Centroid Acorn Plasma Users Manual Beta CNC12 v4.65 rev6
Machine Homing: Two philosophies, Chose to use a ‘machine home position’ or not. See below for pros and cons
of each method.
To home or not to home: The Centroid Plasma CNC controller can be run in main two modes.
1.) A machine coordinate system is employed. This method requires that a type of machine homing be used.
2.) No machine coordinate system is used, only a local “temporary” part zero location. This method does not require
any sort of machine homing.
Each method has its advantages and which one you choose depends on the machine and how it is being used and
often boils down to personal preference. The Centroid CNC controller supports either method.
Advantages of #1
- CNC controller will ‘remember’ Part Zero Locations when powered on and off.
- CNC controller can use ‘soft travel limits’ to avoid crashes
- CNC controller will inform the user before running a job if that job is going to fit within the work envelope based on
the part zero location.
- Homing can be automatic using switches or done semi automatic (user simply jogs or pushes machine to home
position (usually to marks on the machine or urethane hard stops)) to set home position.
- The Reset Home button on the VCP will reset the home position after a loss of steps event when using open loop
steppers
- Auto squaring of Gantry can be used or semi auto squaring (semi auto = push gantry against hard stops before
homing)
- A predefined Torch Tip Change location can be used along with the “Torch Check” button on the VCP.
Cons of #1
- some view homing as an extra step before the machine can be used to cut a part.
- If the machine is constantly losing steps, having to re-home after loss of steps event when using open loop
steppers is viewed by some to be a pain and unnecessary step when the advantages listed above are not important.
- some are confused by the use of two coordinate systems: Machine Coordinates and Work Coordinates and how
the are used together when using this method.
Advantages of #2
- To some using only the Work Coordinate System (WCS) is simpler way of doing things.
- You never have to home the machine.
Cons of #2
- Loss of the advantages of #1. For example: if commanded to move 100 inches even if there is not 100 inches of
travel the machine will do it and crash. Example 2: If part is too large for work envelope of the machine or the part
zero location is set at a position that where the part won’t fit the machine just runs the part until it crashes creating
wasted material.
- Gantry should be square before power up of machine so paired motors lock the gantry in the square position when
powered up. If you forget or if the gantry gets knocked out of square while running you have to power cycle the
machine to get it square.
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