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Valued Mentor
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wh
Posts: 477
Registered: ‎12-27-2003
Message 1 of 11 (711 Views)
Accepted Solution

Constrain / DS challenge

711 Views, 10 Replies
01-16-2014 01:52 PM

I've been struggling with this for quite a while, without acceptable result. Perhaps anyone here can help out.

Attached are the main parts of a retractable gear for model airplanes, actuated by a pneumatic cylinder. The pictures show both end positions.

 

But I'm having troubles with a continuous movement, either constraint driven or in DS environment.

Comments are very welcome.

 

Thanks

Walter

Meanwhile it's mainly solved. I could get it ok in DS, but still no driven constraints in modeling environment

 

A major problem was the origin of the files:

- Original CAD unknown, saved as SAT (>7.0) by KeyCreator. Unreadable for Inventor.

- Converted by me with a demo version of 3DTool (I don't use SATs much) to STEP

- STEP Import into Inventor 2014

 

During my tests, I found minimal angular misalignments in the parts, that prevented good constraining. Therefore, I remodeled the basic parts, and made some small length adjustments in the parts.

 

Now it's moving, as expected. Thanks for your interest

Walter

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wh
Posts: 477
Registered: ‎12-27-2003
Message 2 of 11 (562 Views)

Betreff: Constrain / DS challenge

01-17-2014 11:29 AM in reply to: wh

Meanwhile it's mainly solved. I could get it ok in DS, but still no driven constraints in modeling environment

 

A major problem was the origin of the files:

- Original CAD unknown, saved as SAT (>7.0) by KeyCreator. Unreadable for Inventor.

- Converted by me with a demo version of 3DTool (I don't use SATs much) to STEP

- STEP Import into Inventor 2014

 

During my tests, I found minimal angular misalignments in the parts, that prevented good constraining. Therefore, I remodeled the basic parts, and made some small length adjustments in the parts.

 

Now it's moving, as expected. Thanks for your interest

Walter

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erazorzedge
Posts: 27
Registered: ‎01-05-2014
Message 3 of 11 (518 Views)

Betreff: Constrain / DS challenge

01-17-2014 09:03 PM in reply to: wh

I'm using Inventor 2014 and started off by deleting all of your constraints. I didn't noticed that the parts were slightly out of alignment like you had mentioned, though. I then constrained all of the moving parts (minus the shaft of the cylinder) to the same plane (whichever one was parallel to the movement). I used the Joint command to place a Cylindrical joint between the shaft and the cylinder and gave it a minimum and maximum limit. Then I constrained all of the centerlines of the each parts mating holes to it's mating part. That pretty much got it moving and I was able to drive the Cylindrical joint from that point. I haven't tried it in Dynamic Simulator, however, as I'm kinda new to Inventor.

 

I did notice that the purple part came into contact with the yellow part (strut I'm guessing) before the assembly reached it's fully closed position. I modified the red part by narrowing the dimension between the hole centers and got it to work without any collisions as well.

 

Good to see yout got it working for yourself.

_______________________________________
Eddie

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JDMather
Posts: 26,893
Registered: ‎04-20-2006
Message 4 of 11 (498 Views)

Betreff: Constrain / DS challenge

01-18-2014 07:34 AM in reply to: wh

wh wrote:

...I found minimal angular misalignments in the parts, that prevented good constraining. Therefore, I remodeled the basic parts, ..


Walter,

I was going to put my students on this problem, but you made some pretty significant changes in your "solution".  Now I am confused about what you really want. (especially since it is overconstrained)

Are you only after the kinematics (motion) or are you also interested in the physics?  (acceleration, velocity, forces....)

 

I think we will do the problem anyhow (Dynamic Simulation) for the experience.

I expect the first thing they will do is change the joint between the piston (31) and the cylinder (29) to a Prismatic joint as we are only interested in the translational degree of freedom and the connection to 35 would remove the rotational DOF anyhow.

 

We will be interested in making sure 25 & 36 cannot start to collapse in the wrong direction and contact between 35 & 36 when collapsing.

 

I also found at least one location where there is no clearance between moving parts (both 22.225 dimension) which will cause problems in an contact analysis (and in the real world).

Please mark this response as "Accept as Solution" if it answers your question.
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Valued Mentor
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wh
Posts: 477
Registered: ‎12-27-2003
Message 5 of 11 (488 Views)

Betreff: Constrain / DS challenge

01-18-2014 08:55 AM in reply to: JDMather

Hi Jeffrey,

thanks for your interest. Meanwhile I refined the original parts, and added some more functionality. Give me some more time, and I'll come back later this evening with a small video, and a few screenshots.

I could think of providing your students only the parts. Then the assy could be built up again with help of the screenshots and video, constrained and moved in DS environment.

 

What's your opinion about this proposal?

Walter

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JDMather
Posts: 26,893
Registered: ‎04-20-2006
Message 6 of 11 (484 Views)

Betreff: Constrain / DS challenge

01-18-2014 09:01 AM in reply to: wh

wh wrote:

What's your opinion about this proposal?

Walter


I am not going to give them everything.  I was thinking only the original assembly and then have them rebuild it using considerations that have already been presented to them in class.

 

I would be interested in your final (or enhanced) work so that I can give them a written description of the design intent of the mechanism motion.  Videos would be good for clarification.

Please mark this response as "Accept as Solution" if it answers your question.
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Valued Mentor
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wh
Posts: 477
Registered: ‎12-27-2003
Message 7 of 11 (469 Views)

Betreff: Constrain / DS challenge

01-18-2014 01:22 PM in reply to: JDMather

Now I'm back. I've had a hard time. IMO, DS needs to be better.

In the meantime, I wanted to do that:

 

1. Gear down

2. During gear down, 90° rotation of the wheel

3. With gear down, wheel moving up and down

4. Gear up, wheel rotating 90° back

 

Well, I only got topics 1 and 2 working. Topic 3 showed me the limits of DS. I don't know, if anyone out there is getting further, but I'm still learning ..

Another observation: Nearly ever change in DS environment is ending in a surprise. Sometimes good, but mostly bad.

 

But it's a challenge. Come on, ADesk people and everyone.

 

Now I'll clean up my assy (I don't like SAT imports, because all equal parts get their own files), and upload a STEP for Jeffrey's students.

Then animation can go into a new round. 

Valued Mentor
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wh
Posts: 477
Registered: ‎12-27-2003
Message 8 of 11 (464 Views)

Betreff: Constrain / DS challenge

01-18-2014 02:20 PM in reply to: wh

Here's the STEP.

Normally I'd name parts other than 1,2,3, but that's SAT import setup. I'm glad to see as few SATs as possible.

 

:smileywink: Happy constraining

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JDMather
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Message 9 of 11 (339 Views)

Betreff: Constrain / DS challenge

03-15-2014 08:34 AM in reply to: wh

I never got back to you with this - this was my solution - I had the students take it a bit further (getting rid of interferences, intersecting geometr....).

 

You can drag in assembly environment, but that will mess up the initial condition is DS enviroment.  (I didn't take the time to set all DS initial conditions to zero).

 

Go to DS and click play.

 

Now on to this one

http://forums.autodesk.com/t5/Inventor-General/Question-for-Studio-experts/td-p/4887744

Please mark this response as "Accept as Solution" if it answers your question.
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Valued Mentor
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wh
Posts: 477
Registered: ‎12-27-2003
Message 10 of 11 (319 Views)

Betreff: Constrain / DS challenge

03-15-2014 01:49 PM in reply to: JDMather

Good evening, Jeffrey

Many thanks to you and your students team. I think, you'll agree, that this is a tricky sample.

I've looked at your parts and found, that you added some notches at part 35.ipt. I know the reason for this change, but that doesn't make sense in reality.

 

In my sample (latest version is attached), I'd inserted 3D-Contact:24 instead. Normally that should prevent collision between Federbein.iam and Koppel.iam.

But I noticed, that collision appeared despite of this setup.

 

:smileywink: Where's Chris (Mitchell) and all other ADesk DS experts?

Walter

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