Rembrandt Harmenszoon van Rijn was a brilliant design engineer, though he was quickly fired. His production drawings were beautiful but they had so much detail they took him too long to produce. [citation needed – and because I made it up, probably cannot be found]
Back in the early days of 2D CAD computers were slow. For an example to compensate, if you were putting threads in a plate, the top view would contain one circle (guys on a 286 would add the second, hidden-line hole) and maybe two parallel lines in the side view. We would hardly ever add the fastener. [We didn’t need them, the assembly guys didn’t use the fastener we specified anyway, they just grabbed a handful and put the assembly together. They knew what a tapped hole meant.]
We kept our drawings simple mostly because of computer limitations, but just because today we have bigger computers doesn’t necessarily mean we should put more into our drawings.
The image below is an actual file I found in an “extremely slow” assembly. (Click on it to enlarge.) Takes 4 seconds to rebuild this part. Not too bad, except they had 50 of them in the assembly. Rembrandt may have given it the thumbs up, but there was no return on investment for this detail. This fastener should have been just a cylinder with three steps in it.
A more fun example: I once had a friend who complained that since he had switched to 3D CAD he was significantly slower than he was with 2D. He complained: “It takes too long to create the models and way too long to open them!” He was working on a conveyor design with a chain drive. To give you an idea of the detail in this chain drive, upon closer examination of the chain, I noticed he not only modeled the chain links but the little cotter pins, rivets, even the text on the links were there! A beautiful Rembrandt quality model. I looked at his earlier models of the same assembly as modeled in 2D. This same chain was portrayed as simply two arcs and two tangent lines. The entire drive assembly was a purchased component …I don’t know why he was even modeling the chain in the first place.
With 3D CAD it is tempting to make highly detailed drawings, but just because you can does not mean you should. A production’s drawing job is to convey how a product is to be produced. If it contains more detail than needed, you are wasting money -your time to create that extra detail, and your time having this detail regenerated by CAD at every rebuild.
[If you need this detail for renderings, or for customer approval prints, consider putting this detail in configurations that can be turned off -so you don’t have it slowing your computer down during your normal design process.]
CSWE Engineering Data Specialist 3DVision Technologies