Controlling Thickness
Controlling Thickness
(OP)
I have a plastic part which is injection molded, then subsequently R.F. Welded. One area of the part has fairly thin sections which is where the welding will eventually occur.
We call out a nominal thickness of .030" +/- .005"
The welding operation is not tolerant of SUDDEN changes in thickess (i.e. .005" thickness change in any .250" x .250" area). This can happen from sinking, or other molding abberations. Sudden changes cause "Bridging" in the welding process. This thin section is subject to warpage of up to 1/8", but that does not make a "Bad" part as the welding process will readily flatten this "warp". I don't want to throw away good parts.
I want to define the part so the nominal thickness may float from .025" to .035", yet limit any "sudden" changes to .005" in any .250" x .250" area. Flatness won't work as the warpage blows away the "delta" in the surface.
I can simply "write a book" on the face of the drawing and spell out what I've desribed above, but would rather use GD&T. What do you think?
Thanks
HvyB
We call out a nominal thickness of .030" +/- .005"
The welding operation is not tolerant of SUDDEN changes in thickess (i.e. .005" thickness change in any .250" x .250" area). This can happen from sinking, or other molding abberations. Sudden changes cause "Bridging" in the welding process. This thin section is subject to warpage of up to 1/8", but that does not make a "Bad" part as the welding process will readily flatten this "warp". I don't want to throw away good parts.
I want to define the part so the nominal thickness may float from .025" to .035", yet limit any "sudden" changes to .005" in any .250" x .250" area. Flatness won't work as the warpage blows away the "delta" in the surface.
I can simply "write a book" on the face of the drawing and spell out what I've desribed above, but would rather use GD&T. What do you think?
Thanks
HvyB





RE: Controlling Thickness
I think that you are stuck with writing that note.
Paul
RE: Controlling Thickness
I think the answer to your problem is shown on as a Tec-ease example.
http://www.tec-ease.com/gdt-tips-view.php?q=112
take a look and see if this helps.
Hopefully you get an email notifaction that your thread has risen from the grave.
RE: Controlling Thickness
I was almost going to suggest the new "I" modifier, but that too wouldn't help with the per-unit thickness idea; it would only divorce size from form.
Guess we're back to a note..?
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Controlling Thickness
RE: Controlling Thickness
I checked the OP's history and this is the only thread he has made or replied to so I doubt we will find out if he ever found an answer to his problem.
RE: Controlling Thickness
I went with the note, mainly because the Inspectors at my supplier, as well as my incoming at my factory are not very savvy on the subtleties.
THICKNESS VARIATION NOT
TO EXCEED .005" IN ANY
.250" X .250" AREA
This has been the case many times before, making the translation to the "real" world often means NOT using GD&T. Engineer to Engineer these terms make sense, but all too often, the inspectors (on my incoming) won't understand a concept or symbol, and will just skip it......
I've used this forum over the years under another logon, but forgot what it was.. thanks.