Gentlemen,
Tool length offsetting is BIG subject. It is difficult to get
people to agree on what it is and where it should be measured from.
You must determine how you are going to do it in your shop and then be
consistent with it.
I have two machines that need the tool lengths set to the
programmed tool length. These are 5 axis machines with controls that
do not have 5 axis tool length compensation. I have a tool setting
station to determine and set the tool lengths.
I have two 5 axis machines that have 5 axis tool length compensation.
I can set a tool length in my tool setter and use it in any
machine. We have determined the tool set gauge point for every machine
and adjusted the parameters.
I said all that to make this point. The most flexible way is the
best. My machines with the newest controls have tool change
subroutines that are called by the main gcode program. This allows
calculations and comparisons and the writing of tool attributes to the
tool table(file).
All gcode programs program the center of the spindle and the pivot
point of any rotary axis the spindle moves on. The tool length
compensation adjusts this to the machine and each particular setup.
Three axis machines and multiaxis machines in which the tool axis
spindle does not rotate are much simpler to set the tool length. You
can set the tool length as a minus number from the z axis home
position to the tool set zero position or the program zero position.
A machine that tilts the spindle will have a different tool offset
requirement. To use a 4 or 5 axis tool length offset you will need to
use positive numbers in the tool length table. This tool length value
and the pivot length value in the control will have to sum to the
length from the pivot point to the tool tip. When the tools lengths
are set in this manner you will be able to use the same tools and tool
lengths in a 3 axis or 4 axis or 5 axis program.
There is on gotcha in this. You WILL have to deal with it. When
the tool length offset is cancelled the machine will try to move the
gauge point down to the programmed Z point.
I have a couple machines that will offset the machine as soon as
the offset is changed. These machines respond in the same manner for
g54 work center offsets and tool length offset. I don't like this type
of response. I much prefer the machine to read offset register and
adjust during the next commanded move.
BTW, does EMC have 5 axis tool length offsets? Does EMC have 5 axis
tool radius compensation?
thanks
Stuart
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