FreeCAD: kinematics Skeleton and Animation via a Master Sketch and Python Tutorial
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- เผยแพร่เมื่อ 16 พ.ค. 2024
- In depth tutorial explaining the steps to create a basic piston animation using a master sketch containing constraints as the rigging for a Kinematic skeleton that we can uses as bones for our bodies in FreeCAD.
This technique covers creating clones of your sketch with constraints that are linked to the master sketch which acts as the bones for the movement of the mechanism. Any changes to the master sketch are reflected automatically to the clones.
I also introduce you to using python macros to drive the piston animation by moving constraints via the script. We cover working with macros, programming in python code, using the sketch workbench, creating constraints, using construction constraints, the importance of changing visibility of elements and the issues if we don't, using the part design workbench and generally interpreting and planing the movement of the mechanics and converting these to a CAD solution.
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Simply genius....I spent hours with pencil and computer to evaluate the linear travel of a body with a very similar cam setup. I am impressed with the quality, detail, speed of presentation, and Thought Process....of not only what you were doing but why and how. Especially like the hints and recovery of problems.....just like I will see when I try this. The interface to Python was simply over the top.....your depth of knowledge in this material is very deep indeed. You had great focus on screens and movement through the keystrokes......exceptional. Thank you for sharing with us.
Thank you for such kind praise. I really appreciate the support and such comments really give me the focus to continue what I am doing. Thank you so much.
Excellent tutorial. Maybe the best way to grasp this is to open up FreeCAD and follow along step by step.
Excellent presentation. Thank you!
Thank. this is a wonderful tutorial!
Thank you for showing the way! Thank you Team FreeCAD. I am impress with FreeCAD and every contribution.
Thank you for your kind comments and support. FreeCAD is an impressive software and I am pleased to be part of the community.
Thank you for the tutorial ! I used assembly4 workbench and created a variable to rotate it in the animation assembly. NO CODE NEEDED.
Sorry I missed this comment from you. I haven't yet ventured into assembly4. My ubuntu installation is not letting install the add on so I may switch over to my windows machine. It's something that I have always wanted to look at. Thanks for the heads up.
I thank you for doing this video, it was enough for me to figure out all the code for the motor I am building and I have it working now. Took me about 2 months of learning and this video from you and I have the tools I need to 3D print out a V8 motor I have designed! Thanks and I will pass along my skills as well!
That's is fantastic news, love to hear about people's projects and how their journey through learning CAD is evolving. I am glad this video was of help. Thank you for the comments. This was a very early video in my channel and I am working on some new ones in the same areas.
Based on this terrific tutorial I'm downloading FreeCad now and getting started... thanks!
Thank you for comment so glad to hear that people are enjoying my videos
I love this video. I am using it ever since - not only for animation, but in general for creating parts that need to work together. Manually moving the master sketch then allows me to re-position the parts automatically. Thanks again!
Sorry for the late reply, trying to get through them all and have a back log. It is so good to hear that you are still enjoying the video and it's of use. It's also worth if you haven't already looking at the Assembly 4 workbench which uses the same concept. Just to let you know I have a few tutors coming up on it soon, in a matter of fact one should be released today regarding to topological issues and how to solve them but a full blown tutorial will be up next week. Again thank you for the support.
@@MangoJellySolutions Perfect - if the tutorials are as nice as this one, I will for sure enjoy them. Nice work, thanks!
That was an amazing tutorial. I've always wanted to learn CAD and with this level of tutorials, I think I finally will. Was that really 37 minutes? Flew by! Keep up the good work! :)
Thank you for such a nice comment. It''s comments like this that really keep me going and delivering on a subject that I love. I wish you all the best with your learning venture.
Thank you for this excellent tutorial. I’m bingewatching to learn and know how to organise before I really start drawing. Thank you for pointing out in the comments that Assembly workbench 4 is doing this without having to be programming in python. Last time I programmed something was in Assembler end of the ‘90s. It felt like having flown to Pluto and back…
Glad you are enjoying the channel and finding it useful, always good to hear. I know many user of freecad come from different realms, engineers and hobbyists, some may have scripted or coded before so I try to be mindful of that. If you ever want to try programming again I am running a python tutorial for freecad from scratch released every Sunday over a number of parts. I know what you mean about Assembler (I did a bit of Motorola 680x0 back on the Amiga and that was enough), your really banging the metal there, it's so much easier now days but still gives you a headache.
@@MangoJellySolutions I’m interested
Great job. It would be helpful to post a copy of your final macro since it was a bit hard to read in the low resolution of TH-cam.
Great tutorial for newbies like me, man! Thanks a lot!
Glad you like and I hope you're journey worth freecad if fulfilling. Look out for more.
@@MangoJellySolutions Thanks a lot for these encouraging words! Eagerly awaiting for more tutorials on FreeCad from you, man! Have a great day! 😉👍
What you named cam is called a crank, and the rod is called the coupler. Cool video nonetheless!
Also, to toggle visibility, just select the object and press space.
Thanks for the heads up. I never knew about the spacebar short cut, thanks
Thanks Man!! this was really helpful ^_^
awesome tutorial thank you. Is there a way to limit the motion of a part within the GUI, not python? For example limit the cam to only be able to rotate from +180 to -180 degrees along the x-axis, and always in the positive y-axis. This would be so useful.
Excellent!!!!
Thanks!
Thank you for your Great and Simple tutorial......
Thank you for the kind comment, glad you enjoyed
Your second try was perfect 👏 “Kinematics”
Thanks 😅
Great video, thanks for sharing👍
Thanks for your feedback 👍😁
Thank you for sharing this very informative video.
Thanks, I am planning on doing more with movement in the future
gone down the rabbit hole about what engine part names are yet? yours, except for a small difference would kinda work as a steam layout.
Great tutorial at least it gets me one step closer to moving parts, although the python code got me “invalid syntax” maybe after 3+ years something changed in how the software works or something..
Woww 👍
Fantastic tutorial! Many useful points in this video. One question, When your writing the python instructions I was expecting you to add something to return the value (i) to 0 once it reached 359 deg. You didn't do that, so will it just count up to the variable limit and free cad will manage the rotation angle, e.g. 720deg = 2 full rotations or 3600deg = 10 full rotations ?
It seems like that would overflow something, somewhere after a while.
Thanks again though, plenty of freecad action for me to play with.
Thanks for your comment. I am glad you like the video. Yes the rotation will be handled by freeCAD automatically . Good observation, you can zero the degrees if you want after 360 which will stop it going out of bounds of the floating point type. I think in this one I am also missing a application.doevents /application. ProcessMessages (whatever the python equivalent is). This will free up the CPU and so it hitting 99% usage. Please look out for more python and freecad videos as I will be concentrating on those for a while as I have had many request. Again thank you for your support.
@@MangoJellySolutions I'm literally days old in terms of freecad (or any cad) experience so it's a new venture for me. I'll be sure to sub and watch the many other tutorials you have, it's helping a lot. I've set myself the target of creating an excavator arm to eventually 3d print. I seem to be over constraining everything so i need to get smarter with that but i'll get there. Cheers for the reply. looking forward to future uploads : )
Subbed and please continue what u are doin
Thank you for your kind comment and there will be some more videos this week.
Super useful tutorial!
Thanks for the support 😊
Why use a vertical construction line in the master sketch instead of just constraining on the vertical axis line of the sketch?
The part of the engine you labeled cam would actually be the crank
Yep my mistake 😁
I will have to design complex robotic systems, do you think freecad will work?
That's good. Is there a workbench that allows to drag and drop components affecting the remaining degrees of freedom in underlying sketches?
So you can have models with dynamic parts that can be clicked on and repositioned? So you do not have to reopen the master sketches every time. Dragging a component does not seem to have an implemented function anyway.
PS: Using this technique and spreadsheets with user parameters would allow you to create what Fusion 360 Creates motion links and it also allows implement the Joints of Fusion 360. You just have to have some master sketches that leave for the motion degrees of freedom.
There are a number of assembly workbenches. I have used 2 and getting to grips with a third. The A2 Plus workbench doesn't use master sketches but the parts are dynamic. The a4 workbench uses something called lcs positioning and matter sketches but can be a little tricky to get to grips with. I have covered a couple on my channel with verious tutorials but I want to do something a bit more indepth.
You can also name the constraints in your sketch. When you close the sketch and then select it you will see in the data tab there is a constraint section with all the constraints within which you can modify. This saves going into the sketch.
what a great content
Thank you 😁👍 glad you like
Great Tutorial! Just two questions:
1. How to start/stop the macro instead of copy&pasting the python code?
2. Even with this simple geometry my PC is on 100% on one core. Is this the preferred way to do animations?
Hi so you can actually assign the macro to a button if you desire which means you can setup the macro and then use events to check for a key or mouse press to start / stop the macro. You could add some code to only run the animation for a set amount of time if your not familiar with events.
2. So I just realised that I have left out a piece of code to allow for the PC to process any awaiting work in the background. For the last command in the loop try adding something like
QtGui.QApplication.processEvents() (can't remember the exact command) this will allow an natural pause. The problem is that the loop is chewing up the main thread
@@MangoJellySolutions thank you!
I was with you, right up to when you started coding :/
Are you able to perform measurements? Plotting positions or distances of points relative to the driven variable could be pretty useful. Is collision detection available in FreeCAD? I mainly use Fusion but someone is encouraging me to check out what possible with coding in FreeCAD.
You can plot distances in the draft workbench but I never used this with code. I have never used fusion before but what I have heard that you have to really forget how other CAD programs work when using freecad is the process is somewhat different.
I’m new in Freecad but learning a lot by watching tutorials. I think you can use spreadsheet to make a calculated table.
I do have a question though. If I write the program with a combination of the motion constraint sketch and just rotation would that cause the 'recompute' line an issue that might slow the program down, and would it run faster/smoother if the whole design ran from the motion constraint sketch?
Hi it depends on how you have structured your code. If you are looping then it would be best to do a single recompute as the very last command before starting your loop again. I belive Issuing a recompute only updated the items that need it. I haven't done any experiments regarding speed as of yet but it may be interesting trying the two things you have described and creating some timing code to output the execution time.
@@MangoJellySolutions okay, so the recompute is on the vertical/angular lift for the lifters, connecting rods and pistons and the rotational code is needed(maybe) for the calculations on 2-1 revolutions on cam and crank values, although I could likely change the master geometry sketch to incorporate the 2-1 ratio on the gear directly I just haven't figured out the math o that yet! lol
@@MangoJellySolutions I have just uploaded a video with one of the projects I am working on and the same one I am having the speed issue with, although I am not sure all the code is visible but if you have time to take a look, it is just in processing atm and should be online shortly. Thanks again!
Thank you very much nice video
Thanks, glad you are enjoying
@@MangoJellySolutions thank you so much but i stuck on this error, am beginer just 5 days learning freecad.
when i try your code i get this
>>> from PySide import QtCore
>>>
>>> i=0
>>>
>>> def update ():
... global i
... App.getDocument('coin_body_111').getObject('Sketch014').setDatum(32,App.Units.Quantity(str(i)+' deg'))
... App.getDocument('coin_body_111').recompute()
... i += 0.5
...
... timer = QtCore.QTimer()
File "", line 7
timer = QtCore.QTimer()
^
SyntaxError: invalid syntax
I was able to follow everything until the angle change in python. My freecad (0.18.4) does not update the console when I change the angle. When I tried manually copy and paste the same text you have, it, for sure, did not work :(
What advantage is there to cloning the master sketch vs. using a sub-shape binder?
Looks like referencing using the clone isn't dependent on the order that the objects were created. When I tried using shapebinder I couldn't reference it within the sketch. I had to create a new sketch then I could reference it. But with cloning it didn't matter that it was created after the sketch. Still worked.
Is there a specific reason that you used clone instead of a shape binder? Conceptually a shape binder makes more sense to me, but I might be overlooking something...
To be honest I never really thought of it. Trouble with freeCAD is there are so many ways to skin a cat. Also you could use the Assembly Workbench but I can't get the thing to work on my ubuntu setup. I will give the shape binder a go thanks.
@@MangoJellySolutions you want to use the assembly 4 workbench
I had been wondering about this - thanks. Can it be done in 3D? I don't mean 3D parts but 3D movement.
Thanks for the comment. When you sat 3D am I right in thinking that because it is a 2D sketch it would mean you are restricted to two planes, the x and y. Hmmm good question. Let me have a play with FreeCAD and I will get back to you.
Could you describe the part you are trying to create. I have an idea of how you could do it with, say a very simple robot hand. But at the moment it's just a theory.
I did find this but I am still trying to get my head around how it works forum.freecadweb.org/viewtopic.php?f=24&t=39969&start=10
top!
Thanks for your comment 👍😁
if you cant create the part design. make sure u close the sketch design by right click on Sketch
Excellent tutorial. Keep it up. Is it possible to save the animation as movie file or avi file?
Thanks for the kind comments. Unfortunately I don't think you can save it as a movie file but you could always use something like obs to record your screen. I am not even sure if there are any python libs that you could import . I will look into this to see if I can find a solution.
@@MangoJellySolutions Thanks for your quick reply. Also there is Transform function which allows us to move or rotate a body. I tested today, please advise whether the transform function can be coded in python ?
@@optimistms if your doing this from the part workbench then the easiest way I found was to first make your object a compound object from the part drop down menu at the top, select compond and then make compound. This will allow you to access the placement property in the same way. Check out my tutorial for Geneva Wheel Build Part 6: mechanical movement animation with python in FreeCAD. Let me know if it helps.
I think I may have found a solution for the avi output. I have been working on an idea I had today to generate a screenshot of the view window on every timer tick after each frame of the animation is created. This will result in a directory full of images for each of the frames which can be stitched together via a batch file calling ffmpeg that again is called from the python code. I will put together a video hopefully beginning of next week along with a link to the batch file.
Is it possible to apply this animation technique in Assembly 3 Workbench?
from what i gather, this sort of thing with a master sketch is for assembly 4, not assembly 3
Looks interesting but can you extract velocities and accelerations from it?
Unfortunately not, with some python code then you probably able to calculate but out of the box no.
Are you a FreeCAD developer or something?!?!
I hope I can be as good as you at things one day, I'm only 24 and im big struggling but getting better every day
No I am not a developer on freecad unfortunately , if I was I don't think I would have time to document all of this as the project itself seems a full time job. Give it time and things will start to click just don't give up 😊 I was in exactly the same boat before and nearly gave up multiple times. It will come. Thank you for your kind comments.
Very well presented! Is there a trick to linking external geometries in multiple planes? @MangoJelly Solutions
Thank you for your kind comment. Now I tried doing what you asked a while back but I failed, I was trying to make a robot arm but I ran into problems. I must revist it.
I've made the Digger Arm model. Would be great if you can review the file and give advice on how to construct it better, also how would you go about animating the 3 parts. I've been at this for only 1 week so it might be an interesting thing for all the newbys. Let me know i'll send it to you.
p.s
I couldn't find a contact email for MangoJelly on the "about page" so I commented here.
That's great work. I am away from my studio at the moment but I will be back in a week. My channel will be still producing videos as I have a number lined up on a schedule. I will update the contact information shortly as I need to create a dedicated account. I will let you know when it's done. I be happy to help.
@@MangoJellySolutions thats great. Obviously no obligation but more than welcome to have a look and criticise all you can. Cheers. 👍
@@apbosh1 You caught me on Tea break before I go back to work so I was able create a dedicated email account for this channel and updated my about page with an email you can contact me on. Feel free to hit me up.
💕👌👍
👍
@@MangoJellySolutions 👍
Thank you for helping knock down barriers to entry.
This stuff isn't intuitive...especially for the uninitiated and the culture of design comes with a fair amount of I don't know....pedantic intellectual hazing? Pragmatic gatekeeper personalities cocksure that their way is the best way.
There are ways, and ways of ways.
If I'm understanding what you're doing here you move the clone from part to part to set the constraints and need to hide the actual master sketch because it seems to take precedence?
Hi. Thanks for the comments. What you describe is exactly what I do but there are better ways now. You be better off looking at the A2Plus workbench (there is a tutorial on my channel) or Assembly 4 wb if your on 0.19. I am revisiting animation as a lot has changed since I started this channel.
I drawed hundred lines and I am not able to move points by clicking on them and dragging them. Nothing happens. Here he just clicks and drags it. Been searching for 15minutes for this option, nothing.
If your sketch shows up with orange lines rather than the normal white lines then you have over constrained your sketch. If they are green when not selected then it's fully constrained. Either of those will stop your sketch points from being moved until you fix the constraints. Also make sure you are editing the sketch and not trying to edit the clone
At 2:46 can anyone please explain how to clear the cursor?
I have clicked on the red dot to move the ends of the line. When I constricted the end of the line to the center point I drew a square selection just by clicking and dragging the mouse. If your having problems with your controls look to the bottom right of the screen and you will see a small icon that let's you change the control method from mouse, touch pad etc that may be your issues as I had the same troubles when I first tried to get to grips with free Cad.
If you do get into problems hit the escape key on your keyboard. This will return the cursor back to its normal state.
@@MangoJellySolutions pressing escape works thanks
from Pyside import QtCore
Traceback (most recent call last):
File "", line 1, in
File "C:\Users\user\AppData\Local\Programs\FreeCAD 0.19\bin\Lib\site-packages\shiboken2\files.dir\shibokensupport\__feature__.py", line 142, in _import
return original_import(name, *args, **kwargs)
ModuleNotFoundError: No module named 'Pyside'
>>>
>>> i = 0
>>>
>>> def update () :
... global = i
File "", line 2
global = i
^
SyntaxError: invalid syntax
>>>
Looool
Upper the s so it reads PySide. Yours is lower. That should work and sort out your problems.
Remove the = so it's global i
@@MangoJellySolutions
Done it
Thanks