Define on Molded part Print Exterior vs the Interior 2

[SDETERS]

We have a need to define the exterior of a part from the interior of a part. The reason to do this is to apply a appearance standard for these exterior surfaces. For example no heat check on the exterior surfaces of the part.

The issue I am running into is how to define the location of where the exterior starts and interior surfaces start. Is there a standard practice or way this is done?

Thanks

 

[CheckerHater]

The closest thing I could find would be "surface identification" from Cosmetic Specifications of Molded Parts, also known as SPI publication AQ-103

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[cowski]

In general, the cavity side of the mold will create the exterior surfaces and the core side will create the interior surfaces. On many of our prints where the surface finish/texture will be uniform on the exterior, we'll add a general note such as:
[pre]
Surface finish:
Core: SPI C3 or finer
Cavity: texture MT-11020
[/pre]

If the surface finish/texture is not uniform on the part, we'll note those surfaces in a view with leaders pointing out which surfaces get which texture. When it starts to get complex, we'll also provide screenshots and/or a STEP file where the faces have been colored according to texture/surface finish.

 

[TheTick]

Typically we do this on the part's drawing.

 

[SDETERS]

Thanks for all of the feedback. We are trying to communicate to the suppler, and how to identify the class "A" surfaces on the print. TheTick do you have an Example how you do this on the part's drawing?

Good Feedback Cowski this is a good option for us.

Thanks again.

 

[JNieman]

Not necessarily a "standards sourced" strategy but what I've used for various finishing aspects is a color-coded drawing.

Areas of interest, whether it be for a surface roughness, texture, paint masking, oil-free, wax-covered, etc, will be shown in a shaded view on a drawing sheet, with a note indicating the requirement, and which areas must meet the requirement. Sometimes it's the interior of a hollow piece, shown in section-view, and a brief explanatory note.

In general I try to use as few words as possible, using the colorful views to describe it. I find that some suppliers have better success with pictures than words (no comment...)

I hate using a color-dependent medium, because if someone prints it on a B&W printer, it loses effect. But I haven't had problems with that yet. To mitigate the issue, though, I try to use highly contrasting colors. Example of good - shaded dark red on an otherwise white/light-grey shaded part
Example of bad - shaded yellow on an otherwise white/light-grey shaded part.

Yellow will print almost white on most B&W printers, and dark red will print very, very darkly. Some blues similarly, IME.

We segregate those as "vendor drawings" but otherwise control them all the same with typical title block and revision. A "process drawing" might be a more apt phrase. IIRC there is an ASME standard covering such things, if it applies to you (we don't bother with that one)