Pressure advance tuning with conditional G-code

[CNCModeller]

@schmart

This seems to be working a treat on my machine. Thanks very much for the effort!

The only tweaks I did was to:

• Move the position of the print as I can't print in the centre of my bed, and alter the basic print settings.

• Add a var to control if the file was simulated or not in a single location. I then put an if before the relevant GCode statements w.r.t. setting and un setting simulation mode.

; Single location to activate simulation mode
var sim_mode = 0

if {var.sim_mode > 0}
   M37 S1 ; Enter simulation mode

if {var.sim_mode > 0}
   M37 S0 ; Leave simulation mode

Disable Bed heating if the temperature is set to 0 as I don't have a working heated bed yet.

if {var.bed_temperature > 0}
   M190 S{var.bed_temperature} ; Wait for bed temperature to reach setpoint

if {var.bed_temperature > 0}
   M140 S0 ; Turn off bed

Just thinking a similar approach to retraction / de-retraction distances might be a nice project too, albeit I'm going to have to learn a lot about conditional GCode to figure that out!!

Anyway thanks again, this is great

Best Regards
Barry M

[Schmart]

@heartleander81 that little one-liner you ran (error message pun intended) confirmed that variables in the meta command language are not yet (fully) supported on SBC setups. Unfortunately, my macro heavily relies on variables and I don't see a simple alternative to avoid using them. I think your best chance is to ask one of the RRF developers for an outlook on support for SBC-based setups.

[Schmart]

@medicusdkfz said in Pressure advance tuning with conditional G-code:

Hi,

thank you for your incredible job... Could you tell me, what the latest version is?

TY, Pierre

Thanks Pierre! And yes, the macro in the first post is still the latest version. I'm planning to provide an update with minor changes this week, including the ones from @CNCModeller, but probably nothing drastic. If you have any ideas for improvement, let me know.

[Schmart]

@cncmodeller said in Pressure advance tuning with conditional G-code:

This seems to be working a treat on my machine. Thanks very much for the effort!

You're welcome, I'm happy that you got it working

• Add a var to control if the file was simulated or not in a single location. I then put an if before the relevant GCode statements w.r.t. setting and un setting simulation mode.

I've since learned that M37 also supports simulating a macro based on meta commands, and that doesn't require changing the code itself, so that might even be a more robust option for a less confident user?

On the other hand, your approach 1) puts the code itself in "debugging mode" which is persistent and developer-friendly and 2) doesn't add the "time taken" at the bottom of the macro file.

Disable Bed heating if the temperature is set to 0 as I don't have a working heated bed yet.

That's an excellent point, I hadn't considered printers without a heated bed. If you don't mind, I would like to incorporate your optimizations.

Just thinking a similar approach to retraction / de-retraction distances might be a nice project too, albeit I'm going to have to learn a lot about conditional GCode to figure that out!!

The reason why I found the pressure advance tuning such a good first use case, is because I couldn't convince my slicer to print a contiguous perimeter/wall with different speeds. At least in PrusaSlicer, the modifiers insisted on splitting the model in separate parts.

However, I was also a bit proud and hand-crafted all G-code and calculations myself, with secondary features like the brim taking a disproportional amount of time. So I wouldn't necessarily recommend doing that.

I'm currently tackling retraction tuning with PrusaSlicer entirely. I simply add two cylinder shapes some distance apart, and enter a height-based formula in the "Before layer change G-code" text box in PrusaSlicer that determines the retraction value.

Theoretically, such a test model would not be difficult to convert to a macro. However, I'm dearly missing the concept of a 'function' in the meta command instruction set, which would make it easier to create and maintain such code. Therefore, I think the quickest road to success is to further resist the urge to DIY things like infill and circular perimeters and start by parameterizing the G-code of a pre-sliced model.

Do you have any favorite models to tune retraction?

Anyway thanks again, this is great

[CNCModeller]

@schmart feel free to use anything I've contributed.

I'm only just getting to the point of wanting to dial in my printer by science rather than guessing / witchcraft. Print quality and speed has only just got good enough to warrant the effort.

I believe Teaching Tech's calibration website is a pretty good resource. But I used your code before venturing over there.

link

Personally I was thinking the same way as you, two decent diameter thin wall towers and judge stringing and wall gaps on un-retract when starting a layer on each tower.

Definitely something I need to get to grips with!

Thanks again

All the best.
Barry M

[CNCModeller]

@schmart

PS: w.r.t functions, I think it's possible to call other gcode files as subroutines and I even think you can pass in variables in recent beta firmware but not sure about returning results. More reading required lol.

[T3P3Tony]

@cncmodeller, @Schmart you would need to use a global variable, set in the sub macro, to pass information back to the main calling macro.

[Schmart]

@t3p3tony said in Pressure advance tuning with conditional G-code:

@cncmodeller, @Schmart you would need to use a global variable, set in the sub macro, to pass information back to the main calling macro.

Hi Tony, I had already done some testing with moving subroutine code in separate macros. On the surface, it seems that, between the Neanderthal approach of copying and pasting code, and re-using logic through parameterized macros, the balance tips towards the latter. However, I came across some conceptual and technical downsides that made me decide otherwise:

• Abstraction. I consider the macro as a vehicle for an end-user, not a developer; a cohesive unit of code that an end user would want to run. The macro is the 'public interface' to the functionality provided. A 'submacro' should not be able to have a public interface since it doesn't provide a useful experience by itself.
• Coupling and reliability. Subroutines exist to improve the maintainability of code and are not intended for an end-user to touch or run. If a unit of code is spread across multiple macros, it's easy for the end user to break functionality (e.g. remove a macro) or never get the functionality to run (e.g. not naming macros correctly). The absolute locations and names of macros are suddenly important and tightly coupled to the whole solution.
• Deployment and versioning. Depending on the complexity of the test print I want to generate, there could be many submacros involved, for things like circles, infill, fonts, etc. Splitting a solution in (potentially) many different macros complicates the setup, handling and publishing of code and updates. This becomes even more challenging when the same submacro is used by multiple main macros and the submacro needs an update that maintains backward compatibility.
• Testability. When using submacros, I have even less troubleshooting options and I can't isolate problems in my code properly. The only surefire way to test a multi-macro solution is to actually execute it with M98 and send it to the printer. The developer experience is therefore not optimal:
  1. If I call the main macro with M37 P"parent", the M98 P"child" within the main macro (with the purpose of calling the submacro) is not executed. Submacros are only called when I execute the main macro with M98.
  2. If I send an M37 S1 command in the DWC console, this causes any echo statement to be suppressed, leaving me fully in the dark. Using M37 S1 in the main macro is an option, but then submacros are still not called.
  3. Isolated testing of a 'submacro' is not possible since M37 doesn't accept parameters. Wrapping that submacro with another macro is of no use because of point #1.
• Scope. Traditionally, variables in a parent's scope are available to a subroutine, function, a C++ preprocessor directive or a code fragment that's simply #included from another file. However, variables in a parent macro cannot be shared with a child macro, and that makes sense in terms of separation of concerns. Ways to solve this:
  • Making all or only the necessary variables global is an option, though, to avoid naming clashes, these should be namespaced properly. However, I consider this a workaround. I believe the concept of global variables is more suited to defining a small number of shared and relatively static or read-only printer settings. Global variables don't really seem intended for inter-scope communication where there are a lot of global variables in use and where they continually change.
  • Using parameterized macros is also an option. However, because of parameter naming requirements, the number of variables that can be passed to a macro is limited. You can use single letters only, and three or four letters are already reserved (G, M, N and T). Additionally, this requires me to convert back and forth between highly recognizable local variable names and obscure macro parameter names, and keep the mapping between these logical.
• Performance. I haven't yet determined if the speed with which macros can be called would be an issue, so whether e.g. caching of called macros is implemented. For sections of a print that need to be executed quickly and frequently, this would be a requirement to prevent stuttering in the movement and blobs in the print. Accuracy and timing is pretty important in test prints, so that's something I need to avoid.

All in all, I've settled on putting the code as one big chunk in a single macro for now, and my hopes for the future are that some of the remarks above can be addressed!

---

I've included the test code. I had to slightly clean up the code to include it in this post.

Hopefully that provides some additional clarification to the above epistle (TLDR anyone? ).

_Parent code

Run this with M37 P"0:/macros/_Parent". Note how messages from the child macro are not included. Running this with M98 P"0:/macros/_Parent" does call the child macro, but also actually tries to print this. Wrapping the parent code between M37 S1 and M37 S0 commands and running it with M98 also ignores the call to the child macro. At least on my RepRapFirmware 3.4.0 beta 6.

echo "Parent started"

while {iterations < 10}
  echo "Calling child macro, iteration #" ^ {iterations}
  M98 P"0:/macros/_Child" X50 Y50 F2400 R6000

echo "Parent ended"

_Child code

Note that a standalone simulation with M37 P"0:/macros/_Child" X100 Y100 F2400 R6000 does not work because M37 does not pass parameters, and causes unknown parameter errors.

var size_x = {param.X}
var size_y = {param.Y}
var feedrate = {param.F}
var travel_feedrate = {param.R}

echo "Child started"

; Print single-perimeter rectangle
G90 ; Use absolute coordinates
G1 X{-var.size_x / 2} Y{-var.size_y / 2} F{var.travel_feedrate}
G91 ; Use relative coordinates
G1 X{var.size_x} F{var.feedrate}
G1 Y{var.size_y} F{var.feedrate}
G1 X{-var.size_x} F{var.feedrate}
G1 Y{-var.size_y} F{var.feedrate}

echo "Child ended"

[Schmart]

@cncmodeller said in Pressure advance tuning with conditional G-code:

@schmart feel free to use anything I've contributed.

Thanks! I took the liberty of integrating your suggestions.

Personally I was thinking the same way as you, two decent diameter thin wall towers and judge stringing and wall gaps on un-retract when starting a layer on each tower.

I came across this site which seems to offer an interesting approach to retraction tuning as well. For now, I hacked together a more classical attempt to tune retraction settings . Please see attached file Retraction.g.

I tested this on my printer, but still, please consider this a beta release.

[CNCModeller]

@schmart said in Pressure advance tuning with conditional G-code:

@cncmodeller said in Pressure advance tuning with conditional G-code:

@schmart feel free to use anything I've contributed.

Thanks! I took the liberty of integrating your suggestions.

Personally I was thinking the same way as you, two decent diameter thin wall towers and judge stringing and wall gaps on un-retract when starting a layer on each tower.

I came across this site which seems to offer an interesting approach to retraction tuning as well. For now, I hacked together a more classical attempt to tune retraction settings . Please see attached file Retraction.g.

I tested this on my printer, but still, please consider this a beta release.

@Schmart That's brilliant and it works fine on my machine.

I have added restart length variation as follows so you can run it twice once with zero restart increment to identify optimum retraction, then a second time with a good retraction length start value and zero retraction increment and a restart increment to get the optimum restart length.

See code changes below.

; Retraction restart length to start with
var retraction_restart_length_start = 0.0
; Retraction restart length increment for each (whole) millimeter print height
; e.g. if var.height = 20, var.retraction_length_start = 0.0 and var.retraction_length_increment = 0.05,
; then the retraction test range is from 0.0 to (0.0 + 20 * 0.05) => 0.0 to 1.0.
var retraction_restart_length_increment = 0.05

; Set firmware retraction
M207 S{var.retraction_length_start} R{var.retraction_restart_length_start} F{60 * var.retraction_speed} T{60 * var.deretraction_speed} Z{var.retraction_z_lift}

  ; Set firmware retraction
  var retraction_length = {var.retraction_length_start + var.z * var.retraction_length_increment}
  var retraction_restart_length = {var.retraction_restart_length_start + var.z * var.retraction_restart_length_increment}
  M207 S{var.retraction_length} R{var.retraction_restart_length} F{60 * var.retraction_speed} T{60 * var.deretraction_speed} Z{var.retraction_z_lift}

  ; Output some statistics while printing
  echo "Layer " ^ {var.layer} ^ " (" ^ {var.layer + 1} ^ " of " ^ {var.layers} ^ " at " ^ {var.z} ^ "mm)"
  echo "Retraction length: " ^ {var.retraction_length}
  echo "Retraction Restart length: " ^ {var.retraction_restart_length}

From memory that's all I changed. I can post my full file but it has my customisations for print settings and location.

Many thanks again!!

Cheers
Barry M

[PCR]

@cncmodeller could you post the full file?

[CNCModeller]

@pcr , sorry better late than never...

; This macro generates a test print to determine the best pressure advance factor (M572 S-parameter)
; It uses the test print described in this forum post:
; https://forum.duet3d.com/topic/6698/pressure-advance-calibration
 
; Author: Schmart
 
; WARNING: all dimensions, size units and speeds are in mm and mm/s
 
; Reference for conditional G-code:
; - https://duet3d.dozuki.com/Wiki/GCode_Meta_Commands
 
; Wishes for conditional G-code:
; - Canceling or stopping running conditional G-code
; - Simulation; logging what commands would be executed/generated without actually executing them
; - Dumping the variables (names and values) in a macro, perhaps also treating variable in a meta-way, e.g. {#var} for count, {var[0].name} and {var['layer_height'].value}
; - Assigning an object or array to a variable. E.g. var axis = move.axes[0]; echo {var.axis.letter}
; - Custom subroutine/function definition, e.g. def print_line(var a, var b)
; - ceiling(), pow() and sq() functions
 
; TODO:
; - Many optimizations still remaining
; - Perhaps the most important variables (bed and print temperature, filament diameter, extrusion multiplier, PA stepping)
;   can be made into macro parameters, e.g. M98 P"0:/macros/4 - Print Tuning/Pressure Advance" B40 P204 D1.75 X0.95 S0.02 P0.002

;Log events
var event_log = 1

; Single location to activate simulation mode
var sim_mode = 0
; Starting value for pressure advance
var pa_start = 0.6
; Pressure advance increment for each (whole) millimeter print height
; e.g. if var.height = 20, var.pa_start = 0.1 and var.pa_stepping = 0.004, then
; the PA test range is from 0.1 to (0.1 + 20 * 0.004) => 0.1 to 0.18.
var pa_stepping = 0.01
; The extruder to apply the pressure advance factor to
var pa_extruder = 0
; These values specify the center of the print bed
; The default bed center is at (0,0)
var x_center = 0
var y_center = 150
; Print temperatures
var print_temperature = 225
var standby_temperature = 200
var bed_temperature = 0
; Height of the test print
var height = 60
var layer_height = 0.40
; Number of fast segments
var fast_segments = 3
; Slow segments are at the beginning and the end, and in between fast segments, e.g. SLOW FAST SLOW FAST SLOW
var slow_segment_length = 10
var fast_segment_length = 20
; Definition of speeds
var first_layer_speed = 20
var travel_speed = 80
var fast_segment_speed = 60
var slow_segment_speed = 10
; Number of perimeters around the object as a stable base
var skirt_loops = 6
; Height of the skirt in layers
var skirt_layers = 2
; The tool number to print with
var tool_number = 0
; Extrusion width is calculated here, but can also be set with a literal value
; Note that 1.05 and 1.125 are common factors that result in 0.42mm or 0.45mm width respectively
var nozzle_bore_diameter = 0.60
var extrusion_width = {var.nozzle_bore_diameter * 1.125}
var filament_diameter = 1.78
var extrusion_multiplier = 1.00
; Firmware retraction settings
var retract_length = 3.0
var retract_restart_length = 1.0
var retract_speed = 1200
var deretract_speed = 1200
var retract_z_lift = 0
 
; Flow math
var filament_flow = {pi * var.filament_diameter * var.filament_diameter / 4}
var regular_flow = {(var.extrusion_width - var.layer_height) * var.layer_height + pi * var.layer_height * var.layer_height / 4}
var bridge_flow = {pi * var.nozzle_bore_diameter * var.nozzle_bore_diameter / 4}
var line_spacing = {var.extrusion_width - var.layer_height * (1 - pi / 4)}
var regular_flow_ratio = { var.extrusion_multiplier * var.regular_flow / var.filament_flow}
var purge_line_flow_ratio = { 2.0 * var.regular_flow_ratio }

if {var.event_log > 0}
	M929 P"PA_log.txt" S1 ; start logging to file eventlog.txt

echo "extrusion_width: " ^ var.extrusion_width
echo "layer_height: " ^ var.layer_height
echo "filament_flow: " ^ var.filament_flow
echo "bridge_flow: " ^ var.bridge_flow
echo "regular_flow: " ^ var.regular_flow
echo "line_spacing: " ^ var.line_spacing
echo "regular_flow_ratio: " ^ var.regular_flow_ratio

if {var.sim_mode > 0}
   ;M37 S1 ; Enter simulation mode
 
; Set firmware retraction
M207 S{var.retract_length} R{var.retract_restart_length} F{60 * var.retract_speed} T{60 * var.deretract_speed} Z{var.retract_z_lift}
 
T{var.tool_number} ; Select tool
M106 S0 ; Turn off part cooling fan

M568 P{var.tool_number} S{var.print_temperature} R{var.standby_temperature} A1 ; Set tool to standby temperature

if {var.bed_temperature > 0}
   M190 S{var.bed_temperature} ; Wait for bed temperature to reach setpoint

M116 P{var.tool_number} ; Wait for temperatures associated with the selected tool to be reached

; Make an inventory of axes that have not yet been homed
var axes = ""
echo "Total number of axes: " ^ {#move.axes}
while {iterations < #move.axes}
  if {!move.axes[iterations].homed}
    set var.axes = {var.axes ^ move.axes[iterations].letter}
 
; Home applicable axes
echo "Axes to be homed: " ^ var.axes
G28 {var.axes}
 
;G28 XYZ ; Home the X, Y and Z axes
;G28 XY ; Home the X and Y axes
;G28 Z ; Home the Z axis
 
G21 ; Set units to millimeters
M83 ; Use relative distances for extrusion
 
; Calculate object width
var width = {var.fast_segments * var.fast_segment_length + (1 + var.fast_segments) * var.slow_segment_length}
; Calculate starting coordinates and other constant(s)
var x_start = {var.x_center - 0.5 * var.width + var.skirt_loops * var.line_spacing}
var y_start = {var.y_center - 0.5 * var.line_spacing + var.skirt_loops * var.line_spacing}
var travel_feedrate = {60 * var.travel_speed}
var first_layer_feedrate = {60 * var.first_layer_speed}
 
; Absolute position for purge line in X and Y space, 50 mm behind model
G90 ; Use absolute coordinates
G1 X{var.x_start} Y{var.y_start + 50} F{var.travel_feedrate}
 
; Set heater to final temperature and wait
M568 A2
M116 P{var.tool_number}
 
; Absolute position of nozzle at first layer height
G1 Z{var.layer_height} F{var.travel_feedrate}
 
; Relatively print two fat purge lines
G91 ; Switch to relative coordinates
G1 X{var.width} E{var.width * var.purge_line_flow_ratio} F{var.first_layer_feedrate}
G1 Y{-(2 * var.line_spacing)} F{var.travel_feedrate}
G1 X{-var.width} E{var.width * var.purge_line_flow_ratio} F{var.first_layer_feedrate}
 
G10 ; Retract to prevent oozing
 
; Move to the start of the model in X, Y and Z space
; The skirt code also moves to the start, but the skirt can be disabled.
; Also, the skirt code does not set Z, and there may be no purge line for which Z is set. Safety first.
G90 ; Use absolute coordinates
G1 X{var.x_start} Y{var.y_start} Z{var.layer_height} F{var.travel_feedrate}
G91 ; Switch to relative coordinates
 
G11 ; Advance/unretract/deretract in preparation to print
 
; Routine for printing the test object
var layers = {floor(var.height / var.layer_height)}
echo "Total number of layers: " ^ var.layers
 
while {iterations < var.layers}
  ; Track current layer
  var layer = {iterations + 1}
  ; Current height in mm
  var z = {var.layer * var.layer_height}
  ; Calculate pressure advance factor
  var pa = {var.pa_start + floor(var.z) * var.pa_stepping}
  ; Set pressure advance
  M572 D{var.pa_extruder} S{var.pa}
 
  ; Output some statistics while printing
  echo "Layer " ^ iterations ^ " (" ^ {iterations + 1} ^ " of " ^ {var.layers} ^ " at " ^ {var.z} ^ "mm)"
  echo "Pressure advance: " ^ {var.pa}
  ; Output Filament Sensor Reading
  M591 D0
 
  ; Pre-calculate feedrates for first layer and other layers
  var slow_segment_feedrate = {60 * (var.layer == 1 ? var.first_layer_speed : var.slow_segment_speed)}
  var fast_segment_feedrate = {60 * (var.layer == 1 ? var.first_layer_speed : var.fast_segment_speed)}
 
  ; Print skirt
  if {iterations < var.skirt_layers}
    G90 ; Use absolute coordinates
    ; Move to absolute XY start coordinates
    G1 X{var.x_start} Y{var.y_start} F{var.travel_feedrate}
    G91 ; Switch to relative coordinates
 
    ; Print all loops of the skirt
    while {iterations < var.skirt_loops}
      var skirt_loop = {var.skirt_loops - iterations}
      var x = {var.width + 2 * var.skirt_loop * var.line_spacing}
      var y = {var.line_spacing + 2 * var.skirt_loop * var.line_spacing}
      ; Print one full skirt loop
      while iterations < 2
        var direction = {iterations == 0 ? 1 : -1}
        G1 X{var.direction * var.x} E{var.x * var.regular_flow_ratio} F{var.fast_segment_feedrate}
        G1 Y{var.direction * var.y} E{var.y * var.regular_flow_ratio} F{var.fast_segment_feedrate}
      ; Travel to the start of the next skirt loop
      G1 X{var.line_spacing} Y{var.line_spacing} F{var.travel_feedrate}
 
  ; Print two perimeters back and forth of alternating slow and fast segments
  while iterations < 2
    var direction = {iterations == 0 ? 1 : -1}
    ; Slow starting segment (X)
    G1 X{var.direction * var.slow_segment_length} E{var.slow_segment_length * var.regular_flow_ratio} F{var.slow_segment_feedrate}
    ; Remaining fast and slow segments (X)
    while iterations < var.fast_segments
      G1 X{var.direction * var.fast_segment_length} E{var.fast_segment_length * var.regular_flow_ratio} F{var.fast_segment_feedrate}
      G1 X{var.direction * var.slow_segment_length} E{var.slow_segment_length * var.regular_flow_ratio} F{var.slow_segment_feedrate}
    ; Print the side perimeter (Y)
    G1 Y{var.direction * var.line_spacing} E{var.line_spacing * var.regular_flow_ratio} F{var.slow_segment_feedrate}
 
  ; Move one layer up
  G1 Z{var.layer_height} F{var.travel_feedrate}
 
G10 ; Retract
 
G91 ; Relative positioning
G1 F3000 Z20 ; Move gantry up 20mm
G90 ; Absolute positioning
G28 X ; Home X axis
;M104 S0 ; Turn off nozzle heat block
M568 P{var.tool_number} S0 R0 A2 ; Set required heater temperature off
if {var.bed_temperature > 0}
   M140 S0 ; Turn off bed

M106 S0 ; Turn off part cooling fan
M18 ; Disable stepper motors

if {var.sim_mode > 0}
   M37 S0 ; Leave simulation mode

if {var.event_log > 0}
	M929 S0 ; stop logging