-code
ngc = /home/andypugh/linuxcnc/dragknife

Then save this code as "dragknife", make it executable and put it in the path defined above.

Code:

#! /usr/bin/python

import re
import sys
from math import *
import linuxcnc

# Change this to alter the rotary axis letter
L = "A"

infile = sys.argv[1]

f = open(infile, 'r')

G = -99999.0
X = 0.0
Y = 0.0
oldA = -99999.0
A = 0
A2 = 0

s = linuxcnc.stat()
s.poll()
if 901 in s.gcodes:
    abs_centre = True
else:
    abs_centre = False

oldX = X = s.position[0] + s.g92_offset[0] + s.g5x_offset[0]
oldY = Y = s.position[1] + s.g92_offset[1] + s.g5x_offset[1]

print("(Start X %f, Y %f)" %(oldX, oldY))

for line in f:
    Xf = re.match(r".*X\s*([\d\.,\+\-]+)", line)
    Yf = re.match(r".*Y\s*([\d\.,\+\-]+)", line)
    If = re.match(r".*I\s*([\d\.,\+\-]+)", line)
    Jf = re.match(r".*J\s*([\d\.,\+\-]+)", line)
    Rf = re.match(r".*R\s*([\d\.,\+\-]+)", line)
    Gf = re.match(r".*G\s*([\d\.,\+\-]+)", line)
    
    I = 0
    J = 0
    if Xf:
        oldX = X
        X = float(Xf.group(1))
    if Yf:
        oldY = Y
        Y = float(Yf.group(1))
    if If: 
        I = float(If.group(1))
    if Jf: 
        J = float(Jf.group(1))
    if Rf:
        R = float(Rf.group(1))
    if Gf:
        G = float(Gf.group(1))
        
    if G == 90.1:
        abs_centre = True
    if G == 91.1:
        abs_centre = False

    if G == 0.0 or G == 1.0:
        A = atan2(Y - oldY, X - oldX) * 180/pi
    elif G == 2.0 or G == 3.0:
        if Rf:
            mid_x = (X + oldX) / 2.0;
            mid_y = (Y + oldY) / 2.0;
            l2 = sqrt((mid_x - X)**2 + (mid_y - Y)**2);
            if ((G == 2) and (R > 0)) or ((G == 3) and (R < 0)):
                theta = atan2((Y - oldY), (X - oldX)) - pi/2;
            else:
                theta = atan2((Y - oldY), (X - oldX)) + pi/2;
            turn2 = asin(l2 / abs(R));
            offset = abs(R) * cos(turn2);
            X0 = mid_x + (offset * cos(theta));
            Y0 = mid_y + (offset * sin(theta));
        elif abs_centre:
            X0 = I
            Y0 = J
        else:
            X0 = oldX + I
            Y0 = oldY + J
            
        A = atan2(Y0 - oldY, X0 - oldX) * 180/pi
        alpha = atan2(Y0 - Y, X0 - X) * 180/pi - A
        if G == 2.0:
            A = A + 90
            A2 = A + alpha
        else:
            A = A - 90
            A2 = A + alpha
    if (Xf or Yf) and G == 0.0:
        print("G0 %s%.2f" % (L, A))
        print(line),
        oldA = A
    elif (Xf or Yf) and G == 1.0:
        if oldA != A:
            print("G0 %s%.2f" % (L, A))
            if not Gf:
                line = "G1 %s" % line
        print(line),
        oldA = A
    elif (Xf or Yf) and G == 2 or G == 3:
        if oldA != A:
            print("G0 %s%.2f" % (L, A))
        line = re.sub("\n", " %s%.2f" % (L, A2), line)
        print(line)
        oldA = A2
    else:
        print(line),

The following user(s) said Thank You: jo_key, anpoit00, tiagounderground

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