Build platform woes.

[DBFIU]

Hi Roxy,


This command works.

G29 V4 n4 F75 B125 L75 R125

it probes a 4x4 grid., 16 points

[DBFIU]

Would this work temporarily?

G21 ;metric values
G90 ;absolute positioning
G28 ;move to endstops
G29 V4 n4 F75 B125 L75 R125 ;allows for auto-levelling
G1 X150 Y5 Z15.0 F3000 ;center and move the platform down 15mm
G92 E0 ;zero the extruded length
G1 F300 E30 ;extrude 30mm of feed stock
G92 E0 ;zero the extruded length again
G1 X175 Y25 Z0 F3000 ;remove bugger
G1 X200 F3000 ;remove bugger
G1 X150 Y150 Z15 F3000 ;recenter and begin
G1 F3000

If I use this as my pre gcode would it work?

[Roxy]

Would this work temporarily?

Yes... Take the one that works... And start expanding the boundaries of the X and Y limits. What ever your probe offsets are, they are going to be important in this. But once you make that line probe the full bed you can just use that in your Start Up GCode until you are ready to move to the fully checked out and clean code at GitHub. But my guess is that will be a solid month until you want to migrate.

Update: When you are expanding the boundaries... Have your finger on the Reset button. If you do something wrong and run the probe off the bed, you will end up driving the nozzle into the glass.

[DBFIU]

Yes... Take the one that works... And start expanding the boundaries of the X and Y limits. What ever your probe offsets are, they are going to be important in this. But once you make that line probe the full bed you can just use that in your Start Up GCode until you are ready to move to the fully checked out and clean code at GitHub. But my guess is that will be a solid month until you want to migrate.

Update: When you are expanding the boundaries... Have your finger on the Reset button. If you do something wrong and run the probe off the bed, you will end up driving the nozzle into the glass.

Thanks Roxy, I am used to having my finger near the rest button. I have the reflexes of a mongoose! rawr...

So far, having the Gcode set up like this at start up is working. I dont mind doing it this way for a month, it's no big deal.

Thank you!

[DBFIU]

Roxy,

I want to expand the probing area. I am confused as to where the G29 V4 n4 F75 B125 L75 R125 command takes me.

F means front, B means back, left and right.

Does F75 mean, 75mm from the front edge of the build plate? So if I do F25, it will try to get closer to the edge for example?

I am using this part of my code.

#ifdef AUTO_BED_LEVELING_GRID


// set the rectangle in which to probe
#define LEFT_PROBE_BED_POSITION 25
#define RIGHT_PROBE_BED_POSITION 175
#define BACK_PROBE_BED_POSITION 25
#define FRONT_PROBE_BED_POSITION 175


// set the max number of grid points per dimension
// The G29 command defaults to 3 if nothing is specified. But setting the number of probed
// points higher is very useful when getting a Bed Topology Report (G29 n 5 T)
#define AUTO_BED_LEVELING_GRID_POINTS 4


// Uncomment one of the following four lines so the Bed Topology Report can produce a map
// that relates accurately to your bed orientation.


#define ORIGIN_FRONT_LEFT
//#define ORIGIN_BACK_LEFT
//#define ORIGIN_FRONT_RIGHT
//#define ORIGIN_BACK_RIGHT


#else // not AUTO_BED_LEVELING_GRID
// with no grid, just probe 3 arbitrary points. A simple cross-product
// is used to esimate the plane of the print bed


#define ABL_PROBE_PT_1_X 15
#define ABL_PROBE_PT_1_Y 180
#define ABL_PROBE_PT_2_X 15
#define ABL_PROBE_PT_2_Y 20
#define ABL_PROBE_PT_3_X 170
#define ABL_PROBE_PT_3_Y 20


// these are the offsets to the probe relative to the extruder tip (Hotend - Probe)
#define X_PROBE_OFFSET_FROM_EXTRUDER -26
#define Y_PROBE_OFFSET_FROM_EXTRUDER -30
#define Z_PROBE_OFFSET_FROM_EXTRUDER -2.00


If my build platform is a standard MK3 size platform, about 200mm by 200mm, and I want to probe say a safe 35mm from the edges... and my probe is in front and to the left of my nozzle, then what should my new syntax be?

Note, my X and Y offsets are X -26 and Y -30.

Where does ABL_PROBE_PT_ come into play if I am telling it LEFT_PROBE_BED_POSITION and right position and front and so on, what is the role of each of those snippets of code?


Thanks for the help!

[Roxy]

The origin can be any corner. F-ront means the Y=0 line. If the origin was front left, F means how far from the front it should probe.

The fact we could use the F, B, L, & R parameters to make it work implies you have the wrong values stored in you Configuration.h file. Also, when you are telling it to probe an area, the offsets of the probe are factored into where the nozzle moves. Specifically, the code to probe a point starts like this:

static float probe_pt(float x, float y, float z_before, int retract_probe, int verboseness) {
  // move to right place
  do_blocking_move_to(current_position[X_AXIS], current_position[Y_AXIS], z_before);
  do_blocking_move_to(x - X_PROBE_OFFSET_FROM_EXTRUDER, y - Y_PROBE_OFFSET_FROM_EXTRUDER, current_position[Z_AXIS])

The Z_PROBE_OFFSETS get subtracted from the position you are trying to measure. The area you are probing has the nozzle going to locations outside of that area. Probably, that was at the root of why nothing was moving. So... If your Bed size is 200 x 200 you can only probe locations that take the nozzle to (0,0). And you can't probe locations that take the probe off the bed.

In one of your Configuration.h files you had:

#define X_PROBE_OFFSET_FROM_EXTRUDER -26 // Probe on: -left +right
#define Y_PROBE_OFFSET_FROM_EXTRUDER -30 // Probe on: -front +behind
#define Z_PROBE_OFFSET_FROM_EXTRUDER -3.97 // -below (always!)

This is not compatible with

#define LEFT_PROBE_BED_POSITION 25
#define BACK_PROBE_BED_POSITION 25

because it has to put the Nozzle into negative space to get the probe to X=25. (This is because you have #define'd this up above in the Configuration.h file

#define X_MIN_POS 0
#define Y_MIN_POS 0

If you update your Configuration.h file with the values you have learned by doing G29 commands manually, you will be able to strip those extra numbers out of the G29 command and it will automatically do the full bed (or as much of it as it can without running the nozzle off the bed). You should also set your

#define AUTO_BED_LEVELING_GRID_POINTS 4

up to 4 or 5.

[DBFIU]

Thanks Roxy,

Excuse my ignorance, how do I probe the G29 points manually? Did you outline this for me before, I may have missed it. I went back and read all your replies and couldnt find it.

[Roxy]

how do I probe the G29 points manually?

I don't know what you mean by this.

[DBFIU]

I don't know what you mean by this.

This part of your last comment


"If you update your Configuration.h file with the values you have learned by doing G29 commands manually, you will be able to strip those extra numbers out of the G29 command and it will automatically do the full bed (or as much of it as it can without running the nozzle off the bed). You should also set your "

[Roxy]

What I'm suggesting is keep doing G29's with a bigger and bigger spread of F & B until you have the full Y axis being probed. (Or... As much of as you can because you have fairly large offsets.) Then do G29's with a bigger and bigger spread of L & R values. At some point, you will know what the correct values are. When you know this information, you can edit it into those #define's in your Configuration.h file, compile and load it. At that point, the bare G29 command will have the information it needs to probe a large portion of the bed without specifying L, R, F, and B parameters.

You can issue the G29's by using PronterFace.