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spete10-Marble
10-Marble
August 3, 2017
Question

Mechanism Connection Parameters and Relations

  • August 3, 2017
  • 8 replies
  • 7964 views

I would also like to see if this is possible. 

I have an assembly where I have a wheel that needs to rotate to several different positions around its axis.  I tried using angle offset and using a parameter and relations to rotate the wheel to the set positions, but I can't get the angle past 180°.  I read some posts about using mechanism to control rotation beyond 180° but now I don't have a dimension I can use in my relation.  I tried looking in the connection parameters, but I don't see one that corresponds to its current position.

The following is my relations code:

POSITION:21=0
<current position>=0
IF WHEEL_POS=="SKIMV"
<current position>=90
POSITION:21=12.5
ELSE
IF WHEEL_POS=="SKIMH"
<current position>=180
POSITION:21=12.5
ELSE
IF WHEEL_POS=="ENGAGE"
<current position>=30
POSITION:21=0
ELSE
IF WHEEL_POS=="HOOK"
$<current position>=-15
POSITION:21=0
ELSE
IF WHEEL_POS=="GUIDE"
<current position>=70
POSITION:21=0
ELSE
IF WHEEL_POS=="START"
<current position>=0
POSITION:21=0
ENDIF
ENDIF
ENDIF
ENDIF

Each position has dimensions of parts set to specific values.  I can set all those values at once by entering the wheel position parameter value for that position.

Anyone know how I can do this (or if I can do this) with basic creo 3.0?

I added a secondary constraint set using Angle Offset.  I have a dimension, but it still has issues with positions past 180.

8 replies

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spete10-MarbleAuthor
10-Marble
August 3, 2017

I was able to use values over 180° (my 90° was actually supposed to be 270° - the direction was flipped from my original angle offset attempt).

 

Using the pin connection to control the movement, then a secondary constraint set with an Angle Offset gave me all I needed to show the wheel in its different positions. Go WPI Engineers!!!

S
spete10-MarbleAuthor
10-Marble
August 3, 2017

Forget it.  In order to get to the correct Guide (290°) and Engage (330°) positions, I have to first set my Skimv (270°) position, which has to first have Start (0°) set.  Hook and Skimh also need Start set first.

I guess the connection isn't helping.

S
spete10-MarbleAuthor
10-Marble
August 4, 2017
I am able to sucessfully create the pin connection both unconstrained radially (using only the rotation axis and translation constraints) and also constrained (adding the rotation constraint). I can rotate the part freely to the max and min I set while in the assembly mode using CTRL-ALT & LMB but once I'm out and try to move them Creo tells me it is suppressing the connection because of incorrect constraints. I still didn't have a dimension I could use in my relations. And as I stated I set up the Angle Offset foe the sole purpose of obtaining said dimension only to have issues with the angle.
Having said that, I have never used the Regeneration Value setting, but now I will give that a go to see if that was the missing piece in my setup. Thank you.
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psobejko1-Visitor
1-Visitor
August 3, 2017

I don't think you are setting up the mechanism connections correctly.  For a pin connection, you have to specify at least two reference pairs:

1) to specify the axis of rotation ("Axis alignment" in the connection definition)

 

2) to specify the placement along the axis of rotation axis of the rotating body with respect to the stationary body ("Translation" in the connection definition)

 

If you stop there, then the part is free to rotate without constraints.

However, you have the option of specifying the 3rd pair of references which will allow you to control the angle of rotation ("Rotation axis" in the connection definition).  There, you can "enable regeneration value", and then you will have a placement dimension that you can drive via relations...

 

One warning: if you set the value of this angle to a negative value, then the "sense", i.e., the positive direction of rotation will be reversed.  So best to stick to positive values only.  If you want a rotation of -5 degrees use the value of 355 degrees, or otherwise your part will start to move in the opposite direction upon subsequent regenerations...

 

 

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