Help using Assembly3 workbench

Discussion about the development of the Assembly workbench.
MikeM
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Joined: Fri Aug 27, 2021 7:19 am

Help using Assembly3 workbench

Post by MikeM »

Hello, can anybody give me some hints here? I am using the realthunder version of FreeCAD and wanting to model a CNC router i intent to build. The frame will be made with welded steel box section 50x50x3 50x50x2.5 and 50x25x2.5 I have made the tubes and created the parts required, but am having an insanely difficult time trying to glue the parts together. Been trying for 3 days so far and managed to get a link to several rails and a leg linked into the assembly parts section OK.

The big problem is how do I join one tube perpendicular at the end of another? Can anyone advise?
Also when that problem is solved, how do I use multiple copies of the same tube?
Thanks
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bambuko
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Re: Help using Assembly3 workbench

Post by bambuko »

study this excellent page with instructions and examples - it answers all your questions:
http://help-freecad-jpg87.fr/02_ass_ind.php
and then ... if you still have questions come back
Don't forget to include your FreeCAD version info and (if possible) share your file.
MikeM
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Re: Help using Assembly3 workbench

Post by MikeM »

Hello bambuko, Many thanks for your reply. You are right this is a brillient website, someone put a lot of work into it. I am studying it more deeply but a quick look through didn't answer my questions so I may get back with the same questions, either way I will let you know progress.
MikeM
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Joined: Fri Aug 27, 2021 7:19 am

Re: Help using Assembly3 workbench

Post by MikeM »

No such joy, despite the excellent website I am still stuck. After working most of the day on it I now have a better understanding of how the constraints work and what I am doing seems to be right but does not work as expected. I am using FreeCAD Link Branch 2022.01.11 Revision 28429 (Git).
I have linked in the UpperRail and Leg bodies to an assembly and am trying to connect them. The rail should sit on top of the leg, with the leg front and rail end in alignment. First thing I did was to lock the bottom of the leg.

1. If I select the underside of the rail and the top of the leg and use the attachment tool, the leg gets attached to the top of the rail, after several attempts from scratch I decided the hollow profile or the curved corners were causing a problem so I tried a solid square bar with the same result.

2. If I select the underside of the rail and the top of the leg and use the Plane Coincident tool the leg is attached correctly to the underside of the rail but then I can't find how to fix it at the end. All the options I tried fail.

This seems to be a very basic and fundamental join so it must be possible somehow, just can't find the trick.
Attachments
cnc.FCStd
(25.63 KiB) Downloaded 12 times
RailUpper.FCStd
(29.14 KiB) Downloaded 10 times
Leg.FCStd
(29.13 KiB) Downloaded 11 times
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bambuko
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Re: Help using Assembly3 workbench

Post by bambuko »

MikeM wrote: Mon Jun 13, 2022 8:36 pm I am using FreeCAD Link Branch 2022.01.11 Revision 28429 (Git)....
@chrisb this thread should be in assembly subforum?

MikeM wrote: Mon Jun 13, 2022 8:36 pm I have linked in the UpperRail and Leg bodies to an assembly...
something weird is going on...
why do you have links in original part files as well as in assembly file?

MikeM wrote: Mon Jun 13, 2022 8:36 pmThe rail should sit on top of the leg, with the leg front and rail end in alignment...
I am sure it is pretty obvious to you (after all it is your project :D ) but I haven't got a clue what it should look like?
Can you do a sketch explaining it? (better than hundred words)

BTW - this would be a good starting point ;)
Screenshot from 2022-06-13 22.59.25.png
Screenshot from 2022-06-13 22.59.25.png (38.43 KiB) Viewed 488 times



and below is my FreeCAD info as per :
Screenshot from 2022-06-13 23.04.13.png
Screenshot from 2022-06-13 23.04.13.png (11.75 KiB) Viewed 483 times

Code: Select all

OS: Ubuntu Core 20 (Pantheon/pantheon)
Word size of FreeCAD: 64-bit
Version: 2022.612.14555 (Git shallow)
Build type: Release
Branch: (HEAD detached at 2022.06.12-edge)
Hash: 74806743ec660ce5ad3351c163a7e51db8b717d2
Python version: 3.8.10
Qt version: 5.15.3
Coin version: 4.0.1
OCC version: 7.6.2
Locale: English/United Kingdom (en_GB)
MikeM
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Re: Help using Assembly3 workbench

Post by MikeM »

Sorry for getting the format wrong and posting in the wrong place, I will obviously do better next time!
I tried to copy the format I had seen in a utube video but maybe got it wrong, that could be one reason why its not working as expected.
I will try and emulate your application structure.

What I am trying to do is quite simple, just fix one piece at right angles to the other on the end, as in the project file I attached to the last post, its almost in the right location but I can't line it up and lock it in place (see below)
screen shot.jpg
screen shot.jpg (73.51 KiB) Viewed 448 times
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bambuko
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Re: Help using Assembly3 workbench

Post by bambuko »

MikeM wrote: Tue Jun 14, 2022 7:45 am ...What I am trying to do is quite simple...
no problem at all ;)
now I understand what you are after I will try to get your model going (later on today..)
MikeM
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Re: Help using Assembly3 workbench

Post by MikeM »

Many thanks for your help bambuko
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bambuko
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Re: Help using Assembly3 workbench

Post by bambuko »

Let me start with a warning :)
This is not "the" way or "the best" way to do it - this is "my way" (there are other ways).
For laughs I have linked your leg twice to demonstrate how I do it (you could use link group as well).
I have put all the parts in assembly containers.
Locked the rail and attached both legs using attachment constraint (unless you plan to animate assembly this is most effective way to do it).
Attachment constraint elements were "flipped" to get correct orientation of the legs and were "offset" to align edges as you wanted.
Screenshot from 2022-06-14 11.51.54.png
Screenshot from 2022-06-14 11.51.54.png (127.57 KiB) Viewed 377 times

I may have misinterpreted your requirements, but once you get the idea you can do it exactly as you want.

PS
notice that everything is renamed to make it easy to get round the assembly in future - may not matter in simple one but by the time you got hundreds of components it makes difference.

Screenshot from 2022-06-14 11.41.09.png
Screenshot from 2022-06-14 11.41.09.png (128.12 KiB) Viewed 385 times
and files for your examination, any questions - shout
MikeM(bambuko).zip
(63.27 KiB) Downloaded 8 times
MikeM
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Re: Help using Assembly3 workbench

Post by MikeM »

Hello bambuko,

Just what I needed, I recreated your application by looking at the tree and it works fine up to a point. I have a few questions, which are probably simple and self explanatory but I can't seem to see the answers.

1. Am I correct in assuming a sub class is just an ordinary assembly which becomes a subclass by the fact its contained in a higher assembly

2. You use the constaint assembly to attach the legs to the rail, which is as I would expect, when I do this the attachment is at the centre of the rail
a) how do you align the leg at exactly the end of the rail, I can drag it to the end but this is inexact as I have to zoom out to see the drag controls, when I zoom in to see the junction the controls are off the ecreen
b) when I resolve constaints the leg snaps bck to the middle of the rail how do I weld it in place, I tried plane alignment on the front of the leg and end of the rail, but just got an error, there must be way to hold it in place by removing the remaining degrees of freedom

3. For even the relative few items want to put together the tree wil get very large, is there any way to keep it managable
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