Assembly 4 workbench

Mods Assembly
661

Well but that is exactly what I now think it is meant to do unfortunately. Just attaching final parts to their places and doing some simulation etc…
I’ve look at the examples it is always just final assembly. Maybe hierarchical but not interleaved with solid modeling.

I was hoping that ASM4 would help me “maybe not assemble” but place some repeated features at specific places and then continue with doing solid modeling like booleans with the placed parts and then continue placing and otherwise using these superparts in supersuperparts etc.. each time for the sake of solid modeling but Lattice2 seems to be far superior for this use-case while ASM4 seems to be not meant for such thing at all?

662

I think that it’s going to be a lot easier when the Topological_naming_problem is resolved in the official FreeCAD branch and maybe Asm3 would be more suitable than because of the different way it works.

663

Actually no.

Assembly4 is used in these examples to create all of the bodies in-context and their features in a single file as well as to assemble all of the bodies.

For repeated features I would use PartDesign patterns and Draft arrays for repeated bodies. Or, you can use Assembly4 to arbitrarily place or assemble multiple copies of the same body. Perhaps some of the confusion is whether we are mixing definitions of parts, bodies, and features.

I am not familiar with Lattice2 so probably do not fully understand what you are trying to do. I reviewed the Lattice2 tutorial link you provided and that creation of features can also be done with PartDesign without using Assembly4.

If you could attach a sample file of what you are modelling it would be most helpful.

664

In the tutorial you can see that LatticePattern is able to also create pockets in a target. Draft Array and PathArray can’t AFAIK. They also can’t have other reference placement in source body other than origin. Using pure PD to model same feature in many bodies and also projects is also not a way. Here is a very simple use case:

This is housing for dupont-like connectors
dupont_housing.jpg
Here I have a mode of a holder for such housing
holder.png
Yup is a pocket features galore in a ball.
Here it is used 4 times in an array in target body
TheThing.png
Here is the real thing
TheRealThing.jpg
I would very much like to have the “housing holder” maker in a separate file so I can use it it multiple projects. ASM4 natively supports having parts/bodies in other files right now, however I think it probably is not meant for my usecase.

665

Why not do both: use the Lattice WB to design your part, and an assembly WB to assemble it ?

ANY assembly WB is meant to assemble (position in space) parts that are designed with some other tools. But the assembled parts don’t have to be finalised before being assembled, you can change their design as long as you don’t alter the assembly constraints. In Asm4 the assembly constraints are LCS, which can’t be altered topologically - they’ll always be LCS even if misplaced - so you won’t suffer (or suffer less) from FreeCAD’s dreaded topological naming issue. That’s all there is to it.

666

You can if you create the feature to be reused in a separate body and then use PartDesign (PD) > Boolean to either fuse (add) or cut (subtract). You can also clone the feature for multiple use, locate as desired, and add/subtract by the PD boolean tool to a body or multiple bodies. This is fully parametric since any change in the feature body will be reflected in the boolean.

You can also use Draft > Array to your heart’s content, drop it in a separate body as a base feature, and add/subtract using the PD boolean tool.

The body feature can also be saved in a separate file and merged when needed but there is no link. AFAIK there is no way to add a linked body to another body using the PD boolean tool, but I rarely use links so not too familiar with how they function.
multi_features_from_clones.FCStd (233 KB)
Capture.JPG
OS: Windows 10 (10.0)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.21769 (Git)
Build type: Release
Branch: master
Hash: 801bfe4ba5f0910e9b2885917c521ab7fd8e9020
Python version: 3.6.8
Qt version: 5.12.1
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/United States (en_US)

667

Are you working with a single or multiple files?
I’m working with multiple files and trying your sequence but don’t work for me, can you show your tree?

668

I have checked and it seems that vocx already solved this problem. I tried the changes and was able to make arrays.

669

I’m finally getting the ASM4 and how to assemble, then continue with solid modeling, then again assemble and so on.
I need to fuse the assembled parts manually if they are supposed to be a single continuous solid. :man_facepalming:
And the Make sub-link is just the right tool when one is outside of PartDesign (and its SubShape binder).

Right now I’m modelling a box/case.
Here I have a model of hinges:
Screenshot_20200725_204058.png
Here I place them next to the upper part of the box… i.e. the Hinges0 Link.
Screenshot_20200725_203917.png
And here is just the lower part fused to the rest of the box via Hinge0 SubLink.
Screenshot_20200725_204012.png
I’m so happy right now.

670

This is exactly I want to do, It will be very nice and natural if we can just add new LCS on the Assembly it self just like we add LCS on part

671

then, good practice is to read the forum:


672

Attempting to insert a fastener from the fastener icon in A4. and I get:

Running the Python command 'Asm4_insertScrew' failed:
Traceback (most recent call last):
  File "/home/mac/.FreeCAD/Mod/Assembly4/FastenersLib.py", line 609, in Activated
    if not 'FSChangeParams' in Gui.listCommands():

module 'FreeCADGui' has no attribute 'listCommands'

Haven’t tried a fastener for a week or so…updated A4 from Addon Manager, no change.

(Fastener workbench works fine…)





OS: Ubuntu 20.04.1 LTS (XFCE/ubuntustudio)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.
Build type: Release
Branch: unknown
Hash: 0cf8279f00017ed2913e0c17beda77c733f98350
Python version: 3.8.2
Qt version: 5.12.8
Coin version: 4.0.0
OCC version: 7.3.0
Locale: English/United States (en_US)

673

General question about A4 behavior.

It seems that there are a lot of changes to the assembly file and the part files with very little provocation.

Some times I know of nothing changing in the part files, it doesn’t even appear that they were loaded.

But, if I do a close all, it wants to save them.

In some cases, after the assembly file is closed some of the part files remain, but, weren’t loaded and are greyed in the feature tree.

oh, and why: “Partial loaded document ‘yoke_altern’ cannot be saved” when the file has not been opened or changed… :confused:

Just want to understand what’s going on behind the scenes… :wink:

674

that’s very strange. Can you please try to run the command

>>> Gui.listCommands()

in the python console ?


Version: 0.19.
Build type: Release
Branch: unknown
Hash: 0cf8279f00017ed2913e0c17beda77c733f98350
…
OCC version: 7.3.0

that’s also quite strange. Mine says:


Version: 0.19.21775 (Git) AppImage
Build type: Release
Branch: master
Hash: 1f741aa511e898849e46ed14515fce416fe32acb
…
OCC version: 7.4.0


How did you get that version of FreeCAD ?

675

Partial loading of files doesn’t (always) work very well, better to disable it in the settings. Also, objects are “touched” when recomputed, and thus appear modified to FreeCAD even though they where not modified by the user.

All this is standard (now, since v0.19) App::Link behaviour, not specific to Asm4. Please be aware that while the App::Link interface is very usable and stable, it’s also new to FreeCAD and still has some rough edges. These will hopefully be ironed out in the coming releases.

676

Hello, I tried to make a solver for Assembly 4. The work I have done is in my fork of the assembly under the solver branch. I see it more as a sort of proof of concept of how a solver for Assembly 4 could work. This solver only works on datum objects inside the active document. So it can be used to construct the functional structure of an assembly. So far it only has two types of constraints, an “equality” constraint and a “fix” constraint. The equality constraint can be used to set parameters of the placement of two datum objects equal. For example, to set the x-position of both objects equal and leaving all the other placement parameters free. And the fix constraint sets the parameters of the placement of an object to a certain value. For example, setting the x-position of an object to 5.00mm. I made a video showing the solver in action: https://www.youtube.com/watch?v=jBuW-eqBHUY&t=7s

I don’t really see this solver as a replacement of sketches or attachments since it is slower than both of them. However, I think it is a cool proof of concept since adding the solver to Assembly 4 was rather simple. Maybe in the future we could add a better solver to Assembly 4 in a similar way I added my solver.

677

This looks really cool. I just came back from vacations and will take a look at it ASAP. Thanx

678

This error occurred just in one commit, 9b529bc45c, but since it caused regressions a compatibility fix was quickly made, 76e7429489.

679

First of all, nice dialogs, nice integration with the rest of the UI. Unfortunately, I always get an error when updating the assembly:

Running the Python command 'Asm4_updateAssembly' failed:
Traceback (most recent call last):
  File "/home/hubertz/.FreeCAD/Mod/FreeCAD_Assembly4-solver/updateAssemblyCmd.py", line 55, in Activated
    solved = sol.solve(x_i)
  File "/home/hubertz/.FreeCAD/Mod/FreeCAD_Assembly4-solver/solver/Solver.py", line 44, in solve
    solution = minimize(self.eval, x0,  method="trust-ncg",
  File "/tmp/.mount_FreeCAafOCKi/usr/lib/python3.8/site-packages/scipy/optimize/_minimize.py", line 627, in minimize
    return _minimize_trust_ncg(fun, x0, args, jac, hess, hessp,
  File "/tmp/.mount_FreeCAafOCKi/usr/lib/python3.8/site-packages/scipy/optimize/_trustregion_ncg.py", line 39, in _minimize_trust_ncg
    return _minimize_trust_region(fun, x0, args=args, jac=jac, hess=hess,
  File "/tmp/.mount_FreeCAafOCKi/usr/lib/python3.8/site-packages/scipy/optimize/_trustregion.py", line 182, in _minimize_trust_region
    while m.jac_mag >= gtol:
  File "/tmp/.mount_FreeCAafOCKi/usr/lib/python3.8/site-packages/scipy/optimize/_trustregion.py", line 71, in jac_mag
    self._g_mag = scipy.linalg.norm(self.jac)
  File "/tmp/.mount_FreeCAafOCKi/usr/lib/python3.8/site-packages/scipy/optimize/_trustregion.py", line 51, in jac
    self._g = self._jac(self._x)
  File "/tmp/.mount_FreeCAafOCKi/usr/lib/python3.8/site-packages/scipy/optimize/optimize.py", line 327, in function_wrapper
    return function(*(wrapper_args + args))
  File "/home/hubertz/.FreeCAD/Mod/FreeCAD_Assembly4-solver/solver/Solver.py", line 27, in grad
    return self.val.grad

'NoneType' object has no attribute 'grad'

in line 44, there is


solution = minimize(self.eval, x0,  method="trust-ncg", jac=self.grad, hess=self.hess, options={"gtol": 1e-8, "disp": True})

but the eval method is defined as:

def eval(self, x):

shouldn’t some x values be provided ?




The best test-case to check whether the solver can be used for real-world problems is the hexapod. For that, we need to set the length of a segment, or the distance of a point to a plane, but this constraint doesn’t seem to exist (yet).

I’m really enthusiastic to make this thing work, thank-you for the work.

680

That is interesting. I don’t get this error, does it happen on different documents (even on documents without constraints)? can you upload the document where that error happens?

The minimize function uses several functions to do its calculations. The self.eval is one of them, we need to pass the function as an argument.

I use hyper dual numbers to calculate the gradient and hessian matrices for the solver. Since the minimize function only works with arrays of real values, the solver has to transform the numpy arrays of real values to lists of hyper duals and vice versa. The conversion of numpy arrays of reals to a list of hyper duals happens in the self.eval function. This function stores the resulting hyper dual number in self.val and returns the real part of the hyper dual which is the value of the function at the specified point (the input x). And when self.grad or self.hess are called, they just return the gradient and hessian parts of the hyper dual stored in self.val. Which means that I assume that self.eval is called first. The error you get says that self.val is None when calling self.grad which either means that self.grad was called before self.eval or self.eval failed silently.

Maybe my assumption was wrong. Maybe we are using two different scipy versions. The scipy version I have is 1.5.2 which version are you using?


I am planning on adding more constraints. But first I need to refactor some of the code first and maybe modify the fix and equality constraints. I believe that the way these two constraints work leaves too many objects in the tree. I think that I can combine the equality constraints between two objects into only one constraint object instead of up to 6 constraint objects. Once I finish that, I will work on adding more constraints like distance constraints.