FreeCad Assembly (A2plus V0.4.54b)

rabler

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Learning FreeCad, bought a couple of books from Amazon:
Both of these books recommend installing the "add on" A2plus to build "Assemblies". I found that A2plus works OK for incorporating multiple parts and moving them around manually, but the constraint based "alignment" tools, while they work OK on initial pass, seem to blow up into total crap if you make any changes to the parts. The only way to fix that seems to be to delete all the alignment constraints and rebuild those. Of course the whole point of putting something together as an assembly is to see if the parts go together as expected, so changes are going to happen.

Has anyone had better luck with this? If so, any tips?

Here's my model so far - about 16 parts in total.
grinder1.jpg
 
In my experience there are multiple Assembly modules, each working a somewhat different way. IIRC there is an Assembly 4 that is better behaved than earlier ones, but I could be wrong about that. There are multiple tutorials on various Assembly versions. Here is one on Assembly 4 by Martham Engineering (which, IMO, are pretty good).
 
The assembly looks great.

I've never used FreeCAD, but losing constraints or getting wonky constraint issues in an assembly, after modifying a part file is fairly common across cad platforms. I even had that issue sometimes with Inventor Professional, which is far from cheap.

With the CAD software I'm using now, Alibre Design Pro, you have fewer problems if you select the part and modify it from inside the Assembly module. I'm not sure if that's an option with freecad or not.
The problems tend to occur if the part file is modified outside of the assembly window, in which case, I have to save the changed part file, then close and reopen assembly module. Then everything starts working again.

Of course, this may not apply at all to FreeCAD.
 
Thanks, didn't realize there were different, and doing some reading online, apparently incompatible options.

You get what you pay for ...
 
Thanks, didn't realize there were different, and doing some reading online, apparently incompatible options.

You get what you pay for ...
The Assembly tools are more compatible than you may think, but folk are correct in that you should not mix workbenches, even though they are capable of running independently alongside each other. Also, in this case, you get what you feel like having, and you don't pay a cent! :)

From what I have seen, Assembly 2 workbench was becoming very capable, but there were still lots of guys adding their own extra tools (something you can do with FreeCAD Python scripts). The developers incorporated a whole bunch of "wouldn't it be nice" features, and built Assembly 4, which did make some Assembly 2 features disappear, being rendered unnecessary by the nature of the new concepts.

I do not know exactly at which stage the new Assembly Workbench came in. The "stable" version of FreeCAD is 0.19.3 I use "FreeCAD Daily 0.20. FreeCAD is available for Windows Linux and Mac.

I use Linux, so the "version" number you see is from a Linux repository. To get FreeCAD Daily, I needed to add the freecad-maintainers ppa. This would be the so-called "untrusted" Personal Package Archive, but that is only because Ubuntu and other distros have repositories distributing at versions somewhat behind what the developers have already proven. I have not seen a problem with the developer version, and it has incorporated lots of fixes to remove annoyances, and add nicities.

If you happen to use Linux, then the way to have your software choose FreeCAD-Daily when you do an update and upgrade is like so..
sudo add-apt-repository ppa:freecad-maintainers/freecad-daily
sudo apt-get update
sudo apt-get upgrade
The update command will refresh the available update status of all your software, including FreeCAD, and the last command will actually go ahead and update it. If you are going this way, I would uninstall the old FreeCAD first. You don't have to, but it helps in getting the right one launched without confusions.

Unlike Windows, the whole scene is strictly a download only, (no "Telemetry"), and it happens alongside what you are doing (no forced re-boot), and is over in a minute or two.

Look at the Add-Ons Manager
Regardless of all that, check out Tools--> Addon manager. (or wherever you find the Add-on thing)
See what versions of Assembly Workbench there are. If Assembly 4 is there, then use it. If your model was done in Assembly 2, then stay with it for that model. Clearly you can have both workbenches present, (but use only one at a time). I have no idea what might happen if you go at modifying an Assembly 2 model using Assembly 4. I have not explored Assembly 4 yet, but there are YouTube videos on it.

Updating Older saved Designs
The pictures are a portion of what I see when it comes to available free feature tools. They install automatically in a few seconds. If you select them, they pop up a warning notice if they have been overtaken by one of the other later workbenches. I think the reason they are kept available is so you can get at, and modify, a model you may have made in the past. At least once, I have encountered a Workbench that gave me the instructions on how to "change" the saved model, to default to the later tool.

FreeCAD Add-On Manager1.png _ FreeCAD Add-On Manager2.png

As you can see, right at the top, I was getting interested in the 3D-Printing Workbench, and Assembly4 is selected, and I could not resist the "Bolts" and "Fasteners", and especially the "fcgear" automatic gears generation tool. :)

While we are showing pictures of our FreeCAD models. here is an older picture of my South Bend 9C countershaft and drive wheel. It's not obvious, but the taper pin is also exactly modeled.

Countershaft Drive Wheel-dev1.png
 
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@graham-xrf
Thank you for the detailed answer!
I just started using Freecad last week. Unfortunately for me youtube videos are not an option due to quotas and bandwidth on satellite internet. I’m on the waiting list for Starlink. It can’t come soon enough. I had thought about going to a developer version, I’m currently usng the stable release on windows. I have an Ubuntu laptop for GNUradio that I could try the daily release. At this point I’ve rebuilt my assembly from scratch so many times, doing it over in Assembly 4 would be a good way to try it out.
 
@rabler :)
You are so new to it that I am pretty sure there are a good deal of realizing the concepts, and going up the learning curve, that has yet to happen. It is a real pity about the video bandwidth. I have found the YouTube videos are like a hyper-speed "get started". You find the right level tutorial, and the penny drops. You quickly get it that there are always a whole lot of alternative ways of getting to the same end, and sometimes, it's just convenient to use throw in a part generated a different way.

Getting to understand how using the "Parts Design" workbench, creating "bodies", and generating from sketches in the Sketcher Workbench is a powerful and flexible way to do most things, is greatly helped by the tutorials. Some, I find, I need to set the speed to 0.75, or even 0.5, and I pause the video at stages, while I drive FreeCAD on another screen. I do much prefer those which come with clear explanations in the audio. Just watching some guy's cursor zipping about does nothing much for me.

I have taken to using the Spreadsheet Workbench as the way to keep all the dimensions in a model, with their identify names. Of course, the dimensions shown in the Sketcher are not "presentation". That happens if you invoke the TechDraw workbench, and you want to print out something. I usually switch to OpenInventor mode for casual display, and go to CAD mode when the sketcher is open. I have also messed about with the display options and colours. I found one theme that seems to be hard to tell from Fusion 360, and SolidWorks.

So far, your model looks pretty good!

[Our posts might have crossed while I was adding the image of the countershaft].
 
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@graham-xrf
At this point I’ve rebuilt my assembly from scratch so many times, doing it over in Assembly 4 would be a good way to try it out.
There may not be a need to re-do the whole design. Just save it with a variation to the name, and then delete the "assembly" part, leaving all the already made bits not assembled. Then, invoke Assembly4, and put it together again. Just possibly, Assembly4 might be smart enough to figure out how to load a model made with an earlier tool.
 
@graham-xrf
Those book are underwhelming in their content, the nuances of concepts are the key for me. I’m getting comfortable with parts design, and could probably build much of this that way, without using the assembly route at all.
The lightning on your SB shaft looks a bit better than what I get, did you use anything different or is it just the curved features?
 
@graham-xrf
Those book are underwhelming in their content, the nuances of concepts are the key for me. I’m getting comfortable with parts design, and could probably build much of this that way, without using the assembly route at all.
The lightning on your SB shaft looks a bit better than what I get, did you use anything different or is it just the curved features?
Unlike Fusion, FreeCAD does not (yet) run the overhead of a full-time renderer while working on the design, although you can produce the whole photographic, lighting, and animation glory afterwards. It does have ways of assigning colour, material, ambient, emissive, transparency, reflectivity, highlights, etc.

The drive wheel was made way before Assembly4, and I did it by making all the parts in the correct position relative to a single datum. I constrained both the wheel and the shaft to be on the same axis. Then, I could "slide" the wheel into position. in the end, I entered the dimension to simply place it correctly.

The render on the wheel was by choosing selecting the wheel, and going for "Appearance" options.
If made with "Part", you end up with the "Set Colors" tool, on selected faces.
I will attempt to post a simple example here, given you cant play with the YT video.
 
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