Assembly3 Tutorials

Discussion about the development of the Assembly workbench.
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Zolko
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Re: Assembly3 Tutorials

Postby Zolko » Wed Oct 30, 2019 11:44 am

realthunder wrote:
Tue Oct 29, 2019 11:30 pm
freecad-heini-1 wrote:
Tue Oct 29, 2019 9:17 am
Pistons with cylindrical cam rollers should be mounted on the cam discs.

...be handled by a physics simulator.
I'm not sure that this assembly is physically possible: since axes of the 2 rollers are fixed, the distance between the 2 rollers is fixed also, so the profile of the cam should be such that the 2 rollers always touch both sides of the cam. If the cam is a centered cylinder then it's trivial — and not very useful — but if it's some free shape for some fancy movement then it might not be possible with a single cam. Ducati has developed a push-pull cam system they called desmodromic valves, but they need 2 cams, one for each movement. Alternatively, you need a single roller and a spring.

Doesn't help you with the constraints in the assembly though. If your cam has a mathematical expression — and I bet it has — you should use a spreadsheet, expressing the height of the roller -vs- cam rotation angle. That would be your poor man's physical simulator.
try the Assembly4 workbench for FreCAD v0.19
install with Tools > Addon Manager > Assembly4 — tutorials here and here
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Re: Assembly3 Tutorials

Postby freecad-heini-1 » Fri Nov 01, 2019 2:04 pm

Zolko wrote:
Wed Oct 30, 2019 11:44 am
realthunder wrote:
Tue Oct 29, 2019 11:30 pm
freecad-heini-1 wrote:
Tue Oct 29, 2019 9:17 am
Pistons with cylindrical cam rollers should be mounted on the cam discs.

...be handled by a physics simulator.
I'm not sure that this assembly is physically possible: since axes of the 2 rollers are fixed, the distance between the 2 rollers is fixed also, so the profile of the cam should be such that the 2 rollers always touch both sides of the cam. If the cam is a centered cylinder then it's trivial — and not very useful — but if it's some free shape for some fancy movement then it might not be possible with a single cam. Ducati has developed a push-pull cam system they called desmodromic valves, but they need 2 cams, one for each movement. Alternatively, you need a single roller and a spring.

Doesn't help you with the constraints in the assembly though. If your cam has a mathematical expression — and I bet it has — you should use a spreadsheet, expressing the height of the roller -vs- cam rotation angle. That would be your poor man's physical simulator.
Hi Zolko,

PTC Pro-Engineer Mechanism-Design has a cam-follower:
phpBB [video]


My work with Creo Wildfire 5:
phpBB [video]


Thank you very much for your answer.
Last year we had a discussion in the German Forum. Using the Anination Workbench from microelly2 (Thomas) and his help, the cam plates and cam rollers could be animated, see:
https://forum.freecadweb.org/viewtopic. ... 38#p215838
phpBB [video]


I hope I can find a solution using the ASM3 workbench, I will try the next days.

Best regards
Wilfried
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Re: Assembly3 Tutorials

Postby freecad-heini-1 » Fri Nov 01, 2019 2:15 pm

realthunder wrote:
Tue Oct 29, 2019 11:30 pm
freecad-heini-1 wrote:
Tue Oct 29, 2019 9:17 am
I have here a motor shaft with two cam discs. It is mounted rotatable in a bearing. Pistons with cylindrical cam rollers should be mounted on the cam discs. Which constraint is suitable so that the cam rollers bear tangentially against the cam rollers?
I am afraid it's not possible with SolveSpace solver. I think this 'CAM constraint' probably should belong to motion analysis, and be handled by a physics simulator. The closest alternative I can think of is to fix the shaft, and use arc tangent constraint, or line tangent, depending on where they touched. You can't use the face if it is not cylindrical. And if the edges are not really arc either, you may have to create a sketch to approximate it for constraining.
Hi Realthunder,
thank you so much for your answer.

Is there a documentation / demo / description about the Constraint Trace Part Move?
Is it somehow possible to constrain a point on a curve that moves on it?
trace_part_move.gif
trace_part_move.gif (37.89 KiB) Viewed 836 times
Please let me know.

https://forum.freecadweb.org/viewtopic. ... 31#p206331
Image

Best regards
Wilfried
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saso
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Re: Assembly3 Tutorials

Postby saso » Fri Nov 01, 2019 2:31 pm

realthunder wrote:
Tue Oct 29, 2019 11:30 pm
I am afraid it's not possible with SolveSpace solver. I think this 'CAM constraint' probably should belong to motion analysis, and be handled by a physics simulator.
I also think so yes, OpenModelica, MBDyn, PROJECTCHRONO could be the possible solvers for this... I don't know about the others but OpenModelica does have the option for interactive simulations
freecad-heini-1 wrote:
Fri Nov 01, 2019 2:15 pm
...
Wilfried, when you set up this 'CAM constraint' in Pro/E, does it take some time before it starts to work, if yes, how long?

Update: Ok, from the following video it is quite clear that this Mechanism Dynamics in Pro/E is based on such a simulation engine
https://www.youtube.com/watch?v=BfDzk_U_xgo
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Re: Assembly3 Tutorials

Postby realthunder » Sat Nov 02, 2019 12:28 am

freecad-heini-1 wrote:
Fri Nov 01, 2019 2:15 pm
Is there a documentation / demo / description about the Constraint Trace Part Move?
You can select the geometry element first, click the button to enable Trace, select the part you want to move, and finally click any of the mover button to move. If the tracing element is the same as the moving part, you can enable trace any time when you move the part.

Is it somehow possible to constrain a point on a curve that moves on it?
There is no constraint to follow an arbitrary curve. There are PointOnLine and PointsOnCircle constraint. Note that PointOnLine only constrain on the infinite line, not a line segment, and PointsOnCircle actually constrains on the infinite cylindrical surface defined by the circle. That's how SolveSpace define them. My guess is SolveSpace try to relax a basic constraint as much as possible so that it can be used together with others for more complex constraining, like the post you linked.

freecad-heini-1 wrote:
Fri Nov 01, 2019 2:04 pm
Last year we had a discussion in the German Forum. Using the Anination Workbench from microelly2 (Thomas) and his help, the cam plates and cam rollers could be animated, see:
If the CAM follower motion is very restricted, I mean the the CAM has only one rotational DOF, and the follower has one axial DOF, then it would be relatively easy to find an analytical solution of the follower's offset given the CAM angle. Is that what the video is showing? If so, maybe I can add something like that as well. It won't be easy for the reverse. I mean finding the CAM angle given the follower's offset, maybe with some iterative try with decreasing rotation angles.
Try Assembly3 (latest version 0.10.2) along with my custom build of FreeCAD at here.
And if you'd like to show your support, you can donate through patreon, liberapay, or paypal
HoWil
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Re: Assembly3 Tutorials

Postby HoWil » Sun Dec 15, 2019 1:46 pm

Anyone interested in building the following model as asm3 tutorial?
https://forum.freecadweb.org/viewtopic.php?f=20&t=34530
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jpg87
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Re: Assembly3 Tutorials

Postby jpg87 » Tue Jan 14, 2020 8:16 pm

HoWil wrote:
Sun Dec 15, 2019 1:46 pm
Anyone interested in building the following model as asm3 tutorial?
https://forum.freecadweb.org/viewtopic.php?f=20&t=34530
Hello,
I made a video for this example with Asm 3 WB :
http://help-freecad-jpg87.fr/025_ass_ex_creat.php

hypnotic2.png
hypnotic2.png (22.95 KiB) Viewed 362 times
My website : http://help-freecad-jpg87.fr updated 2020/03/08
HoWil
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Re: Assembly3 Tutorials

Postby HoWil » Wed Jan 15, 2020 6:43 am

jpg87 wrote:
Tue Jan 14, 2020 8:16 pm
HoWil wrote:
Sun Dec 15, 2019 1:46 pm
Anyone interested in building the following model as asm3 tutorial?
https://forum.freecadweb.org/viewtopic.php?f=20&t=34530
Hello,
I made a video for this example with Asm 3 WB :
http://help-freecad-jpg87.fr/025_ass_ex_creat.php


hypnotic2.png
Nice!
If you do not mind, I directly link your video here:
phpBB [video]


BTW: is it possible to share the model? I am curious if it is possible to assign for all three cylinders a "points plane distance".
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jpg87
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Re: Assembly3 Tutorials

Postby jpg87 » Wed Jan 15, 2020 8:12 am

My configuration :

OS: Windows 10 (10.0)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.17089 +1543 (Git)
Build type: Release
Branch: LinkStage3
Hash: 950c082111ae5ebeefb4dddc90a80dc9b54b2408
Python version: 3.6.8
Qt version: 5.12.1
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: French/France (fr_FR)
Attachments
hypnotic_asm3_tuto.FCStd
(139.17 KiB) Downloaded 4 times
My website : http://help-freecad-jpg87.fr updated 2020/03/08
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jpg87
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Re: Assembly3 Tutorials

Postby jpg87 » Fri Jan 17, 2020 9:56 am

Hello,
I also put this video on my site

http://help-freecad-jpg87.fr/02assembla ... toEol.html

asm3TutoEol2.png
asm3TutoEol2.png (96.19 KiB) Viewed 247 times
My website : http://help-freecad-jpg87.fr updated 2020/03/08