Torch Height Offset Confusion?

Tom,

I am trying to offset the Z axis on a plasma table to find the material. I am doing something wrong and need some assistance. I am using KMCNC version 4.33cc. My test G code looks like this.

Code:

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G17 G20 G90
G00 X1.0 Y1.0
M100         
G91 G00 Z.1
(Start Torch)
(Move X & Y)
(Stop Torch)
M101

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This is the c program for the M100 and I am using Exec/Wait in the Tool Setup. The torch is spring loaded and hits a switch when it runs into the material.

Code:

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#include "KMotionDef.h"

#define TS 19                        //Tool Sensor Input

//Program to send Z axis down and find top of material
main()
{
Jog(2,-50000);                                //Down speed and direction
while(!ReadBit(TS));
Jog(2,0);                                        //Stop at material
while(!CheckDone(2));
Jog(2,30000);                                //Reverse off of switch
while(ReadBit(TS));
Jog(2,0);                                        //Stop off switch
while(!CheckDone(2)); 
MoveRelAtVel(2,900,5000);          //Retract length to top of material
while(!CheckDone(2));
}

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The problem is when the M100 completes the Z axis DRO goes to Zero on the machine coords. This is a problem when returning the Z to the "home" position. I wrote a c program to reference the Z (M101) but it holds the last value from when the M101 was executed. So if I end the cut at Z.1 the Z DRO shows a .1 when the M101 completes.

Here is the M101 c program.

Code:

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#include "KMotionDef.h"
#include "Init_Burn Table.c"

main()
{
    int SaveZLimits,ZSWN,ZSWP,LZ;  //place to save limit switch settings
       
    // disable the limits (first save how they were set)
    SaveZLimits = ch2->LimitSwitchOptions;
    ZSWN = ch2->SoftLimitNeg;
    ZSWP = ch2->SoftLimitPos;
    ch2->LimitSwitchOptions = 0;
    ch2->SoftLimitNeg = -1000000;
    ch2->SoftLimitPos = 1000000;
 
    // Home Z
    Jog(2,60000);           
    while(ReadBit(Limit_Z));
    Jog(2,0);                               
    while(!CheckDone(2)) ;
    Jog(2,-15000);
    while (!ReadBit(Limit_Z));
    Jog(2,0);
    while (!CheckDone(2)) ;
    MoveRelAtVel(2,-3000,30000);
    while (!CheckDone(2)) ;
    Zero(2);                                               
    ch2->LimitSwitchOptions = SaveZLimits;  // restore limit settings
    ch2->SoftLimitNeg = ZSWN;
    ch2->SoftLimitPos = ZSWP;
 }

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Thanks

Hi Epiphany,

I don't really follow that entirely, but with any C Program like this that moves any axes use the Exec/wait/sync option. Otherwise the Interpreter will be out-of-sync and a discontinuous motion may result in a position loss.

HTH
Regards

Tom,

That did it. I was not using the sync option and that caused the problem. Now when the M100 completes my machine coords remain unchanged.

Cheers