GD&T - Use of Restrained State/Non-rigid

optomist1

A Sea of Statistics
Super Moderator
Hi To All,

I don't have a problem per se, however, for those GD&T practioners, I am curious as to proper application of the Restraint Notes in industry. Where and when Y14.5M is called out/applied + restraint on non-rigid parts, is this requirement strictly adhered to? When a restraint note(s) is used are they accompanied by the necessary direction, amounts/magnitutdes and sequence of restraint, etc?

Thanks,

Marty
 

Stijloor

Leader
Super Moderator
Hi To All,

I don't have a problem per se, however, for those GD&T practitioners, I am curious as to proper application of the Restraint Notes in industry. Where and when Y14.5M is called out/applied + restraint on non-rigid parts, is this requirement strictly adhered to? When a restraint note(s) is used are they accompanied by the necessary direction, amounts/magnitudes and sequence of restraint, etc?

Thanks,

Marty

Marty,

It depends greatly on the (1) quality (clarity) of the engineering drawing, and (2) the GD&T competence of folks on the receiving end.

A solid dFMEA and pFMEA process should identify and assess the risks associated with manufacturing and inspecting "flimsy" parts.

I am curious to hear from other GD&T Practitioners. :agree1:

Stijloor.
 
H

Hodgepodge

...is this requirement strictly adhered to?
Yes, the requirement is strictly adhered to.
...When a restraint note(s) is used are they accompanied by the necessary direction, amounts/magnitutdes and sequence of restraint, etc?
Yes and no. Depending on the assembly requirements, specific instructions detailing how to restrain or how much restraint will be in a B/P note to ensure repeatability in the restraining process. However, in my industry, quite often the nomenclature will just be similar to, "All dimensions apply when Datums -A- & -B- are restrained within the specified limits of size."
 

optomist1

A Sea of Statistics
Super Moderator
Hi Hodgepodge,

so if I understand you correctly, although restraints are required the methods & means are left up to the drawing user/inspector. Are the drawings per Y14.5M??

Thanks...
Marty
 
T

True Position

If it is not specified, a part should be checked in free state. If a part needs particular clamping, it should be specified on the drawing. I've seen drawings that specify the torque to be applied to particular bolt patterns, usually on sheet metal parts.
 
H

Hodgepodge

Hi Hodgepodge,

so if I understand you correctly, although restraints are required the methods & means are left up to the drawing user/inspector. Are the drawings per Y14.5M??

Thanks...
Marty

You are correct. Here is a direct quote from a print that is designated, “Interpret dimensions and tolerances IAW ANSI Y14.5M - 1994.” (This isn’t the latest version of Y14.5 but you can see what I mean.):

“All dimensions apply when Datums C and A, and surfaces B and H are held flat.”

That is all it says. No description of method.
 
H

Hodgepodge

If it is not specified, a part should be checked in free state. If a part needs particular clamping, it should be specified on the drawing. I've seen drawings that specify the torque to be applied to particular bolt patterns, usually on sheet metal parts.

I have seen this as well, however, I have also seen it not specified.
 

optomist1

A Sea of Statistics
Super Moderator
Thanks to all for your input.....and as a side note I feel so, so, dwarfed by all you "Karma Kings".....thanks again.

Marty :tg:
 

Paul Sarrach

Registered
If the print states Must Be Restrained but we are in the proto type stage and there is no fixture what options are there? I have Pc-Dmis can do either an Iterative or a Best Fit as an alternative? If not what? I was told to use the base as my -A- datum but the part is not completely flat, is that acceptable?
 

John Predmore

Trusted Information Resource
[if] there is no fixture, what options are there?
@Paul Sarrach tacked your question onto a discussion which is more than 10 years old.

The purpose of the "restrained" note is so a floppy, flexible part is measured the same way every time (in agreement between you and your suppliers and your customer) and to minimize repeatability variation arising from measurements.

Without a lot of details about your circumstances, I think one solution is to construct temporary fixturing using gage blocks and pins on the work surface of your CMM. Be sure to make detailed notes and take photographs, so the temporary fixturing can be reliably re-created the next time. A note on the first article inspection report should explain temporary fixturing was used, in case different tooling is used in future inspections.
 
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