[mocnc]

Ok this is prob a shot in the dark, it seems like hardly anyone is using sketchup. I am starting off with it cause first of all its seems to be easy to use and two its free. I do plan on going to an other cad program in the future. I haven't yet decided on one that is good, easy to use and at a fair price. So for now I just want to get my cnc working as well as the ideas in my head on paper, or in this case on my personnel confuser. For my first project I want to build a shifter knob for my 1978 CJ7 jeep. I want to have an area to inlay a emblem in or have some sort of relief cut with a jeep logo on it. Later on I like to make signs and mess around with pool cue designs. Possible making them or more then likely carving on them. My question after my long winded statement here is.....I have drawn my shifter knob in sketchup 8, and it looks 3d, I even have saved it as a dxf file, but I don't think it will cut out as a 3d work. I have 4 axis with my cnc. The 4th being a rotating one. Is there something I am missing? Is there maybe a program (hopeully free) out there that will allow me to view my work before I actually start to cut it? Basically to do a simulated tool path? Maybe my dxf to g-code isn't good. Any help would be great!!:tired:

[BurrMan]

Hi mocnc,
Well, Sketchup is a polygon modeling tool and wouldnt be optimal for starting out for cnc... It's best to go with a NURBS package...

You may want to look at a new autodesk app that is in beta right now, so it's free, although, this may mean that at some point it will cost outrageous dollars!!! lol But it can be a good start to get you going with NURBS, and it's free... The user interface "Usability", will just be up to you. You may find it nice and easy, or disgusting, but it's free...

Here's a link:

Autodesk 123D - Free 3D Modeling Software, 3D Models, DIY Projects, Personal Fabrication Tools

Good luck.

[lovebugjunkie]

If you save it as an .stl file in sketchup you can use FreeMILL to generate g-code. VcarvePro demo versions lets you load a dxf (2D) file and generate a cut path but you will not be able to save the g-code.

When you say "looks 3d" can you give an example?

[CNC Lurker]

I have drawn my shifter knob in sketchup 8

<snip>

saved it as a dxf file

Your DXF is in 2D format, therefore you will have to tell your CAM program what depth to cut things. You could save the part as a STL format (which is 3D) and import that into your CAM program if it's capable of that.

Use this Sketchup plugin to get you half-way there:
Convert Sketchup SKP files to DXF or STL

To view your g-code, use the free CNC Viewer:
Basic CNC Viewer

You can also try the CNC Simulator, but there are many g-code files that it doesn't work with:
CncSimulator

[BurrMan]

Your DXF is in 2D format, therefore you will have to tell your CAM program what depth to cut things. You could save the part as a STL format (which is 3D) and import that into your CAM program if it's capable of that.

Use this Sketchup plugin to get you half-way there:
Convert Sketchup SKP files to DXF or STL

To view your g-code, use the free CNC Viewer:
Basic CNC Viewer

You can also try the CNC Simulator, but there are many g-code files that it doesn't work with:
CncSimulator

Hi Lurker,
I think you answered the questions that he posted.. Just so you know, poly software can save their models as "dxf" and they will be 3d models, but essentially useless to a cnc programmer. It will just be a polyhedral mesh. The STL will be how he gets a 3d model to a machine for sure though, it wont contain any line geometry...

A 2 step process may be needed. 3d data as stl and any planar 2d geometry needed as a dxf.

[ger21]

Just so you know, poly software can save their models as "dxf" and they will be 3d models, but essentially useless to a cnc programmer.

And just so you know, you can also save a 3D .dxf that will load just like an .stl file. I use them with MeshCAM all the time, and I believe most CAM programs can load them. The trick, is knowing how to create them and save them in your particular CAD program.

You can also save a .dxf with 3D solids, but not many CAM programs can read them. At least the inexpensive ones.

[BurrMan]

And just so you know, you can also save a 3D .dxf that will load just like an .stl file. I use them with MeshCAM all the time, and I believe most CAM programs can load them. The trick, is knowing how to create them and save them in your particular CAD program.

You can also save a .dxf with 3D solids, but not many CAM programs can read them. At least the inexpensive ones.

Yes, though most "Polygonal" modelers are not CAD packages and only save out a polyhedral mesh object that has no surface data to work with.. I am not sure about sketchup, maybe the op can post a sketchup dxf of a 3d model??? Most CAD (NURBS) modelers that use a dxf translator will be using the surface data also.

[ger21]

Yes, though most "Polygonal" modelers are not CAD packages and only save out a polyhedral mesh object that has no surface data to work with.

All the ones I've used do the opposite, and save a polygon mesh of triangular or 4 sided faces. or the individual faces themselves.

I believe the Sketchup plugin mentioned above will save a proper 3D .dxf with poygon faces. I've tried it in the past, but not recently.

Exporting a 3D model as "lines only" is absolutely useless for anything. But I have seen plenty of people post them, wondering what's wrong.

[BurrMan]

I believe the Sketchup plugin mentioned above will save a proper 3D .dxf with poygon faces. I've tried it in the past, but not recently..

Ah, good to know....

I think I read the Op's original post wrong anyway, as he was looking for a free sim package and possible 4th axis.. Not a problem with the model...