Machsupport Forum
G-Code, CAD, and CAM => G-Code, CAD, and CAM discussions => Topic started by: tmsmith on December 19, 2006, 06:02:33 PM
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I'm newcomer to CNC; having problems generating Gcode
I can generate gcode by checking the co-ordinates of a cad drawing and adding the 'M' and 'G' words and that seems to work but is tedious.
If I generate a DXF file and put it into LazyCam that gives good output as long as the drawn part is simple eg a triangular cut out within a triangle.
More complex shapes when dropped into LC need editing because of extra lines (not only rapids) which were not seen on the original CAD drawing
They then come apart because a required part is deleted by mistake,ie selecting and deleting one line takes a required line with it
Editing in Acad until only the outline required is present stilll results in extra lines when dropped into LC.
I have dropped DXF files into Acad2000 and saved them as ver12 and ver14 with little success.
How are you guys doing this, what are the ways of preparing the drawing so that LC can fix it and generate the gcode successfully.
tmsmith
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Well I think the best thing to do is post a few files... We will see if we can get them to work in Lcam
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Some study of my problems shows that only the bare outline of the part should be put into LC since removal of for example a dimension can cause problems.
Further problems were caused by failure to join lines giving overlaps or small gaps as covered in one of your tutorials.
Other problems not have obvious reasons to me.
My Cad package is RiscCad which will generate a DXF file which I then need to resave from Autocad 2000 which I do has a release 12 or 14 DXF file.
Are there prefered ways of constructing drawings in a Cad package to ensure success, I gather splines are a no-no.
Anyway I am attaching a simple DXF file that gave me problems as per your suggestion.
thanks for your interest
Malcolm Smith
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Hi Malcolm,
As a lover of all things Acorn and a programmer for RiscOS and the BBC for 26 years I hate to say it, but RiscCAD is just not accurate enough for this type of work, I have spoken to Dave Buck on this subject many times and he is reluctant to do anything about it.
RiscCAD only works to 4 decimal places so its fine for structural and picture drawing but poor at CAM drawing, Oaks PDT is far better as it works to 16 places of decimal. PDT works fine on a SA-RPC but I have never tried it on an Iyonics, I won't pay Jacks prices.
If you want more detail contact me off forum.
Graham.
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Your .dxf has duplicate arcs, endpoints that don't meet and multiple stray points. If you want good results from any CAM program, you need a good .dxf to start with.
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Thanks for that Ger21.
I will have to look at an alternative CAD package and work from there. :(
TMSmith
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On seconf thoughts,isn't the LazyCam cleanup option supposed to remove stray pints?
tmsmith