Content Preview
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
Objective This document will guide Acorn and AcornSix users in the setup of their Laser machines It
will outline the output wiring for common Lasers used with the Acorn and Wizard configurations
Laser and PWM Primer
• Pulse Width Modulation PWM is a process of delivering digital pulses of varying “pulse widths”
to the Laser rapidly turning it on and off
• PWM output allows for the controller to deliver varying amounts of power to the Laser reducing
the average power while keeping peak power constant
• The pulse widths the duration of time the Laser is on combined with the duty cycle the
percentage of each pulse cycle the Laser is on of the output give the controller more precise
control over the Laser cutting process reducing potential heat damage caused to the material and
optimizing the cutting process for workloads of differing materials and thickness
• Centroid Velocity Modulation Feature is where the Laser Power is adjusted automatically based
on actual machine velocity to prevent burning in the corners or on any slow down area
• For more information about Pulse Width Modulation basic see https //en wikipedia org/wiki/Pulse
width_modulation
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 1 of 19
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
Requirements
Acorn Rev3 or newer or AcornSix
Acorn CNC12 v5 24+ Mill or Router
Download the latest version of CNC12 here
https //www centroidcnc com/centroid_diy/centroid_cnc_software_downloads html
Supporting Documents
• Tech Bulletin 314 Instructions to Add Door Interlock Logic
◦ This document details adding safety door logic via Wizard or PLC
• Typical Hookup schematics
◦ S15049 Jtech Photonics Laser
◦ S15056 Jtech Photonics Laser Generic VFD Enable Direction
◦ S15057 Jtech Photonics Laser BLDC Spindle Control
◦ S15061 OPT Laser
◦ S15062 NEJE Laser
◦ S15063 Comcrow D B500F Laser
◦ S15192 AcornSix Jtech Photonics Laser
◦ S15217 AcornSix NEJE Laser
Supporting Video
https //youtu be/bMN7kDUnpWE?si=1p1q0dF3h1oox0jP
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 2 of 19
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
PWM Output for Spindles and Lasers Basics
Acorn 5 volt PWM output signal on Acorn is DB25 pin14 H6 and OUT2 H10 OUT2 is also
connected to Relay 2 via the ribbon cable When Acorn PWM output is used Acorn relay 2 must be
disabled See schematic S15049 for guidance on where to cut ribbon cable leading to Relay 2
AcornSix 5 volt PWM output signal on AcornSix is provided for Lasers by a dedicated terminal on H9
labeled PWM2 Unlike the Acorn this PWM output is not connected to Output2 so that output is free to
use while utilizing PWM and PWMOutput does not need to be assigned
PWM is based on 0 100 OR 0 1000 S command
User selects the PWM range of 0 100 or 0 1000 in the Acorn Wizard
M37 turns ON Laser PWM Output
M38 Turns Laser output OFF
M37 will also activate the canned Acorn Wizard outputs
Laser Enable
Laser Reset
Laser Cooling Fan
After 0 5s LaserReset will turn off At this point the Laser controller will look at the PWM signal from
OUT2
M38 will wait 30s to allow J Tech or other Laser controller to cool then performs a M95 /37 /38 to turn
off both LaserEnable and PWMSelect
G37 Centroid’s PWM Velocity Modulation feature adjusts the PWM output based on velocity of the
machine tool so over burning is avoided in the corners and turn arounds
G37 is used to turn ON and OFF PWM Velocity Modulation
G37 ON = PWM VM ON
G37 OFF = PWM VM OFF
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 3 of 19
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
Acorn Wizard PWM Setup
PWM setup controls are located in the Acorn Wizard
Note In addition to the custom setup PWM controls found a the top of the PWM Setup menu the Wizard
also has preset buttons for common J Tech configurations and these presets have matching schematics
to follow S15049 S15056 S15057
When using one of the presets be sure to follow the corresponding hookup
schematic exactly as these presets configure the Acorn Wizard inputs and outputs to
match the schematic!
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 4 of 19Presets with matching schematics Custom PWM Setup
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
Setting Up Custom Laser Outputs using the Wizard
Acorn Laser Outputs
For preset Laser setups like J tech schematics S15049 S15056 and S15057 the Wizard will place the
Laser outputs in their appropriate slots automatically To assign them yourself simply click and drag the
outputs into the desired output slots
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 5 of 19Click
and drag
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
AcornSix Laser Outputs
Note AcornSix does not need PWM Output assigned to an output since AcornSix handles PWM through
the dedicated PWM2 terminal on H9
The AcornSix wizard also handles preset J tech Laser setups listed on the PWM Setup tab automatically
For custom Laser setups click and drag the outputs to the desired output slots
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 6 of 19Click
and drag
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
PWM related I/O in the Wizard
a PWMOutput For Acorn the PWM signal is OUT2 H10 /DB25 pin14 H6 Remember to cut OUT2
on the ribbon cable as shown in the schematic to the Output 2 Relay
AcornSix has a dedicated PWM output Use H9 terminal labeled PWM2 and See schematic # S15192
b LaserEnable Used to either send or prevent sending the PWM signal to the Laser When active the
Laser diode will pulse with the PWM signal sent to it When inactive no signal is sent to the Laser
preventing the diode from pulsing while keeping power supplied to the board
c LaserReset Momentary output to Reset Laser Used to send a reset signal to the Laser controller
see J Tech schematic S15049 as an example
d PWMSelect Output to move PWM signal from Spindle to Laser PWMSelect is used when the PWM
signal is required to be sent to different devices For example a machine that has both a Spindle Motor
and a Laser that require PWM to run PWM from output 2 is connected to the COM of the relay
PWMSelect is assigned to To use with Standard Layout Spindle PWM should be connected to NC side
of Relay and Laser should be connected to NO side of relay When PWMSelect is deactivated PWM is
being sent to Spindle When PWMSelect is activated the PWM signal is being sent to Laser Follow
Schematic J TECH Photonics Laser BLDC Spindle Control # S15057
e LaserCooling_Fan This output can be used to activate an external Laser cooling fan It automatically
turns on with M37 Laser ON and turns off with M38 Laser OFF There is a delay timer if you wish for
the Cooling fan to stay on for an amount of time after the Laser has turned off The delay timer that will
keep the fan on for the set amount of seconds after M38 is issued The default value for the timer is 0
seconds
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 7 of 19
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
Acorn Example Hookup Using schematic S15061 OPT Laser PLH3D 6W as an example let’s see
how to assign the Laser outputs to match the schematic
To setup up the PWM output navigate to PWM Setup tab in the wizard under the Spindle section Set
PWM Enable to ON this will automatically set PWMOutput in OUTPUT2 in the Output Definitions tab
Also set the base frequency to the recommended value for the particular Laser; for the PLH3D 6W a
value between 5 10kHz is recommended The PWM minimum S command Inverse Output and Laser
cooling fan timer can be set as desired but will be left at default for the example
The Laser will be cut off from power whenever the E Stop is pressed or another fault is present Along
with hard wiring power to Laser through the E Stop NoFaultOut output also disconnects the power in the
relay when NoFaultOut is LOW Assign NoFaultOut to OUTPUT1 in the Output Definitions tab
OUT4 from the relay controls whether the PWM signal is sent to the Laser or not This allows for the
controller to choose when the Laser diode is active through the LaserEnable output while still providing
power to the Laser Assign LaserEnable to OUTPUT4 in the Output Definitions tab
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 8 of 19
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 9 of 19
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
AcornSix Example Hookup Using AcornSix schematic S15217 NEJE Laser as an example follow
these steps for setting up a Laser using the AcornSix Wizard
In the PWM Setup tab under the Spindle section of the Wizard PWM should already be enabled and
grayed out since AcornSix always has PWM enabled through its dedicated PWM terminal The default
base frequency of 4883 Hz works for the NEJE so can be left at default The PWM minimum S
command Inverse Output and Laser cooling fan timer can be set as desired but will be left at default for
this example
The Laser will be cut off from power whenever the E Stop is pressed or another fault is present Along
with hard wiring power to Laser through the E Stop NoFaultOut output also disconnects the power in the
relay when NoFaultOut is LOW Assign NoFaultOut to OUTPUT1 in the Output Definitions tab
OUT4 from the relay controls whether the PWM signal is sent to the Laser or not This allows for the
controller to choose when the Laser receives the PWM signal via the LaserEnable output Assign
LaserEnable to OUTPUT4 in the Output Definitions tab
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 10 of 19
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 11 of 19
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
ZigZagSyncTest Instruction
These two test programs are included with the CNC12 Mill and Router v5 0+ installation in the laser folder cncm\ncfiles\laser
ZigZagLaserSyncTest X_Axis cnc
ZigZagLaserSyncTest Y_Axis cnc
Purpose
These two programs were created to test for and adjust backlash in your Laser table axes
The program will create four lines in either the X or Y direction by moving back and forth in that axis and firing the Laser in
short 0 006 inch pulses at specific points while moving in each direction
Below is an example of what is expected from running ZigZagLaserSyncTest X_Axis cnc
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 12 of 19GOOD Laser Sync Test ResultsGOOD Laser Sync Test Results
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
Backlash in an axis will produce a line that looks similar to the below image when examined under magnification
As you can see the dots are not aligned down the axis which shows that the machine has backlash in the X axis and is
losing motion when changing directions Since each “dot” is 0 006 inches long we can make an educated guess at the
backlash adjustment need to align the “dot”
See this video for a detailed example of this procedure
https //youtu be/bMN7kDUnpWE?si=UVaGYfOslT4 bjh3
Use the Wizard to adjust the backlash compensation for that axis and run the program again to verify or determine if more or
less compensation is needed
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 13 of 19BAD Laser Sync Test Results
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
In CNC12 v5 24 a PWM Laser output delay parameter #424 was introduced for Clearpath users that are
using the Teknic Clearpath axis motors with the Teknic RAS feature RAS is Teknic’s own internal motor
smoothing feature which while it does a great job in making the axis motor act smooth RAS delays the
actual movement of the machine tool from the commanded and expected position in time The result is
CNC12 thinks the machine is at one location while it is really at another point in space behind and
delayed This of course interferes with the Laser ON/OFF and power level being ON or Off at the right
time and place So we created Parameter # that will delay the Laser on/off/power commands by a
millisecond amount P424 allows CNC12 to make up for and match back up the commanded Laser
ON/OFF/Powerlevel with the actual machine position in time and space
Setup and use
1 All machine setups configured and verified working properly Steps per rev overall turns ratio drive
tuning machine is square and straight The steps below are the last thing you do
2 Accurately measure the machine Backlash with a dial indicator not the method described above
configure and verify Note Take all action to reduce mechanical backlash from the axis system to the
absolute minimum And make sure it is consistent over the work area If backlash is changing over the
work area Stop and fix that issue
Here is a link on how to measure the actual machine lost motion backlash amount
https //centroidcncforum com/viewtopic php?f=63&t=5404
3 Run the zig zag and observe the gap
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 14 of 19
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
Trail and Error take an educated guess on the number of milliseconds
Try 2 4 8 ms values for P424 be sure to save and rerun the test observe results
In the example above P424 = 4 ms is looking good!
Other non Clearpath drives do seem to introduce a small delay 2 to 6 ms as well so P424 can be used
as a fine tuning technique to line up the Laser to the actual intended target
Clearpath typical results we observed with Teknic RAS is set to 16 ms were
P424 set to 9 ms produced good results and lined up the test
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 15 of 19
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
Example Centroid Laser G code
Sample G code of a cutting/burning type file
G21 ; select metric units
G90 ; absolute positioning
G0 X0 Y0 ; rapid to X0Y0
Z0 ; Move to Z zero
G37 ON ; PWM Laser Power Velocity Modulation ON
M3S0 ; Laser power off
M37 ; Laser on/enable
G0 X 74 Y 36 5 F2000
M3 S650 ; Laser on at 65% power when using 0 1000
G1 X 73 833 S207
X 73 667 S203
X 73 333 S201
X 73 167 S203
X 73 S209
X 72 667 S213
X 72 5 S211
X 72 333 S215
X 72 167 S217
X 71 833 S215
X 71 667 S213
X 71 5 S205
X 71 333 S211
X 71 167 S207
X 71 S200
X 70 667 S203
X 70 5 S196
X 70 333 S190
X 70 167 S192
X 70 S194
X 69 333 S200
X 69 167 S198
X 69 S196
X 68 833 S198
X 68 667 S203
X 68 5 S207
X 68 333 S205………
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 16 of 19
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
The CNC12 Installer comes with a few sample Laser G code programs located in the folder cncm\ncfiles\laser
Note when performing Photo burns the Laser power S command should be on every line that it changes
For example
G1 X 0 103 S103 ; laser power at 103
G1 X 0 109 Y 01 ; no change in laser power stays at 103
G1 X 0 113 S112 ; laser power changed to 112
G1 X 0 123 S98 ; laser power changed to 98
G1 X 0 133 S400 ; laser power changed to 400
G1 X 0 143 S800 ; laser power changed to 800
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 17 of 19
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
LaserGRBL Post Processor Header and Footer info for Centroid Acorn Laser compatible G code
HEADER
G21 ; select metric units
G90 ; absolute positioning
G0 X0 Y0 ; rapid to X0Y0
Z0 ; Move to Z zero
G37 ON ; Auto Laser power Velocity Modulation ON
M3S0 ; Laser power OFF
M37 ; Laser PWM ON
MULTIPLE PASSES
; Uncomment these lines below if you want to sink Z axis
;G91 use relative coordinates
;G0 Z 1 sinks the Z axis 1mm
;G90 use absolute coordinates
FOOTER
S0
G90 ; Absolute positioning
M38 ; Laser cool down time
;END
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 18 of 19
TB326 Rev6 – Acorn and AcornSix PWM Laser Setup
LightBurn setup and workflow information is here
https //centroidcncforum com/viewtopic php?p=95845#p95845
Document History
Revision 1 created on 2023 10 20 by 490
Revision 2 created on 2023 11 28 by km
Revision 3 created on 2023 11 30 by 490
Revision 4 created on 2023 12 05 by 490
Revision 5 created on 2025 01 16 by km
Revision 6 created on 2025 04 30 by km
Z \tech\Technical bulletins\TB326\TB326_acorn_pwm_laser_setup_rev6 odt Page 19 of 19