Export for CNC Milling - Newbie 1 oh 1

[DunkyDunk]

Ladies and Gentleman,
I have seen a few tutorials and read some pages.. so on and so on...
I might be barking up the wrong tree here, but Such an awesome program, and really good users here. So I'll see if I get some good answers. Thanks in advance


Problem - When I export my part, and get it into Mach 3, The visual on mach 3 is nothing like what FreeCAD displays... possibly a Mach 3 issue, OK.
- When I run the G-Code is acts like a 3D printer, as in It starts at the bottom and works it's way up, as apposed to starting at the top and working it's way down. also cutting where a printer would build. As apposed to cutting the outside and leaving the material in place.
- For some reason it's using the 4th axis (rotary).

Questions - How do I set the start material size, as if I wanted to cut the part from a 100 x 100 x 100 block of alloy for example, OR if I wanted to cut the part from a tube of alloy? So I guess this would be the margins?
- How do I control which axis are to be used, being a CNC machine I am forced to use Z for the milling, X and Y for direction, and A for rotation (in a lathe direction, I assume B or C would be spinning on the X or Y plane).


Any help would be great guys, I'm as new as newbies get. starting here before I annoy the Mach 3 guys, because this FreeCAD seems to be pretty awesome.

[danielfalck]

You're going to have to give us a bit more info on how you are actually generating the G-code that Mach is using. I've been working on a CAM workbench called Path for FreeCAD and we aren't very far yet. We certainly don't have any 4th axis CAM modules for it yet.
Describe your process of getting code and give us some info about what version of FreeCAD you are using.

Thanks.

[quick61]

Hello DunkyDunk, Welcome to FreeCAD and the forum.

I do not believe your problem is with FreeCAD or Mach3, but with whatever CAM program your using to produce your Gcode. There are a number of them out there, some better than others. The low end ones use a mesh to generate their paths from while the higher end packages will use solids, like STEP and/or IGES. One thing that might be an issue is if your using exported IGES models and their being exported in trimmed surface mode instead of B-Rep mode. If this is the case, try changing your IGES export type in Edit > Preferences... > Import-Export > IGES tab. Of course, this is if your actually exporting your models in IGES.

As Dan mentioned, without having more exact info, we can only guess. Also, please read - IMPORTANT: Please read first before asking for help. It's the topic directly below where you clicked to create a new thread, unless this got posted somewhere else and one of out moderators or admins moved it?

Mark

[DunkyDunk]

Thanks Guys.
I think with a little time and trial and error, and some tips on the "CAM" program will solve it.

I think if you guys can tell me the order, programs and "way" I should be heading I'll be able to spend some time learning properly. I'm hoping there is some freeware or very cheap software, as this is purely a hobby for me. And being that, I don't expect it to run smooth and seamlessly every time lol.



I use FreeCAD 0.15 (64bit 4671(git)) to create a 30mm Cube, with a 10mm Cube cut out from the Z axis down (Made it a lot simpler than the first few attempts).

Using FreeCAD I "select all", and export to an AutoCAD file (cube with cutout.dxf)

Open Mach 3 and launch "Lazycam" from within Mach 3

Lazy cam, import CAD file, open said file. All I see this time around, is the very top layer, as if I didn't Pad the first cube and pocket the smaller second cube, so a 2D square with a smaller square inside it.

I hit the G-Code button and it sends be back to Mach 3 with some G-Code in the command list.

Running it, the machine starts to make some sense as to following the 2D lines without using the 4th axis, and without dropping the Z axis (to cut).


Sooo.... am I close and just missing the layers, or completely off track? be honest lol

[quick61]

OK, LazyCam is a more or less basic 2D CAM package that will do drilling, routing and pocketing. As far as i know it will only process 2D DXF type files to define the paths. I am not all that familiar with it, but you should be able to set a path for inside or outside and tell it the depth you want and the tool to be used so it can compute your offsets.

What you are doing for export is wrong on several levels. If you have a cube that was Cut with a smaller cube to make a pocket, then the only thing you should be selecting is the Cut, not the Cut and the 2 cubes, just the cut, and that is only if you want to export the 3D solid, which in this case you do not.

So what you want to do is to go to the Draft workbench and select the Cut and then use the Draft Shape2DView tool to make a 2D projection of the part, like so -

2D.png (9.44 KiB) Viewed 5140 times

Once you have the Shape2DView you will want to select that, and only that and export that to DXF. As for the exact operation of LazyCam, there are at least a few videos on youtube that should be able to give you proper instruction on just how to us it with you DXF file now that you have a good one exported. Try this link for LazyCam tutorials - https://www.youtube.com/results?search_ ... +tutorials

It's late and I went through this rather quickly, so if there is anything your not understanding, please let us know and my own self, or someone else will get you straightened out.

Oh, and when we ask which version of FreeCAD your using, we are most of the time expecting the response to look something like my version information below -

OS: Kubuntu 14.04.2 LTS
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.16.5235 (Git)
Build type: Release
Branch: master
Hash: 6b3d7b17a749e03bcbf2cf79bbbb903137298c44
Python version: 2.7.6
Qt version: 4.8.6
Coin version: 4.0.0a
OCC version: 6.8.0.oce-0.17

For this question, it's not that important. Just keep it in mind in the future.

Mark

[DunkyDunk]

Thanks Mark, I'll read it a few times and see how much I can comprehend before I keep nagging lol.

My newbie level is "Microsoft", so I'll learn a bit more and see how I go, thanks again for the effort. much appreciated.

[quick61]

Your welcome. As a bit of a teaser and preview, here is what a tool path from a 2D shape might look like. This was done in FreeCAD's Path module. While Path is not ready for prime time, it can be made to work for things like this with a little effort. I have done a milling path for the outside profile, and a path for the inside Pocket, along with some peck drilling for the 4 holes.

Path.png (89.21 KiB) Viewed 5112 times

I'm not a windows guy, but I do think that the path module is in the latest development builds if you want to check it out. The development snapshots for windows can be found here - http://sourceforge.net/projects/free-ca ... velopment/ - and one of the first two should do, either 32 or 64 bit, depending on your OS. The development snapshots do not install, and simply unzip and run from the executable in the ~/bin directory, so you can have both versions living on your machine at the same time.

Mark

[DunkyDunk]

Made a few advancements and learned a few things...

So I Cut a simple project, and to see what happened I downloaded a more complex FreeCAD drawing (baseball cap) and milled it out as well.

Process I followed:

Made a FreeCAD drawing, "Export" as a "Mesh Format" with the extension ".stl"

Opened in MeshCAM (Still trying to find a Freeware program that has appropriate features, hopes are dwindling along with the 15day trial period), made a tool path appropriate to my stock/tool bits/so on and so on. Saved tool path as a ".nc" file.

Opened in Mach3 (again I had to pay for this, as it suit's my CNC machine very well.. GRRRRR), played with some more settings to do with the mill and stuff's. Ran the file and out came my timber Baseball cap lol


Hope anyone starting in the CNC hobby field can use the above to get started. The hardest bit I find is learning how to use FreeCAD (even though I'm sure it's easier than AutoCAD or any other CAD with full features). The creating a Tool Path is pretty easy with MeshCAM from the exported file from FreeCAD, I was advised above that I need to basically select the opposite to what I was selecting to get the cut out and not the object, which is probably right doing things in the correct fashion, but I don't have the brain power to keep up with the people that do this for a living.
So to get started, Get FreeCAD and watch some u-tube videos on it, get MeshCAM and watch 1 or 2 video's on that, and your mill program should be functional.