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Thread: Help me understand...

  1. #1
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    Help me understand...

    ...the process to go from a customer-supplied DWG file, to finished product?

    Or from customer-supplied DWG file(s), and STL file(s).

    Is there that much variability in DWG files, that one person/firm's software can make it, specifically for CNC router production... but another shop can't open the file at all, or would have to completely re-create it from scratch in their software because of "something weird" in the file?

    The couple projects that I've talked with local shops about were not overly complex (I think, might be wrong) - a router jig base plate with about 20 holes of various sizes, and an MFT type table top (MFSlab).

  2. #2
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    Monte,
    Unless your vendor uses the same CAD program as you do, I would suggest supplying your drawings in dxf format. What program are you using to create your drawings? Most have the capability to export as dxf.
    David
    Last edited by David Buchhauser; 07-10-2020 at 9:05 PM.

  3. #3
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    This is a situation where a person (me) purchases and downloads "plans" for a 'thing', that come with a DWG file that you can take to a CNC shop to have it made.

    I was under the impression that it was supposed to be a simple / straightforward process.

    So far, it's been anything but.

  4. #4
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    Hi Monte,
    The question is - what type of dwg file is it. The ones I am familiar with are the AutoCAD dwg files that I use. There may be other CAD programs that also use "dwg" files, but the format may be different. Perhaps you could provide a link to the vendor you purchased the plans from and I will take a look. Another option would be for you to send me your DWG file so I can see exactly what format it is, and perhaps convert it to dxf format for you. 99.99 % of cnc vendors can work with a dxf file to generate the tool paths to cut your parts. I will pm you with my email address.
    David

  5. #5
    Your fastest and easiest option might be to contact the seller and ask them for the file in as a DXF file. They might already even have that one saved in that format anyway unless they of coarse hade stolen it from someone else and was reselling it which happens quite often.

  6. #6
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    Quote Originally Posted by bobby milam View Post
    Your fastest and easiest option might be to contact the seller and ask them for the file in as a DXF file. They might already even have that one saved in that format anyway unless they of coarse hade stolen it from someone else and was reselling it which happens quite often.

    Bobby - I'm guessing that custom router base fixtures are not often pirated. Of course I could be wrong.
    David

  7. #7
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    The DXF file defines the project and can provide the vectors (the type of lines that are turned into CNC instructions) to the maker. But that's just the start of the journey. Those drawings need to be massaged to be sure all the vectors are valid (most need to be "closed" vectors when "areas" are involved) and then the CNC maker needs to take each of those vectors and create what are called toolpaths which define the boundaries, the tool characteristics, speeds and feeds for that particular cutting operation. Most jobs have more than one toolpath and many have, well...many toolpaths. Those toolpaths are written to a file or files that are then transferred to the CNC machine so they can be cut. This is not generally an automated process. It's not complicated, per se, especially with 2D machining, but there is still some work involved. That's why there is a setup cost for any job you farm out to someone like myself that does CNC subcontract work.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  8. #8
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    DXF/DWG are virtually interchangeable. DXF format basically came about for users who did not own Autocad eons ago. Nowadays most software can read either. DWG/DWF will have exact geometry for circles, arcs, and linework. STL is a format you need to be careful with except for 3D carvings where geometry is usually less important. An STL file is a triangulated mesh (see image below) and its accuracy will depend upon the level of detail included when the stl file is created. I would not accept a stl file for a jig that needs holes. Many software packages will not recognize the geometry from a triangulated hole and you will need to best fit something. That tends to lead to re-doing parts for a customer that is clueless about the different files.

    If you are dealing with a 3D part you will want a .step or .iges, igs, file or something like that. 3D solid modeling software can read the exact geometry of those file types.

    STL.JPG

    Here is a wire frame image of a .stl file for a part I recently 3D printed. You can see how the geometry of a hole changed from an exact radii to short lines.
    STL2.JPG
    Last edited by Brad Shipton; 07-11-2020 at 2:13 PM.

  9. #9
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    There are minor differences between Versions of ACAD DXF files. I started making DWG files back in the early - mid 1990's. Its interesting that I can open nearly all those files with modern software.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  10. #10
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    Quote Originally Posted by Brad Shipton View Post
    DXF/DWG are virtually interchangeable.
    This is "news" to me - so I wanted to see which programs that I use will open an AutoCAD dwg file.
    SolidWorks - YES
    Fusion 360 - YES
    Aspire - YES
    Design Edge - NO
    LightBurn - NO
    MasterCAM - NO

    If I convert my dwg file to dxf format, then it will open with all 6 programs.
    David

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