Used helix, and then flow, to create a toroidally square wrapped core.

Another way was with the toroidal helix script.

Great job bemfarmer!

That's a great use of MoI's Flow tool.


It sure beats the old fashioned way:




I had to do this one by hand. ;-)

how do you get the helix to wrap in a square way around the straight beam?
tnx
wim

The helix is used to find 6 intersection points of the corners of the square extrusion, for one wire turn.
The radius of the corner of the working square needs to be enlarged from the ferrite measurement, by the amount of the wire radius.
Then did a polyline connecting the 5 points of one coil (Plus extra line to point six for the fillet by the 5th point). The helix is deleted.
Then did fillet radius.
Also moved one tiny fillet radius from the end to the beginning of the one turn of the wire.
Just did one turn of the coil, then used Transform Array Dir, to copy to the straight square extrusion for the solenoid.
Also did a fillet on the original smaller square, at the same radius. So there may be a slight gap between the ferrite corners and the wire.

So there was a whole lot of fiddling to do :-) , but good moi practice.

Unwrap was used on the center radius of the ferrite core to get the proper length for Flow.

tnx Bemfarmer, I get it now! I thought I missed a function or script that could shrink a helix to an inner shape ;-)

wim

Well, glad you brought that up.
Tried Construct Curve Project on a helix, to a rounded, extruded square, and guess what
happened?
It worked, when the extrusion extended beyond the ends of the helix. !

(I also had a problem with MoI, or my computer, see next post...)

Question for Michael:
Just experienced a problem trying to place a point, or a line, when there is both a helix,
and a square inside it, in a end view. There is a two second delay in placing the point.
Seems to involve Object Snap.
I don't think it is my computer...
Tried it in Moi2, and older beta3, same thing happens.
I guess the object snap is operating in 3d on a 2d image?

I was able to create one single turn on the surface of an extrusion of a rounded-corner-square that was Rebuilt to have only one seam (using "closest-point" setting), you could then array/copy that.

I also noted some kind of lag when moving the helix in Top view... could be unrelated.

Hi Brian,

> Just experienced a problem trying to place a point, or a line, when there is both a helix,
> and a square inside it, in a end view. There is a two second delay in placing the point.

That's due to intersection object snap trying to process the projected 2D intersection of the helix, it's a complex case since a projected helix is a highly self overlapping curve.

If you turn off projected intersection snap that delay should go away, more info here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3699.2

That's on my todo list to try and figure out some way of not attempting an projected intersection on something similar to that, or to make some way to limit how long it tries to calculate the intersection.

- Michael

Thank you Michael. Its not really much of a problem, just had not come across it before.

Due to uncertainty of what half-width and fillet radius to use for the rounded square used for the sweep rail, did a sketch of the various parameters:

Given a FerriteCrossSection half-width,
and given a FerriteFillet, (less than or equal to the half-width),
and given a RadiusOfWire , (which is relatively small):

The half-width of the Square to Sweep can be calculated,
as well as it's Fillet.

Edit: redid the sketch, due to inconsistent names.

Deleted, projection of helix onto extruded rectangle, did not produce a straight line.

Was able to use Flow to project a one turn helix onto an extruded rounded rectangle,
without squiggly lines.

The object to flow is the helix.
The base surface is a cylinder extruded from a circle.
The target is the extruded rounded rectangle, the same height as the cylinder.

The circumference of the circle DOES NOT need to equal the perimeter of the rounded square.

The radius of the helix must equal the radius of the circle.

Swept a small rectangle to represent the wire.




Can this be Generalized to make a radial projection command?

Hi Brian, re: radial projection method, what about the "fin construction" method as shown by Danny here:

http://moi3d.com/forum/index.php?webtag=MOI&msg=4084.3
http://moi3d.com/forum/index.php?webtag=MOI&msg=3530.2

That's where you sweep a line along your helix (with Twist : flat option set) to build the fin surface and then use Construct > Curve > Isect to generate an intersection curve between the fin and the rounded rectangle.

Although I guess now that I try that it's maybe not what you want, the intersection along the longer sides will be a little wavy since the object does not have radial symmetry.

So possibly an exact radial projection is not really what you want here?

- Michael

Thank you Michael.
Did the "fin construction" method yesterday, and the long sides were a bit wiggly.
I'll have to try it with a different helix radius...maybe there is one which will "match"?

The flow method seemed to yield straight sides, not sure about the corner radius.

Hi Brian, I think the fin method is equivalent to a "radial projection", but a radial type projection probably isn't what you really want. With a radial projection things that are further away from the radial axis are traversing a longer distance than things close to the radial axis, and so on a shape like your rounded rectangle that is not symmetrical around the axis and has some portions further away and some closer to the radial axis it will yield that curved result that you don't want.

Flow is probably more what you want, since that can map an elevation onto a path just based on distance traveled along the path.

- Michael

Thank you for the explainations and clarifications.

"based on distance traveled along the path" makes sense.

So in Flow, the cylindrical (extruded_circle) base surface maps onto the rounded square extrused target surface, for the distance traveled, scaling up or down as
needed, causing a similar scaling of the helix...

Got to try some different target surfaces...

Hi Brian, actually I had thought that you were using curve-to-curve flow.

Surface to surface flow is done by mapping "position in UV space" from one surface to another, it does not necessarily map from distance to distance because UV space is not necessarily uniformly distributed, a squishy surface can be narrow across in one area but wider in a different area of the same surface.

If you are dealing with extrusions then that's a particular case where they are uniform, but also if you're dealing with extrusions using curve-to-curve flow should just be easier in general.

Check out here for an example of using curve-to-curve flow for this sort of "height mapping" from one 2D profile onto a bendy curve:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4785.13


Or here's another example - here is an angled line with a base line under neath it:



Select that angled line, it's the one you want to remap onto the bendy curve. Run Transform > Deform > Flow, select the base line underneath it as the base curve, and the bendy curve as the target curve and then you'll get a result like this:




Initially the curve will occupy the same length of the target curve as the length of the base line. You can enable the "Stretch" option (which I did here) to make the result stretch across the full length of the target curve.

But curve to curve flow works by traveling across curves by distance traveled along the curve, surface-to-surface flow uses the UV parameter space of the surface which can be compressed or expanded in different zones of the surface and so if you want to do stuff that maintains distances the curve-to-curve flow may be better.

- Michael

Here's another example - basically any pattern that is easy to draw in 2D can be put onto a curve this way. Just an angled line will work for a ramp like result that just gains height as it marches along the curve but other patterns like this will work with the same thing as well:





- Michael

Thank you Michael.
Using curve to curve flow is much easier.

Having trouble with flow getting the start of the square helix to begin at the beginning of
the red helix. Tried rotating the circle multiple times to adjust the start position.

Is there a script to find the start of a circle, other than by extruding it ? :-)

Also for several days, when typing these forum messages, my arrow keys do not cause a visible movement
of the vertical bar cursor. The arrow keys do cause the cursor to move, invisibly. The cursor does not show up in its
correct position until another character is typed. ?

(The arrow keys work fine in notepad or onenote)