G3 support for negative R

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  • October 17, 2013 at 5:06 pm #4814
    vane
    Member

    Hello,
    I’m running tinyg firmware 0.95. I’m having problems with generated g-code that contains G3 codes with negative R. Is this particular g-code supported? The wiki isn’t clear about it

    October 18, 2013 at 1:42 am #4822
    Makerboost
    Member

    What kinds of problems are you experiencing?

    October 18, 2013 at 7:33 am #4824
    Makerboost
    Member

    Correct me if I’m totally off base, but shouldn’t negative radius create a G2 code instead?

    If you wanted a G3 code, but you’re inverting the radius, then you’re telling it to go CW instead?

    Long day at work, so my mind is not working at peak efficency 😉

    • This reply was modified 11 years, 1 month ago by Makerboost.
    October 18, 2013 at 8:37 am #4826
    alden
    Member

    G3 should work with negative Rs. Can you post or make available the Gcode you are having problems with and some description of the problem?


    @Makerboost     : For a discussion of negative R see here:
    http://www.cnccookbook.com/CCCNCGCodeArcsG02G03.htm

    October 18, 2013 at 9:41 am #4827
    Makerboost
    Member

    Ah, my mistake. Thank you for the informative link!

    October 21, 2013 at 10:58 am #4839
    vane
    Member

    Hello,
    Sorry for the late reply (vacation). I can use any negative R example really.
    Like this in CoolTerm:

    G17 F300
tinyg [mm] ok> 
G2 X10 Y15 R20
tinyg [mm] ok> 
posx:0.004,posy:0.019,vel:149.997,momo:2,stat:5
..............................
posx:9.921,posy:14.958,vel:300.011
posx:10.000,posy:15.000,vel:0.000,stat:3
g0 x0 y0
tinyg [mm] ok> 
posx:9.393,posy:14.090,vel:2781.455,momo:0,stat:5
posx:3.844,posy:5.766,vel:7258.114
posx:0.067,posy:0.101,vel:806.456
posx:0.000,posy:0.000,vel:0.000,stat:3

    But now when I try this:

    G2 X10 Y15 R-20
tinyg [mm] err: Arc specification error: G2 X10 Y15 R-20

    Here is a dump of my settings:

    $$
[fb]  firmware build            380.02
[fv]  firmware version            0.95
[hv]  hardware version            7.00
[id]  TinyG ID                    1H4973-HSY
[ja]  junction acceleration 2000000 mm
[ct]  chordal tolerance           0.001 mm
[st]  switch type                 0 [0=NO,1=NC]
[mt]  motor disble timeout       60 Sec
[ej]  enable json mode            0 [0=text,1=JSON]
[jv]  json verbosity              3 [0=silent,1=footer,2=messages,3=configs,4=linenum,5=verbose]
[tv]  text verbosity              1 [0=silent,1=verbose]
[qv]  queue report verbosity      0 [0=off,1=filtered,2=verbose]
[sv]  status report verbosity     1 [0=off,1=filtered,2=verbose]
[si]  status interval           100 ms
[ic]  ignore CR or LF on RX       0 [0=off,1=CR,2=LF]
[ec]  expand LF to CRLF on TX     0 [0=off,1=on]
[ee]  enable echo                 1 [0=off,1=on]
[ex]  enable xon xoff             1 [0=off,1=on]
[baud] USB baud rate              5 [1=9600,2=19200,3=38400,4=57600,5=115200,6=230400]
[gpl] default gcode plane         0 [0=G17,1=G18,2=G19]
[gun] default gcode units mode    1 [0=G20,1=G21]
[gco] default gcode coord system  1 [1-6 (G54-G59)]
[gpa] default gcode path control  2 [0=G61,1=G61.1,2=G64]
[gdi] default gcode distance mode 0 [0=G90,1=G91]
[1ma] m1 map to axis              0 [0=X,1=Y,2=Z...]
[1sa] m1 step angle               1.800 deg
[1tr] m1 travel per revolution   36.540 mm
[1mi] m1 microsteps               8 [1,2,4,8]
[1po] m1 polarity                 1 [0=normal,1=reverse]
[1pm] m1 power management         1 [0=remain powered,1=shut off when idle]
[2ma] m2 map to axis              1 [0=X,1=Y,2=Z...]
[2sa] m2 step angle               1.800 deg
[2tr] m2 travel per revolution   36.540 mm
[2mi] m2 microsteps               8 [1,2,4,8]
[2po] m2 polarity                 1 [0=normal,1=reverse]
[2pm] m2 power management         1 [0=remain powered,1=shut off when idle]
[3ma] m3 map to axis              1 [0=X,1=Y,2=Z...]
[3sa] m3 step angle               1.800 deg
[3tr] m3 travel per revolution   36.540 mm
[3mi] m3 microsteps               8 [1,2,4,8]
[3po] m3 polarity                 0 [0=normal,1=reverse]
[3pm] m3 power management         1 [0=remain powered,1=shut off when idle]
[4ma] m4 map to axis              2 [0=X,1=Y,2=Z...]
[4sa] m4 step angle               1.800 deg
[4tr] m4 travel per revolution    1.250 mm
[4mi] m4 microsteps               4 [1,2,4,8]
[4po] m4 polarity                 0 [0=normal,1=reverse]
[4pm] m4 power management         1 [0=remain powered,1=shut off when idle]
[xam] x axis mode                 1 [standard]
[xvm] x velocity maximum      10000.000 mm/min
[xfr] x feedrate maximum      10000.000 mm/min
[xtm] x travel maximum          220.000 mm
[xjm] x jerk maximum     5000000000 mm/min^3
[xjh] x jerk homing     10000000000 mm/min^3
[xjd] x junction deviation        0.0100 mm (larger is faster)
[xsn] x switch min                1 [0=off,1=homing,2=limit,3=limit+homing]
[xsx] x switch max                0 [0=off,1=homing,2=limit,3=limit+homing]
[xsv] x search velocity        3000.000 mm/min
[xlv] x latch velocity          100.000 mm/min
[xlb] x latch backoff             2.000 mm
[xzb] x zero backoff              3.000 mm
[yam] y axis mode                 1 [standard]
[yvm] y velocity maximum      10000.000 mm/min
[yfr] y feedrate maximum      10000.000 mm/min
[ytm] y travel maximum          220.000 mm
[yjm] y jerk maximum     5000000000 mm/min^3
[yjh] y jerk homing     10000000000 mm/min^3
[yjd] y junction deviation        0.0100 mm (larger is faster)
[ysn] y switch min                1 [0=off,1=homing,2=limit,3=limit+homing]
[ysx] y switch max                0 [0=off,1=homing,2=limit,3=limit+homing]
[ysv] y search velocity        3000.000 mm/min
[ylv] y latch velocity          100.000 mm/min
[ylb] y latch backoff             2.000 mm
[yzb] y zero backoff              3.000 mm
[zam] z axis mode                 1 [standard]
[zvm] z velocity maximum        300.000 mm/min
[zfr] z feedrate maximum        600.000 mm/min
[ztm] z travel maximum          100.000 mm
[zjm] z jerk maximum       50000000 mm/min^3
[zjh] z jerk homing       100000000 mm/min^3
[zjd] z junction deviation        0.0100 mm (larger is faster)
[zsn] z switch min                0 [0=off,1=homing,2=limit,3=limit+homing]
[zsx] z switch max                1 [0=off,1=homing,2=limit,3=limit+homing]
[zsv] z search velocity         600.000 mm/min
[zlv] z latch velocity          100.000 mm/min
[zlb] z latch backoff             2.000 mm
[zzb] z zero backoff              3.000 mm
[aam] a axis mode                 3 [radius]
[avm] a velocity maximum     172800.000 deg/min
[afr] a feedrate maximum     172800.000 deg/min
[atm] a travel maximum           -1.000 deg
[ajm] a jerk maximum     5760000000 deg/min^3
[ajh] a jerk homing      5760000000 mm/min^3
[ajd] a junction deviation        0.0500 deg (larger is faster)
[ara] a radius value              0.1989 deg
[asn] a switch min                1 [0=off,1=homing,2=limit,3=limit+homing]
[asx] a switch max                0 [0=off,1=homing,2=limit,3=limit+homing]
[asv] a search velocity         600.000 deg/min
[alv] a latch velocity          100.000 deg/min
[alb] a latch backoff             5.000 deg
[azb] a zero backoff              2.000 deg
[bam] b axis mode                 0 [disabled]
[bvm] b velocity maximum       3600.000 deg/min
[bfr] b feedrate maximum       3600.000 deg/min
[btm] b travel maximum           -1.000 deg
[bjm] b jerk maximum       20000000 deg/min^3
[bjd] b junction deviation        0.0500 deg (larger is faster)
[bra] b radius value              1.0000 deg
[cam] c axis mode                 0 [disabled]
[cvm] c velocity maximum       3600.000 deg/min
[cfr] c feedrate maximum       3600.000 deg/min
[ctm] c travel maximum           -1.000 deg
[cjm] c jerk maximum       20000000 deg/min^3
[cjd] c junction deviation        0.0500 deg (larger is faster)
[cra] c radius value              1.0000 deg
[p1frq] pwm frequency           100.000 Hz
[p1csl] pwm cw speed lo        1000.000 RPM
[p1csh] pwm cw speed hi        2000.000 RPM
[p1cpl] pwm cw phase lo           0.125 [0..1]
[p1cph] pwm cw phase hi           0.200 [0..1]
[p1wsl] pwm ccw speed lo       1000.000 RPM
[p1wsh] pwm ccw speed hi       2000.000 RPM
[p1wpl] pwm ccw phase lo          0.125 [0..1]
[p1wph] pwm ccw phase hi          0.200 [0..1]
[p1pof] pwm phase off             0.100 [0..1]
[g54x] g54 x offset               0.000 mm
[g54y] g54 y offset               0.000 mm
[g54z] g54 z offset               0.000 mm
[g54a] g54 a offset               0.000 deg
[g54b] g54 b offset               0.000 deg
[g54c] g54 c offset               0.000 deg
[g55x] g55 x offset              75.000 mm
[g55y] g55 y offset              75.000 mm
[g55z] g55 z offset               0.000 mm
[g55a] g55 a offset               0.000 deg
[g55b] g55 b offset               0.000 deg
[g55c] g55 c offset               0.000 deg
[g56x] g56 x offset               0.000 mm
[g56y] g56 y offset               0.000 mm
[g56z] g56 z offset               0.000 mm
[g56a] g56 a offset               0.000 deg
[g56b] g56 b offset               0.000 deg
[g56c] g56 c offset               0.000 deg
[g57x] g57 x offset               0.000 mm
[g57y] g57 y offset               0.000 mm
[g57z] g57 z offset               0.000 mm
[g57a] g57 a offset               0.000 deg
[g57b] g57 b offset               0.000 deg
[g57c] g57 c offset               0.000 deg
[g58x] g58 x offset               0.000 mm
[g58y] g58 y offset               0.000 mm
[g58z] g58 z offset               0.000 mm
[g58a] g58 a offset               0.000 deg
[g58b] g58 b offset               0.000 deg
[g58c] g58 c offset               0.000 deg
[g59x] g59 x offset               0.000 mm
[g59y] g59 y offset               0.000 mm
[g59z] g59 z offset               0.000 mm
[g59a] g59 a offset               0.000 deg
[g59b] g59 b offset               0.000 deg
[g59c] g59 c offset               0.000 deg
[g92x] g92 x offset               0.000 mm
[g92y] g92 y offset               0.000 mm
[g92z] g92 z offset               0.000 mm
[g92a] g92 a offset               0.000 deg
[g92b] g92 b offset               0.000 deg
[g92c] g92 c offset               0.000 deg
[g28x] g28 x location             0.000 mm
[g28y] g28 y location             0.000 mm
[g28z] g28 z location             0.000 mm
[g28a] g28 a location             0.000 deg
[g28b] g28 b location             0.000 deg
[g28c] g28 c location             0.000 deg
[g30x] g30 x location             0.000 mm
[g30y] g30 y location             0.000 mm
[g30z] g30 z location             0.000 mm
[g30a] g30 a location             0.000 deg
[g30b] g30 b location             0.000 deg
[g30c] g30 c location             0.000 deg
tinyg [mm] ok>

    I use a (commercial) g-code generator from work, and I can’t for the life or me make it not generate G2-G3 Rs (positive or negative)

    October 21, 2013 at 6:50 pm #4840
    alden
    Member

    Try returning to g0 x0 y0 before attempting the negative arc. Entering the second arc command was trying to draw a 360 degree arc in radius mode – same start and end points. Radius mode is not supposed to be used for arcs more than about 180 degrees, or they lose too much accuracy. The system tries to compensate the best it can, but at some point it gives up and throws an arc specification error.

    October 21, 2013 at 7:09 pm #4842
    vane
    Member

    The log I posted contained a return to 0. The commands were copied from the same coolterm session. So omitting the verbose responses, they went like this:

    G17 F300
G2 X10 Y15 R20
G0 X0 Y0
G2 X10 Y15 R-20

    … with the error reply for the last command. In fact, even after a fresh reset (coordinates at 0 0 0), I can’t find a combination of -R values that work (they all give the same error).
    Just to rule it out, can you confirm that my example works for you, or give me a sequence of g-code that eventually contain -R that works for you?
    Thanks

    October 21, 2013 at 8:52 pm #4843
    alden
    Member

    I ran your test on build 380.02, and 380.08, which is the current master branch. Both fail the way you have experienced. The test I ran that worked was on the development branch – build 396.03. So you ave discovered a bug in the earlier revisions. We can walk you through a firmware upgrade or swap out your board.

    October 22, 2013 at 9:16 am #4845
    vane
    Member

    Alden, I’ve loaded this binary https://github.com/synthetos/TinyG/blob/dev/firmware/tinyg/Debug/tinyg.hex via avrdude/bootloader, and negative Rs look like they work now. Is that a a sufficiently up-to-date binary (I suspect it was compiled with debug option on, given the URL)? I will compile the project myself at some point (to poke my nose in a little), by I’m a little busy atm. If you have a fresher binary please push it, and post a link.
    Thanks again for the support

    October 22, 2013 at 12:45 pm #4847
    alden
    Member

    The hex file you loaded (build 396.03) is the current file in the dev branch. Dev is used for development and testing. Once things are relatively stable in dev they are moved to edge, where they are tested some more, then finally to master for general release.

    The hex you got was not a “debug” hex, per se – in that it did not have any extra debugging code – that’s just where the complier puts things.

    Build 396.03 should actually be pretty stable as I’ve been incrementally moving things along in dev. You should stick with that until there’s an edge push – probably some time in the next few weeks. Please let me know if you have any problems with it.

    October 24, 2013 at 9:50 am #4857
    vane
    Member

    I’ve made some simple tests using G2/G3 and R. I don’t know if this is normal, but there are dramatic differences between R arcs and IJ arcs of the same dimensions. Example: a 50mm 90deg arc expressed with R diverges from the same IJ arc with ~7mm. The R arcs are way flatter than they should be.
    On the brighter side, I’ve managed to make my g-code generator to generate only IJ arcs, which work just fine, so this issue is concluded for me.

    October 24, 2013 at 10:07 am #4858
    alden
    Member

    Thanks for doing these tests. I’m glad the issue is closed for you.

    It’s a known property (of Gcode) that radius arcs suffer from accuracy errors; which is the reason center arcs are always recommended. Usually this is only obvious on arcs with larger angular travel – and error blows up completely for 360 degree arcs (cannot be drawn).

    Separately, center arcs are supposed to be specified with the center falling on the normal line bisecting the chord spanning the arc endpoints. As mentioned before, there is some tolerance in the arc algorithm if this is not exactly true. If the center is too far off the line the arc will err out with a specification error. So it’s possible that the differences between R and IJ arcs is due to the fact that the R will (or should) compute the exact centerline and the IJ center may be off. I don’t know if this is happening here.

    What angles are you testing? Can you copy and paste some Gcode? I’d like to know if the R arcs are within tolerance or if I still have work to do on R arc generation.

    Thanks

    October 24, 2013 at 12:35 pm #4859
    vane
    Member

    A basic example:

    g0 x0 y0
f300
g2 x30 y30 i30 j0
g3 x0 y0 r30

    This should make a clockwise quadrant from (0, 0) with ij, and return to (0, 0) counter-clockwise with a R quadrant. The quadrants should ideally be identical. In reality, they are visibly distinct (at most 2mm+ apart), only their ends coincide. I’m sure it’s easy to reproduce, otherwise i would take a pic of an engraving test i made.
    Again, I’m not sure that 90 degrees is not too big an arc, but some g-code example i saw in a tutorial was making a circle out of 4 G2+R quadrants, so it seems this should be acceptable precision-wise

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