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ball pattern in BALL SCREW assembly

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Message 1 of 19
lis_wang
2288 Views, 18 Replies

ball pattern in BALL SCREW assembly

May I know how to pattern the ball in BALL SCREW assembly? The ball screw assembly is attached.

 

Thanks

18 REPLIES 18
Message 2 of 19
lis_wang
in reply to: lis_wang

May I know how to pattern the ball in BALL SCREW assembly? The ball screw assembly is attached.

 

As the file is big, so I posted here in two messages.

 

Thanks

Message 3 of 19
JDMather
in reply to: lis_wang

Really it depends on what you want to do with this.

 

The easiest solution is a curve driven pattern of Workpoints in the screw part and then use that pattern to place the balls in the assembly.

 

If your end goal is Dynamic Simulation then a bit more work is required.


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Message 4 of 19
lis_wang
in reply to: JDMather

I do not undertand what you said. Could you please pattern the ball inside the nut. I do not do the Dynamic Simulation.

 

Thanks

Message 5 of 19
JDMather
in reply to: lis_wang

See Tips 43-47 here http://home.pct.edu/~jmather/SkillsUSA%20University.pdf

 

and also

 

the slot and the ball are the same size (no allowance for clearance and manufacturing tolerance) - we can't make perfect parts in the real world.

 

and also

 

the circle sketch for the coil is not perpendicular to the start of the helix - therefore the slot is not round in cross-section and there is interference between the ball and the screw and nut.

 

Start with a Natural start condition (off the end of the part far enough that only the helix is cut or use a single line Coil to create a surface body coil to use with Sweep.  This will be needed to place and pattern the WorkPoints, so that is how I would do the part.


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Message 6 of 19
JDMather
in reply to: JDMather

The blue "line" is your circle profile on edge view.
The purple curve is the Helix.

Notice that the blue line is not perpendicular to the start of the helix.

The orange "line" is a Workplane created perpendicular to the start of the helix.

 

very few people catch this mistake that results in incorrect geometry.

Helix Curve.PNG


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Message 7 of 19
lis_wang
in reply to: JDMather

I do not get what your mean. Is that possible give me the file, I take a look myself?

 

Thanks

Message 8 of 19
JDMather
in reply to: lis_wang

I am using 2013 - so you would not be able to open my file even if I posted it.

 

In this image there are two circles - the 6mm circle you used with Coil to cut the face shown in orange.

I cut back overtop that feature (red) with a 5.99mm circle and notice that it cuts the sides more even though the circle is smaller.

My circle is perpendicular to the helix, yours is not.

 

I made a mistake earlier when I said one solution was Natural on the start of the Coil.  That is the default.  You would need a flat start to have the circle perpendicular to the coil curve.  But don't use that technique unless you start the Coil well off of the part, and in any case it will give you results that are harder to understand than simply doing a Coil surface of a line and using the edge of the surface body helix for a Sweep.

Lead Screw.PNG


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Message 9 of 19
JDMather
in reply to: JDMather

I just realized I left out some steps in that other document - see this one

http://home.pct.edu/~jmather/AU2007/MA105-1L%20Mather.pdf


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Message 10 of 19
lis_wang
in reply to: JDMather

Could you please posted the file here? I will installed 2013 in another PC to try it.

 

Thanks

Message 11 of 19
WHolzwarth
in reply to: lis_wang

Here's my approach.

I've made changes to spindle and ball screw, and made an array of the balls.

 

In the end I tried to turn the spindle and move it through the ball screw, but no luck. I suspect, that this is another sample of Inventor's unsatisfying constraint capabilities.

 

Remark: I know, that normally the balls are moving, too, but I neglected that, because of simplification. And I know, that normally the spindle is axially fixed and just rotating, and the ball screw does the axial movement. I'm in doubt, if this version would be running better.

 

EOP of parts needs to be moved down. Files are Rel. 2012

 

Walter

Walter Holzwarth

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Message 12 of 19
lis_wang
in reply to: WHolzwarth

It is really a clever approach. By usin this method, I have to manually change the quantity of ball in BOM.

 

Thank you very much

Message 13 of 19
WHolzwarth
in reply to: lis_wang

You can do the array as separate bodies as well, Lis.

But unless you're in ball screw manufacturing, you're ordering complete elements. It doesn't matter, how many balls are inside.

 

Walter

Walter Holzwarth

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Message 14 of 19
JDMather
in reply to: lis_wang

Pattern Component will give multiple instances of one ball.  (rather than having multiple balls in one part file)

I have assigned this problem to my class.
I will post my solution once they have attempted the solution.

 

oops, I keep forgetting you are on 2012 - well I'll post a screen shot when they get done.


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Message 15 of 19
lis_wang
in reply to: JDMather

Thanks JD. I will try your approach as well.

Message 16 of 19
WHolzwarth
in reply to: JDMather

Did you try the solution with your class meanwhile, Jeffrey?

Walter Holzwarth

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Message 17 of 19
JDMather
in reply to: lis_wang

Ah yes, we came up with a good solution, but I forgot about this thread.  I will try to remember to attach the solution tomorrow.  (what is left of a hurricane is sitting right over the top of my head today)


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Message 18 of 19
WHolzwarth
in reply to: JDMather

My best wishes for not too much damage by the storm.

Good to see, that you still have access to electricity.

Walter Holzwarth

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Message 19 of 19
JDMather
in reply to: WHolzwarth


@WHolzwarth wrote:

 

Good to see, that you still have access to electricity.


My wife is peddling the bicycle generator as fast as she can.
The wind has died down here, just some left-over rain. 

We didn't experience any damage on our property, but I haven't ventured down the road yet to check the neighborhood.


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