Associative Dimension?

Hello All,

Lets say I have an image inserted into my drawing at 14.08" from a line. I want to make the image exactly 14.0" from the line. How can I move the image, so the current displayed dimension also changes as I move the image?

Thanks

CAD has three available choices for the system variable DIMASSOC (accessed by typing DIMASSOC at control line)

 

0 - When you draw a dimension it is non associative and exploded (i.e. broken into its component parts) DO NOT USE!

1 - When you draw a dimension it is non associative

2 - When you draw a dimension it is associative

 

So if you type DIMASSOC and set it to 2 before you draw your dimension then the dimension will be associated with the geometry it is representing. So if you move it it will move with it..

I would use Parametric dimensions so that I can edit the dimension value and have the image move.

 

Start by drawing a line along the edge of the image so that you will have a point to reference for the parametric dimension line. Now make a block that includes the image and the line. Add a parametric dimension line from the reference line to the end of the line in the block. You should now be able to edit the value of the parametric dimension line and have the image move. You may want to add a fix constraint to the reference line to ensure that the image, and not the reference line, moves.

Depending on your AutoCad release, parametric constraints may not be available. At the moment, it appears that the OP is using the "Not Applicable" program. At any rate, in the beginners area, when the question is how to use associative dimensions, parametric constraints will add an unnecessarily steep learning curve to the exercise.

 

Now, let me come in the back door and ask if lrm is correct in assuming that the issue is after all, how to move something .08" without pulling your hair out. Are you trying to use the dimension as a guide to show you when you have moved the image far enough? If that is it, there is a much easier way.

 

Select the image, type m(ove), click a base point, move the cursor any comfortable distance in the direction you want the object to go, type .08, hit enter, done. Some fine points, this method doesn't always work with Ortho on. Polar Tracking (including showing tracking vectors) works best. I don't know why, but Ortho mode just does not like letting one move or copy something an explicit distance by data entry.

 

Now, back to Associative Dimensions.

 

First off, do you know whether you are using associative dimensions? If you are, then you are there. If not, you can try typing the command DIMMREASSOCIATE, to see if it will let you associate your dimension to the objects you want it to live with. Before you do this, it is best to assure that the dimension is actually ON the objects in question and not just really really close to them.

 

If that didn't work, and your dimensions are not already associative, simply set DIMASSOC to the correct value as outlined, and re-do the dimensions you need to have associative. Then, from now on, use associative dimensions exclusively, especially if you are one of those people who dimension in paperspace.

 

We might add that once the system variable DIMASSOC is set to 2, one need not set it again. It will stay that way. Then ALL dimensions you make will be associative, even those in the next drawing, and all drawings following that one, until the value is changed again. DIMASSOC is an environment variable that is not stored in the drawing, but in the AutoCad system.

 

There is also a check box that sets this variable to 1 (unchecked) or 2 (checked). The box is about half way down the page on the right of the Options dialog, User Preferences tab.

 

Now, associative dimensions obviously have to be associated with something. They will take up a lifelong association with a single point in modelspace if you let them. If you move or stretch an object and the dimension does not update, or only one end moves, then one or more of your dimension nodes missed the object just far enough so it thinks it belongs to a single point in space rather than a line or something. Associative dimensions don't have to be on a snap point, grip or vertex, but they do have to be touching part of some object, on both ends. Dimensions that miss an object by less than half of your precision level will lie to you. AutoCad will round it to the nearest whole 0.0~~ whatever that you told it to use.

 

For future reference; When you use multiple lines of dimensions to dimension major and minor divisions in an object try not to get in the habit of associating the next higher line to the dimensions below them, snap them to the object also. In other words, don't associate dimensions to other dimensions. They get particularly testy when it's modification time.

Edited October 23, 2014 by Dana W

Depending on your AutoCad release, parametric constraints may not be available. At the moment, it appears that the OP is using the "Not Applicable" program. At any rate, in the beginners area, when the question is how to use associative dimensions, parametric constraints will add an unnecessarily steep learning curve to the exercise.

 

 

For future reference; When you use multiple lines of dimensions to dimension major and minor divisions in an object try not to get in the habit of associating the next higher line to the dimensions below them, snap them to the object also. In other words, don't associate dimensions to other dimensions. They get particularly testy when it's modification time.

 

Ensuring that your NODE osnap is turned off will help avoid this sticky wicket, meaning mis-associated dimensions connected to other dimensions.

CAD has three available choices for the system variable DIMASSOC (accessed by typing DIMASSOC at control line)

 

0 - When you draw a dimension it is non associative and exploded (i.e. broken into its component parts) DO NOT USE!

1 - When you draw a dimension it is non associative

2 - When you draw a dimension it is associative

 

So if you type DIMASSOC and set it to 2 before you draw your dimension then the dimension will be associated with the geometry it is representing. So if you move it it will move with it..

 

 

hehehe - i think some fun is to be had here

Ensuring that your NODE osnap is turned off will help avoid this sticky wicket, meaning mis-associated dimensions connected to other dimensions.

Yeah, good catch. Type DSettings, uncheck Node, while one is dimensioning. It's much faster than cycling through snap symbols for each dimension point. Sometimes one must attach a new dimension node smack on top of another, because there is no other option. Often one will have three or four dimensions attached to the same outside corner of a house, or of a toaster oven, for that matter.

 

Turning node off lets you get through to the object snap point without the prior dimension's node getting in the way.

Then ALL dimensions you make will be associative, even those in the next drawing, and all drawings following that one, until the value is changed again. DIMASSOC is an environment variable that is not stored in the drawing, but in the AutoCad system.

Are u sure?

 

Type: Integer

Saved in: Drawing

Initial value: 2

If the "drawing" in question was the basis for a template then it would be true. Or if it is included in the user-defined start up file acaddoc.lsp as a setvar.

I have found that in order to make associative dimensions work with images you must embed the image in a block. If you do not the associative dimension will not update if the image is moved even if you use the OSNAP modifier Insert to snap the dimension line to the reference point of the image. However, if you define a block that includes a line and the image, the associative dimension will update when the block is moved.

 

I suggested the use of Parametric dimensions because it allows you to specify the precise dimension you want rather than having to calculate the move distance required for an associative dimension. The process is not rocket science. Just add a Fix constraint to the end of the reference line then add a parametric dimension from the fixed end of the reference line to the end of the line in the block that contains the image. Edit the parametric dimension to the desired full value and the image will move accordingly. Simple!

 

Casio47, have you tried either or both of these methods - Associative vs. Parametric?

Are u sure?

You know, you are right. I guess having always left it set to 2, I never really looked it up, and have been assuming it is a system variable because it always came back as I left it. Throwing that switch in the Options, User Preferences dialog doesn't even retain the value through to the next drawing either, so there is no extra layer there.

 

You are also right about the associative dimension and images. I just assumed that the image frame was a polyline, which it is not. It isn't really anything. I have never once needed to dimension to an image frame.

 

However, getting associative dimensions to work with an image frame doesn't really require a block. One simply can draw a line directly on top of one side of the frame and move the image and the line together.

 

At any rate, since the OP doesn't have parametric constraints to get a headache over in their release, the best way for them to move something as small a distance as 0.08" is by directly entering the distance within the move command. No dimensions or constraints needed.

 

Even though one can zoom in close enough to see 0.08" it is still very difficult to make the move accurately only using the cursor and tracking data as a guide.

Edited October 24, 2014 by Dana W