Like some help or guidance on motion/motion link/contact set with this model

[btulloh]

I'm pretty new to F360 and trying to get some motion joints to work for me.  I was making some progress at first with this mock-up, but the more I worked on the motion and tried different approaches, my results got worse instead of better.  I looked at the documentation and related posts but couldn't solve my problem.  I would really appreciate it if someone could point me in the right direction.

(Link to model: https://a360.co/2V0j58I )

I believe what I'm trying to do can be accomplished if I can find out how to implement it correctly.  This is a simple mock-up of a claw turner to use on a small sawmill to rotate logs.  At this point I'm just using the motion of the joint at the fixed end of the articulated arm to drive the motion.  The claw would normally stay in contact with the log while in use (through about 90 degrees of log rotation).  It is typically held in contact by a spring between the two arms.  I tried to use a contact set to maintain contact at first, and it was trying to work but I had other issues.  I tried motion links, and resting positions, all with some initial success, but declining success as I went.  Now there is something constraining the primary arm.  I am basically progressing backwards 😀.

At any rate, I need some guidance, either from direct input about the model and what I'm doing incorrectly, or a reference to a tutorial that may set me straight.

Thanks in advance for any help or suggestion. 

RDT, retired, new member of the forum

[Ajay_Kumar_Reddy · Accepted solution]

Hey!

Just delete the joints, then apply them in reverse. start joining from the claw instead of arm.

Watch the screencast to understand it in a better way.

Hope this helps.

[btulloh]

Thank you.  I will give that a try a little later today when I can get back to this and I'll take a look at the screen cast.  

Even though I burned quite a bit of time on this yesterday going backwards, I consider it a necessary part of learning my way around F360.  I hope to come out with a decent understanding of motion and contact sets.  Funny thing is, when I first created a contact set between the claw and log it wanted to work, but had other elements that needed to be addressed.  Overall I like the capability of F360 and I just need to work my way up the learning curve.

I also thought of a work-around that would allow me to tune in my geometry, but I'd rather go down the right path so I'll understand this better at the end.

Thanks again for the help.  Wish I had to jump on it first thing.  

[jeff_strater]

one small piece of advice:  if you are really looking to do this in the correct way, I would recommend against using contact sets.  They are pretty limited in what they can do, and computationally very expensive.  Instead, use Joint Limits on your joints to restrict mechanism motion.

[btulloh]

Thanks for taking the effort.  This indeed solved my problem and got me back on track.  In addition, I learned some things indirectly from your screen cast that are helpful.  Re-doing the joints gave me back the motion I needed.  Seeing that I can just drag the assembly to different positions is good to know.  Simple and obvious now that I see it in your screen cast.  I can work out my geometry doing that without the need for animations.  I have to expand this mock up to accommodate logs from 8" to 25" inches in diameter, and I have to deal with a number  of interference issues and space constraints.

This is an actual design I will build and add to my bandsaw mill, so it's a good learning exercise as well as a practical thing.  If I continue through after getting my geometry worked out, it seems that it has enough elements to lead me into a good understanding of the joint and motion capability of F360.

Thanks again for your time and effort.

[btulloh]

Good to know.  Thanks.  I've seen this mentioned while I was looking around at previous posts.  I have to put in some time on all this to get an understanding of joints, motion links, and contact sets and how and when to use what.  I suppose that there is an appropriate time to use contact sets, although it sounds like it's best avoided.  It worked fine in this case with no apparent impact on overhead, but I'm assuming that's because this is a pretty simple model.  I am running F360 in a pretty good machine too, which I've noticed makes a huge difference on everything.

So I have a lot to learn about these motion tools but at least I'm back on track for now.  Seems that my flailing around randomly led to some unpredictable results.  No real surprise there.  Things work better when they're operated coherently.

Thanks for weighing in on this.  

[Ajay_Kumar_Reddy]

Glad you get to know the solution.

Since you are working on a project, changing the dimensions may affect the design only related to that particular parameter.  But there is a cool thing you can try to change the entire model on the go.

Follow this TUTORIAL which I highly recommend you.

Just watch first 2min and last 2min.

It reveals you the power of parametric modelling.

hope this is indeed for you.

[btulloh]

Thanks for that link.  I learned some good general techniques watching him work.  Very helpful for my learning process.

I am already a big fan of parameters.  They are part of my standard routine when working on a design.  The model in my link uses them to control critical design elements like the arm lengths.  It makes it easy to get my geometry dialed in as I work through the constraints of this design.

I appreciate your help.