Author Topic: Draw line analysis for mould making  (Read 7112 times)

jimuk

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Draw line analysis for mould making
« on: August 30, 2014, 02:52:57 PM »
One feature that would be extremely valuable to me would be the ability to set a parting line on an STL, and then show any issues with undercuts with coloured highlighting similar to the excellent overhang highlighter.

I do a lot of work with printing stuff for casting in two part moulds, and even more with testing out STLs for production in injection moulded plastic. Right now, the tools we have to use are extremely complex and overpriced, and prohibit community level development as a result. If meshmixer was able to extend the overhang highlighter to offer this option, it would be amazing.

Thanks for your time and the excellent software!

MagWeb

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Re: Draw line analysis for mould making
« Reply #1 on: August 30, 2014, 04:32:22 PM »
Milling objects  on 3 axis I have  a (maybe) similar problem detecting areas which can not be milled using a 2 side milling strategy (flipping the stock 180°).

Here's how I detect these areas with current MM means (it isn't perfect for there's no orthographic view and it does not update on the fly as the overhangs shader):

(Let's say I want to get the undercuts in Y direction)

Enable camera snapping in the hotbox (popping up if spacebar is pressed)

Move your scene to snap to top view;
Go to Select and select a small area being totally visible;
Do Modify/SelectVisible and Modify/CreateFaceGroup

The surface staying white now, cann't be reached from the top direction

Move your scene to snap to the view from blow;
Go to Select and select a small area being totally visible;
Do Modify/SelectVisible and Modify/CreateFaceGroup

The surface staying white now, cann't be reached from both directions

Could be easier, but maybe that's of some help.
I'm just a user as you are. Being no Autodesk employee: I do not know where this road will lead to, nor do I claim to've all stuff got right.

MagWeb

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Re: Draw line analysis for mould making
« Reply #2 on: August 30, 2014, 06:33:18 PM »
Forgot to mention:

The overhangs shader "remembers" the AngleTresh value of  Analysis/Overhangs. Setting it to 90° it shows the cutting line (in case of undercuts:lines) in Y of the current object's orientation. Together with the way described above and running Analysis/Overhangs/OptimizeOrientation you get such a result:
« Last Edit: August 30, 2014, 06:38:19 PM by MagWeb »
I'm just a user as you are. Being no Autodesk employee: I do not know where this road will lead to, nor do I claim to've all stuff got right.

jimuk

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Re: Draw line analysis for mould making
« Reply #3 on: September 01, 2014, 06:08:34 AM »
That is incredibly helpful MagWeb, thanks very much for taking the time to share and post!

With luck maybe this could be a fairly simple change to make into a refined and dedicated tool/option for us :)

RMS

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Re: Draw line analysis for mould making
« Reply #4 on: October 06, 2014, 10:52:30 AM »
Can you explain what you mean by "set a parting line"? Is that a plane cutting through the model? Or is it an arbitrary curve?
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MagWeb

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Re: Draw line analysis for mould making
« Reply #5 on: October 06, 2014, 01:12:27 PM »
Imagine you want to cast a 3 dimensional object using a metal mold (which isn't flexible) and a not flexible resin: You'll need at least two molds (an upper and a lower mold).
Casting a sphere: The "parting line" would be on a plane (any plane that hits the sphere's center). That's easy...
More complex objects instead need a parting line being not planar.
Please see e.g. here: http://atelierpoupee.blogspot.de/2012/09/05-molding-design-n-4.html
If there would be an orthogonal cam, SelectVisible is pretty near to the surface needed for one mold.

To know this line and to opimize the objects' orientation is needed to get as simply molds as possible. Same problem happens on two sided CNC machining.
Think it is also that line were 3D printing supports switch from being needed outside to being needed inside a hollow object.

I'm just a user as you are. Being no Autodesk employee: I do not know where this road will lead to, nor do I claim to've all stuff got right.

RMS

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Re: Draw line analysis for mould making
« Reply #6 on: October 06, 2014, 09:44:00 PM »
I get what a parting line is, but I'm still not clear on what it means to "set a parting line". Does that mean basically to pick a specific Y-height for where the mold is split in two?
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MagWeb

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Re: Draw line analysis for mould making
« Reply #7 on: October 07, 2014, 04:22:45 AM »
Think the main issue concerning this isn't that much to define a parting line, but to find an optimal object's orientation. For simple 2 parts molds this line is a result of the orientation.
Using the overhangs shader (set at 90°) an optimal orientation would be were the red shaded surface owns a single boundary (= parting line) without some white islands. (Transforming the object or slight modifications of the object may allow to get rid of resulting undercuts).
This has to be done manually:
Against your OptimizeOrientation, which is meant for 3D printing (avoiding overhangs) mold making (same as 2 sided milling) needs to have the overhangs as big as possible (to make removing the casted part out of the mold easy).



 






I'm just a user as you are. Being no Autodesk employee: I do not know where this road will lead to, nor do I claim to've all stuff got right.

stagwolf

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Re: Draw line analysis for mould making
« Reply #8 on: November 12, 2014, 03:26:30 PM »
This is a fairly complicated notion ( as noted above), but I would also find this feature VERY useful.

I print rigid molds for casting semi-rigid materials, and this would be a life saver.

Nojvok

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Re: Draw line analysis for mould making
« Reply #9 on: March 19, 2016, 02:29:00 PM »
Being able to find the "best" part line would be super useful. I have heard there is at least one software package out there that can do it but it's very cost prohibitive. As it was described to me, you can load a surface model into the software and you end up with a two part split line with SIDE-A (one half of the part) showing in GREEN and the SIDE-B (other side of part) showing in RED. Apparently, the software can virtually rotate the model around (like in a gimbal) updating the model LIVE showing show the part line moves around. If any GREEN is on the RED side or visa-versa then that would indicate and undercut and the model would not easily release from the mold. Also I was told the mold was could mathematically rotate the model around and show the "BEST OPTION" for the part line. Once you have that rotation set, your modeler or digital sculptor can work on the visible undercuts LIVE and the color will actually change what working on the surface until there are no more undercuts. If meshmixer can do this, its a huge game changer and worth some of my hard earned cash.  :D

Regardless, Meshmixer is super usefully already but to be able to do this would be amazing.

PranakaT

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Re: Draw line analysis for mould making
« Reply #10 on: August 02, 2016, 04:53:25 PM »
I woud also be grateful for that tool.
I am making molds and making parting line is mind blowing. Somethimes I must try and fail to see that it is not working, and then is my orginal work locked inside not working mold. It is painful.

I found some science work on that thread, searching for information how to learn beter to detect undercuts.
Maby this science work is relevant for you programers, maby you coud easyer make it work in meshmixer. Maby you will wish to make it.
It is science work about making program for computing parting line and undercuts with problems in computing and mathematical solutions.
"Molds for Meshes: Computing Smooth Parting
Lines and Undercut Removal"http://ralph.cs.cf.ac.uk/papers/Geometry/moulds.pdf
I don't understand them, but it looks serious work.

Thank you for making meshmixer, I am having great time with it. Have nice day!
Thank you.