Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Mpones on May 19, 2011, 12:41:11 AM
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I'm fairly new to this, but a lot of this seems like it should be pretty intuitive (that is to say, if the software is as automated as they make it seem). I have a CNC Blacktoe machine, ready to run a mach3 milling profile which is all configured. I just need to get the g-code to post properly so I can cut away...
First, I have a .BMP file that I convert to a .dxf using A9tech. When I open the .dxf in lazycam, the image looks exactly like it should, but with an insane amount of chains. So, I go into Setup -> Loading Options... Autoclean Settings -> "Connection like Tol. used in Optomise" and I change the value all the way to 11. That seems to clean up the chains to the point in the screenshot I post. (If changing the tolerance that high is the problem, how do I can those chains without changing the tolerance so much?).
Next, I click the "post G-code" button in LazyCam, I save the imported .dxf file to a ##.tap. When I try to open it in Mach3, I get this weird small ball of lines that looks nothing like it should... what am I doing wrong? I have the drawing files, I just want to get them into mach3 to be cut on my CNC machine!
Yes, the original .BMP file is drawn to scale, and the proper size. Yes, my mach3 is registered, and not a demo version, and yes, all software is up to date. I am running Windows XP.
I'm uploading the .BMP file (converted to .JPG so it wouldn't be so big), the .dxf file, and the .tap file. I'm also uploading a few screenshots of how the software looks when I'm using them.
/HALP
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could the machine be in metric and the drawing in inches?
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could the machine be in metric and the drawing in inches?
No... even if that were true, that wouldn't give crazy different shapes in mach3's g-code... it would all still be somewhat proportional...
EDIT: Ignore that third pic, for some reason I selected the wrong image.
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It could be caused by posting the Gcode in absolute IJ mode and mach is in incremental IJ mode. ( they need to match)
ATB
Derek.
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Can you post the DXF file and the LCAM file?
Probable reason for so manny entities in the chains is that the there are numerous lines which make up the arcs. Need to look at the
dxf.
See page 16 in the manual for info on the Connection line tolerance.
small ball of lines that looks nothing like it should... what am I doing wrong
Try changing your IJ setting and mode in MACH.
RICH
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Can you post the DXF file and the LCAM file?
Probable reason for so manny entities in the chains is that the there are numerous lines which make up the arcs. Need to look at the
dxf.
See page 16 in the manual for info on the Connection line tolerance.
small ball of lines that looks nothing like it should... what am I doing wrong
Try changing your IJ setting and mode in MACH.
RICH
Yah! Here are the DXF and LCAM files, hope anyone can help in anyway...
Also, I think I mentioned it up top, but we already played with the tolerance, and it seems to have the cut in order just fine now, when the tolerance is at 11, and has minimal chains, but maybe I'm way off...
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You can't really use that .dxf file as is. It's an axcellent example of how bad rater to vector conversions are for CNC cutting. The attached image shows 1/2" of the perimeter of your part, and this is what you're asking the tool to do in that 1/2". There are over 50 moves, in all different directions.
You really need to draw that part with arcs in a CAD program.
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Mpones,
Want is drawn is what you get. Tolerance provides for connecting entities which are are not connected within some distance.
Clean and optimise tries to minimize the number of rapids / pathing and cleans out items which exceed the tolerance and as such you reduce the number of entities. The pathing generated from the file is still crap with a whole lot extra moves.
I know nothing about A9tech, but there may be settings in the program which will help clean / remove manny of the bits which make up the profile.
Shown in the attachments are enlargements of profile sections. "A" is what A9tech generated and "B" is what is desired.
If you look at the LC screen capture you will see that on import of the dxf it still accepts the ragged profile. Your not improving things
a whole lot.To clean that up in LC manualy would be rather time consuming. LC is an importer and should not be used as CAD.
What you draw is what you get.
RICH
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The originals for this project were hand drawn, scanned into a high quality BMP file, then converted to a DXF... as I understand it, he should create his work in a CAD software, then save it as autoCAD r12 format, then import to Lazycam, then post up the G-code. He has purchased mach3, so it is licensed. Seems pretty straight forward, but we're probably getting these issues because he hand-wrote the files, right?
This is actually a project for a client of mine, I am an independent IT contractor, and I'm helping him learn the entire process from CAD to CNC.
My client has a Wacom Bamboo Pen n' Touch tablet, might he be able to theoretically redraw his work with it using, say perhaps, autoDESK sketchbook design, and then save it using the same software, or autoCAD, into the aforementioned process and be successful? I originally thought that the use of pencil would render strenuous and tedious chains and entities, and apparently it is insanely affecting the G-code to the point where it posts next to nothing.
I'm just trying to figure out the easiest way for my client to get his CNC up and running, we appreciate all of the great help.
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In this case I would:-
In Autocad - insert the scanned image as follows.
Drop down insert menu, insert > 'Raster image reference' ( this inserts say a 'jpg image onto the ACAD drwing)
Use the image as a guide to draw the geometry. i.e trace the shape with arcs and lines.
If you have some known dimensions such as the slot width and pitch, set these exactly in ACAD.
Only draw 1/2 of your shape and mirror to ensure that the part is exactly symetrical.
Import the geometry to your CAM package.
ATB
Derek.
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Use a CAD program or a program that is vector based and can be saved as a DXF file.
RICH
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Hi Mpones,
Here is a DXF of your design.
Iserted the image, traced it manually in Autocad and then deleted the bitmap to leave just the line and arc geometry....
There are just 48 objects.
If you know the slot widths / overall size, it can be drawn exactly to scale.
My size is a guess, I supose the item could be as big as a battle ship ;D
ATB
Derek