CNC routing machines and Rhino

Hi,

I'm sure there are numerous previous posts regarding my question but I didn't see them. I have a friend who wants to explore purchasing a low to medium cost CNC milling machine
to machine wood model boat hulls. He wants to be able to
mill a hull at least 24" in length. He asked me if Rhino would
work with one of the smaller milling machines and I told him
that I have never had the experience but I know of people who
do cut wood with such a devise. If anybody can recommend
a low to medium price machine I would appreciate it.

Thanks

Kirk

 

http://www.shopbottools.com/

http://cnczone.com/

Here is a start. I’m gone most of the day; yes Rhino will work for CNC. Do a search for RhinoCam. The links above will lead you to some info on those building there own.

Gary

 

A few things to think about if you build your own or get a low end machine. To cut a 3D shape you will need CAD software to produce a victor file, CAM software to produce cutting path code, and control software to read the code and tell the axis motors what to do.

RhinoCam is Rhino and VisualMill combined. There is also Cam software that will import Rhino files.

The one thing I have against ShopBot is they use a strange code. They have a converter, but editing is a pain for me.

If you have the time and the interest you can design your own. I started one a while ago. This is my 18X24X5 fixed gantry.

 

At our lab another group has a low cost custom "2.5 D" CNC machine that uses HPGL files. The software converts the HPGL files to vector code for the tool paths. The problem is the z height is driven by pen number, and the HPGL format we are using only supports 8 pens, so there are only 8 z heights that can be set up. I have made true "3D" tool paths by opening the machine path vector code in Word to get the format, then using Rhino, ACAD and Excel to turn contour plots into the correct format vector code. This is not easy, but was worth it to me for the ocasional one off machining job (actually, it was easy, but tedious).

Paul

 

There's always a way to make it work. If you wanted to you could build a new controler that would work from G-code.

Gary

 

I want to build a 13ft barrel back carvel planked mahogany runabout, using rhino to design hull and interior, and then make it as close to a kit as possible with idea of cutting as much as possible with a cnc machine. Tell me how much of this is dream vs reality given dimensional stability of P-mahogany vs plywood. I'd like to cut the frames from solid mahogany, so each frame would have a constant changing bevel to accommodate the helix of the barrel, the idea being a more precise start at fairing the hull. Each frame would be cut to fit the hard chine and sheer, and battens. Ultimately you would have a list of parts, programmed for cutter path control, that you could randomly select and place for cutting on your cnc using mahogany stock that would be random widths and lengths, trying to minimize waste. You would be trying to select those parts that would "fit" to that particular piece of mahogany stock. Can you cut that changing bevel with a 3 axis machine, if not how many? If I use rhino to design hull, what software would compliment that for cutter path control and the planning and placing of parts to stock. Planks would be another thing as they would be as much as 14ft, outside of 4x8. I'd like to make more than a few of these, maybe even production as a finished product, not a kit.Any help appreciated..Thanks! Jim

 

I use Rhino with VisualMill to drive a ShopBot. I have my list of gripes... there are certainly tricks you use over time to make it do what you want to, and some features just don't seem to work (like defining entry angles when starting new rough cuts...) but overall it does the job well at an affordable price.

Bear in mind that the advertized 6" vertical lift is reduced by the length of your router bit, so if using a 3" bit then you only get 3" of vertical lift. Only mentioning this because its very applicable to cutting models. When I mill study models I break the cad file up into vertical slices of reasonable thickness, then glue the slices back up after milling each individually.

Phil

 

Hi greatcircle2,

This might be better in another thread?
anyway - I use a 3 axis machine to cut variable bevels on the edges of frames.

Assume we are making frames for a hull. We have the 3d hull surface (minus planking/skin thickness etc) on Rhino.
Assume there is a frame with the fwd face 1000 mm aft of the fp. Frames to be made of 16mm material.
So, section the hull surf at 1000, 1004, 1008, and 1012mm aft of the fp (at 4mm spacing).
I then project the resultant curves to one plane (each currve on a seperate layer).

Now you can apply different z depths (with 4mm differences) to each curve.
ie: the 1000mm aft of fp curve has a cut depth of 4mm,
1004mm aft curve has a cut depth of 8mm,
1008mm aft curve has a cut depth of 12mm,
and the 1012mm aft curve has a cut depth of 16mm.

When you cut the frame using the four curves you will have a variable bevel.
It seems that using four depths for the bevel is suitable for plug building, if I was to use the method for a custom build then a smoother bevel would be possible by using more cuts. It is a balance of machine time versus smoothness.

Is my description comprehensible?
Rob