G0 skipping steps

vasficem · August 10, 2020, 2:59pm

Hi everyone. I use marlin with a SKR 1.3 board and an LCD (Marlin 2.0.x, LCD is the standart Ender 3, 6560 stepper drivers for x and y; tmc2208 for Z, cncjs as software to control the machine). This set up is used for my cnc router. When i try to jog with cncjs control menu, my z axis works with a very high feedrate so it fails to jog (there is no such problem with x and y and when i jog with the LCD menu, no problem occurs also.). Despite I rearranged z axis feedrate with m203 (which is 300) and overwrite the existing values with m500, when i want to jog with cncjs ui it doesn’t use the specified feedrate. Why do you think this happnes?

Moreover when i use g1 f300 or g0 f300 after entering a g91, (what i mean, when i enter the feedrate manually for that specific movement and that specific axis) no problem occurs for the z axis and it jogs exact mm that i enter. But after g1 f300 (or g0 f300), x and y axis use the same feedrate and (because their feedrate is normally 4500 and 3000) they jog very slow. Most probably there is a common feedrate for x,y and z and when I change for one axis it changes for all.

So my questions are:)

1- Why do you think feedrate doesn’t change despite i override it with m203,?

2-What type of gcode the lcd screen uses and why ther is a difference etween lcd and cncjs gcodes. (or dose it use G1 or G0 for jogging axes)

2- Do you have any ideas/advices about (after entering the feedrate manually) seperating the feedrates for x,y and z.

Thanks in advance.

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jeffeb3 · August 10, 2020, 3:48pm

That is the max feedrate, and it should slow it down. Do you have the right units? That is mm/s, not mm/min.

ttraband · August 10, 2020, 8:38pm

If I’m reading the gcode documentation correctly, M203 expects mm per second and for G01 the F parameter is mm per minute.

G0 or G00 is a rapid move and always goes at max rate unless I’m mistaken.

jeffeb3 · August 10, 2020, 8:58pm

Nope. It shortcuts to G1 unless you have the separate travel speed option set. The default is to just treat it as a G1 command, including saving the speed for the next command.

ttraband · August 10, 2020, 9:22pm

That’s specific to Marlin firmware, right? (I realize that’s the default for most MPCNC users.)

jeffeb3 · August 10, 2020, 11:48pm

At least.

jamiek · August 11, 2020, 4:06am

Definitely true in Marlin, and I’m not sure about other 3d-print-oriented firmware.

Recent versions of Marlin have the option (not enabled by default) for treating G0 as rapids, which was discussed recently here.

vasficem · August 11, 2020, 6:32am

Guys thanks for quick responds,

Jeff, I really didn’t check units but i didn’t change the original units anywhere so i think this is not the problem. I made some tests and find the appropriate feedrate for the axises. To do this, i write;

G91
G1 (or G0) ZxFx

Then set my max feedrates with m203.

Tom, thanks for detail:) I have never seen it. Despite i cannot go to shop and test it for a few days, i think this is not the answer:) As I have already enabled seperate G0 feedrate as Jamie says, and set it to 300 mm/m, (which i think means 5mm/s) it shouldn’t skip steps.

Thanks anyway:)

jeffeb3 · August 11, 2020, 11:39am

The screen sends G1 commands:

github.com

V1EngineeringInc/BIGTREETECH-TouchScreenFirmware/blob/master/TFT/src/User/Menu/Move.c#L7


      
          #include "Move.h"
          #include "includes.h"
          
          #define LOAD_XYZ_LABEL_INDEX(p0, dir0, p1, dir1, axis) do { \
                                                                   moveItems.items[p0].label.index = LABEL_##axis##_##dir0; \
                                                                   moveItems.items[p1].label.index = LABEL_##axis##_##dir1; \
                                                                 } while(0)
          #define X_MOVE_GCODE "G1 X%.2f F%d\n"
          #define Y_MOVE_GCODE "G1 Y%.2f F%d\n"
          #define Z_MOVE_GCODE "G1 Z%.2f F%d\n"
          #define GANTRY_UPDATE_DELAY 500  // 1 seconds is 1000
          
          #ifdef PORTRAIT_MODE
            #define OFFSET 0
          #else
            #define OFFSET 1
          #endif

Yeah, so in that case you should set M203 Z5, not M203 Z300.

The firmware should have already set it to 10mm/s, unless you made your own. 10mm/s should be pretty good for a 400steps/mm machine. If you have a 1 start leadscrew with 1600 steps/mm, then you’ll have to drop it.

vasficem · August 11, 2020, 12:08pm

I didn’t get your point to set M203 Z5? Won’t be very slow? (For instance when i write G1 Z10 F300, it jogs very smooth and not loosing steps. Besides my x and y axis max feedrates are set to 3000&4500. so if i set z feedrate to 5 mm/s won’t i be waiting all day to jog down/up:)???)
I have 404 steps/mm for my Z axis (i measured the distance it jogs and did some calculations)

vasficem · August 11, 2020, 12:12pm

And thanks for the info…

//const GUI_RECT RecXYZ = {START_X + 1ICON_WIDTH, STATUS_GANTRY_YOFFSET,
// 4ICON_WIDTH+3*SPACE_X+START_X,ICON_START_Y-STATUS_GANTRY_YOFFSET};
#define X_MOVE_GCODE “G1 X%.1f\n”
#define Y_MOVE_GCODE “G1 Y%.1f\n”
#define Z_MOVE_GCODE “G1 Z%.1f\n”

[/quote]

jeffeb3 · August 11, 2020, 3:13pm

I think you’re still missing the point (or I’ve missed the point).

G1 Z10 F300 is moving 10mm at 300 mm per minute. So 5mm per second.

M203 Z5 will tell the firmware to never move the Z axis faster than 5mm per second or 300mm per minute.

Those are the same limits. If you later have a mistake in the gcode and send something like this:

G1 X100 F1200
G1 Z-1

The M203 will slow that Z command down so you don’t skip steps.

vasficem · August 12, 2020, 6:02am

Ok Jeff, I will try and let you know about the results.