what’s inspection and basic dimension?

[zeta]

I am not sure this question can be posted here or not. In proe, I can
set the dimension to basic (rectangular block) and inpsection
(round-end block). What's the purpose of these dimensions? for what
applications?



esp the inspection dimension, what's the true meaning behind? because
IQC told me that they should check the inspection dimension, the
anothers won't be checked at most time but just a random check!



If the drawing without inpection dimensions, how the incoming
inpsection do?....I would like to hear your what you do for these,
when/where's I need to put inpection/basic or neither of it.

 

[prohammy]

Zeta,


Basic dimensions are foundation dimensions for items that are geometrically tolerenced.


Inspection dimensions are used to mark what dimensions the Quality Dept. have to measure on a part /assembly, in conjunction with the geometric tolerences. Anyone I have worked for as a rule does not use the inspection dims, which by default means that all dimensions shown on a drawing must be checked.


The above can open a whole can of worms with regards who does what and what info should be supplied by Engineering on a drawing


Kev

 

[dr_gallup]

Basic dimensions do not have any tolerance, they are used with True Position geometric tolerances and to tolerance tapered shafts and holes. Read ANSI Y14.5 for a full definition. There is a corresponding ISO standard as well.

I don't know of any standard that defines the inspection dims. We do not use them. Instead, our receiving inspection uses control plans which tell the inspector what to measure. We do put special characteristic symbols on critical dimensions for fit or safety. Those will always be measured but QA will determine other characteristics to measure as well. We are a TS16949 certified facility and our procedure conforms to that spec.

 

[ankarl]

We use inspection dimensions on some parts that are difficult to measure.


Instead of evaluating a lot of dimensions we simply add an inspection dimension that more represents the functional requirements instead of just geometric demands.


An example is a tapered hole for a sealing, instead of measuring depths, diameters and angle they just need to measure one diameter at a predefined depth (were the sealing actually sits).

 

[magneplanar]

Zeta,

In my situation we make so many plastic and metal parts that full dimensional checks are prohibitive during production runs. So, the engineers designate critical dimensions and set them to be inspection dimensions. A few critical points can be measured to verify the tools are making the part as intended. Of course a full dimensional study is done to qualify the tool before allowing these critical dimensions to control production. Occasionaly, we rerun the qualification to make sure the whole part is still correct and that the mold is ok.

cheers,

M

 

[zeta]

We are also making many plastic and metal parts by mould and die, we
have a few metal part by machining. It seems the inspection dimension
can be applied to the parts manfactured by mould and die to verify it.

Basically, there are 3 types of dimensions I will set it to inspection dimensions:

1) Main Outline Dimension, e.g. Total Length, width, height

2) Assembled related dimension: e.g. tapped hole location, stopper, guide pin.....

3) Safety related dimension: e.g. thickness of plastic sheet for electircal insulation

 

[dr_gallup]

Is there any ANSI or ISO standard for inspection dimensions? I have never seen one. We conform strictly to ISO drawing standards so we never use inspection dimensions.