Re: Tool tables

[Ray <rehenry-at-up.net>]

On Thu, 23 Aug 2001, you wrote:
> Has anyone modified the Tkemc to allow for changing the tool table data on the fly?
> 
> Does the program need to be reloaded to take the new settings into
account after tool table changes have been made.

Yes the EMC program reads from the tool file when you ask for the tool
length offset using g43 or the radius offset using g41 or g42.  The length
offset does not show up until it is commanded with g43 hn.  The radius
offset never shows up, it is an offset between the tool path programmed and
the actual tool path computed.

-----handbook snippet-----
Tool length offsets are given as positive numbers in the tool table.  A
tool length offset is programmed using G43 Hn, where n is the desired table
index. It is expected that all entries in the tool table will be positive.
The H number is checked for being a non-negative integer when it is read.
The interpreter behaves as follows.  

1. If G43 Hn is programmed, A USE_TOOL_LENGTH_OFFSET(length) function call
is made (where length is the value of the tool length offset entry in the
tool table whose index is n), tool_length_offset is reset in the machine
settings model, and the value of current_z in the model is adjusted. Note
that n does not have to be the same as the slot number of the tool
currently in the spindle. 

2. If G49 is programmed, USE_TOOL_LENGTH_OFFSET(0.0) is called,
tool_length_offset is reset to 0.0 in the machine settings model, and the
value of current_z in the model is adjusted. The effect of tool length
compensation is illustrated in the screen shot below. Notice that the
length of the tool is subtracted from the z setting so that the tool tip
appears at the programmed setting.  You should note that the effect of tool
length compensation is immediate when you view the z position as a relative
coordinate but it does affect actual machine position until you program a z
move.   
-----end of snip-----

Try this.  First set tool 1 to 2" length and 0.5 diameter by clicking on
offset or the number widget after it.  Call up tool 1 (M6 T1) then activate
length compensation (g43 h1) and you should see the 2" offset in the number
window.  If you plot moves using both no offset and tool length offset you
should set the display to machine rather than relative so that you will
see the differences in the path made. 

You can do the same with radius compensation by following the examples in
the handbook.  This is a little bit trickier to figure out the start move.

HTH

Ray