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Mach4 General Discussion / Re: Confusion about home switch location
« on: December 10, 2017, 02:23:13 AM »
Hi,
it doesn't really matter where the home switches are with 'home offset' you can effectively nominate any location as your home or reference position.
When you hit <Ref All> each axis in turn drives until its home switch activates, then it backs off until the home switch deactivates and THEN......
it can do one of two things:
1) It can set the machine co-ordinate for the axis as zero....or
2) It can set the machine co-ordinate as your home offset per your designation.
Imagine you have home switch on your X axis 50mm from the lefthand end. When referencing if you select option 1) above the machine co-ordinate at that
location would be 0. So your X axis can range from -50 at the extreme left to (max-50) at the extreme right. This would work fine but its likely to be confusing,
a reference location that is not in the centre or at either end is not that logical.
You could choose option 2) and nominate your X home offset as 50mm. Under this circumstance when the machine homes the X axis it drives until the home
switch activates as normal but it resets the machine co-ordinates to 50. If you then jogged the axis further to the left the machine co-ords would reduce
until you were at or near the limit switch at the extreme left of the axis at X machine co-ordinate 0. Note that the axis does not drive anywhere unusual or
anything like that it just resets the machine co-ordinate to some value other than 0. This has the effect of saying that the machine zero is 50mm from the
home switch.
May I suggest experimenting a bit. Put some different values in the X home offset on the homing page and watch what happens. Make sure that your DROs
are displaying machine co-ordinates. With some offset see which way and by how much you would have to jog to bring the X axis machine co-ord to zero.
Craig
it doesn't really matter where the home switches are with 'home offset' you can effectively nominate any location as your home or reference position.
When you hit <Ref All> each axis in turn drives until its home switch activates, then it backs off until the home switch deactivates and THEN......
it can do one of two things:
1) It can set the machine co-ordinate for the axis as zero....or
2) It can set the machine co-ordinate as your home offset per your designation.
Imagine you have home switch on your X axis 50mm from the lefthand end. When referencing if you select option 1) above the machine co-ordinate at that
location would be 0. So your X axis can range from -50 at the extreme left to (max-50) at the extreme right. This would work fine but its likely to be confusing,
a reference location that is not in the centre or at either end is not that logical.
You could choose option 2) and nominate your X home offset as 50mm. Under this circumstance when the machine homes the X axis it drives until the home
switch activates as normal but it resets the machine co-ordinates to 50. If you then jogged the axis further to the left the machine co-ords would reduce
until you were at or near the limit switch at the extreme left of the axis at X machine co-ordinate 0. Note that the axis does not drive anywhere unusual or
anything like that it just resets the machine co-ordinate to some value other than 0. This has the effect of saying that the machine zero is 50mm from the
home switch.
May I suggest experimenting a bit. Put some different values in the X home offset on the homing page and watch what happens. Make sure that your DROs
are displaying machine co-ordinates. With some offset see which way and by how much you would have to jog to bring the X axis machine co-ord to zero.
Craig