Dimensioning, annotation and graphic effects

Abstract

We have drawn attention occasionally in previous chapters to the great value of dimensioning operations in CAD. First and foremost they reduce the risk of human error by putting on to the drawing the actual calculated length or angle and not what the designer thought he meant. Secondly, they automate quite a bit of actual drawing. The designer indicates the length to be dimensioned and the position for the written value. The software generates the written value and tolerance and all the related lines and arrows. It is a pity that (certainly at the time of writing) dimensioning facilities are the ones most often skimped in a CAD program when it is first launched. I have even seen facilities which would barely pass muster in one of the most expensive packages on the market! The trouble is that dimensioning is not glamorous, has to cover a wide range of different styles, and requires a lot of tedious detail to implement and a lot of knowledge of drawing practice. None of this is attractive to software writers trying to launch a new program in a competitive market where the latest fashionable feature and buzz-word counts. Nevertheless, the range of styles should meet the requirements of the appropriate national or international standard.