A2+: how to set the distance between two parallel axis?

[Giulio Buccini]

Hello,

I do not understand how I can constrain the distance between the axis of two objects.

I would like to to set the distance between the axis of the stepper motor and the center of the spur gear to 48 mm:

Selection_7104.jpg (21.4 KiB) Viewed 1933 times

(Both objects are imported from external files.)

Maybe the solution is quite easy, but I cannot see it...
Any clue?

[Syres]

The only way I'm aware of is to use a Sketch in your assembly project file with two circles and a connecting line which you can constrain to the correct length and use an angle constraint if required. When you click one circle and the corresponding axis face you will then get the option for the PointOnLine Constraint. You can hide the Sketch when you've finished.

[Giulio Buccini]

Quite rudimentary solution. Computer was not created to avoid tedious manual labor?

P.S.
What if I switch to Assembly 4? I will have more options there?

[Syres]

What if I switch to Assembly 4? I will have more options there?

Can't comment on Assembly 4, I tried it in it's early days but gave up. Personally for realistic animations I've moved to rigging in Blender for hydraulics, car suspension etc using models created in FreeCAD and imported into Blender 2.83 but I'm probably in a minority using this workflow.

[Giulio Buccini]

I know Blender, it is fantastic. But I don't want to fire with a big naval gun to a little bird.

My need is just to have an overview of my project once that I have designed all of my components.

For projects with three or four components I just draw them all in one file and then I manually move the components in their location in the space to have a a rudimentary general "assembly view".
Nevertheless my menu-tree on the left side of the screen get very soon crowded when I start to stuff like 2D-dimensioning (Techdraw workbench), milling operations (Path workbench), and so on.

So, keeping things separated is quite helpful for people like me. Producing sophisticated animation is not very important.

Do you want to know my previous approach (don't laugh, please):

1. make a "simple copy" of the object by using the Part workbench
2. open the freecad file containing my "assembly"
3. paste the object and move it manually to his exact location
4. repeat step 1 to 3 for all objects


Obviously this rapidly become a nightmare when you do even a little modification to one of your components...

[Giulio Buccini]

The only way I'm aware of is to use a Sketch in your assembly project file with two circles and a connecting line which you can constrain to the correct length and use an angle constraint if required. When you click one circle and the corresponding axis face you will then get the option for the PointOnLine Constraint. You can hide the Sketch when you've finished.

Not Working...

1. I have selected the circle on the sketch 48 mm away from the gear axis;
2. I have selected the rounded edge of motor shaft;
3. I have clicked on the "PointOnLine" constrain.

------------------------------------------------------------------
OS: Ubuntu 16.04.7 LTS (XFCE/xfce)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.22846 (Git) AppImage
Build type: Release
Branch: master
Hash: 1f46b72491a0008384a6db4f2615a656249f6f08
Python version: 3.8.6
Qt version: 5.12.5
Coin version: 4.0.0
OCC version: 7.4.0
Locale: English/United States (en_US)

[aapo]

What if I switch to Assembly 4? I will have more options there?

Yes. Just put a LCS in the dead center of both shafts, let's say that they are named LCS_motor_center and LCS_wheel_center. Then, add LCS_motor_48mm by putting an LCS into the motor part, and move that LCS 48mm to the direction you want. Then, attach the wheel by fixing LCS_wheel_center to LCS_motor_48mm, and there you are.

But remember, there are no solvers in Asm4. So, basically you just add LCS:s in the interesting positions/rotations in your parts, and then chain the parts to each other by the LCS:s. What Asm4 does for you, is to move your parts around when you change the relative positions of the LCS:s (by hand, by Python, by Variables, or by attaching them to animating Sketches).

[Giulio Buccini]

Not Working...

1. I have selected the circle on the sketch 48 mm away from the gear axis;
2. I have selected the rounded edge of motor shaft;
3. I have clicked on the "PointOnLine" constrain.

You're wrong. It works instead!
You have only to make some actions on the sketch before using it:

1. select the sketch
2. click on the command "Convert to a full functional A2+ part" on the toolbar
3. a special copy of the sketch will be created
4. make the previous sketch invisible or delete it
3. select the new sketch
4. look at the properties
5. toggle the "fixed position" propery from false to true

Now you can select the circle on the sketch and use it to build a constrain

[Giulio Buccini]

UPDATE

Setting the "fixed position" toggle to true is not necessary if you use the A2+ to align both circles: one to the axis of the first circular object and on to the second circular object.
In this way, all of the assembly objects will move if you move one single object, while in the previous way some objects will stay there. This because they were constrained to the (derived) sketch in fixed/unmutable position.