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From: cadguru on 18 Nov 2005 03:56
James,

What you are trying to do is actually more complex than one would think.

There are multiple ways to create the slot with actual machine tools. The
most common misconception is that you can just plunge the tool in and then
rotate the part about Y for instance while traversing in X. This will
create a slot with the requested width, pitch and max depth, however the
slot will
be shallower at the side walls due to the undercut created by the diameter
of the tool. The correct way to create such a slot is to use a small tool
(roughly 25% of the slot diameter) and perform a pocketing routine using the
slot outline as your boundary. The easiest way I have found to create this
is to model the slot in 2D then wrap the profile using Y axis substitution
to control the Y rotation. (in mastercam not SolidWorks)

That said, the second method of creating the slot on an actual machine takes
longer than the first to program (not too much though) so we calculate the
undercut for a given tool diameter and pitch then select the appropriate
depth to compensate for that undercut. Then we create the helical blind
slot the easy way as is modeled in the SolidWorks Part below.

You can also make sure your CAM that follows the slot has a generous enough
radius that the undercut doesn't matter.

I have inserted a link below to the part for you to look at in SW2006 SP0

Cadguru

http://home.comcast.net/~productcreationstudio/Simple_Machined_Spiral_Slot.SLDPRT



"james" <kevlar9296(a)aol.com> wrote in message
news:1132283828.054296.206290(a)g49g2000cwa.googlegroups.com...
>I am attempting to model a helical cut on a shaft.
>
> That is, a cut like the spiral that you see on a barbershop pole. But
> rather than just a painted red stripe, I want a groove that's the width
> of the stripe, and cuts into the cylinder. An example would be a 1/2"
> diameter cylinder, with a 1/16" endmill helical cut going around it,
> just like the barbershop stripe.
>
> I am coming to the conclusion that it is not an easy thing to do at
> all.
>
> Has anyone accurately modeled a helical cut on a shaft?
>
> I now believe it's not as simple as sweeping a rectangular cross
> section. This seems right, until I try to model the entry and exit
> points of the endmill. These entry and exit points clearly show
> there's a problem.
>
> I've tried making the sweeping cross section be tangent to the path of
> the helix, and all seems well until modeling the "start" and "end"
> positions of the endmill. If they walk off the ends of the barbershop
> pole, the error isn't noticable. But if you try to start and end while
> still on the barbershop pole, the error is obvious.
>
> Pretty interesting stuff, and frustrating!!!
>
> I read some old posts on a mechanical desktop or something or other
> forum, and people were claiming it's not quite possible to do. I'm
> beginning to agree with them.
>


From: james on 18 Nov 2005 12:29
Thanks for the tips guys.

Cadguru, thanks for posting the part. However, my SW2006 is still
sitting in its pretty little box on the shelf. None of my clients have
upgraded yet. I'd love to, but until at least one of my clients do, I
probably won't.

I agree with Jeff Howard - what the machinist probably really wants is
the centerline of the endmill cutting the helix. The rest is sort of
for looks.

For the function of the part, I need to have a pin follow the helical
path. I know if a 1/16" end mill could do it, that a slightly
undersized pin will follow the groove. So really, the rest is just for
looks in my case.

From: WT on 18 Nov 2005 13:05
You don't have to upgrade to 2006 - just load it as a new installation.
That way you can have both. I install each version in its own folder
such as C:\Program Files\SolidWorks2006 and the same thing with the
common files. However, I don't have toolbox, so there may be an issue
there. Someone that does, please chime in here.

WT

From: james on 18 Nov 2005 13:11
Yeah, I'm sure I'll end up using both simultaneously, but I'm not
looking forward to it.

"Ooops, I opened the SW2005 client's files in SW2006...". I'm dreading
the day I do that. The longer I postopone installing 2006 as a second
installation, the longer I'm safe from that happening.

It's frustrating though, because I'd really like to start playing with
it!

From: cadguru on 18 Nov 2005 17:39
Here is a link to the part you can open in 2005. It is featureless, but
shows the actual geometry created by the tool in this type of cut path.

Cadguru

http://home.comcast.net/~productcreationstudio/Simple_Machined_Spiral_Slot.x_t

r-click save target as. Then open with SolidWorks 2000-2006




"james" <kevlar9296(a)aol.com> wrote in message
news:1132334982.624396.290770(a)o13g2000cwo.googlegroups.com...
> Thanks for the tips guys.
>
> Cadguru, thanks for posting the part. However, my SW2006 is still
> sitting in its pretty little box on the shelf. None of my clients have
> upgraded yet. I'd love to, but until at least one of my clients do, I
> probably won't.
>
> I agree with Jeff Howard - what the machinist probably really wants is
> the centerline of the endmill cutting the helix. The rest is sort of
> for looks.
>
> For the function of the part, I need to have a pin follow the helical
> path. I know if a 1/16" end mill could do it, that a slightly
> undersized pin will follow the groove. So really, the rest is just for
> looks in my case.
>


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