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January 18, 2019, 04:28:33 am


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Author Topic: Non Planar Parting Line  (Read 378 times)
Bob La Londe
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« on: January 10, 2019, 16:10:50 pm »

I asked about this before, but I may not have phrased it as well as I would have liked. 

When there is no possible parting line that does not create undercuts its not practical to machine a mold on a 3 axis machine.  Even if the material is flexible enough to be demolded.  Orienting to machine using 4th axis is tricky at best.  Of course you don't have to actually have a 4th axis.  You just have to have a way to accurately reorient the work piece.  I've done this before by suspending a work piece between two spindexers.  It works. 

An alternative solutions in many cases would be to create a nonplanar parting like.  Usually I would be starting with an organic solid model.  A posed human form would be as good of an example as any.  I can convert that to a water tight STL and use the silhouette function in CamBam, but that just creates planar cross section lines.  Its a useful tool, but its not a true sillhouette and it doesn't work for creating a non planar parting line. 

Another perhaps useful tool is project lines to surface.  You might be able to project an array of "scan lines" onto the surfce and then manually go thru the resulting poly lines to find the maximum extreme + & - X/Y dimensions.  Then delete all points in the list beyond after/before that point.  Even for just a few scan lines the process would be laborious and time consuming.  It would also be limited to whatever resoluton you picked for your array of initial lines.  To finish up you would need to repeat the process in an oppose direction to the first set of lines.  Now you would have a set of lines with end points that would approximate the nonplanar parting line you seek.  One answer might be to then tediously draw a polyline from end point to end point point along the ends of the existing projected and truncated lines.  You would than have a 3 dimensional polyline that approximates the parting line you are after.  I'm not sure I am ready to invest the time into that sort of process. 

Project scan lines sounds like it might work, but I see a couple issues.  First thing is this is a huge amount of manual up close detailed work.  I can see it taking from hours to days.  Second is how do you use that to create the 3 dimensional profile cut you need?

Just thinking out loud so to speak.  I have some things to test now, but I can't think my way past the huge amount of manual brute force and repetitive work required to even try this. 
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EddyCurrent
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« Reply #1 on: January 10, 2019, 18:17:18 pm »

Does this Rhino video show the feature you are talking about ? https://www.youtube.com/watch?v=lN0FB9zjM9M

I don't know if ViaCAD will do that.
« Last Edit: January 10, 2019, 18:32:27 pm by EddyCurrent » Logged
Garyhlucas
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« Reply #2 on: January 10, 2019, 18:54:03 pm »

Rhino can do this, but not as easily as SolidWorks or SolidEdge. This is getting to where those programs earn their keep. Rhino is a really great tool to have. It is the swiss army knife of 3d. Even if you have those other programs you’ll find it useful. I use it all the time to defeature part models from vendors.
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Bob La Londe
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« Reply #3 on: January 10, 2019, 19:46:33 pm »

Not even close.  That's just using surfaces to split solids.  Yes.  ViaCad can do that.  Not even much differently.  

A parting line is the seam where two or more parts of a mold meet each other.  Idealy with a two part mold both halves will meet with the cavity divided between the two halves at exactly the maximum extreme X&Y dimensions.  With many "simple" molds this is done such that the parting line is all at Z=0.  However with many shapes there is no plane in existence such that all maximum dimensions are on the same plane.  It would be beneficial to be able to FIND a polyline such that all of its control points are located accurately in 3 dimensions at the exact maximum (+/- both) of X&Y and the Z dimension at which that X&Y dimensions is located in 3D Cartesian space.  







« Last Edit: January 10, 2019, 20:29:00 pm by Bob La Londe » Logged

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EddyCurrent
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« Reply #4 on: January 11, 2019, 14:32:20 pm »

In that case try the attached plugin. It appears in the Plugin menu as "NonPlanarSilhouette"

I've attached David's "venus" as a sample cb file.

Select the surface then run the plugin.

Works in 0.9.8 and 1.0 but seems to work better in CamBam 0.9.8  Huh

Edit: version 2 attached later in this thread.

* venus_cb_file.zip (1265.04 KB - downloaded 21 times.)
« Last Edit: January 14, 2019, 15:57:20 pm by EddyCurrent » Logged
lloydsp
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« Reply #5 on: January 11, 2019, 15:01:22 pm »

Man!  Eddy, you are FAST!

Lloyd
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EddyCurrent
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« Reply #6 on: January 11, 2019, 15:04:46 pm »

No, it's just that I join bits of other plugins together to make a new one  Cheesy
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Bob La Londe
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« Reply #7 on: January 11, 2019, 17:11:29 pm »

In that case try the attached plugin. It appears in the Plugin menu as "NonPlanarSilhouette"

I've attached David's "venus" as a sample cb file.

Select the surface then run the plugin.

Works in 0.9.8 and 1.0 but seems to work better in CamBam 0.9.8  Huh

Wow!  Thank you EC.  I am swamped today, but I hope to test this later today or over the weekend.  I'd test it right now, but this computer no longer seems to handle CamBam very well.  I'll have to wait until I am in the office. 
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Bob La Londe
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« Reply #8 on: January 11, 2019, 22:41:50 pm »

I've got a pretty fast computer for my design computer so that may be a factor, but it seems to work just fine in 1.0 for me.  The polylines look a little blocky in some places, but that may be a display resolution issue.  I exported it as a DXF and imported it into ViaCad where it looks much smoother.  I have the display resolution cranked up in my VC settings.  I don't have 098 installed on this machine to compare to, but it looks ok.  

To be honest when I posted I didn't expect to get an answer at all, much less so quickly.  Now that I have this tool I have to figure out the next step.  LOL.  Maybe one of the extrude mesh tools will create a surface I can machine to.  Time to play a bit. 
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Bob La Londe
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« Reply #9 on: January 11, 2019, 22:44:49 pm »

David,  We should definitely move this to the Plug-Ins board. 

Wow! Eddy.  That's an incredible tool, and surprisingly quick.  I don't mean just you, but the plugin is faster than I would have expected.   


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EddyCurrent
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« Reply #10 on: January 11, 2019, 22:51:25 pm »

It just uses methods supplied by Andy.
Create a normal silhouette then ray trace from each point up to the surface until it intersects and that's the Z position.
Now draw a new polyline with the original X,Y and the found Z coordinates, also include bulge from the original silhouette line segments.

As you say, what happens next  Cheesy
« Last Edit: January 11, 2019, 22:54:10 pm by EddyCurrent » Logged
Bob La Londe
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« Reply #11 on: January 12, 2019, 17:16:58 pm »

One of the things I recall being discussed for 1.0.x was an option for 3D Profile MOPs like the Engrave MOP.  That would allow for the parting line non-planer surface to be machined maybe.  I suspect the math for the program would be quite complex. 

I already tried using a rail surface tool with the poly line in ViaCad.  No dice.  It produced only a smaller portion of the surface.  I might be able to break up the polyline and produce the surface one section at a time I suppose.  Seems like I am still faced with a lot of brute force work to get a usable result.  A lot less than before, but still a lot. 

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EddyCurrent
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« Reply #12 on: January 12, 2019, 21:19:02 pm »

Version 2 attached

1. Added 'worker threading' to increase efficiency
2. added UNDO
3. added Translation of error message

Also attached source project for Visual Studio, this was mainly as a contribution to "code snippets" as posted here; http://www.cambam.co.uk/forum/index.php?topic=7806.msg62518#msg62518

* NonPlanarSilhouette.zip (4.75 KB - downloaded 8 times.)
* NonPlanarSilhouette_VSProject_source.zip (13.67 KB - downloaded 7 times.)
« Last Edit: January 12, 2019, 21:29:36 pm by EddyCurrent » Logged
Garyhlucas
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« Reply #13 on: January 13, 2019, 00:35:39 am »

Bob,
So as I understand where you are at the moment. Eddy's plugin give you a line around the part at the desired mold parting line?  If so how about if the line had points at your desired step over for a ball mill. Then the plugin attached parallel horizontal lines to each point.  You'd use engrave to machine those lines.
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Gary H. Lucas

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Bob La Londe
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« Reply #14 on: January 13, 2019, 01:36:57 am »

Bob,
So as I understand where you are at the moment. Eddy's plugin give you a line around the part at the desired mold parting line?  If so how about if the line had points at your desired step over for a ball mill. Then the plugin attached parallel horizontal lines to each point.  You'd use engrave to machine those lines.

That's not an unreasonable work around.  I might even be able to do that with the existing tools.  For even a modestly complex parting line it will still require a lot of tedious brute force hands on work while zoomed way in, but it may well be possible.


Draw point list > Divide Geomtry
Copy > Paste> Scale++
Start drawing lines.  


I guess I have to test it now.  

Another way might be to copy, paste, and scale the parting polyline several times and engrave them such that minimal scallop results and a wide enough surface is created to engage the opposite mating surface.  That's a little more brute forces, but maybe a little less hands on. 
« Last Edit: January 13, 2019, 01:41:40 am by Bob La Londe » Logged

Getting started on CNC?  In or passing through my area?
If I have the time I'll be glad to show you a little in my shop. 

Some Stuff I Make with CamBam
http://www.CNCMOLDS.com
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