Who does the FLAT

[Independent CNC]

I have been working at a company for almost 15 years doing programming / engineering for mostly CNC sheet metal equipment. The company started out using AutoCAD for drawings they would draw the formed view and flat view on the same drawing. I think in about 1998 they purchased Pro-E and stared drawing everything in the formed view and would generate a flat DXF file for programming. For the most part everything is good and they get what they ask for.

Recently we have found some trouble with the flats and my new boss seems to think that flats should be the responsibility of Programming. His reasoning is that’s the way it’s been done at all the other places he’s worked before. Now I do agree that we should check the flats but for programmers to have and learn a CAD package just to open a file and create a flat is not good use of our time. I also agree with comments the COO said several years ago that the design engineers need to understand the process to better design parts. If you work for a job shop where you are receiving other customer’s drawings then I would agree programmers need to develop the flat. I am interested in who owns the flat and why at companies that design their own sheet metal parts.

Greg
Home Page: http://www.ctcn.net/~3kings

“Eagles may soar but weasels don’t get sucked up in jet engines”

[Cmott]

Where I work, the flat is the shops responsibility. The engineering department designs the product, how it is cut and formed is "owned" by the shop.

Since this is a new company, that responsibility has just recently changed. It use to be the engineers responsibility to design and flatten the parts.

[keebler303]

I don't know about pro-e or others but in solidworks you can draw a sheet metal part, then unfold it within the program. from there you can open it in a drawing and save as a dxf. I have only played with this feature a little but it seems pretty nice.

Matt

[NC Cams]

I love the fact that with higher technology, we create MORE problems between the engineering and fab departments.

Whan I learned mechanical drawing, it was the responsibility of the engineer/designer to design the finished part.

Due to the shrink/growth problem that had to be dealt with at the time by the fabricators, THEY were responsible for "unfolding" the drawing, cutting the flat and making sure it met the print when the fab work was done.

More than once, a fab shop guy told me, "show me what you want, it is my responsibility to make it to print for you". To which I inquired, "What about shrink, bend alowances?". To which I got the same reply.

Now, as we have this trick CAD/CAM software, it SHOULD be possible to electronically "unfold" the drawing.

We essentially did this in a fab shop that I worked with that made prototype headers. It stopped the cad guys from spec'ing out tube radii that didn't exist and it greatly facilitated fabrication as each "section" of the pieced together header was much less difficult to cut and make.

HOWEVER, when it came to "unfolding" a duct or something of the like, the results were NOT so cut and dried.

Seems that there is STILL a degree of skill in metal fabrication (where bending/folding is concerned) that just did not quite get translated well from CAD to the flat and then back to the folded part. After all, few CAD guys work in fab shops and vice versa - ditto that for the guys who write the software.

I've had more than one situation where a CAD jockey tried to convince a fabricator that a part could be made (after all, he drew the damn thing) even though he had no clue as to how to get the metal into that unbelieveable form.

This obviously has something to do about the perverse nature of inanimate opjects.

This is where a design review is essential - no mandatory. A shop foreman familiar with fabrication techniques should be part of the design review BEFORE the CAD dwg is kicked out onto the floor to have it built.

THis way, the "you can't do that's" are conveyed and the inevitable conflicts are prevented before it is too late and the design finalized.

We started doing that and you'd be amaze how the "textbook" bend allowance factors got "cheat sheet correction factored" to much more realistic ones that both the designer and fabricator agreed to use for that gage and type of material.

I contend that it is MANAGEMENT'S responsibility to make sure that the fab and engineering shops are in sync with each other.

To allow one to run rough-shod over the other (or may the better man win the argument) is asking for problems. You'd be amazed at what progress occurs when the fab guys and design guys talk to and listen to each other.

One would expect that the use of CAD/CAM to flatten the parts would be MUCH more efficient. True, if the bend allowances are "correct" and the forming technology that is being uses is capable of duplicating the assumptions made by the software. Is it? Not from what I've seen.

If not, you're better off letting the fab guys flatten it - but strive to get the forming and desiging technologies more in tune with each other as they need to be in the real world.

Most importantly, the G/D childish finger pointing stops and stuff gets done better, faster and more profitably when the fab and design guys are working as a team as opposed to vendor and consumer - after all, they both get the paycheck from the same company, don't they????