dr wogz
Fly caster
OK, let's go thru the process of designing a fin.
A fin is a fin is a fin..
I'm going to print a swept fin with 4 sides, pretty standard.
As mentioned in a previous 'tips & tricks' post, let's design our fin as we intend it to be: sticking up, not flat. (It's just better practice to pick a work plane that's more representative of the actual part & the part's interacting with the world.)
I intend to 'extrude' the overall fin shape. I'll start on either the front or right plane
and I start my sketch:
Once constrained / dimensioned I will extrude it to the thickness I want. Extruding will either go one way (up / towards us), or the other way (down / away from us). Or, we can extrude both ways equally from the work plane; split extrusion. This is preferable as it maintains the workplane thru the centre of the fin.
(While I have initially given a thickness of 0.125", I have made it 0.375" for the later examples)
Extruded 'front'. you can see the workplane it was built on..
You can see that the fin is both this side & that side of the work plane. The work plane is in the middle / center of the fin. This helps with other geometries we may want to add later, and when trying to assemble the fins.
We can stop here, as we have our fin. It's a simple flat geometry. But let's go a bit further!
What if we want a taper on the fin, that is, the tip is thinner than the root. Here we will remove material. We will draw some geometry and remove / cut instead of adding to the model.
You can see, I chose the next available workplane to put my sketch on. In this case, it' the front workplane. I've drawn two triangles to denote the material I want t remove. (I've used some reference lines to show the limits of the outer portions of the triangles. Since these references, or 'construction geometry', is linked to the outside surfaces of the part, that relation will always remain.) I've also made the two upper parts of the triangle equal, so the .063" dim will be centered due to geometric laws)
I then extrude this geometry 'thru all,' or some large distance to make sure I cut away what I want.
But that BIG wide base / root (its 3/8"!) won't nicely fit / glue to a tube, it needs a curved surface. Like we did for the taper, we will extrude a cut, a radius, to fit the intended 4" dia tube. We select the same work plane (front) and draw an arc constrained to the central workplane and the lower points of the fin. (the 2" show in the radius, not the diameter of the intended tube.)
We could have drawn this bit of geometry at the same time as the taper, but sometimes geometries that share the same points causes errors. Also, we should treat the taper as one feature and the curve as another feature, for editing purposes & overall simplicity.
Lastly, I like a rounded leading edge. The better programs will allow you to do a 'full round fillet' as opposed to just a fillet on an edge. You might have to do a tapered fillet per edge, but that math should be simple: half the root thickness & half the tip thickness.
(a fancy 3D line drawing of the fin. Sometimes a different view of the object makes it easier to see!)
And there's our fin! I would lay it so that the back / training edge in on the printer bed. Or as is stands, knowing I'll get some support material under the fin (and not so great adhesion to the printer bed..)
We could have made the leading edge a curve instead of a strait line..
We can now always go back and edit any feature of the fin, and the fin will change as needed. Be warned though, the full round leading edge my get lost do to changes to the previous parts of the geometry. but it should be simple enough to fix..
hope that helps!
A fin is a fin is a fin..
I'm going to print a swept fin with 4 sides, pretty standard.
As mentioned in a previous 'tips & tricks' post, let's design our fin as we intend it to be: sticking up, not flat. (It's just better practice to pick a work plane that's more representative of the actual part & the part's interacting with the world.)
I intend to 'extrude' the overall fin shape. I'll start on either the front or right plane
and I start my sketch:
Once constrained / dimensioned I will extrude it to the thickness I want. Extruding will either go one way (up / towards us), or the other way (down / away from us). Or, we can extrude both ways equally from the work plane; split extrusion. This is preferable as it maintains the workplane thru the centre of the fin.
(While I have initially given a thickness of 0.125", I have made it 0.375" for the later examples)
Extruded 'front'. you can see the workplane it was built on..
You can see that the fin is both this side & that side of the work plane. The work plane is in the middle / center of the fin. This helps with other geometries we may want to add later, and when trying to assemble the fins.
We can stop here, as we have our fin. It's a simple flat geometry. But let's go a bit further!
What if we want a taper on the fin, that is, the tip is thinner than the root. Here we will remove material. We will draw some geometry and remove / cut instead of adding to the model.
You can see, I chose the next available workplane to put my sketch on. In this case, it' the front workplane. I've drawn two triangles to denote the material I want t remove. (I've used some reference lines to show the limits of the outer portions of the triangles. Since these references, or 'construction geometry', is linked to the outside surfaces of the part, that relation will always remain.) I've also made the two upper parts of the triangle equal, so the .063" dim will be centered due to geometric laws)
I then extrude this geometry 'thru all,' or some large distance to make sure I cut away what I want.
But that BIG wide base / root (its 3/8"!) won't nicely fit / glue to a tube, it needs a curved surface. Like we did for the taper, we will extrude a cut, a radius, to fit the intended 4" dia tube. We select the same work plane (front) and draw an arc constrained to the central workplane and the lower points of the fin. (the 2" show in the radius, not the diameter of the intended tube.)
We could have drawn this bit of geometry at the same time as the taper, but sometimes geometries that share the same points causes errors. Also, we should treat the taper as one feature and the curve as another feature, for editing purposes & overall simplicity.
Lastly, I like a rounded leading edge. The better programs will allow you to do a 'full round fillet' as opposed to just a fillet on an edge. You might have to do a tapered fillet per edge, but that math should be simple: half the root thickness & half the tip thickness.
(a fancy 3D line drawing of the fin. Sometimes a different view of the object makes it easier to see!)
And there's our fin! I would lay it so that the back / training edge in on the printer bed. Or as is stands, knowing I'll get some support material under the fin (and not so great adhesion to the printer bed..)
We could have made the leading edge a curve instead of a strait line..
We can now always go back and edit any feature of the fin, and the fin will change as needed. Be warned though, the full round leading edge my get lost do to changes to the previous parts of the geometry. but it should be simple enough to fix..
hope that helps!
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