suggestion for a mechanical engineering forum

[Mechatrommer]

the problem is not the CAD (its nothing but drafting with computer), the problem is skills and experience. tell me if any junior doesnt make mistake? once i was told by a seasoned engineer about his young age, he almost got fired for his mistake. as with drafting with pencil, die skil etc, those skills are no longer necessary, they deserve in archive book just in case of armaggedon. drawing exploded 3D can now be done in no time with CAD, and any angle view you want in case the draftman make mistake, not to mention uploading to cnc machine.

[robrenz]

"Simultaneous Engineering" is an attempt to minimize these occurrences and to spread multidisciplinary knowledge. In other words have all groups involved from the beginning instead of the throw it over the wall mentality.  If implemented well with cooperative groups everyone benefits and the learning curve for newbies is shortened.  Many entrepreneurs embody simultaneous engineering because they are all of the disciplines combined in one person.

[HLA-27b]

People often make the erroneous assumption that CNC means inherent accuracy. Nothing can be farther than the truth. Accuracy only happens if YOU care (and know how) to measure it! If you want to manufacture an R8 collet for example, as seen on robenz's videos you need a grinding machine and more importantly an accurate set of gages. To manufacture the gages you will be doing mostly manual work and you will be measuring the hell out of it regardless of the method of manufacture.

CNC is good if you want to churn out many parts with averagely skilled workforce. Then again if you want to churn out millions of parts CNC is no good, you get yourself a good old cam operated lathe (aka. screw machine).  If you want plumbing fittings or ammo cases by the million and dirt cheap this is your tool of choice since the beginning of the 20th century until at least the end of the 21st, not even remotely threatened by the advent of CNC machines as they require 4 times more energy and floor space and are slower.

If you need a die for some aircraft fuselage part with crazy compound curvature CNC is your friend. But then again there was no CNC during WWII yet no lack of aircraft, so I might be missing something.

To cut it short

Manual machines  - One offs, Repair work, Home shops (I'd go manual for a home shop every day of the week)
CNC Mashines - Small batches 1000 to 10.000 pcs, Complex curvatures, compound surfaces
Cam lathes, Screw machines, Thread rollers, Broaches - Million part batches

Of course all of these machines work on soft annealed metals. After machining most parts undergo heat treatment which is notorious for crooking an distorting parts to ruin any accuracy so far attained. This is why manufacturing people don't fuss all that much about accuracy up to this point. The main object is to remove the bulk of the material and to leave just enough to be machined after heat treatment. At this stage most parts are too hard to be machined conventionally. So the final and most accurate machining is done by grinding and for the ultimate in accuracy lapping and super-finishing.

For any of these you need a full set of measuring tools. If you can't measure it, it ain't accurate.

[G7PSK]

No the problem is not the CAD it is the fact that the operators of many computers running CAD programs have had no experience on the shop floor or know how to use the tools or materials that are required for the job,they do a course on how to use the cad software at tech and then are set loose designing the machines and equipment that others are then expected to make. Some of the CAD operators that I have run up against have no knowledge of engineering either, they have replied to a job advert for a CAD operator having got a school certificate and the numb skulls doing the hiring have hired them. I have seen bendy beams and wobbly floors and a whole host of other horrors in my life due to so called CAD designers.

[Mechatrommer]

you dont expect a draftmen to design something and works wonderfully, thats not within their skillset by definition, but a good draftmen knows how his drawing converted into reality. thats what a team for, to support and educate each other esp the one below you. and thats also make a junior become experienced. but also a very good junior is self-taught and quick learn to become multidiciplinary, but how many person you expect to have such ability?

[chickenHeadKnob]

This thread is drifting from simon's original question. My vote would be to go to cnczone for CAD discussions.

[G7PSK]

All the old school draftsmen had the skills due to the requirement during their training to work on the shop floor.
That is my argument, these days they do not insist that someone should do time on the shop floor during their training, they just go to tech and learn how to use a computer program. And as they say Garbage in Garbage out with computers.