You can use loop o-words with PlanetCNC TNG.

Sometimes you need to execute line(s) of g-code in a loop while evaluating specific condition.  When condition evaluates to false, program will exit loop. This comes useful for e.g. repetitive motion sequences, parameter manipulation etc…

O-word loop commands consist of:
O-do – Begin loop block
O-while – End loop block [or condition evaluation]
O-endwhile – End loop block
O-break – Exit loop block immediately
O-continue – Skip to next condition evaluation of  the while condition

You can use two types of loops: While – Endwhile or Do – While.

While – Endwhile:
Evaluates condition on the beginning of loop and then executes the lines of code inside the loop.

Do – While:
First executes the lines of code inside the loop and then evaluates condition at the end of loop.

Example of Do – While loop:

%
 #1 = 1
 o100 do
 (print, #1)
 #1 = [#1+1]
 o100 while[#1 LE 10]
 (print,loop finished)
 %

The content of the loop will repeat for as long as while condition at the end will remain true. Which means that as soon as parameter #1 exceeds value of 10, program will exit the loop and print

loop finished

 

Example of While – Endwhile loop:

%
#1 = 1
o100 while [#1 LE 10]
 (print, #1)
 #1 = [#1+1]
o100 endwhile
 (print,loop finished)
%

The content of the loop will repeat for as long as while condition at the beginning will remain true. Which means that as soon as parameter #1 exceeds value of 10, program will exit the loop and print

loop finished

Example of break used in a Do – While loop:

%
#<A> = [2**0]
#<B> = 0
#1 = 0
o100 do
 (print, #1)
 #1 = [#1+1]
 G04 P1
 o200 if [AND[#<A>, #<_hw_input>]]
  #<B> = 1
  o100 break
 o200 endif
o100 while[#1 LE 10]

o300 if [#<B> EQ 0]
 (print,loop finished)
 o300 else 
 (print,preemptive loop break)
o300 endif
%

The content of the loop will repeat for as long as input 1 of controller is not active and while condition at the end remains true. Which means that as long as input 1 remains un-active, counter will count to 10 and program will exit the loop normally and print:

loop finished

As soon as input becomes active during counting, program will exit loop and print:

preemptive loop break

Some CNC jobs demand repetition of the same motion over and over again, e.g.: drilling of a 100 holes. If we want to re-use the existing g-code pattern throughout the main program,  we can use subroutines.

Subroutine is basically a program block which is executed the moment it gets called from main program.

Subroutine program can be located within the same g-code program from where it gets called, or it can be standalone program file.

Subroutine o-word commands:
o-sub – Begin subroutine
o-endsub – End subroutine
o-call – Call subroutine
o-return – Exit subroutine

 

o-call:
Subroutine is called using o-call command.

o-sub and o-endsub:
Subroutine program block is defined with o-sub and o-endsub brackets. Everything within these brackets will be executed when related subroutine is called.

When o-endsub is encountered, program jumps back to the line where subroutine was called and continues with execution or remaining main program.

o-return :
User can achieve the same effect as o-endsub also with the use of o-return command.

 

Example of subroutine call:
Program below will call three subroutines from main program.
First and second subroutine will print to log window while third one will print nothing since o-return command will be used.

To observe the subroutine behavior open log window: Help/Show Log

 

%
(Main program)
(PRINT,Start main program)

(PRINT,Calling subroutine 1)
o100 call
(PRINT,End of subroutine 1, return to main program)

(PRINT,Calling subroutine 2)
o101 call
(PRINT,End of subroutine 2, return to main program)

(PRINT,Calling subroutine 3)
o102 call
(PRINT,Preemptive end of subroutine 3,o-return command was used)

o100 sub
(PRINT,Subroutine 1)
o100 endsub

o101 sub
(PRINT,Subroutine 2)
o101 endsub

o102 sub
o102 return
(PRINT,This should never be printed)
o102 endsub
%

Log window will display this:

User can also call external subroutine program files.
In such case, syntax is slightly different than when calling subroutines that are located withing the same g-code program.

Subroutine program file location is defined in settings: File/Settings/Program Options-> G-code folders. Insert pathway to files location:

 

Subroutine program file should have an filename.sub file extension.

Subroutine program file code is defined with o<filename> sub and o<filename> endsub brackets.
When o-endsub is encountered, program jumps back to the line where subroutine was called and continues with program execution. User can achieve the same effect with the use of o-Return command.

Subroutine program file is called using o<filename>call command.

 

Example of subroutine file call:

Create file: Sub_example.sub

Open it with text editor and write:

o<Sub_example> sub
(PRINT,Subroutine file program)
o<Sub_example> endsub

Main program will call subroutine file:

%
(PRINT, call subroutine file)
o<Sub_example> call
(PRINT,This should be printed last)
%

Program above will call external subroutine file from main program.
To observe subroutine file behavior open log terminal: Help/Show Log

Log window will display this:

With PlanetCNC TNG it is possible to control g-code program flow. For this purpose you can use o-word g-codes.

o-words are formed as blocks and can be, based on their functionality, categorized into 4 groups:

SUBROUTINE
(subroutine block)

CONDITION
(if..endif,elseif,else…block)

LOOP
(do…while, ehile..endwhile loop block)

REPEAT
(repeat…endrepeat block)

 

During this multipart tutorial series we will try to explain the use and behaviour of each particular O-word group.

To understand the working principles and behaviour of a different o-word block we would recommend that user first gets
familliar with the PRINT command.

 

Another two g-codes used to specify machine movements are G02 and G03. They move the machine in an arc, in contrast to G00 and G01 which move the machine in a straight line.

G02 moves the machine in a clockwise arc and G03 moves the machine in a counterclockwise arc.
To use these codes we need to specify the coordinates to which the machine will travel, the offsets to the center of the arc or the arc radius and optionally the number of additional turns the machine will make while performing the move. The speed of these movements is also defined by the F-word (feed rate).

For example: Starting from X0 Y0 Z0, we would like to round a 90 degree corner using a counterclockwise arc to X50 Y50 Z0. To do this we will use the command G03 X50 Y50. But this command isn’t complete yet and the program would signal an error if we tried to use it like that. We still need to specify the center of the arc. This is done by specifying offsets from the starting position or with the deprecated method of specifying the radius.

The offsets are simply the distance from the starting position to the center of the arc. The offsets are separated into components for each axis. The center also needs to be equidistant from both the starting and the destination point. Otherwise the arc won’t be part of a circle and the controller will signal an error accordingly.

As we said, the offsets are the distance the machine would need to move along each axis separately to get to the center. In our case (starting from the origin) this would be 50 units along the Y axis. This also means that the radius of the circle will be 50 units (the radius equals the distance from the center to the origin or destination). Now we need to specify the offsets to the machine. To do this we use I, J and K-words for the X, Y and Z axes accordingly. When we put all this together we get the final code that looks like this: G03 X50 Y50 J50.

When it comes to g-codes that specify machine motion we need to mention G00 and G01.
G00 or also known as rapid or traverse move. G00 command is usually used for moves when machine travels from position to position above the material and when no cutting is applied.
When G00 command is stated we also need to specify in which direction move will occur. For example: G00 X100 Y50
Speed at which this move will be executed is usually maximum speed of machine.

G01 command activates linear motion of machine. We use G01 with moves when machine is moving tool trough material and therefore applying various types of cutting.
Normally speed of G01 move is set with F-word(distance/time). In this case F stands for feed rate, which specifies speed in mm/min or inch/min.
When G01 command is stated we also need to specify in which direction move will occur. For example: G00 X10 Y5 F1000