GD&T Percentage tolerance 1

[GaG1234]

Hi everybody,
I have designed a plastic tank (12" x 12" x 18"), not square, with different embossing & pocket.
The manufacturer (Rotomolding process) have a capability tolerance of +/-2% for the outside shape and 5% for the planar surface. How I can transpose these tolerance on my 2D sheet?
Thanks for help!

 

[MintJulep]

As an example:

0.02 x 12 = .24

 

[IRstuff]

Is that a process variation or a mold variation? In one case there'll be a tank to tank variation, while in the other case all tanks will off by the same value. A quarter inch seems rather gigantic for something like this.

http://www.solarplastics.com/rotational-molding/#tolerance

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[IRstuff]

This:

http://duracast.com/wp-content/uplo...-Guide-Introduction-to-Rotational-Molding.pdf

seems to be consistent with the OP, but it indicates that the tolerance is material dependent, so if the OP wants precision, polycarbonate appears to be the better material, compared with polyethylene.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

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[GaG1234]

Hi IRstuff
The material of my recovery coolant tank is polyethylene HDPE, it must resist to high & low temperature.
After looked your reference, I am agree with the excessive tolerance of my supplier, I will communicate with him and discuss the competitor's tolerance.
Also, you have resolved my GD&T problem, I will inscribe on my 2D drawing a linear tolerance as I have seen; "linear dimensions by a basic +/- .030″ plus .005″ per linear inch".

Thank you very much for your help, I appreciate.

Have a great day.