Sheetcam and plasmabot

[HakBot]

Hey guys,

I'm running into kind of a strange issue. First some background info. I am using Autocad to generate my drawings, just simple squares and circles to start out. I am then using SheetCam to convert the dfx files into gcode. From here importing into Mach3. According to tulsaturbo I should be using the MP 100-THC post processor. Everything looks fine in Autocad and sheetcam but the problem is when using this post processor I get some strange gcode generated when there are are arcs present. What happens is sometimes the arcs totally reverse or are much larger than what they should be; say if there is a rounded corner instead of just rounding the corner you get the opposite of that arc generated. See the image below. I believe there is something in this post processor causing this because I tried the Mach3 post processor and the arcs are generated correctly. Anyone have any ideas about what I'm doing wrong here? Thanks!

[HakBot]

Fooled around with the post processor code a bit and it seems that the following codes: G53 G90 G40 have something to do with it. I compared this to the standard Mach3 post processor and it has: G40 G90 G91.1 listed. Looked them up but I really dont understand the definitions.

[johndjmix]

Hakbot, slightly off topic ... I'm building a machine right now so I'm a bit new to this.

My understanding is you do drawings in autocad, convert to Gcode in sheetcam, then feed into mach3 to run the machine.

Are you saying mach3 can do the conversion so there is no need for sheetcam? Why not just use that then since your problem isn't happening that way?

--John

[overkillrc]

you have to use shhetcam or a similar cam program to create the G-code. mach3 only reads the G-code

[HakBot]

Here is my post processor code for the MP 1000-THC, does this match what you guys are using?


function OnAbout(event)
ctrl = event:GetTextCtrl()
ctrl:AppendText("plasma MP1000-THC post processor\n")
ctrl:AppendText("\n")
ctrl:AppendText("Modal G-codes and coordinates\n")
ctrl:AppendText("Comments enclosed with ( and )\n")
ctrl:AppendText("M03/M05 turn the torch on/off\n")
ctrl:AppendText("Incremental IJ - set in mach2\n")
ctrl:AppendText("The torch is referenced at cut start and every 500mm of movement thereafter\n")
ctrl:AppendText("Designed for use with Mach3 and CandCNC MP1000-THC and Floating head Touch-n-Go\n")
ctrl:AppendText("Post variables:\n")
ctrl:AppendText("refdistance - set the distance between each reference\n")
ctrl:AppendText("switchoffset - set your net switch offset amount \n")
end


--post.SetOptions(post.ARC_SEGMENTS)


-- created 1/1/06
-- Based on plasma1.post



function OnInit()

post.SetCommentChars ("()", "[]") --make sure ( and ) characters do not appear in system text
post.Text (" (Filename: ", fileName, ")\n")
post.Text (" (Post processor: ", postName, ")\n")
post.Text (" (Date: ", date, ")\n")
if(scale == metric) then
post.Text (" G21 (Units: Metric)\n") --metric mode
else
post.Text (" G20 (Units: Inches)\n") --inch mode
end
post.Text (" G53 G90 G40\n F1\n")
minArcSize = 0.2 --arcs smaller than this are converted to moves

dist = 9999999
refdistance = 10* scale
--Put your switch offset value here
switchoffset =.052
lastz = 0
end

function OnNewLine()
post.Text ("N")
post.Number (lineNumber, "0000")
lineNumber = lineNumber + 10
end


function OnFinish()
endZ = safeZ
OnRapid()
endX = 0
endY = 0
OnRapid()
post.Text (" M05 M30\n")
end

function OnRapid()
dist = dist + math.hypot(endX-currentX , endY-currentY)
post.ModalText (" G00")
post.ModalNumber (" X", endX * scale, "0.0000")
post.ModalNumber (" Y", endY * scale, "0.0000")
post.ModalNumber (" Z", endZ * scale, "0.0000")
post.Eol()
end

function OnMove()
dist = dist + math.hypot(endX-currentX , endY-currentY)
post.ModalText (" G01")
post.ModalNumber (" X", endX * scale, "0.0000")
post.ModalNumber (" Y", endY * scale, "0.0000")
post.ModalNumber (" Z", endZ * scale, "0.0000")
post.ModalNumber (" F", feedRate * scale, "0.0###")
post.Eol()
end

function OnArc()
dist = dist + math.hypot(endX-currentX , endY-currentY)
if(arcAngle <0) then
post.ModalText (" G03")
else
post.ModalText (" G02")
end
post.ModalNumber (" X", endX * scale, "0.0000")
post.ModalNumber (" Y", endY * scale, "0.0000")
post.ModalNumber (" Z", endZ * scale, "0.0000")
post.Text (" I")
post.Number ((arcCentreX - currentX) * scale, "0.0000")
post.Text (" J")
post.Number ((arcCentreY - currentY) * scale, "0.0000")
post.ModalNumber (" F", feedRate * scale, "0.0###")
post.Eol()
end


function OnPenDown()
if(dist >= (refdistance/scale)) then
dist = 0
-- modaltext (" G00")
-- text(" Z")
-- number (pierceheight * scale, "0.0000")
-- eol()
post.ModalText(" G28.1 Z")
post.Number(3 * scale, "0.00")
post.Eol()
post.ModalText(" G92 Z0.0\n")
post.ModalText (" G00")
post.Text(" Z")
post.Number (switchoffset, "0.0000")
post.Eol()
post.ModalText(" G92 Z0.0\n")
post.ModalText (" G00")
post.Text(" Z")
post.Number (pierceHeight * scale, "0.0000")
post.Eol()
else
post.ModalText (" G00")
post.Text(" Z")
post.Number (pierceHeight * scale, "0.0000")
post.Eol()
end
if (preheat > 0) then
post.Text ("\n G04 P")
post.Number (preheat,"0.###")
post.Eol()
end
post.Text ("\n M03\n")
if (pierceDelay > 0) then
post.Text (" G04 P")
post.Number (pierceDelay,"0.###")
post.Eol()
end
end


function OnPenUp()
post.Text (" M05\n")
if (endDelay > 0) then
post.Text (" G04 P")
post.Number (endDelay,"0.###")
post.Eol()
end
end


function OnNewOperation()
post.Text (" (Process: ", operationName, ")\n")
if (plungeRate <= 0) then
post.Warning("WARNING: Plunge rate is zero")
end
if (feedRate <= 0) then
post.Warning("WARNING: Feed rate is zero")
end
end

function OnToolChange()
post.Text (" M06 T")
post.Number (tool, "0")
post.ModalNumber(" F",feedRate * scale,"0.#")
post.Text (" (", toolName, ")\n")
end

function OnNewPart()
post.Text(" (Part: ",partName,")\n");
end

function OnDrill()
OnRapid()
OnPenDown()
endZ = drillZ
OnMove()
OnPenUp()
endZ = safeZ
OnRapid()
end

[tulsaturbo]

I did a comparison with the MP 1000-THC post file that I use and I don't have the following line:

minArcSize = 0.2 --arcs smaller than this are converted to moves

[HakBot]

Removing that line didn't seem to help. I am guessing its something with this latest version of sheetcam, went back to a previous version and it was fine.