Sheet development on drawing
Sheet development on drawing
(OP)
Dear all,
I've read many times this forum, but this is the first time for a thread. This is a wonderful forum.
I have a little question for you.
In the drawings relevant to parts made by bended metal sheet I always represent the development.
Some suppliers have a problem if they follow this development because the final product doesen't guarantee the final dimension.
Some other suppliers haven't any problems and the final piece is correct although they'are using the same drawing.
This happens because the machinery/equipment are different.
At this point I've decided that the future drawing won't have the development representation.
What do you thik about?
Thanking you in advance,
regards
I've read many times this forum, but this is the first time for a thread. This is a wonderful forum.
I have a little question for you.
In the drawings relevant to parts made by bended metal sheet I always represent the development.
Some suppliers have a problem if they follow this development because the final product doesen't guarantee the final dimension.
Some other suppliers haven't any problems and the final piece is correct although they'are using the same drawing.
This happens because the machinery/equipment are different.
At this point I've decided that the future drawing won't have the development representation.
What do you thik about?
Thanking you in advance,
regards





RE: Sheet development on drawing
The formed part is what you require and are paying for. Let the fab shop create their own flat.
On the rare occasions the shop requests a DXF flat, I ensure they understand it is for "lookalike" purposes only. If the part turns out to be out of spec, they own it.
RE: Sheet development on drawing
RE: Sheet development on drawing
RE: Sheet development on drawing
Different shops have different methods so a flat pattern generated by the customer may or may not be accurate. I would say always dimension the finished part and make it the fab shops responsibility to make sure that is what you get.
11echo, I have never seen a shop move bends or welds without as least asking for customer approval first.
RE: Sheet development on drawing
Specify what your inspector will accept. Don't tell them how to make it.
RE: Sheet development on drawing
"Wildfires are dangerous, hard to control, and economically catastrophic."
Ben Loosli
RE: Sheet development on drawing
different vendors making the parts with different processes, making work for engineering ... say it isn't so ! we've recently had to redo done a bunch of pipe details (with all sorts of bends) ... initially the fab people worked from 3D drawings (no surprise there) but then along came a cheaper guy who worked from a bend table ... sigh^2
RE: Sheet development on drawing
If you do feel the need to put the flat pattern on the drawing, I'd make all the dimensions on it reference, and if necessary add an explicit note explaining that the 'flat' view is for reference only etc.
Given that many CAD packages can 'unfold' the finished item to get the pattern it always seems a shame not to use it, but a few of the stories above pretty well demonstrate the issues.
If you share a common/interchangeable CAD format, there may be merit in supplying the model though this has it's own configuration control issues.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Sheet development on drawing
We send our sheet metal out to be fabricated. Our vendors routinely ask for our SolidWorks files so that they can flatten them and apply their favourite K factor. They also convert our drawings from millimeter units to inches.
This all is fine with me, as long as our inspector accepts the results.
RE: Sheet development on drawing