SPI tolerancing standards for drawings
SPI tolerancing standards for drawings
(OP)
Morning all,
First time poster here. I am a new employee here at my company and will be visiting a new mold house to go over plastic part design and moldflow with them. I have been asked by my company to make sure they can and will adhere to SPI tolerancing for our part prints once they receive them from us. In my experience from other lives, we just give them a .stp, igs, or a 3D CAD file and they go from there developing the tool. As far as SPI tolerancing on the print we would just tolerance part prints according to the material we are using and the knowledge of the material and shrink rates etc. Maybe include in the notes a volume and weight of the part given to us by the CAD software. Can someone please fill me in on a generic plastic part SPI tolerance or maybe even a DIN tolerance for plastic parts?
First time poster here. I am a new employee here at my company and will be visiting a new mold house to go over plastic part design and moldflow with them. I have been asked by my company to make sure they can and will adhere to SPI tolerancing for our part prints once they receive them from us. In my experience from other lives, we just give them a .stp, igs, or a 3D CAD file and they go from there developing the tool. As far as SPI tolerancing on the print we would just tolerance part prints according to the material we are using and the knowledge of the material and shrink rates etc. Maybe include in the notes a volume and weight of the part given to us by the CAD software. Can someone please fill me in on a generic plastic part SPI tolerance or maybe even a DIN tolerance for plastic parts?






RE: SPI tolerancing standards for drawings
What should govern the finished product's dimension limits is its function and fit within the end product. The tolerances necessary to make the finished product work properly must be conveyed to the mold maker and the molder. So far, CAD models don't do that, so you need a part print, and it must govern for moldmaking and inspection.
Conveying tolerance information is just one of the many ways that CAD modeling has fallen far short of its alleged potential.
Mike Halloran
Pembroke Pines, FL, USA
RE: SPI tolerancing standards for drawings
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RE: SPI tolerancing standards for drawings
Thanks all.
Sid
RE: SPI tolerancing standards for drawings
I (as a moulder), like CAD files, for as well as containing all the drawing errors, they contain all the design errors too!!
H
www.tynevalleyplastics.co.uk
It's ok to soar like an eagle, but weasels don't get sucked into jet engines.
RE: SPI tolerancing standards for drawings
Thanks all.
Sid
RE: SPI tolerancing standards for drawings
The unequal drafts could be part of the design too and need to be that way to allow it to fit somewhere or whatever.
And as someone who HATES doing 2d drawings I can't wait for the day that 100% design intent/tolerances/design notes,etc.. can all be incorporated into the 3d model. Its getting there but not fast enough IMO.
RE: SPI tolerancing standards for drawings
RE: SPI tolerancing standards for drawings
Thank you
Sid
RE: SPI tolerancing standards for drawings
cosmetics
possibly packaging
cleanliness (mold release?, dust, dirt)
manufacturer and grade of material
UL requirements ect.
color
RE: SPI tolerancing standards for drawings
What we suggest to our clients is this: generate an e.g. pdf file with ALL design notes (the more the better) and tolerance requirements, attach it to the 3D design and indicate the latter must not be used w/o the former. The tolerancing issue is rather simple if we refer to (attach) the DIN 16901 standard (din_16901_eng_plastic_tolerance.pdf that has been around since the 60's(?))that takes into consideration the material, required part quality levels and the dimension itself (longer dimensions require wider tolerances and v.v.). If anybody finds a good replacement for the DIN 16901, please let us know. As to very high precision applications tested computer programs have been available for decades that can determine the attainable part tolerances at +/-x.xxxx inch accuracy for critical dimensional by taking into consideration apx. 25 variables (material, design(wall thickness, fiber/molecular orientation, etc), gate number/size, location(s), molding and part inspection environment, mold temp. distribution, molding/packing conditions just to name a few) and for the analyzed dimensions, compute precision shrinkage also at x.xxxx in/in accuracy.
G. Markus
www.robustmolding.com
RE: SPI tolerancing standards for drawings
RE: SPI tolerancing standards for drawings
G. Markus
www.robustmolding.com