Hi Mike, so maybe something more like the attached quick attempt (see attached 3DM file).

That's done by making the bottom ridge as an open curve, do not try to make it a squished down closed curve as that will be problematic in the squish area. Then various segments are done by lofting like this:


For pivot areas you would select this piece and run Sweep along the 2 adjacent edges to make those cone-like (by cone like I mean collapsing into a single point at the tip area) corner juncture areas:



- Michael

Some rough thoughts:

A 60 degree vbit is a cone. For each depth, there is a circle of a different radius.
If a maximum depth is selected, There is a circle, maxCircle, of maximum radius.

For two intersecting curves, using the Moi tantan circle, a series of largest circles can be created touching the upper curve,
and also touching the lower curve. If the separation between the two curves exceeds the maxCircle, the maxCircle would hug
the upper curve. The zDepth of the center of the circle is determined by the vBit angle.
The centers of all the tangent circles would create tipCurve, the path of the tip of the vBit.
Then sweep a line along the top curve and the tipCurve.

Repeat for the bottom curve if maxCircle is exceeded, and also form plane between tipCurve1 and tipCurve2.

(This is a rough "algorithm")

- Brian





I did locate a Rhino/Grasshopper reference: http://www.grasshopper3d.com/forum/topics/tangent-circles-between-2-curves

I have actually been using MoI for this very purpose recently.

I do have a program for V-Carving, aka Centre Line Machining, but for the mould I'm making it's not quite the right tool for the job.

MoI made it about as easy as is possible although it's still turned out to be something of an awkward task because of the fairly complex geometry.

The way I found to create V-Carve(ish) style toolpaths involves Sweeping an angled line (45 deg cutter in my case) around the shape so that intersecting surfaces are produced. When these surfaces are Trimmed with each other, the trim lines are extracted and used as the cutting path for the milling tool to follow.

In the attached file, I've imported some of the toolpaths that were generated by my V-Carving program, along with the characters they are derived from. The sample letter "F" has some Sweep surfaces around it, so it's possible to compare with proper V-Carving.

PS. Turn off Edges in my attached file to better see the comparison.
 

Martin.

Thanks for the tips, guys. Looks like I'll have to do some experimentation. It'll be fun to mess around with, anyway. I've had some luck breaking my complex shape into two curves and using them as two rails for a sweep. I'm not getting quite what you get with a router bit in a v carve, but it's similar in some ways. I think for me, the "cleanliness" of the model is more important than getting the same exact result as a v carve.

Martin, that's an interesting approach, to use the toolpaths in MoI. But I can't quite figure out how to trim the resulting surfaces. Any tips on getting the final result?

It's really a matter of splitting up the geometry so that separate fully intersecting surfaces are produced that are good candidates for Trimming with one another... it can and does get quite messy on screen, but is doable.

On the other hand, if all you really want to do is produce V-Carved shapes, then I would strongly suggest you buy CamBam and use the totally free and unrestricted V-Engrave plugin - it works a treat and CamBam is the most bang per buck of CAM software anywhere, anyway.

See here: http://www.cambam.co.uk/forum/index.php?topic=3513.0

 

Martin.

Here is a couple visuals of me fooling around with it...

I thought as Blowlamp and just used a Vcarving program to generate some gcode, then I converted the gcode to dxf and brought it into MoI. I could do a simple loft on the outer profiles of the toolpath and get the vcarve surface...



The second one is my "fake" vcarve. It's fake because the proper calculations for a vbit or specific tool, to rise and fall in the shape aren't attainable with my eye.. I just made a shape that looked kindof "vcarvy"... It does show the surface trimming thing that I think Blowlamp is referring to, though... I've attached a 3dm of the second method with the surface and the curves I used....



The file I posted is a little different than the video. The file has just a center morphed curve, rotated by "end" down to a depth. The 2 meet up, and are lofted and trimmed the same as the video...

MorphBetween2curve is a good trick ! ;)
http://moi3d.com/forum/index.php?webtag=MOI&msg=6373.1

Another file here.

In it, I swept the green curves around the magenta letters to make intersecting surfaces, which were then trimmed to leave those as shown.

The next step was to Copy & Paste the 'ridge' curves to make them into the orange curves placed at the surface intersections.

Finally, copies of the orange curves were mirrored below the surfaces to give the blue curves and it is these that can be used directly as toolpaths for an engraving style of machining operation.

If I'd modelled the surfaces to peak in the opposite Z direction it would have saved having to create and mirror the orange curves to get the blue ones, but I just find it a bit easier to do it this way.

Using a Tapered Extrude that trims at the peaks would be an easy & quick way for us to get the right shape, but this isn't possible due to the complexity of such a task.



Martin.