a new requirement about composite flatness.

huangyhg

Paul and BV,

There is a new requirement about composite flatness.

Composite flatness has two new parameters as per unit length and per unit width when per unit is checked. Have Graphic display and CAD database supported composite flatness? If not, Rick, could you create a new task about it?

Rick,

Could you create a new task about IP translator parse PERUNIT(tolerance, length, width)?

I completed code to add the three parameters (tolerance, length, width) into CIPTolerance command in IP 1.2. I also added PERUNIT (tolerance, length, width) into IP Language,

Yanhua

[9:58:55 PM] yanhua Huang 说： Question about Per unit length and per unit width
[9:59:26 PM] yanhua Huang 说： The two parameters just for flatness?

[10:00:09 PM] yanhua Huang 说： Other geometrical tolerance types have not the two parameters, is this right?

[10:00:20 PM] Donald Turcotte 说： Yes, composite flatness includes both total flatness and flatness per unit area (length X width).

[10:00:34 PM] Donald Turcotte 说： This is only for flatness per unit area.

huangyhg

I looked in my GD&T reference book, Geo-Metrics III, and could find no mention of the "per unit length" and "per unit width" for the flatness tolerance. Is this a non-standard specification? Is it necessary for us to support it?

Paul

huangyhg

Don,

Yanhua wants to add support for "per unit length" and "per unit width" to the flatness tolerance (see her dialog example below).

I looked in my GD&T reference book, Geo-Metrics III, and could find no mention of the "per unit length" and "per unit width" for the flatness tolerance. Is this a non-standard specification? Do you think we should support it?

Thanks,

Paul

huangyhg

Paul,

This is flatness per unit area as described in “ASME Y14.5M-1994 Dimensioning and Tolerancing”, p.161, section 6.4.2.1.1 “Applied on Unit Basis”.  This is composite flatness where the top line gives the total flatness tolerance and the lower line gives the flatness per unit area (length X width).  Page 162 of the cited document has an example at the end of section 6.4.2.1.1.  This is supported by PC-DMIS V42+.  Flatness per unit area is often used in sheet metal applications.



Regards,

Don

huangyhg

I don't have the ASME manual. Can I access the manual online somewhere?

For the line that has the flatness per unit area, is it displayed simply as "A x B" where A and B are two numeric values? Yanhua is showing "<len> A x B". I don't know what the preceding <len> is for. Yanhua, could you please explain what <len> is for?

Thanks,

Paul

huangyhg

www.ansi.org





This is an example of flatness per unit area (the upper line is the total flatness over the whole measured surface; the lower line gives the per unit area specification):

Don

huangyhg

Don,



Does PC-DMIS actually use this area specification, or is it a kind of comment?



Rick Tischler

huangyhg

This is not a comment.  The upper line of the composite flatness in the example says that the flatness over the entire surface shall not be more than 0.025 mm.  The lower line in the example says that the flatness over any 10 X 10 mm area of the surface shall not be more than 0.012 mm (typo in the example since the lower line is a tighter spec than the upper line, so 0.12 should be 0.012).  PC-DMIS actually performs this analysis and reports both the total flatness and the flatness per unit area.



Regards,

Don

huangyhg

Hi Paul,

Why not add a CString to the CCadToleranceSpecification?

If the CString has a zero length, then process the object’s information as we do today.

If the CString is not zero length, then just use the CString.



There have been a few CAD & Graphics GD&T specifications that have changed over the last several weeks.  By having a generic CString as an option, the DCIs, Datakit, Tolerance Dialog, etc can format them once without making changes to CAD or Graphics.



Two things to consider if we add a CString:

1. If there are special GD&T display symbols that need to be encoded in the string.  Robert has already dealt with this in the UG DCI, where he uses a unique GD&T character that Graphics & PC-DMIS also use.  This info in accessible to any DLL – I believe it is just an include file and/or macro.

2. When the user selects the callout in the IP, it is decoded in the GD&T dialog.  If this type of CString info is critical to GD&T callout (as Don stated it is not a comment), then maybe a new or existing enumeration can be added to the CCadToleranceSpecification (enum EFlag ?) and a non-cad specific decoding scheme can be used to convert the string to the desired individual components.  The later could be part of a generic encoding/decoding class available to the DCIs, Tolerance Dialog, etc.



I’m not familiar with GD&T specs, but it seems like we (Cad & Graphics) are both having to do modifications with each GD&T function that is added.

BV