In reply to No Time :
I am not in a model based environment. LOL. Well, we do have some capabilities and are trying to move in that direction. I still typically need to create drawings for machining, fabrication, assembly, inspection, and customer documentation.
We have additive manufacturing and several CNC machines, but those guys still want drawings. They are working on moving the machine shop over from dimension driven to tool driven programming so they can use our CAD data directly. The 3D printer can take CAD models directly.
It is possible to put tolerance and GD&T in model based design. I don't know how CAM software interprets that stuff. I have never done CNC. I assume it might effect tool speed and feed to achieve tolerance? Still, human beings have to set up the parts on the table, verify flatness, locate zero, fixture the parts, etc. I will have to ask one of our CNC guys.
I'm old fashioned....I like drawings.....proper drawings, done on a drafting board. It's an art form. Now , get off my lawn!!
No Time said:
I'm not on board with relying on the model, even if you fully dimension your sketches. The drawing is an important part of defining the critical reference point and dimensions required for a part.
The model can be dimensioned a million different ways, and not all will produce the same result when you start adding tolerances and doing a tolerance stack for the assembly. Start to include GD&T and the models don't provide nearly the level of control that a drawing can (not to mention bonus tolerance for MMC and LMC).
There are scenarios where all of that is critical, and scenarios where none of that matters.
I manage a prototype shop. Its rare that our quantities are higher than single digits. Our CNC machines will be within ~0.005" (and tighter, depending on material) without any real effort, so the only time any dimensional notes are needed are for a extremely critical fit, or an insert of some sort. Critical fits are not super common - we aren't making engines. Usually press-fit-like things are toleranced, but that's about it.
By default, we don't use drawings. They add a time consuming and unnecessary step to the work.
When we have similar parts made outside, we do use drawings. Usually whats dimensioned is: Overall (helps with quoting), inserts, and really critical fits. Largely the drawing is undimensioned and its mainly a place to put a few notes, primarily what material is being used.
Now if you are a production environment and you are making thousands or millions of an item, sure GD&T or highly detailed dimensions and tolerances make sense. Or if you are working on some super precise stuff.
I'd argue that in the context of many Grassroots Motorsports-ish projects (for example the bracket Tom posted above), the precision required does not exceed the inherent precision of most fabrication environments.
Drawings show design intent, without them you just have a blob in space.
Are those holes a bolt pattern? What is more important? Having them dead nuts to one end or centered about the body? Do I want the pattern right and the positioning can float or does the positioning need to be spot on?
How do I check this item to make sure its good to hand off to the next process? Blobs don't tell me that.
Where do the weld beads go? How about fillets and chamfers? Do I need weld clearance? Can I weld one side or the other? Skip weld or full weld? Welds ground flush?
If I had a dollar for every time I heard "it fits in solidworks"
