2D or 3D first? What do you think?

[jason.davis05]

Hello all:

I just started working for a new mold shop just less than a year ago, and here they do all their 2D work first then 3D work after. I have been machining for 14 years and never done this. What do you guys think is it better to do 2D then 3D or 3D first? I think doing the 2D first causes more problems for the cutters that have to do the 3D work but that’s just my thoughts.

Thanks for the input.

[blowmebigtime]

I have found that when guys do 2d work first in our Hurco's , then give it to me in the 5 axis machine , alot of times it makes more work for me, they rough out material on flat areas and pockets and I dont know what they did or didn't do, then when I get it alot of times I recut what they just finished unless I write the Hurco program for them in my software.. I have to spend alot of time to see what they did and make sure I dont crash into anything they left behind,, in the long run its much easier AND SAFER for us to do the 3d first with my program and then do the remaining 2d after I am done.

[NC Cams]

Having been taught the "old way" (2D pencil on paper drawings) and then migrating into the 21st century, the answer to your question is best based on perspective and education.

When 2D was the only way to draw and w/o CAD, you had to think 3D although you could only draw in 2D. This forced designers to think differently - as in how do I get a tool to get in there to do that?

The trips that older designers had to make to the shop floor in order to show some hard core machinist how to do something that could never be done often resulted in either the designer getting better at his trade or finding a new one.

When CAD came along, the fact that the "computer" was involved implied a bit of invulnerability to the designer. Granted, they were now better tooled with faster and easier ways to convey a drawing BUT since it was now easier to "UNDO" than to erase and redraw by hand, I contend that designers were allowed to to get sloppy and a bit undiscipline.

Moreover, when they got imersed in their drawings and layers, they don't always realize that other people can't "see" what the hell they're trying to convey. Or, worse, the use of layers confuses you into thinking something can be done when it really can't.

Moreover and more importantly, when you have a computer you can dimension off of ANYTHING that is ANYPLACE on the drawing - even a gage line out in space someplace.

The trick is, geometrically this is correct and perfect, HOWEVER, how the hell is a machinist supposed to gage off of something that doesn't exist yet or is an arbitrary point in space that can'te be touched off of????

3D CAD allows you to create building blocks and carve out beautiful works of art. However, the sad fact is that a lot of designers fail to consider that a lot of machining (complex and/or multi axis) machining is/may be needed to generate the square hole at the bottom of a round cylinder - in other words, how the hell are you going to do that??? THe layer you turned off to expose that surface may unfortunately be M42 tool steel and you ain't gonna make that disappear in real life as easily as turning off a drawing layer.

I worked at a place where they had 3D modeling capabilities. The CAD jockeys were always cheating to get the job done. They'd do the drawing and then toss it over the wall and let the machinists figure out how to make the damn thing. A never ending sourcd of strife and turmoil was this perfect wire framed concoction that was damn near impossible for a spatially challenged machinist to interpret, let alone machine.

Due to a health situation a particularly well talented machinist had to get off the floor so he took CAD lessons and moved over into design. His drawings were not only works of art but they were makeable, functional and very well thought out/applied. I wonder why? Same tools - vastly different results - (see first paragraph in this posting for the reason why).

Hell, this guy carved a "swiss cheesed" billet head (rifle drilled in every direction imagineable) out of 2D paper drawings using a Bridgeport mill and a Sine plate and rotary table - a fete that a 5 axis machining house said couldn't be done.

I contend that whether it is 2D, 3D or paper or CAD, it is the skills of the designer (not the tools used) that makes for the more successful design. I"ve seen more instances than not where the trick CAD merely covers up for the deficiencies of a spatially challenged designer who should be sweeping floors instead of creating compter havoc with state of the art CAD systems.

Until/unless you have a machinist who knows how to make something from a chunk of unshaped whatever, involed in the design process, 2D or 3D can be just as good or bad as the other. Any shop that doesn't have regular design reviews and relies solely on the CAD tube for design "expertise" is asking for grief beyond what they need to endure.

[jason.davis05]

NC Cams.... Hold on man,

I'm talking about machining your 2D work first or machining your 3D surfaces first. I think I agree with what your saying a good designer was a machinist first, and before that he/she cleaned the bathrooms. But thats not what I'm getting at here. Thanks though.

blowmebigtime:

I'm finding that I have the same problems. Thanks