2D fillets and CNC

fredo6

Fredo - are you adding this to your Bezier Spline plugin?

One thing though, the behaviour would depend if the edges that make up the corner is an inner or outer loop. I'd think you'd need to have the base shape - as a face first. In order to determine this.

Tom,

You are right. My initial idea was to integrate it as an extension of BezierSpline, which is the quick path.
However, the T-Bone is not symetrical and the question of inner vs outer is very relevant.

So maybe it's not a good idea.

Fredo

thomthom

I was looking briefly at it yesterday. My initial idea was letting the user pick Face Loops - like my Select Edge Loop tool in Selection Toys. you can click on an edge and it's use that loop, or pick a face where it'd take all loops.

Only thing which had me puzzled was - how to determine the offset of a point to go into the face?

Also - it's now the question to if outland86 want to pick each corner one by one.

Dog-bones are easy to determine, but with T-bones, you have two possible outcomes. What should determine this? the user pick each point and indicate direction. Or user pick loops and indicate which direction the tool would take around the loop and keep all T-Bone fillets going in the same direction.

Dave R

Considering the application in outland86's original request, these cuts would only be used on the outside of a corner. Think of the rectangular tab that needs to be inserted in the hole. That's the reason for the relief cuts in the first place. I think if you selected the inner face of the rectangle, ran the tool, entered the diameter of the cutter and hit Enter. It would be enough. Perhaps there would be two menu entries. One for Dogbone and one for T-Bone In the case of the T-bone, I think you'd either settle on a convention or extending the short side of the rectangle or you'd have to choose the correct side.

thomthom

I was thinking of that - but surely, there must be a way to calculate this without going through the overhead of testing points.

My idea - which I haven't tested, was using the angle of the corner (returned by .angle_between, using the normal of each edge segment) and determine if it needs to be rotated left or right depending on the direction of the edges on the face. As I understand, edges normally run counter-clockwise around a face, unless they are reversed. Which I'd then think could be used to determine if you should rotate left/right.

thomthom

@dave r said:

I think if you selected the inner face of the rectangle, ran the tool, entered the diameter of the cutter and hit Enter. It would be enough. Perhaps there would be two menu entries. One for Dogbone and one for T-Bone In the case of the T-bone, I think you'd either settle on a convention or extending the short side of the rectangle or you'd have to choose the correct side.

"Outside" would depend if your on the outer loop of a face, or on a inner loop (a hole).

@dave r said:

Considering the application in outland86's original request, these cuts would only be used on the outside of a corner.

But what if the shape isn't a simple rectangle? That was just the example given.

TIG

@thomthom said:

I was looking briefly at it yesterday. My initial idea was letting the user pick Face Loops - like my Select Edge Loop tool in Selection Toys. you can click on an edge and it's use that loop, or pick a face where it'd take all loops.

Only thing which had me puzzled was - how to determine the offset of a point to go into the face?

Also - it's now the question to if outland86 want to pick each corner one by one.

Dog-bones are easy to determine, but with T-bones, you have two possible outcomes. What should determine this? the user pick each point and indicate direction. Or user pick loops and indicate which direction the tool would take around the loop and keep all T-Bone fillets going in the same direction.

RickW wrote an extra offset.rb method that's very useful.
To see which side of an edge a face is yo can offset the vertex_point a tiny amount by a +small_degree vector [use face.normal for rotation] and use a face.classify_point test to see if the point is on the face, if it's not the the face is on the other side of the edge...

TIG

If you are picking each point then only corners <180 degrees need the extra arc-hole, so place it on the smaller angle formed by the edges?

thomthom

.angle_between doesn't give a result in a 360 direction. Only 180. If you get a result of 15 degrees - it could be in either left or right direction. That's why it's a little bit more complicated.

TIG

@thomthom said:

.angle_between doesn't give a result in a 360 direction. Only 180. If you get a result of 15 degrees - it could be in either left or right direction. That's why it's a little bit more complicated.

Get a 'cross' of the normal and edge vectors and if it's '-ve' you can make 180 adjustment?

thomthom

Cross of the face's normal and the edge normal? If it's '-ve' - what does that mean?

TIG

Sorry- I was too quickly typing that up - I had to go somewhere urgently...
If you take the vectors of the two edges 'outwards' from the vertex.position you can then get the angle_between them.
The angle will always be returned as <=180 degrees - even if it's really >.
If you use edge_vector.cross(face.normal) you get +/-ve values in the result.
You can then 'cross' these together.
Getting the cross value returns different results depending on whether the angle is <180 or not - I think it will be 0,0,0 if it's <=180degrees ?
By noting the appropriate value of the z (?) you can add 180 to the angle if it's found to be needed when z != 0 [-ve?]...
You'll need to check the way these values change - unfortunately I haven't go access to my 'code-snippets' right now...
Sorry for the bad explanation - but it is possible to test for angles >180 this way - I have done it...

outland86

Hello again and thanks for all the input
to better illustrate what the needs are for this plugin i have drawn a picture of the typical use of these fillets in a bit of sheet material say 3/8 inch MDF
while T bones would be good they are not critical .
however the dogbone type fillets are as you can see. t bones are just another way to get the same result.
when i drew this i noticed that the weld and trim comands were different for the inside square and the outside trims just thought i would note that..as the mathe must be different for both?
the options shown in the picture would be typical of the actual uses. i have uses a larger arc for this drawing but in real life the arc would be usually say 1/4 inch if cutting 3/8 thickness sheet material say plywood or MDF. i hope this better shows what i am trying to achieve..some of the projetcs i have in mind have hundreds of parts so doing it all by hand with circles etc would be a nightmare hence the need for a plugin to help automate this process. if you imagine when drawing if a guy or gal enter a radius then could point to the coner intersection of a square or inside corner then click and it would be selected then click again and presto a fillet appears one would be in CNC heaven

thomthom

That works for edges on any plane in 3D space?

thomthom

outland86: do you need control over each corner? or would it be ok to just click a face and have the script process all the corners?

TIG

@thomthom said:

That works for edges on any plane in 3D space?

I used face.normal since these edges will have faces, BUT you could also use a plane defined by the picked vertex.position and the two edges' other_vertex.positions [plane=Geom.fit_plane_to_points(p1,p2,p3)] and then get the plane's normal=[plane[0],plane[1],plane[2]] ???
Unfortunately this is all from memory...

thomthom

think I got it working... hmm.... but I don't have much more time today to test this.

outland86

Hi all

to answer your question you do not need control over the parameters other than setting the tool radius before you start

so it would be the same every time

outland86

hey it would be perfect to have both options to process all and also indervidual corners
can this be done?

fredo6

@outland86 said:

hey it would be perfect to have both options to process all and also indervidual corners
can this be done?

I included a DogBone extension in BezierSpline.
This allows to create directly dogbone when drawing a polyline, or to convert an existing contour. You can further change the radius.

So it is not a point and click, and more oriented to handle contours.

It is advised to install first the new upgrade BezierSpline 1.3, because it now converts a sequence of edges without having to weld them as a curve beforehands.

Here is a short video
[flash=425,344:2aed5ook]http://www.youtube.com/v/GN6xmiYRi7E&hl=fr_FR&fs=1[/flash:2aed5ook]

For BezierSpline 1.3, see http://forums.sketchucation.com/viewtopic.php?f=323&t=13563&p=100509#p100509

Fredo

outland86

thanks for your help so much
i did notice that when you apply the dog bone or t bone to a set of poly lines it made them
at every single intersection of polylines which is not what is needed only on the inside corners is it needed as that is where the cutting tool raduis is a problem for getting fits
the cutting tool can make sharp outside corners no problem .
if you take a look at the picture i uploaded you can see which places need dog or t bones in them and which do not
is there way to make the script only apply the t or dog bones to inside corners of a drawing as shown in my picture
i hope this makes sense?

and thanks again for all your help