creating an helicoidal slot around a cylinder

[helio_teixeira]

I'm trying represent an helicoidal slot, done by a endmill, in a cylinder's face. I can't achieve this because when i try to extrude (also i don't know what polygon to extrude) around an helix, the form starts to rotate and does not end the way it started. Its a round mill(perpendicular to the cylinder's surface) that moves around the cylinder axis while it turns, milling a slot in its surface.I've already done the helix that represents the real path of the mill around the cylinder. First i want to make the "spiral solid" representing the slot and then subtract it from the cylinder. I can't do it cause i dont figure the polygon neither can extrude a simple example rectangle around the path.
I'd really apreciate some help. this is for a university work[/img]

[Flores]

What you're trying to do isn't possible in vanilla ACAD using solids, unless someone is able to make a custom AutoLISP routine. Whenever you extrude a polyline using a helix as a path, it rotates about the axis and twists. One option would be to create the slot-helix cut-out using mesh, and then use the mesh2solid routine (m2s?). But sometimes that routine doesn't create smooth edges.
Fucarro did a routine similar to what you need, but you need to do a search for it because I don't think it's in the LISP archive. I won't tell you that you can simply do what you want with a dialog box in Mechanical Desktop, or I wont tell you that it can be done in Solidworks. :)

Flores

[Flores]

Give "Spirex" a try, but read the instructions carefully:
http://www.cadtutor.net/forum/viewtopic.php?t=477

Flores

[David Bethel]

I must admit, I'm a little lost as to what you are trying model. A picture can be worth a thousand words. -David

http://www.davidbethel.com/0-talkg/-sprl.jpg

[Flores]

Open "Design Variables"

2" Diameter (cylinder)
4" Long (cylinder
1/8" slot depth
3/8" slot diameter
4 revolutions
1" pitch
http://www.cadimage.net/postimages/DesignVar1.jpg

You have:
http://www.cadimage.net/postimages/Helix1.jpg

Open "Design Variables" and change slot perimeters:
3/8" slot depth
1/2" slot diameter
2 revolutions
2" pitch
http://www.cadimage.net/postimages/DesignVar2.jpg

Now you have:
http://www.cadimage.net/postimages/Helix2.jpg

May take you a whole 25 seconds to change the perimeters :D

Sorry, couldn't resist.
Flores

[helio_teixeira]

Give "Spirex" a try, but read the instructions carefully:
http://www.cadtutor.net/forum/viewtopic.php?t=477

Flores

Many thanks to ya all. But the spirex lisp does not have the option to change or configure the flatness.. :? i tried to rotate the form but it changes the diameter ... Acad is a big problem isn't it?
any help please...you know exactly what i want..

[Flores]

... Acad is a big problem isn't it?
any help please...you know exactly what i want..
Sadly, the solids and solids-editing tools have not been improved since r2000. They continue to add tools and try to improve ACAD, but they choose to ignore the solids department.
I believe they added the "solids editing" tools in r2000, which I don't think r14 had. Please correct me if I'm wrong, but I don't thing even ACAD 2004 has any improvements in the solids area. Maybe they believe that if you want more solids "creating" and "editing" tools, you need to buy the inventor series. Not a month goes by on an ACAD related forum that someone asks how to create a helix of some sort with ACAD, and there still isn't a fool-proof way to make them in vanilla ACAD.

Flores

[fuccaro]

Helio_teixeira
Before the use of the Spirex program you can stretch the rectangle in the opposite direction to compensate the "flatness".