Assembly3 Tutorials

[freecad-heini-1]

A short question

How can two cube surfaces be counter-aligned or aligned?

The document is very outdated, but still helpful on this topic: https://www.dropbox.com/s/k40drc9rlkflr ... n.pdf?dl=0

You can select both surfaces and add a "PlaneAlignment Constraint".

Hi Ceremcem,
thank you so much for your help. I know this document and I know the "PlaneAlignment Constraint".
the question is: how can you change the direction? Is there a switch or a button?
I found out that you can rotate the part with the move tools, that changes the direction, aligned or opposite, I'm looking for an easier way.
A2 plus has such a tool, like to see in the following two pictures:

aligned.png (13.57 KiB) Viewed 3137 times

opposed.png (13.42 KiB) Viewed 3137 times

Best regards
Wilfried

[freecad-heini-1]

I found this answer:
https://forum.freecadweb.org/viewtopic. ... 12#p218912

I will read the 138 page Assembly3 preview.

[freecad-heini-1]

ping

Hi Ceremcem,
unfortunately, I still have a problem understanding if features are to be deleted or added.

I made a video about the problem, it takes about 5 minutes:
https://peertube.mastodon.host/videos/w ... 61022bda28

I built on datum-planes, so topo-naming shouldn't play a role, but the assembly can't be recompute
What error do I make, what is the correct procedure?

Many thanks for your help and many greetings

Wilfried

[ceremcem]

ping

Hi Ceremcem,
unfortunately, I still have a problem understanding if features are to be deleted or added.

I made a video about the problem, it takes about 5 minutes:
https://peertube.mastodon.host/videos/w ... 61022bda28

I built on datum-planes, so topo-naming shouldn't play a role, but the assembly can't be recompute
What error do I make, what is the correct procedure?

Many thanks for your help and many greetings

Wilfried

Hi,

It's a relatively easy issue. There are two things you should consider:

1. Use only geometries belongs to the object itself (Vertices, Edges, Faces), not a "datum plane".
2. Topological naming improvements solved lots of problems and brought great abilities, but it (obviously) has also limits. To make such changes work between dramatical changes, use a geometry that belongs to the early state of the object: https://youtu.be/Nt6Rkt4-uvE

[freecad-heini-1]

ping

Hi Ceremcem,
unfortunately, I still have a problem understanding if features are to be deleted or added.

I made a video about the problem, it takes about 5 minutes:
https://peertube.mastodon.host/videos/w ... 61022bda28

I built on datum-planes, so topo-naming shouldn't play a role, but the assembly can't be recompute
What error do I make, what is the correct procedure?

Many thanks for your help and many greetings

Wilfried

Hi,

It's a relatively easy issue. There are two things you should consider:

1. Use only geometries belongs to the object itself (Vertices, Edges, Faces), not a "datum plane".
2. Topological naming improvements solved lots of problems and brought great abilities, but it (obviously) has also limits. To make such changes work between dramatical changes, use a geometry that belongs to the early state of the object: https://youtu.be/Nt6Rkt4-uvE

Hi Ceremcem,
thank you so much for your answer. I agree to use geometry that belongs to the early state of the object, because of toponaming issue.
The linked pages helped me a lot, as did your video, thank you very much for that.
Regarding the use of datum features I would like to disagree. Many years ago I worked as a CAD trainer for Creo / Pro-Engineer. Datum features have the advantage that it can't even lead to topo naming problems. I did a test with Assembly 3 and couldn't find any problems.

Please be so kind and explain why you advise against using Date Features as assembly references.

Best regards
Wilfried

[ceremcem]

Regarding the use of datum features I would like to disagree. Many years ago I worked as a CAD trainer for Creo / Pro-Engineer. Datum features have the advantage that it can't even lead to topo naming problems. I did a test with Assembly 3 and couldn't find any problems.

I can provide no technical reason actually, maybe @realthunder can. I adviced that because I never saw an example that uses datum planes as Element sources and it seemed a little bit awkward to me. Anyway, as we could interpret datum planes as "earliest stage of the object", it still won't bring much benefit. IMHO, using datum planes as element sources might make the model harder to reason about.

ping

[realthunder]

Regarding the use of datum features I would like to disagree. Many years ago I worked as a CAD trainer for Creo / Pro-Engineer. Datum features have the advantage that it can't even lead to topo naming problems. I did a test with Assembly 3 and couldn't find any problems.

I can provide no technical reason actually, maybe @realthunder can. I adviced that because I never saw an example that uses datum planes as Element sources and it seemed a little bit awkward to me. Anyway, as we could interpret datum planes as "earliest stage of the object", it still won't bring much benefit. IMHO, using datum planes as element sources might make the model harder to reason about.

Generally speaking, datum objects are good candidates for constraining element. But still, they can be attached to some model elements and suffer the same problem as a sketch mapped to some face. At the end of the day, it still depends on how they are used.

[freecad-heini-1]

Thank you Realthunder. Creo from PTC has special training courses for designers. In these trainings methods and construction techniques are imparted, one calls it Top-Down Design. Teamwork on large assemblies in particular requires methods to be able to process assemblies and sub-assemblies in parallel from several groups on large projects.
The basis is always a skeleton model, consisting of a framework of planes, axes, points but also surfaces that are copied downwards as the first features in the model tree, which is why the Top Down method is called from top to bottom. Such assemblies are very stable and even allow variants of sub-assemblies. However, it requires that all designers adhere to this technique. Freecad also allows such techniques. So far, I have always come to terms with this well. In PartDesign you can start with a master sketch, which you use to reference axes and planes, and then you can use to reference features or other sketches. Even the depths of holes or bodies can be referenced on datum planes, circles also on existing reference datum axes. Whoever works structured, renames features, axes, planes and construction elements, masters his model and is able to master changes.

Best regards
Wilfried

[freecad-heini-1]

Ping

ing

Hi Ceremcem, hi Realthunder,
I would like to ask for your help again.
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?
Here is a video of how the pistons with stud type track rollers roll against the cam plates:

phpBB [video]

phpBB [video]

rotary_cam.gif (391.53 KiB) Viewed 2421 times

Best regards
Wilfried

My files zipped:

Two_Piston_Motor_ASM.zip

(439.91 KiB) Downloaded 67 times

Assembly: Tandemtriebwerk_Motorwelle_mit_Kolben
When you turn the motor shaft (Motorwelle_mit_Kurvenscheiben), the pistons should move up and down, along the cams.

[realthunder]

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.