What is your way to put spark gap in electrodes?

[GlennM.MCAM]

Hello,

we are changing some workflow for our electrodes. Until now, the sparkgap was put into the cad model by the cad engineers.

This will change and the spark gap (negative offset) needs to be added by myself within PowerMill (no Powershape or Electrode Wizard available).

How do you guys do it? As far as I know, there are 2 possibilities with the same results:

• Using the "Default Thickness" option and select the surfaces to add a negative thickness

     or

• Using the thickness fields in the toolpath menu.

Do you have more or better solutions?

An existing project (toolpaths and boundaries) need to be "easily" changed from one offset to another (rough and finishing electrodes).

Thanks for your feedback!

Glenn

[DanMcDan]

Hi Glenn, we put all our offset on during powermill as a negative overall thickness for each toolpath and typically we don't use rough and finish electrodes as this doesn't really work for our parts. 90% of our electrodes are machined from a macro that i have on a right click menu, whereas i just select whatever orbit (undersize) and the macro writes and sorts out the rest.

This is a example of my -0.25 undersize macro :

(note: the template is for our diamond tooling for graphite which are generally an extra 0.015mm undersize)

//FORM BLOCK
EDIT BLOCKTYPE BOX
EDIT BLOCK COORDINATE WORKPLANE
EDIT BLOCK TOLERANCE ".01"
EDIT BLOCK RESETLIMIT "1"
EDIT BLOCK LIMITTYPE MODEL
EDIT BLOCK RESET
EDIT BLOCK ZMAX LOCK
//BLOCK ACCEPT
//FORM FEEDRATE
//FEEDRATE ACCEPT
//FORM TOOLZHEIGHTS
EDIT TOOLPATH SAFEAREA TYPE PLANE
EDIT TOOLPATH SAFEAREA RESET
//TOOLZHEIGHTS ACCEPT
//FORM DATUM
EDIT TOOLPATH START TYPE BLOCK
EDIT DATUM PAGE END
EDIT TOOLPATH END TYPE BLOCK
//DATUM ACCEPT
//FORM LEADLINK
EDIT TOOLPATH LEADS PAGE ZHEIGHTS
EDIT TOOLPATH LEADS SKIMDIST "5"
EDIT TOOLPATH LEADS PLUNGEDIST "0.15"
EDIT TOOLPATH LEADS INCREMENT_FROM_STOCK N
EDIT TOOLPATH LEADS RADIAL_CLEARANCE  "0"
EDIT TOOLPATH LEADS GOUGECHECK N
EDIT TOOLPATH LEADS GOUGECHECK Y
EDIT TOOLPATH LEADS PAGE FIRSTLEADIN
EDIT TOOLPATH LEADS PAGE LEADIN
EDIT TOOLPATH LEADS LEADIN SNARC
EDIT TOOLPATH LEADS LEADIN DISTANCE "0"
EDIT TOOLPATH LEADS LEADIN ANGLE "60"
EDIT TOOLPATH LEADS LEADIN LRAD "0.5"
EDIT TOOLPATH LEADS GOUGECHECK N
EDIT TOOLPATH LEADS GOUGECHECK Y
EDIT TOOLPATH LEADS LEADOUT COPY
EDIT TOOLPATH LEADS PAGE LEADSOUT
EDIT TOOLPATH LEADS PAGE LASTLEADOUT
EDIT TOOLPATH LEADS PAGE LEADEXTENSIONS
EDIT TOOLPATH LEADS PAGE LINK
EDIT TOOLPATH LEADS LINK SKIM
EDIT TOOLPATH LEADS LONGLINK SKIM
EDIT TOOLPATH LEADS SAFELINK SKIM
EDIT TOOLPATH LEADS GOUGECHECK N
EDIT TOOLPATH LEADS GOUGECHECK Y
//LEADS ACCEPT
IMPORT TEMPLATE PROJECT FILEOPEN
"C:\dcam\Pmill2\Graphite_Elec_01_Undersize.ptf"
EXPLORER SELECT Tool "Tool\DIA10.0REM0.5TPRD*40" NEW
ACTIVATE Tool "DIA10.0REM0.5TPRD*40"
EXPLORER SELECT Tool "Tool\DIA10.0REM0.5TPRD*40" NEW
IMPORT TEMPLATE ENTITY TOOLPATH "3D-Area-Clearance\Model-Area-Clearance.002.ptf"
EDIT TPPAGE WORKPLANE
EDIT TPPAGE BLOCK
EDIT TPPAGE TOOL
EDIT TPPAGE CURVELIMIT
EDIT TPPAGE AREACLEARCOMMON
EDIT PAR 'Strategy' 'offset_area_clear' EDIT PAR 'AreaClearance.Offset.Type' 'model'
EDIT PAR 'AreaClearance.Profile.CutDirection' 'climb'
EDIT PAR 'CutDirection' 'climb'
EDIT PAR 'Tolerance' ".1"
EDIT PAR 'Thickness' ".2"
EDIT PAR 'RadialDepthOfCut.UserDefined' '1' EDIT PAR 'Stepover' "3"
EDIT ZHEIGHTS AUTOMATIC STEPDOWN "5"
EDIT TPPAGE AREACLEAROFFSET
EDIT PAR 'AreaClearance.Offset.RemoveCusps' '0'
EDIT PAR 'AreaClearance.Offset.RemoveCusps' '1'
EDIT TPPAGE STEPCUTTING
EDIT PAR 'AreaClearance.StepCutting' 1
EDIT PAR 'AreaClearance.Stepup' "1"
EDIT TPPAGE AREACLEARWALLFIN
EDIT TPPAGE AREACLEARFILTER
EDIT TPPAGE AREACLEARFLAT
EDIT PAR 'AreaClearance.ZHeights.Flats' 'area'
EDIT TPPAGE AREACLEARHIGHSPEED
EDIT PAR 'AreaClearance.Profile.CornerRadius.Active' '0'
EDIT PAR 'AreaClearance.Profile.CornerRadius.Active' '1'
EDIT PAR 'AreaClearance.Offset.SmoothingAllowance.Active' '0'
EDIT PAR 'AreaClearance.Offset.SmoothingAllowance.Active' '1'
EDIT TPPAGE AREACLEARORDER
EDIT TPPAGE CURVEAREAAPP
EDIT TPPAGE CURVEAUTOVERIFY
EDIT TOOLPATH "1" REAPPLYFROMGUI
EXPLORER SELECT Tool "Tool\DIA6.0REM0.5TPRD*35" NEW
ACTIVATE Tool "DIA6.0REM0.5TPRD*35"
EXPLORER SELECT Tool "Tool\DIA6.0REM0.5TPRD*35" NEW
//FORM BLOCK
EDIT BLOCK ZMIN LOCK
EDIT BLOCK RESETLIMIT "3"
EDIT BLOCK RESET
//BLOCK ACCEPT
IMPORT TEMPLATE ENTITY TOOLPATH "Finishing\Offset-Flat-Finishing.ptf"
EDIT TPPAGE WORKPLANE
EDIT TPPAGE BLOCK
EDIT TPPAGE TOOL
EDIT TPPAGE CURVELIMIT
EDIT TPPAGE OFFSETFLAT
EDIT PAR 'AreaClearance.Slicer.Flat.Tolerance' ".1"
EDIT PAR 'AreaClearance.Slicer.Flat.ConsiderTriangles' '0'
EDIT PAR 'AreaClearance.LeadIn.ApproachOutside' '0'
EDIT PAR 'Tolerance' ".005"
EDIT PAR 'CutDirection' 'climb'
EDIT PAR 'UseAxialThickness' '1'
EDIT PAR 'Thickness' "0.1"
EDIT PAR 'AxialThickness' "-.25"
EDIT PAR 'RadialDepthOfCut.UserDefined' '1' Edit Par 'Stepover' ".5"
EDIT TPPAGE FINFLATHIGHSPEED
EDIT PAR 'AreaClearance.Profile.CornerRadius.Active' '0'
EDIT PAR 'AreaClearance.Profile.CornerRadius.Active' '1'
EDIT PAR 'AreaClearance.Offset.SmoothingAllowance.Active' '0'
EDIT PAR 'AreaClearance.Offset.SmoothingAllowance.Active' '1'
EDIT TPPAGE CURVELEADSNLINKS
EDIT TPPAGE LEADIN
EDIT TOOLPATH LEADS LEADIN HARC
EDIT TOOLPATH LEADS LEADOUT COPY
EDIT TOOLPATH "2" REAPPLYFROMGUI
EXPLORER SELECT Tool "Tool\DIA6.0REM0.5TPRD*35" NEW
ACTIVATE Tool "DIA6.0REM0.5TPRD*35"
EXPLORER SELECT Tool "Tool\DIA6.0REM0.5TPRD*35" NEW
IMPORT TEMPLATE ENTITY TOOLPATH "Finishing\Optimised-Constant-Z-Finishing.ptf"
EDIT TPPAGE BLOCK
EDIT BLOCK RESETLIMIT "3"
EDIT BLOCK RESET
EDIT TPPAGE OPTIMIZEDZ
EDIT PAR 'Spiral' 1
EDIT PAR 'OffsetSmoothing' '1'
EDIT PAR 'Tolerance' ".005"
EDIT PAR 'CutDirection' 'climb'
EDIT PAR 'UseAxialThickness' '0'
EDIT PAR 'Thickness' "-.25"
EDIT PAR 'RadialDepthOfCut.UserDefined' '1' Edit Par 'Stepover' ".1"
EDIT TPPAGE AUTOVERIFY2
EDIT TPPAGE CURVELEADSNLINKS
EDIT TPPAGE LEADIN
EDIT TOOLPATH LEADS LEADIN SNARC
EDIT TOOLPATH LEADS LEADIN ANGLE "60"
EDIT TOOLPATH LEADS LEADIN LRAD "0.5"
EDIT TOOLPATH LEADS LEADOUT COPY
EDIT TPPAGE LINKS
EDIT TOOLPATH LEADS SAFELINK SKIM
EDIT TOOLPATH "3" REAPPLYFROMGUI
EXPLORER SELECT Tool "Tool\DIA10.0REM0.5TPRD*40" NEW
ACTIVATE Tool "DIA10.0REM0.5TPRD*40"
EXPLORER SELECT Tool "Tool\DIA10.0REM0.5TPRD*40" NEW
//FORM BLOCK
EDIT BLOCK RESETLIMIT "6"
EDIT BLOCK RESET
//BLOCK ACCEPT
IMPORT TEMPLATE ENTITY TOOLPATH "Finishing\Constant-Z-Finishing.ptf"
EDIT PAR 'Thickness' "-.0"
EDIT PAR 'Thickness' "-.0"
EDIT PAR 'AxialDepthOfCut.UserDefined' '1' EDIT PAR 'Stepdown' "2"
Edit Par 'MachineFlats' 1
EDIT TPPAGE CURVELEADSNLINKS
EDIT TPPAGE LEADIN
EDIT TOOLPATH LEADS LEADIN HARC
EDIT TOOLPATH LEADS LEADOUT COPY
EDIT TPPAGE LINKS
EDIT TOOLPATH "4" REAPPLYFROMGUI
BATCH PROCESS

Dan

[GlennM.MCAM]

Thanks Dan for your input.

I also think that the undersize is best put into the toolpath and not the "Default Thickness" option.

For me it is almost impossible to use a basic macro to finish my electrodes since they are (sometimes) way too complicated for automation.

I only do this for roughing and finishing my bottom block of the electrode.

Additional tips are welcome.

Glenn

[Anonymous]

 Would a simple solution be when you create your tool to input a bigger diameter than its actual size, eg 10mm ball nose input the diameter size as say 10.25mm. Would this then leave your .25mm thickness on and also when you create a boundary too.

[GlennM.MCAM]

Not an option for me. Also, offset is per side which makes it a diameter of 10,5 (0,25 per side).

Thanks anyway.

[Pijetro]

Thickness field is the way to go...

If you ever need to do 2D orbits, simply input your Radial thickness, and set axial thickness to zero...

[GlennM.MCAM]

Thanks @Pijetro, exactly what I think.

I just made a macro to automate the sparkgap change into all toolpaths and boundaries.

This makes it easy to switch from a 0.2mm offset electrode to an electrode with a bigger offset or vice versa.

Active limits in the toolpath are also changed.

REAL $sparkgap = INPUT "Sparkgap change? (positive value = more gap)"

FOREACH tp IN FOLDER('toolpath') {
	ACTIVATE TOOLPATH $tp.name
	EDIT TOOLPATH # RECYCLE
	YES
	REAL RadialThicknessSG = ($Thickness - $sparkgap)
	REAL AxialThicknessSG = ($AxialThickness - $sparkgap)
	$Thickness = $RadialThicknessSG
	$AxialThickness = $AxialThicknessSG
	REAL LimitZmax = ($ZRange.Maximum.Value - $sparkgap)
	REAL LimitZmin = ($ZRange.Minimum.Value - $sparkgap)
	$ZRange.Maximum.Value = $LimitZmax
	$ZRange.Minimum.Value = $LimitZmin
	EDIT TOOLPATH # REAPPLYFROMGUI
	YES
	DEACTIVATE TOOLPATH
}

FOREACH b IN FOLDER('boundary')	{
	ACTIVATE BOUNDARY $b.name
	FORM BOUNDARY #
	REAL BoundaryThicknessSG = ($b.Thickness - $sparkgap)
	REAL BoundaryAxialThicknessSG = ($b.AxialThickness - $sparkgap)	
	$b.Thickness = $BoundaryThicknessSG
	$b.AxialThickness = $BoundaryAxialThicknessSG
	EDIT BOUNDARY # ACCEPT BOUNDARY ACCEPT
	DEACTIVATE BOUNDARY
}

MESSAGE INFO "Toolpaths and boundaries have been edited with an offset of $sparkgap"

[Pijetro]

And of course, the other advantage to this...

If you ever need to do localized thicknesses, like Collision surfaces, or additional safety allowance on a face, etc...The option is always open to use the surface thickness tab...

[GlennM.MCAM]

How do you handle sparkgap with mills that have a smaller tool tip radius than the undersize?

Do you ignore this message or how do you fix this?

[Pijetro]

It's been awhile, but from what I remembered, we ignored it..

Essentially, you'll be left with material PLUS, meaning that in the past, we had some benching to do...

But I guess, you can make local electrodes with larger orbits come to think of it...

[Anonymous]

I use the thickness to set orbit/undersize also. If you are using 2D orbit, the Z is set to size though. We just put in a Makino and Erowa cell for our edm work and are using the rough(.01 orbit), semi(.008 orbit), and finish(.005 orbit) system now. I'll attach a macro that I use to accomplish this for you to check out if you want. I'm not great with macros but this works for me. Maybe you could make some suggestions for improvement too.

[mshahruddin.mshid]

my method use strategy selector..just "save as strategy"..and whenever u wanna use just select