Mechanism of flexible components

Forum|Forum|8 years ago
March 30, 2018
4 replies
5443 views

Is it possible to make mechanisms of flexible components like spring ( user created models) or rubber components. I am not proficient in parametric equations or pro programming . If the animation require them please suggest some reference to learn them.

General

T

TomD.inPDX

17-Peridot

There are limitations in core Creo when it comes to motion.

But we all find work-around for many things.

Just know that regeneration between motion does not happened.

This means that most of your flexibility has to be done with assembly relations.

In the case of a spring, for instance, it can be constructed with hinges at every 180 degrees of bend.

Or energy chains need to be linked so you can drag them correctly in order to use them in a mechanism analysis.

There is a more comprehensive extension for mechanism. I don't have that and I cannot speak to that. But there you do have more analysis tools, just not sure about the remaining limitations.

D

dcokin

14-Alexandrite

First lets get on the same page with vocabulary to avoid confusion. There is a feature within Creo called "flexibility" which allows dimensions or features in one model to be adjusted when it's used in another. There is another feature called "Flexible Modeling" which allows you to import from another CAD system and recognize features (such as holes) and adjust them, even though there is no feature tree. It seems you're using the word "flexible" in it's natural sense ("can be bent"), and not referring to either of these feature sets within Creo.

Creo does include a robust mechanism simulation toolkit, that lets you simulate things with real physics, including gravity, friction, etc. This does include adding springs & belts between components. But... It doesn't really show them, the rigid items they're connected to just behave as if they're there. So if you're after a nice looking animation rather than a technical result, this may not be suitable for your purposes.

I have created neato looking animations with complicated flexible components (Storable Tubular Extendible Members, compression springs, clock springs, etc) at various points in the past, but I don't think you'll like how I did it! The shape of the components relied on equations set up in the relations dialog, and could get complicated. Would also include a "VALUE = VALUE + 1" sort of statement, so the motion would increment with each regeneration. Regenerate, screengrab, regenerate, screengrab, etc, and compile animation from the frames afterwards.

You can get fancy with these regeneration controls too. I had a model where I was running these sequences a lot, and going into the relations dialog each time was a drag, so I set up fancy rules. Parameters would have included "ANIMATION_START = YES/NO", which I would just have to flip to start. Other parameters would give the start and stop positions, and increment (or frame rate). The relations included if-then statements which would check the value of the "ANIMATION_START" parameter and do the incrementation if it was set to yes. An "ANIMATION_IN_PROGRESS = YES/NO" parameter was controlled without user interaction, and would set the "ANIMATION_START" value back to "NO" when the increment reached the last desired value.

D

dschenken

1-Visitor

I agree with @dcokin that there is a difference between (1) elastic deformation, (2) changing values, and (3)

direct (non-parametric) modeling, all of which can be called 'flexible.'

Creo handles cases (2) and (3) and the user can simulate (1) by creating equations and predefining potential shape changes, but Creo cannot create those case (1) deformations on its own.

In the past I have automated by creating a trail file that explicitly changes values rather than adding increments/relations. This allows a lot more flexibility as the animation can affect every factor, even those that are not parameterized parts of the model, such as transparency/color/texture and camera position and viewing angle. It's a significant pain to do it, but at least it can run overnight. Since then I have come across AutoIt, which would allow better error recovery and less trouble than generating the trail file. Other tools are available, but I like the hurdles to be low and the tools more universal.

D

dcokin

14-Alexandrite

@dschenken, I would be very interested in learning more about how camera position and viewing angle can be controlled with trail files. How much control can this give you?

(When creating new start part templates, I had to revert to Wildfire 4, because I could not create standard "top", "front", "right" views that both auto-zoomed and auto-panned properly using the GUI of Creo 2. Lack of proper view control is my biggest gripe day in and day out with Creo. Can't create a view locked at a specific position & scale, so it'll still be consistent tomorrow when the bounding box has changed size... It's even worse if you want to use perspective view.)

D

dschenken

1-Visitor

Bounding box is easy. For framing I create a datum curve feature rectangle that is bigger than and exceeds the assembly/part as the first non-default feature ("Start" parts often have a CSYS and some datum planes as default.) This should prevent any further change to the bounding box based on other geometry. It can go on a blanked layer if it's a problem by showing up in the image.

Other than that, anything that can be captured in the trail file is possible. It's easiest if you can type a number into a dialog box. Auto-pan and auto-zoom should not be depended on for animation as they are unpredictable, especially when models can change extents and mess with the bounding box; presetting the bounding box should alleviate the need.

M

mbonka