Add a math formula to a dimension.

Is there a way to add a specific amount/length to a dimension by using a formula? For example, say I wanted to measure a length of conduit between two fittings. The clear distance between the fittings is 48" and the conduit is recessed into the fittings by 3/4" on each side. If I dimension between the fittings, normally it would read 48", but I want it to read 49-1/2" so my shop people know what length to cut.

Then why not call out the cut-to-length dimension?

I'm trying to avoid doing this manually since I have to call out dimensions for roughly 400 lengths of conduit. Too many chances for error (and not enough time) if I have to manually call out each cut-to-length dimension.

This extra length is the same no matter what fitting is used?

There are only two types of fittings being used (couplings and pull elbows) and the difference between the two is negligible.

You do know you can add text to an AutoCAD dimension right?

Would you be comfortable with this to your dimension(s)?

Add 1.5in for cut length

I could show you how to somewhat automate the process.

I don't want them doing any more math than they already have to!

Actually, I'm with ReMark on this one - if you state that the distance between the fittings is 1-1/2" bigger than it actually is, some clever person in the shop will probably add an extra 1-1/2" on top of that again because they know it should be there, so at the very least each dim should carry the annotation 'cut length' (as well as the mathematical bit you want doing)

That's all fine and dandy, but the original question remains unanswered. Can you add a predetermined amount to a dimension?

And I really, REALLY, don't want these guys trying to do the math on the cutting room floor. Yea, adding a note for them to add a 1-1/2" to all lengths is easy for me to do, but I guarantee half of the conduit will be cut short if I go that route.

I think it would require a lisp routine of some sort.

Why not dimension the actual length by using the point within each fitting as the start/end of the dimension line?

Look, there are many ways that I "could" do this. However, many of these ways present complications that I would like to avoid by "not" doing them.

I don't want my shop guys doing math. They need to be able to look at the plans and quickly get what they need to build the product. Asking them to add this or that to each dimension is only asking for trouble.

I don't want to (although it looks like I have to) manually go through each and ever piece and adjust the dimensions to reflect what they need to cut. I'm human, and prone to error (it comes with the species).

I also don't want to dimension things through other objects. That would require that I show all of the hidden lines, and then go back and clean up the lines that I don't want.

It would just be nice to write a formula in the dimension that reads like X + 1-1/2" = Y and be done with it. Apparently I can't do that, so option two is going to be what I have to do.

Here is something you could use to modify already existing dimensions. It adds the number you put in and then overwrites selected dimensions. It also remembers the last number (you put in) for as long as the current drawing is open.

(defun c:wrt (/ a b n n1 n2 e e1 f g h)
 (command "_.undo" "_begin")
 (if c1
   ()
   (setq c1 0.0)
 )
 (princ "\n Add to main dimension:  ")
 (princ c1)
 (princ " ? ")
 (setq b (getdist))
 (if (= b nil)
   (setq b c1)(setq c1 b)
 )
 
 (princ "\nSelect Dimensions to add ")
 (princ c1)
 (princ " to:")
 (setq a (ssget '((0 . "DIMENSION")))
n (sslength a)
n1 n)
 (repeat n
   (setq n2 (1- n1)
  e  (ssname a n2)
  e1 (entget e)
  f  (cdr (assoc 42 e1))
  g  (+ b f)
  h  (strcat (rtos f 5 3) " + " (rtos b 5 3) " = " (rtos g 5 3))
  n1 n2
  )
(command "._DimEdit" "_N" h e "")
 )
 (command "_.undo" "_end")
 (princ)
)

I just find it misleading to show the dimension from face of fitting to face of fitting and add another inch and a half to the dimension text. Would you put a break line in or append a note such as "cut length"?

I think you can in 2010:

http://rcd.typepad.com/rcd/2009/02/autocad-2010---its-parametric.html

I just find it misleading to show the dimension from face of fitting to face of fitting and add another inch and a half to the dimension text. Would you put a break line in or append a note such as "cut length"?

It is misleading but that's the way the 'customer' wants it, isn't it?

...dimension that reads like X + 1-1/2" = Y and be done with it.

For example:

You run the risk of someone on the shop floor who knows that in the past he was instructed to add 1.5" to a dimension to arrive at the cut length. If the dimension on the drawing already includes the additional length and it is not noted somewhere, somehow on the drawing then the worker may add it in again and cut the piece wrong. It is literally out of the customer's hands at that point.

what about a dynamic block?

If you are going to show it one way, face of coupling to face of coupling, but indicate a dimension that is longer than what is depicted then shouldn't there be a break symbol in the dimension line?