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October 20, 2017, 11:33:35 am


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Author Topic: roughing around a 3D polyline  (Read 1094 times)
lloydsp
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« on: May 08, 2017, 19:54:41 pm »

I have an instance where I have a nice 3D polyline (for milling a positive hemisphere).  

It works as-is, even though the bit must cut along its full depth at depth.  But it works.

I have never explored this, so I'm just "in the dark".  Is there a simple script or method to do depth-incremental roughing out to a boundary shape around a 3D poly?

I should clarify a bit.  This 3D line is a spiraling toolpath that when followed by a ball-nose bit, causes a positive hemisphere to be milled.  As it gets further-out toward the outer diameter of the sphere, it -of needs- cuts deeper into the sidewalls of the un-cut material outside the hemi's periphery.

What I'd like to do is use the spiral line as the 'inside boundary' and an outside Z=0 boundary shape as the limits of an incremental roughing pass, so the ball-nose bit doesn't have to do really-deep side-cutting.

When I get done, I'll pass it on.  This is an offshoot of the work I did with the French group a couple of years ago.  Then, it was negative hemis (hemispherical pockets).  Now, because they're 'positive hemis', there's a LOT more stock to clear away.

Thanks,
Lloyd
« Last Edit: May 08, 2017, 20:00:11 pm by lloydsp » Logged

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Bubba
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« Reply #1 on: May 08, 2017, 20:55:13 pm »

 Is there a simple script or method to do depth-incremental roughing out to a boundary shape around a 3D poly?
****************
Never done this, so I follow this link closely. Solid can be done by means of clipping in Z. This one.. no idea. Wink
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EddyCurrent
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« Reply #2 on: May 08, 2017, 21:19:07 pm »

Does this plugin do it ?

http://www.atelier-des-fougeres.fr/Cambam/Aide/Plugins/Spiral2helix.html
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Dragonfly
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« Reply #3 on: May 08, 2017, 21:33:47 pm »

Wouldn't  a 'side profile' -> 'convex' with a radius to leave a reasonable amount of material do? There is an option to cut the excess material so that after finishing the outer contour will be a cylinder and a rough hemisphere inside.
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lloydsp
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« Reply #4 on: May 08, 2017, 22:23:15 pm »

Eddy, that's a 'negative' curve, and I already have a routine that does a really nice job on that.

What I need is a 'roughing routine' to work out all the excess stock around a positive hemisphere BEFORE the actual profiling operation.

Fly... that may be just the ticket.  I'll explore it.  Thanks.

Lloyd
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EddyCurrent
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« Reply #5 on: May 08, 2017, 23:49:53 pm »

Use this plugin; http://www.atelier-des-fougeres.fr/Cambam/Aide/Plugins/RevolveExtrude.html
to draw a surface that fits over your positive hemisphere, then use a Waterline 3D MOP on it to remove the waste.
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lloydsp
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« Reply #6 on: May 09, 2017, 01:29:49 am »

Thanks, Eddy.

'Took a while to realize what was happening with the arc I tried to use.  But I got it licked. 

That'll work!

Lloyd

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dh42
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« Reply #7 on: May 09, 2017, 02:27:05 am »

Hello

Something like this ?

I draw the dome with this plugin
http://www.atelier-des-fougeres.fr/Cambam/Aide/Plugins/Solids.html

++
David

* dome_rough.cb (127.18 KB - downloaded 21 times.)
« Last Edit: May 09, 2017, 02:29:29 am by dh42 » Logged
lloydsp
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« Reply #8 on: May 09, 2017, 02:34:01 am »

No, actually, David.

(because there are no drawing primitives in that file! <grin>)

But I was able to draw the solid surface and do a waterline rough much as you had done there, using Eddy's revolve routine.

Lloyd
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dh42
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« Reply #9 on: May 09, 2017, 05:05:35 am »

Quote
(because there are no drawing primitives in that file! <grin>)

Ah, yes, you need the plugin to see it, I forgot to convert the sphere to surface.  Roll Eyes

++
David

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lloydsp
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« Reply #10 on: May 09, 2017, 19:13:54 pm »

Eddy,
The whole process worked admirably well.  I can now do both negative and positive hemisphere cuts with roughing as necessary.

Right now, I'm just generating the 3D solid for roughing by manually running your plugin, then incorporating that solid into my file.

With your permission (and also as soon as I can understand your code, because I'm not a "sharp" guy<grin>), I'd like to excerpt and translate to VBS parts of your code in my script, so that it will generate the solid automatically.

I will, of course, include credits to you for those portions of code that were 'translated' from yours.

Thanks,
Lloyd
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lloydsp
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« Reply #11 on: May 26, 2017, 18:17:06 pm »

UPDATE... duh!  I had an error in my drawing.  It just wasn't 'apparent' to me, because I nearly always work in 2.5D.
--------------------
Sorry... I put the wrong file on... corrected.
Also... When I said 'flattened', I didn't mean at the apex. but rather that the first few passes cut deeper into the hemi than I want them to.

------------
Ok... Eddy, I'm suffering from some sort of "mental block".

I experimentally laid out a curve that 'works' to give me the roughing profile I want.  But it was by trial-and-error, and I just can't seem to wrap my head around what's actually happening!  HELP!

Here's the deal... I've got a 2.5" D hemisphere I want to rough (out to a boundary line) using a 0.5" endmill.

It works fine using 3D waterline roughing, but I have to make the 'hemisphere' solid oblate... higher by 0.125" than it's nominal radius, or the waterline rough operation cuts deeper than it should, and I don't get a hemi -- I get a 'flattened' hemi, shorter in Z than it should be.

0.125" has NO 'trigonometric' relationship to the toolpath, so I cannot seem to figure out why the rouging op wouldn't work with a proper 'spherical' hemi, instead of one taller than its nominal radius.

I guess I'm just in brain-freeze here, but I cannot see the relationships.  Can someone (Eddy, since you suggested the method?) explain why/how/what the heck is going on?

Thanks, guys.  I don't normally mentally lock-up like this, but I'm at my wits' end right now.  Why won't waterline rough work with a proper hemi solid?

Lloyd

* positive-Hemi-test-example.cb (538.31 KB - downloaded 13 times.)
« Last Edit: May 26, 2017, 19:06:21 pm by lloydsp » Logged

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dh42
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« Reply #12 on: May 26, 2017, 19:01:14 pm »

Hello Lloyd

Quote
Here's the deal... I've got a 2.5" D hemisphere I want to rough (out to a boundary line) using a 0.5" endmill.

I don't understand the pb, but the MOP in your file is not a WL roughing but a WL finish, and the tool is not set to Endmill

Have a look on this file

++
David

* positive-Hemi-test-DH.cb (284.87 KB - downloaded 14 times.)
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lloydsp
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« Reply #13 on: May 26, 2017, 19:05:09 pm »

Yeah.  I corrected the file.  I put the wrong one there.

BUT... 'never mind'... <grin>

I think I found my block!  It was a drawing error!

Lloyd
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dh42
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« Reply #14 on: May 26, 2017, 19:05:57 pm »

change list  Wink

- I add a roughing clearance to the roughing mop and also increase boudaries (if not the tool don't go uo to the bottom of the 3D model) I aslo set it to WL rough.

- I add 2 WL finish mop ; one is designed to do only the top with a small depth inc to avoid flat top.

- also I change resolution for the finish mop to increase precision.
 
- on all mop, I set the clearance plane higher (It was = to stock surface)

++
David
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