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# Neutral factor

Solution Partner Pioneer
I have created development of a job. I am getting wrong dimensions of the development.
If I change neutral factor still the dimension doesn't change.
How should I apply neutral factor any specific guidelines for it

Regardd,
Ashish Sarode
7 REPLIES

# Re: Neutral factor

Gears Esteemed Contributor

Not sure what you are doing as you are talking about a "development" from a "job" and the terms do not mean anything to me.

The Neutral factor does not affect the formed part.  The neutral factor affects the flat pattern created from the formed part as it dictates the percentage of the material from the inside bend face where the the material does not stretch or shrink when bent.

Ken
Production: ST10 MP9, Testing: SE 2019
http://Grundey.blogspot.com
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# Re: Neutral factor

Valued Contributor

As Ken stated, the neutral axis factor will only affect the flat pattern, not the formed piece as designed.  It essentially considers the material dimensional changes that occur when the metal stretches as it is bent.  Here is a good website that describes the effect as well as giving you some generic K Factors to use based on material, process and bend radius:K Factor

That being said, if you are doing precision sheet metal in large production, you must take samples and bend them to obtain the K factor for a specific piece of material and process and then apply that to your model to generate the precision flat patterns.  For most applications this is not necessary, and you can use the much more generic numbers provided.

# Re: Neutral factor

Honored Contributor

k=1/3 is a good estimate most of the time for bending sheet metal.

The real problem is guessing the actual bend radius. One must assume a bend radius. Depending on the machine measurements my need to be taken for every material and every length of bend at each setting of the machine. The starting place is R=thickness. R=1.5 thickness is much better if your machine can do it.

The limiting factor for SE is that the gage table selection slows down the more entries there are in the table. At 50 entries, it take me 7 second just to open the gage selection on a really fast machine. 13 second is how long the GTAC guys take to open that menu with my files. This is to be fixed in ST9.

Complicating things, springback varies wildly. Stainless can require up to 9 deg spring back.

# Re: Neutral factor

Gears Esteemed Contributor

And of course, this all varies based on the metal type (aluminum, CRS, HRPO, SS, etc...), thickness, grain direction, process type, bend angle, tooling, machine parameters, and sometimes the operator...

Ken
Production: ST10 MP9, Testing: SE 2019
http://Grundey.blogspot.com

# Re: Neutral factor

PLM World Member Phenom

And there is no way to model coining or other permenant deformation.  Parasolid thinks everything stays smooth and constant thickness.

____________________________________
--Scott Wertel, P.E.

# Re: Neutral factor

Phenom

@swertel Geez...all the cars, missles, space ships, boats, and planes all are smooth aren't they?

I think most sheet metal design in the mid-range CAD market is based on air or straight break bending operations.

# Re: Neutral factor

PLM World Member Phenom

@RyanM, yes, all based on basic manufacturing methods.  Nothing to really help the progressive die designer.  I would really like a software that could make using the strip as the guide too all things in the die, and then include springback and coining calculations in the design process.

____________________________________
--Scott Wertel, P.E.