topic Re: How to center align a rigid group to a body center line? in Fusion Design, Validate & Document Forum

How to center align a rigid group to a body center line?

kkkwj — Sat, 22 Dec 2018 05:43:39 GMT

I want to use a rigid group of two triangles to cut two triangles into a block. The rigid group cutting tool is one triangle sketch/body copied, pasted, moved to the right separation distance, and made into a two-body rigid group. The target block to have the holes cut is just a block with a sketched midpoint center line on one face. See the screenshot...

I am a newbie and know how to use the generated alignment icons to align parts, but in this case, I have a center line on the target and no center line surface between the two triangles. My plan was to align the triangles in the right place and then use a combine operation to cut the holes.

In the future, I would be adjusting the block size and the separation and sizes of the triangles, so I wanted to align using a center line to do the alignment.

Is that a good approach? (I think probably not, since I can't figure out to align a rigid group that has no center line.) If someone could show me how or point me to a tutorial, I would be grateful. I looked around in forums and on YouTube, but could not find anything relevant. Thank you

Re: How to center align a rigid group to a body center line?

davebYYPCU — Sat, 22 Dec 2018 05:52:52 GMT

Without your f3d file there are possibilities.

How deep will the cutter bodies go?

Re: How to center align a rigid group to a body center line?

kkkwj — Sat, 22 Dec 2018 06:22:03 GMT

Hi Dave, thank you for your help (newbies need help, I know...)

I figured out a better way to do it, based on the idea (guess) that I needed a plane with a center point in the rigid body group in order to get Fusion to generate a center alignment point that I could use. I took a guess and tried to create a plane (a non-construction rectangle) in the rigid group component, on the back of one of the triangles. (The triangles were supposed to be flush with the block after the cut.)

But that did not work since the rectangle would never overlap the first triangle (but would overlap the cut/pasted triangle). Then I turned on the sketch during the alignment operation. That almost worked, but the center point on the rectangle was off.

So, I made a new component from a plane with two rectangles sketched into it. I extruded the two end blocks and then sketched on the side of one and cut both. Now I had one component with two triangles (no need for a rigid group) AND a plane that was properly centered so Fusion could generate a centered alignment handle. That approach worked fine. Here's another screenshot.

Re: How to center align a rigid group to a body center line?

davebYYPCU — Sat, 22 Dec 2018 06:51:53 GMT

Pleased you sorted it out.

Re: How to center align a rigid group to a body center line?

chrisplyler — Sat, 22 Dec 2018 15:27:45 GMT

There is something I don't get.

If you have two Bodies within a Component, their relative position is fixed anyway (unless you intentionally move one of the Bodies). And you can't select Bodies to be part of a Rigid Group, you can only select Components for this. So you've confused me.

Re: How to center align a rigid group to a body center line?

kkkwj — Sat, 22 Dec 2018 16:46:42 GMT

Hi Chris, wow! Thank you for the video - it showed me exactly how to create a center plane between the two triangles. I didn't know that was possible. And you showed clearly how to move the pair of triangles around in different orientations too. Thank you for that clear example. There's nothing like a screencast to show how to do something in Fusion! With a center plane like that, will Fusion generate a snap point on it so that I can bury the triangles flush with a box surface to use them as cutting tools?

Sorry about the confusion - I am only a newbie (confused myself!) and I imagine it could be hard to follow a confused newbie. I think it has to do with thinking patterns (and my original workflow thoughts were inadequate). You are obviously right about bodies within a component being rigidly positioned.

At the time, I was practicing mentally with bodies, components, assemblies, library components, and joints (after watching some tutorials). If I remember correctly, my thinking was that I would make the two triangles two components by cut/paste so that the second was a reference and they would both change dimensions when I adjusted the size of the first one. Then I needed a rigid group to fix their relative positions.

My end goal was to a use a rigid-join to join one part with triangular holes with a second part with triangular protrusions. The triangular cutting tools and triangular protrusions were intended to be library parts that could be used on multiple subassemblies. I would insert them into my current design, and if necessary, break the library link, adjust them to the size I needed in the current design. I hope that helps.

(I think it would be helpful if the Fusion tutorials and my tutorial book had a little more on these kinds of thinking patterns to help newbies. At the beginning of the newbie journey, it's not the technology (menu choices, etc) that is difficult, because those are usually small, atomic things to understand. It's finding the workflow path (involving multiple things) that is difficult.

Thank you for your helpful video again. It really made things clear. I'll try to use that offset trick in the future.

Re: How to center align a rigid group to a body center line?

kkkwj — Sat, 22 Dec 2018 16:48:13 GMT

PS. Could you please say a few words on why the timeline in your video looks so different from my timeline? I have seen a few videos with timelines that have tracks and would like to find out more about them. Thank you.

Re: How to center align a rigid group to a body center line?

chrisplyler — Sat, 22 Dec 2018 22:28:44 GMT

You notice how I used a single sketch from which to extrude the two triangles? Well, resizing something in that sketch will resize both triangles that were made from it.

Also, you know you can just cut the triangles out from the block directly, right? I mean...without making addition bodies to cut with.

So far in this thread, you have only shown a couple of pictures, neither of which show your time line, so I have no idea what to say about your time line.

Re: How to center align a rigid group to a body center line?

kkkwj — Sun, 23 Dec 2018 01:19:32 GMT

Hi Chris, thank you again for another educational video. I had never seen that technique of extruding symmetrically from a plane with an offset as well. It's clear that a person can get a lot accomplished with that.

In my case, I don't expect to be building the block at the same as the triangles, so I doubt that workflow will work for what I have in mind. I need to cut (identical) holes in at least 4 different places on multiple different objects that will be constructed separately, so probably cutting holes in the objects is the way to go. I thought that creating a reusable cutting tool would be the right way since I could just insert it into any design and apply it to make a "standard" cutout in the middle of the face of some object. And, I could move the location around easily too.

Regarding my timeline, I think I've learned something else. The timeline that I'm talking about is not the usual single-line Fusion timeline shown in your video as you record it. My timeline looks the same for that - a sketch and a couple of extrusions, etc.

The timeline I was asking about is shown underneath your video attachment - it shows Tracks, multiple lines, Commands, Dialogs, and Product. Does it have something to do with the recording, or is it an advanced Fusion option or something?

Re: How to center align a rigid group to a body center line?

chrisplyler — Sun, 23 Dec 2018 02:40:06 GMT

That's just how Autodesk's Screencast video recorder displays everything while you watch the vid. It's not part of my Fusion window, and I don't see it as I make the recording either.

Re: How to center align a rigid group to a body center line?

chrisplyler — Sun, 23 Dec 2018 02:54:20 GMT

And honestly, I think it will be easier/faster just to make the cutouts as you make each block as I did, instead of trying to manage a separate Component containing the triangles, Joining it to each block's center line and outer face, doing a Combine/Cut operation on them, unjoining them, rejoining them to a different block, etc.

It's going to be a pain in the rear, and clutter up your time line with a bunch of useless crap. Heck, yours isn't a complex geometry at all. It only takes drawing one extra line (to make a triangle) after you've already drawn a rectangle for the block itself.

Re: How to center align a rigid group to a body center line?

kkkwj — Sun, 23 Dec 2018 06:29:47 GMT

Hi Chris, thank you again for taking the time to reply. I learn something new from you every time you make an informative post.

I have practiced now four cycles of creating triangles using your offset plane technique and can do it fairly well now. I can see how it is efficient. I just manually move the pair of them to the right position and do a cut operation on the block. And I can see how you are right about having many extra operations in the timeline because of my original workflow of many steps. (I've never had a timeline long enough to worry about the length of it! My longest timeline ever was only 25 icons... 🙂

Keep in mind part of my effort is learning. When I read about some method in a tutorial (on the Fusion site or in a book), I assume the author is implicitly saying, "This is a good way of doing things." Unfortunately, no one and no place that I have seen has taken the time to discuss "This is the easiest / best way of doing X" or "Nine times out of ten you should just cut triangles out of the block as you create it, otherwise, you will end up with a much longer timeline filled with crap and a growing library of little-used components that just occupy space..."

I had watched a Fusion tutorial on building assemblies and doing parts explosions. In there, they used joints of various kinds. So, I was trying to create components (block, triangle cutters, triangle tabs, block2) that I could assemble with snap points like in the video tutorial.

I really appreciate you taking the time to explain these things to me. You don't happen to have a Kindle book that I could buy that would teach me things like this, do you? I would buy it in a heartbeat.

Re: How to center align a rigid group to a body center line?

TrippyLighting — Sun, 23 Dec 2018 14:23:28 GMT

@kkkwj wrote:

Unfortunately, no one and no place that I have seen has taken the time to discuss "This is the easiest / best way of doing X"

That is often not possible as such fairly basic things can be accomplished many ways and which one is the best might only be valid an tie context of a specific design. It takes some practice to be able to pre-plan your next steps in order to doing things efficiently.

The technique you've chosen is not wrong. It might not be the best or most efficient practice this particular case, but let's assume you've imported some more complex geometry. In that case using your method is quite efficient.

Re: How to center align a rigid group to a body center line?

kkkwj — Sun, 23 Dec 2018 17:15:48 GMT

Hi Trippy, thank you for your comment. Yes, I can see the truth in what you say. There are many ways to do some things in the context of a particular design, and people have different motivations for what they want to do (like me, as a newbie versus an experienced designer).

As a newbie, I am at zero, cannot see the many ways to do things, and have no basis for preferring one way over another. So, it's easy to waste time creating workflows that are not appropriate and that waste yet more time (and may not even have even the possibility of achieving the goal). It's one form of learning, for sure. But it is wasteful and not usually fun for the newbie.

As a newbie, I would happy to learn about one or two general "proper" or "trusted" paths or approaches that work for many cases and that are reasonably efficient and effective. Newbies don't care about being 20% more productive by using an optimal workflow for a particular design. Heck, I feel like I _have_ no design! 🙂 I'm making a test block of arbitrary size to figure out how to make part-alignment tabs that fit into the holes...

I really do appreciate you experts giving your comments. They all help.

Re: How to center align a rigid group to a body center line?

chrisplyler — Sun, 23 Dec 2018 22:45:32 GMT

Sorry, I haven't written a Kindle book. But I'm happy to help out here on the forums. If you ever donate to some charitable cause, maybe a few coins into a Salvation Army bucket or whatever, just think to yourself, "I'm doing this in recognition of the helpful folks on the Autodesk forums."

Re: How to center align a rigid group to a body center line?

kkkwj — Sun, 23 Dec 2018 23:41:34 GMT

Hi Chris, what a nice thought and nice way of putting it! I will do as you suggest.

Perhaps I can restate my original question now that I've learned quite a bit from this thread.

Suppose I want to manufacture and align any two arbitrary objects OB1 and OB2 (blocks, blades, etc) that have facing planes on them. I want to enforce the alignment by having sockets in OB1 and matching protrusions ("pins", triangles, cones, or whatever) on OB2.

To implement the sockets/pins, I want to create a first component cutting tool comprised of two bodies (cylinders, triangles, cones) that would cut two matching sockets in an object OB1. Then I want to create a second component comprised of two matching protruding bodies (but slightly 0.2mm smaller, to fit inside the sockets). These would be library components that I could reuse on multiple projects or on multiple assemblies by adjusting spacings, etc.

Ideally, the pin lengths on the and socket depths would not be the same so that I could control the spacing between the facing planes on OB1 and OB2 (so I could leave a gap between them) while still maintaining alignment. For example, if I had a pin length of 10mm and socket depth of 3mm, I could create a 7mm gap between OB1 and OB2 while still having them aligned. (In my ideal world, the tips of the triangles/cones/pins would be flat to match the flat inside of the sockets so that I could use a rigid joint to join the components OB1 and OB2 easily.)

What would be the best kind of workflow to achieve these goals?

For the cutting tools and pins, I can sketch a shape and extrude 2 bodies using offsets from the center plane. Then I would align the cutters and pins as required and combine/cut to create the sockets and combine/join to add the protruding pins. (I'm not yet comfortable aligning things in Fusion compared to Tinkercad. Tinkercad snaps objects and gives me three obvious (left, center, right) alignment buttons to click on each axis, whereas Fusion always wants me to use precision numbers.)

Does that workflow sound right? Thank you

I have prepared an f3d file with a box and two cutters (built with the offset plane technique). The cutters are ready to be positioned for the combine/cut operation. What is the easy way to align the back side of the cutter objects flush with the front surface of the box? I have also added a construction line 3mm up from the bottom edge of the box where the bottom edge of the cutters should go (be coincident with). I wish Fusion had a "snap to object surface" feature for making such alignments easy. (Maybe it does and I don't know about it.)

Re: How to center align a rigid group to a body center line?

etfrench — Mon, 24 Dec 2018 00:03:24 GMT

You're over thinking this. Use a joint to move components into the desired position. If a joint origin doesn't exist create one with the proper orientation:

Note: I neglected to move the triangles up 3mm in the joint dialog Fortunately this is easy to remedy by editing the joint.

This Knowledge base article will explain how to create a joint origin if it doesn't exist where you want it to be.

Re: How to center align a rigid group to a body center line?

kkkwj — Mon, 24 Dec 2018 00:28:03 GMT

Hi ET, wow! Thank you for another big lesson! I wanted to use joints but did not know that I could create one anywhere that I wanted to. Now I know how. Create a joint point, snap to it, and then adjust along easy lines after the joint does the main positioning.

It's so easy when an expert shows you how to do it. I will practice joints next. Thank you, thank you, again.

Re: How to center align a rigid group to a body center line?

chrisplyler — Tue, 25 Dec 2018 15:45:47 GMT

Re: How to center align a rigid group to a body center line?

kkkwj — Wed, 26 Dec 2018 03:34:03 GMT

Wow, Chris! Another SUPERB teaching video! That's exactly what I was trying to do with tapered cylinders and pyramids. I learned how to use the 'd9' dimension labels to make other circles the same size (no need to use equals constraints); how to use midpoint constraints to move a construction line to a midpoint; how to put joint origins on construction lines that specify the spacing of my alignment pins and holes from the edge and surface of bodies; how to delete joints after cutting and joining; how to suppress/un-suppress joints; and how to adjust the depth of the pins/holes to control the spacing between the bodies. What an awesome video! You make it look so easy! I will dutifully practice to learn those techniques and will make a donation somewhere and think of you. Best wishes for the holiday season and new year. You've taught me a big lesson about helping people too - you don't have to know them or donate locally. You can help people simply by helping them in forums. Wow. You're an inspiration, for sure. - Kevin