chuck/tailstock barriers

[HuFlungDung]

Its been a while since I've been programming in Camsoft, but it is a lot of fun to try to make hazy notions work out correctly in hardware operation

I finally came up with a method to set chuck barriers based on the tool number. I've always had a pet peeve about setting barriers on the lathes I've owned, since the barriers are typically too stupid to take into consideration the length of the tool.

For example, if you are OD turning right up close to the chuck, and then have to use a bar to bore inside the chuck jaws, a typical fixed Z barrier is useless because either it permits the turning tool to crash into the jaws or it prevents the boring bar from getting all the way into the bottom of the hole. This is because ordinary barrier limits are based on the carriage position, not the tool tip position.

My primary concern is the Z barrier, and fortunately, there are just enough empty parameters in the tool parameter table to accomplish this easily. I use custom1st and custom2nd for the forward and back limits in Z. Part of my tool offset measuring logic asks me to enter barrier distances for each tool as it is being set up, so I don't forget.

The X values of the barrier I simply leave the same all the time, and they are set just before the physical limit switches. Since my machine has front and rear toolposts, and machines in either CW or CCW this is about the only way to operate it.

The nice thing about the Camsoft soft limits is that the machine doesn't make the current move if it is not possible to reach the endpoint. So this can be expedient when proving a new program.

So with each tool call, I have a custom gcode written to call up the barrier values of the current tool. So my tool call looks like this:
T1 M6 G177

G177 contains logic to reset the softlimits forwards and backwards from the current tool number parameters, and turn them on. Its not rocket science to figure out once its done

[Karl_T]

Hu,

This is a GREAT idea. I think I'll use this on my lathe also. Did you just use the TOOLHEIGHT parameter of your tool number for calculating the new softlimits? Set up a special new parameter in your tools setup screen?

I'm wondering how to allow for drills and boring tools to have more travel than turning and facing tools.

Karl

[HuFlungDung]

Karl,
I used the available empty spots in my tool parameters table, called TOOLCUS1ST AND TOOLCUS2ND. I suppose you could use whatever you have open, as they are just providing data storage.

Thus far, I do not attempt to autocalculate the distance to the barrier. This is because I have 6 different chucks on the machine, and workpieces anywhere from 0 to 20 inches long in the chuck.

So, what I do is this: first move the carriage to machine zero, because this is the reference point for all barriers to be measured from. Then, with the help of a special machinist's tape measure , measure the distance from each tool to the right and to the left barrier (be it chuck or tailstock), and insert these values into the tool parameter table.

In cncsetup, I have zeros for the Z axis forward and back softlimits (which means they are disabled), but I do have fixed X softlimits. I turn softlimits on immediately after the machine is homed. This would still mean that there is no Z soft limits in place until the program runs, reads the G177 logic along with the T call.

Here is sample logic for the G177, which is pretty much the basic Camsoft examples given in G171 and G172 combined into one gcode.

' Set Chuck Tailstock Barriers
'use this gcode after a T call to calculate and install chuck barrier params for a given tool
\82=t
TOOLCUS1ST\82 \171
SOFTLIMITS BACKWARD \171;-2.85;0
' Set Foreward Crash Fixture or Chuck Barriers
TOOLCUS2ND\82 \172
SOFTLIMITS FOREWARD \172;2.9;0
SOFTLIMITS ON
BUTTON19 IN; SOFTLIMITS ENABLED

From what I read, all axis must be named in the SOFTLIMITS FOREWARD and SOFTLIMITS BACKWARD command syntax, thus I have restated my axis 2 (which is X on lathe) softlimits in constant radial distances.

My 'floating barrier' values (\171 and \172) are then pulled from the tool parameters table for the current tool in \82

After this is completed, then you can do whatever you wish so far as setting a new program home for the carriage to start from. All you need to consider when setting up the barrier length for the right, is that you take into account how far right the carriage has to travel to accomodate the longer drills. The unique barrier to the left never need change for each tool until you change chucks.