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Mechanism Automation

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Mechanism Automation

I am putting together a rather complex gearbox, and have done all of the math to get the correct paramaters for the entire assembly.

Many of my parts automatically regen upon changing the paramaters, but one thing I seem to have to change every time I change my gear ratio is the gear ratio in my mechanism link. Anyone have any ides on how to enter reduction ratios, certain pitch diameters, etc. into a mechanism link?

Thanks

5 REPLIES 5

Re: Mechanism Automation

I looked for that too and cannot seem to find those parameters. You should see something in the information screens for the connections but I gave up.

Normally these ratios are fixed and should be cumulative, but in my triple planetary system, I could not get them to follow each other... I had to set all the ratios based on the input, bypassing all the automatic calculations for the final ratio. Never could figure that one out. They should have been serial.

Another thing you will learn quickly is that the ratios are not very accurate. The calculations only go to 5 digits, and less if the value is more than 9.99999. This has been reported to R&D, but I don't know when they will fix this. Again, a cumulative error could cause you some grief if you have a lot of ratios tied together.

Re: Mechanism Automation

Unless you are looking for an animation or a low-power, don't care about wear, cost, power loss, working for more than a few minutes kind of transmission, I'd suggest a dedicated tool for the analysis. There are a number of dedicated programs that can do a much more complete analysis of gear boxes in a more direct way.

The favorite name that comes to mind is KISSsoft, which says it can handle the analysis of the entire gearbox - bearings, gears, shafts.

ZAKGEAR is one that handles form and stress on single pairs of gears.

Some, like KISSsoft, can export the resulting model so that you don't have to re-create the analysis geometry in CAD.

There are others found by searching for 'gearbox design software.' There are too many papers on 'gearbox analysis'

Re: Mechanism Automation

There are methods to calculate wear and everything analytically, to a certain degree of accuracy. I don't work for NASA, so a rough estimate is fine. A stress analysis would be nice, but not a necessity. I've heard of ZAKGEAR before, but unfortunately, the company has basically handcuffed themselves to Creo for all mechanical engineering applications. Basically, for intents and purposes of implementing operational examples for visuals of the entire working system, I want to automate the connections so that any "replace" will automatically update with the correct reductions.

I have a family table set up with all my bearing models, complete with motion skeletons. All of the math is done inside those specific assemblies, the reduction numbers are solved, etc. What I want to do is automate the connection into a large level assembly, and automatically set the gear ratios when I pull in my bearing.

Re: Mechanism Automation

If you're interested, there is a way to do all of your calculations on MathCAD and read them into a layout, or some sort of excel data file, and that could carry into the modeling. I would assume the roundoff and truncation error in MathCAD is much less than that of relations and paramaters in Creo. Might be something to look into (good marketing for PTC too - "use product X to make product Y better"). I was just hoping there was some sort of area to add in a Paramater into a gear pairing as reduction. A way around this would be to use motion skeletons, make the reduction based on the pitch circles and use Intelligent design intent. It is a degree of automation, but not what I had in mind.

Re: Mechanism Automation

When I do ratio calculations, the results are in milliradians. Creo can't do that to the level of accuracy I need.

Fortunately, it is a rare event and a piece of paper is a very reliable calculator.