Its been a while

A project log for CNC Plasma Table

Plasma Cutter + CNC Table + Auto Load/Unload = Tool to build other projects faster

willbadenwillbaden 01/30/2020 at 01:020 Comments

Its been a while since I last typed up a log on this project.  The plasma table is still cutting and the latest cut can be viewed below:

I haven't really made many updates to the machine.  The remaining two plastic ball bearing guides for the floating head have been replaced with aluminum ones.  The plastic ones were allowing the head to float left, right, forward and backwards too much.  after replacing, it had less play.

The plasma cutter supply also had a shelf made to allow it to stay mounted on the table itself.  This helped out with some room around the table.

Lastly, the torch cable got something to hang it from.  Cable management was an issue keeping it out of the cut and off of the material.  A 1x1" square tube was cut to length.  A simple swing hook was placed up top with the cable zip tied to it. The 1x1" tube was then welded to a round tube that seated in a larger tube on the bottom. This allows the hanger to swivel around as needed with the cable.

To make the bend near the top, multiple cuts were made through to the other side.  The tube was then bent and welded.  

So far so good. 

As for the missing steps issue. . . it has not gone so well.  Depending on the wear on the tip, the plasma table can jump/miss steps when firing the arc.  Recently, I switched over to Fusion 360 jumping on the free software bandwagon.  Which turned in to me subscribing to the yearly subscription fee, but that is a side note.  The switch to Fusion was a good decision since there is more control on the post processor.  I modified the grbl post processor and added a homing sequence prior to the first cut.

  // absolute coordinates
  if (properties.useZ) {
    writeBlock(gAbsIncModal.format(90), conditional(properties.useZ, gPlaneModal.format(17)));
  } else {
  zOutput.reset() ;
  //reset any z axis offsets
  writeBlock("G92.1") ;
  writeBlock("G90G0G59" ) ;
  writeBlock("X0.Y0.Z0." ) ;
  //Add dwell to prevent the homing cycle from stopping the x0y0z0 move
  writeBlock("G4P.1") ;
  //Home Machine to start with fresh zeroes
  writeBlock("$H") ;
  //Set G59 location to remember the shortest location to home 
  writeBlock("(Set G59 X0 Y0 Z0 Location)") ;
  writeBlock("G10L20P6X0.Y0.Z0.")  ;
  //Set G54 Z height to speed up plasma cutting height detect
  writeBlock("(Set G54 Z0 Location)") ;
  writeBlock("G10L20P1", zFormat.format(properties.homeZOffset))  ;
  //Move to G54 Z zero to save time on the first cut
  writeBlock("G0G54" ) ;
  currentHomeCutCount = properties.numberCutsHome ;

Then an option was added to home the plasma table after a set amount of cuts:

      if (properties.useHoming){
		if (currentHomeCutCount <= 0 ){
		  //home machine 
		  currentHomeCutCount = properties.numberCutsHome ;
		  isHoming = true ;
		} else {
		  currentHomeCutCount -= 1 ;  
      if (isHoming){
		//home machine 
		writeBlock("G0G59" ) ;
		writeBlock("X0.Y0.Z0.") ;
		//Add dwell to prevent the homing cycle from stopping the x0y0z0 move
		writeBlock("G4P.1") ;
		writeBlock("$H") ;		  
	    writeBlock("G0G54" + xOutput.format(getCurrentPosition().x), yOutput.format(getCurrentPosition().y), zFormat.format(0)) ;

The video above shows this homing between cuts on some of the pieces for the jet.

Along with the homing additions, the torch tip touch off was added prior to every cut: 

	  writeBlock("G38.2Z-300.F1000") ;
	  writeBlock("G92Z-19.") ;
	  writeBlock("G90G0Z.5") ;
	  writeBlock("M03S10000") ;
	  if (isHoming || isFirstTime){
	    writeBlock("G4",pFormat.format(properties.homingDwell)) ; 
	  }else {
		writeBlock("G4",pFormat.format(properties.normalDwell)) ;
	  isFirstTime=false ;
	  writeBlock("G1 Z-0.05") ;	

 All in all, the plasma table is coming together being a good hobby tool.  I have gone down the route of production yard art, but find that without torch height control, a water table or a more powerful plasma cutter, it will be a hill to climb until I can upgrade with profits.  We will see where this project goes in the future. . .