3D formats for a 3D CNC machine ?

3D printers usually use STL files.

If you are actually doing 3D machining on a mill or router then you need a CAM software package like Master Cam, Gibbs Cam, or Bobcad to generate the 3D tool paths for you and output the G-code for the machine to use.

Firas, I would agree that you would typically only use *.dwg and *.dxf files for what we would consider flat pattern (2D) work on our Water-Jet and Laser machines.

To add to what Timothy mentioned, we typically use *.step (think the latest we use is *.step 242 format, we don't use any of the MBD based step files yet) files for anything that requires 3D milling or a 3D model for programming a CMM.

Export in-house, or outside?

CAM software can use most type of 3D solids. But, ask them what they want to use.

We use MasterCAM. I have used both CAMWorks and MasterCAM within SolidWorks and the code is saved within the models.

When there are updates, the code is auto updated.

With exported models, the code is not updated as easily.

The same goes for 2D. Both DXF and 3D models can be used for flat bed routing, laser, and cutting, etc.

All the above can be used for 3D printing.

I'd be inclined to use a STEP or an IGES file, that way your curves remain curves. STL files break the geometry into tiny triangles of flat surfaces(tessellate). These can often be seen when printed or CNC'd. If they haven't told you which they accept, send them a selection.

Sending your native file is not recommended for IP reasons as well as the fact an exported file is harder to alter.

Some cam software now can directly import files from other 3D CAD such as inventor or solidworks

DSTV files are common for equipment like beam lines, 8 axis machines and etc.

I would first do what Chris Saller said and "Ask them" what format they want it in.  They might only need a 2d drawing for something simple and then you don't even need to send the model.

It will depend on what type of CNC they are using and what software they use (and what version).

As has already been said, you also need to be concerned with the IP.  Do you trust the shop? - and even if you do, still don't give them more than they need.

I would also lean heavily to sending only in generic parasolid format - not a SWX (or Inventor) file. SWX files can be simply opened and copied with all your critical information.

I like Paul Salvador's method.  That is a much safer way - they get what they need to make the part with none of the details they don't need.

We use this method even in our own shop - but that is because our CAM software (Gibbs) is an older version than our SWX software and they are not fully compatible for direct import, but the parasolid  .x_t file is version independent and works for both SWX and Inventor (we use both).

Firas,

One consideration is also the seat of cam software your vendor is using. We have SW 2017 and Gibbs cam 2016. The Gibbs software cannot open native 2017 SW files. So we have to save out Parasolids for machining purposes.

Firas,

We design in Solidworks and Machine using Gibbs cam software here.

Rule of thumb for exporting models to a cam software is whatever the solid is, is what is going to get cut. Now prints help define intent and what may or may not be critical, but a toolmaker is expecting surfaces to be an accurate representation of what the final part is going to be.

"i mean like a surface made in SW which is in contact with other surface and not tangent ?"

Your comment above is what  I am referring to. If your model has bad edges, your part will as well. Is it possible to fix a model in cam software? Most definitely, but most shops will cut to your model using your prints as their basis for final parts. If you have faulty edges it will show up in the part more times than not.

I design and program all my parts  in house, SW2017 and Alphacam 2017.

Each machine needs a custom post processor to function properly, one of our machines has the origin in the upper left instead of lower left so all of our Y values must be in the negative. This is just a small example of how complex programming for cnc machines is.

I have over 8 years of setup and operation on various cnc machines and that is why I am capable of programming proficiently.

I would suggest getting experience setting up and operating a CNC machine before attempting to program one. This is where you learn a lot of the proper feeds and speeds, entry types, and various setup techniques.

The models do affect what the final cnc product is, I suggest working with their cam programmer and adjusting the model per his requests.