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TB319 Rev6 – Acorn/AcornSix Teknic Clearpath Hard Stop Homing Setup
Centroid Acorn Teknic Clearpath Hard Stop Homing setup
What is hard stop homing?
CNC machine tool hard stop homing is when each Clearpath axis motor moves the axes to the end of
travel until it hits a hard stop to determine a repeatable home position No switches are used in the hard
stop homing process Hard Stop Machine Homing is required on machine power up or after an E Stop
event
Why you would want to use it?
Hard stop homing does not require homing switches Less switches means less wiring Eliminates
problems associated with broken switches wiring and the initial expense of buying and installing home
switches Some cheap home switches may be less accurate and prone to varying trip distances and also
may induce electrical noise into the CNC system so these issues are avoided with hard stop homing
Auto squaring can be achieved with either a software paired axis or a hardware paired axis
Hardware paired axes have advantage that auto squaring is easily achieved without having to utilize the
software pairing feature which consumes the 4 th
axis on an Acorn Hard Stop homing with hardware pairing
leaves the Acorn’s 4 th
axis free for other uses such as a rotary table
Pitfalls of hard stop homing
Each axis motor presses against the hard stop when homing to determine the end of axis travel Hitting the
end of axis travel can damage the machine if the Clearpath MSP software motor hard stop threshold is not
set properly Typical threshold limits for Routers are 25% more stout machines can withstand higher
thresholds But these values completely depend on the motors being used and the machine tool design
Determining a good torque threshold is a trail and error process and is the responsibility of the machine tool
cnc integrator
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TB319 Rev6 – Acorn/AcornSix Teknic Clearpath Hard Stop Homing Setup
Clearpath Hard Stop Homing Setup
Step 1 Configure Clearpath MSP software for hard stop homing
Step 2 Configure the Centroid Wizard and Home Program for hard stop homing
1 In the Clearpath MSP Software set the homing option to “enabled”
Select “setup” in the Homing Menu
And the Homing Setup menu appears
For basic linear axis for Homing Mode Set to “Normal”
In Homing Style set to “ClearPath Homes Automatically”
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TB319 Rev6 – Acorn/AcornSix Teknic Clearpath Hard Stop Homing Setup
In Homing Occurs Set to “Upon first Enable after power up or motor reset ”
In Homing Direction Set to the direction of the motor to move that axis towards the desired hardstop for
homing
In Homing Move Settings Set Speed “Speed RPM ” is the Motor Revolution speed rate which the
motor rotates to move the axis towards the hard stop The “Accel/Decel RPM/S ” Is the rate which the rpm
Accelerates and decelerates during homing movements These numbers show below are for a typical mill
or lathe with a turns ratio of 5 or 10 Routers will need different numbers
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TB319 Rev6 – Acorn/AcornSix Teknic Clearpath Hard Stop Homing Setup
In Miscellaneous Set the Physical Home Clearance cnts This is the user defined distance between
Physical Home and Software Home in encoder counts It is intended to provide safety spacing between
the load and Physical Home Default setting is 1 motor revolution = 6400 counts in this case
Set Home Offset Move Distance cnts This parameter determines the final position of the axis relative
to the Software Home If this parameter is set to zero the motor will remain at the Software Home zero
position when homing is complete Note This setting can be used to offset a motor that is part of a paired
axes motor set to perfectly square a gantry after hard stops get it in the ballpark
Set Homing Torque Limit Hard Stop Homing only When homing is initiated ClearPath lowers the motor
torque limit to this value Set this Torque value to as low of a value as possible to ensure no machine
damage occurs when pressure is applied to the Hard Stop Note The Main Torque Limit is automatically
restored after homing cycle is complete Typical values are 25% for Routers
Enable Clearpath’s “Restore Commanded position”
Enter the “Advanced” in the Clearpath software Tab from the main screen
Choose Enable Actions then
Select “Restore Commanded Position”
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TB319 Rev6 – Acorn/AcornSix Teknic Clearpath Hard Stop Homing Setup
Restore commanded position prevents a position loss when the Reset button or E Stop condition is
encountered if the
Before proceeding to Step 2
Use the Clearpath software to test each individual axes to determine the best Torque threshold
percentage setting for each axis so there is no physical damage to the machine occurs
Test that the Clearpath home to hard stop feature that it repeats each axis to same position
Test that any paired Gantry axes motors are moving at the same rate and in the same direction Set hard
stop to be as square as possible Adjust Home Offset move distance to perfectly square the gantry
2 For CNC12 v4 99+ Configure the entire machine with the Wizard and then do this step last
In the Acorn Wizard Homing menu select Clearpath Hard Stop Homing
If using a Software Paired axis such as a Plasma or Router Gantry In the Wizard Axis Pairing Menu
Set the Wizard to Manual Axis Squaring/Alignment
Do not use Centroid’s Autosquaring which requires home switches in combination with Clearpath Hard
Stop Homing Autosquaring is achieved with the Clearpath Hard Stop homing cycle
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TB319 Rev6 – Acorn/AcornSix Teknic Clearpath Hard Stop Homing Setup
If using Hardware Pairing for instance on Acorn 4 to save an axis drive connection for another use
Leave the Pairing Wizard menu set to “Not Paired” which means no software paired
Gantry Auto squaring is then achieved by the Clearpath hard stop homing homing off of hard stops that
are square
Press “Write Settings to CNC control configuration” follow instructions on the screen Make sure the
Clearpath software is setup correctly and you are done
Note For CNC12 v4 82 The Clearpath Hard Stop Homing preset feature doesn’t exist in the Wizard but
we can still set it up to work
These are the steps
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TB319 Rev6 – Acorn/AcornSix Teknic Clearpath Hard Stop Homing Setup
1 Configure the Acorn Wizard home menu for hard stop homing
2 Set CNC12 Machine Home at power up selection
3 Edit the home program
Set the Wizard up for Hard Stop Homing
In the Homing and Travel menu
Select “Automatic Homing” ignore that it says “machine seeks switches to home”
Select “Wizard to generate Automatic home program based on selections below”
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TB319 Rev6 – Acorn/AcornSix Teknic Clearpath Hard Stop Homing Setup
If using a Paired axis such as a Plasma or Router Gantry In the Wizard Axis Pairing Menu
Set Wizard to Manual Axis Squaring/Alignment
Do not use Centroid’s Autosquaring which requires home switches in combination with Clearpath Hard
Stop Homing Autosquaring is achieved with the Clearpath Hard Stop homing cycle
If using Hardware Pairing for instance on Acorn 4 to save an axis drive connection for another use
Leave the Pairing Wizard menu set to “Not Paired” which means no software paired
Gantry Autosquaring is then achieved by the Clearpath hard stop homing homing off of hard stops that are
square
After completing the Wizard setup Go to the CNC12 control configuration menu F1 Setup F3 Config
pass = 137 F1 Control choose “Ref Mark HS” and press F10 to save
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TB319 Rev6 – Acorn/AcornSix Teknic Clearpath Hard Stop Homing Setup
Edit the Home program
Open Notepad ++ and navigate cncm hom mill router plasma or cnct hom lathe and edit the file with
notepad ++ and make the changes below or copy the example cncm hom/cnct hom file and overwrite the
stock file in the cncm/cnct directory download hard stop homing programs here
https /www centroidcnc com/centroid_diy/downloads/acorn_cnc_software/
acorn_clearpath_hard_stop_homing_programs zip
Below is an example Mill/Router/Plasma table Centroid Home to Hard Stop home program
Centroid Clearpath Hard Stop Homing program
; Clearpath ‘Home To Hard Stop’ homing program
;
; Hard Stop Homing Requirements
;
; 1 Setup Clearpath MSP software for automatic homing to hard stop see TB#319 for detailed instructions
;
; Using the Clearpath MSP software test each individual axes to determine
; the best Torque threshold percentage setting for each axis
; so there is no physical damage to the machine
; Verify Clearpath home to hard stop feature repeats to same position for each axis
; For Paired Axis such as a Gantry set Gantry hard stops to be as square as possible
;
; 2 Set the Wizard up for Hard Stop Homing
; In the Homing and Travel menu
; Select “I will create my own home program do not overwrite cncm hom”
;
; M225 prompts the operator for action
;
M225 #100 " Wait for Clearpath Hard Stop Homing cycle to complete Then Press Cycle Start to set the
Machine Home Position "
;
; Once the Clearpath Homing cycle is complete
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TB319 Rev6 – Acorn/AcornSix Teknic Clearpath Hard Stop Homing Setup
; All axes will be holding at the Clearpath determined Machine Home position
; M26 Sets CNC12's Machine Home position at the current location
;
;
M26 /X/Y/Z ; M26 /X/Y/Z sets Machine Coordinates system X0 Y0 Z0 at current location
Warning! Before running a hard stop homing program the Teknic Clearpath MSP Software has to be
configured for use with this home file Step 1 of this document otherwise machine damage to the machine
tool will occur see Clearpath notes at the top of this file press Cycle Cancel to quit ”
Note For testing you can use F2 Load to run the cncm hom/cnct hom like any other G code program and
run it over and over to test with
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