Just thought i would try to gather some thoughts on where on a CNC Mill you would mount proximity switches, some say "HOME" should be in the centre of the X&Y Axis, some say at the extreme + end of each Axis, i would like to hear your thoughts.
I have my XY homes at the extreme of the table. You have to tell your controller which direction to go in the setup for home. If your position is on the wrong side of home if you have it in the middle, the controller will go off in the wrong direction until it hits the end of travel and not find the home switch!
On the other hand, work coordinates can be any place.Art
AKA Country Bubba
(Older than Dirt)
I have my XY homes set to the 0,0 on the X,Y coordinates and top of travel on the Z axis. It is just a personal preference, as I suspect a lot of set-ups are.
When I was considering CNC'ing my little Clarke CMD10 (which never happened) I thought about having a toggle switch on the centre of each of the X and Y, with spring loaded flaps to operate them. The idea was that you then had some input to say which part of the table you were on and could home accordingly to the centre.
Many great inventors start off with what other people rate as stupid ideas. My end point seems to be the stupid idea.
As I look at the table, 0,0 is nearest me and to the left, just as though it were a graph on a piece of paper. I have a gantry machine BTW.
I can't see how it matters in reality, the home position is just a datum point that is repeatable. If you want to use the centre as zero then just apply an offset in your CAM software.Spelling mistakes are not intentional, I only seem to see them some time after I've posted
My home position is head all the way up with the spindle centre over the back right hand corner of the envelope.
I have Home Offsets programmed into Mach3 which then set my zero at X & Y centres of movement with my standard edge finder touching the table surface (with it's tool offset selected), this way when you Ref All Home Mach3 goes and finds the home switches then applies your Home Offsets.
Then you have multiple Work Offsets which allow stored settings for all 3 axes for clamps, vices, fixtures, standard workpieces etc.
Then you have Tool Offsets which allow stored settings for the lengths of the various standard tools you use.
Once you've got your head around it all set-ups become far faster and simpler, Ref All Home the machine, select the tool of your choice and the work offset of your choice and your zero can be where you want it in little more time than it takes to fit the tool and position a vice on the bed,
I found the huge disadvantage to using G code was you threw the original drawing away. I changed to cutting from the .dxf which meant I could see the original shape on screen. I then made circles into datum points. Circles that have depth in the Z axis cut, those without depth merely exist.
If starting from a blank piece of metal, I print the .dxf then stick it on with Pritt. I like Pritt because it dissolves in soluble oil.
Left mouse moves the table to a circle centre XY when you click on it, right mouse sets the XY position to a circle centre XY when you click on it.
That sounds like an interesting thread you're responding to, which one is it?
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