Category: ASME Standards

ADDA’s Annual Technical & Educational Conference

The American Design Drafting Association (ADDA) is hosting its 52nd Annual Technical & Educational Conference in Kansas City, MO on April 12-15, 2011.  ADDA is heavily focused on the professions of drafting, design, and graphics.  ADDA has a certification program for drafters (mechanical and architectural), civil design drafters, design technicians, and digital designers (which include imaging and editing).  Not everyone has heard of ADDA, and that may be intentional.  Olen Parker, Executive Director, states,

It [ADDA] is small, yet sets the stage for many changes within the profession.  We don’t make noise, we don’t promote ourselves, we are the best kept secret in the profession.  ADDA is very involved in the standards and regulations related to our industry.

Best kept secret?  Well, maybe not anymore. 🙂  Parker also mentioned that ADDA made final reviews to ASME Y14.5-2009, and has members that are involved in a number of national committees and organizations.

The conference

This year’s Annual Technical & Educational Conference will have sessions that cover ASME and GD&T fundamentals, CAD and drawing standards, building codes, graphics, etc.  In particular, they will have sessions for CAD and graphic art applications such as PhotoShop, SolidWorks, Pro/E, AutoCAD, Revit, Sketch-Up, Illustrator, and several others.  Other sessions of note will discuss sustainability, BIM, and even workplace ethics. 

I’m also presenting a talk on establishing company CAD procedures at this year’s conference.  Though this presentation will be similar to my breakout session at SolidWorks World 2011, it will be more applicable to the broader audience at the Annual Technical & Educational Conference.

I will write about many aspects of this conference on SolidWorks Legion, including special attention to the quality and depth of several presentations.  I also hope to have a least a couple of interviews.  I also plan to post tweets on hashtag #atec11 during the event.

This will be my first year attending ADDA’s Annual Technical & Educational Conference, though I’ve been looking for an opportunity for several years.  Please note that ADDA is non-profit.  Although ADDA is giving me full conference access (including some meals) at no cost, I am sorta earning my keep by being one of the presenters.  I am personally paying for all other costs associated with my attendance, including airfare and hotel.

If you are interested in the ADDA, their certification process, or the Annual Technical & Educational Conference, please visit their website for further details.

To what extent should a company comply with ASME standards on their drawings?

ASME cutSome time ago, a visitor to SolidWorks Legion asked something similar to this:  Now that we decided to use them, to what extent should my company comply with the ASME standards on our drawings versus our own internal rules?

That is a complex and difficult question.  Purist will say, “Follow the standard exactly! Otherwise, why have a standard at all?”  Internal traditionalists will say, “We already have a way that works for us.  Why change what works?”

The answer, in my opinion, is in the middle.  ASME Y14.100-2004 paragraph 1.1 states that the ASME standard establishes essential requirements for the creation and revision of drawings and BOMs.  However, paragraph 1.2 then allows for “tailoring” of the standard to exclude unnecessary requirements.  Though this is not an explicit statement that allows outright customization, it does provide a crack in the door that may be used to justify such customization of the standard.  It is important to note that the ASME standard does not take the place of internal standards; it forms their foundation.  The ASME standard still leaves options open for individual companies to define for themselves.

In a company’s internal drafting standard, I recommend including the statement, “Exclude from practice any portions of any standards (e.g., ASME Y14.100) that differ from instructions within this document.”  This formalizes the effort to employ exceptions to the ASME standard.  However, this must be used with caution.

One area that is a good case for exceptions is in how a company might handle BOMs within the context of a PLM.  In such cases, it is often considered bad practice to list BOMs in two places (on the drawing and within the PLM).  It may be advantageous to store and control the BOM within the PLM, rather than on the drawing.  ASME does not address this.  However, as long as the PLM displays the BOM in a manner consistent with the intent of ASME, I don’t personally see any issue with relying solely on that PLM for BOMs.  The internal drafting standard should address such exceptions to ASME.

An area that is bad for exceptions is in the non-standard use of established symbols or abbreviations.  This is because the symbols and abbreviations are already defined by the ASME standards.  For example, if a company allows GD&T symbols to be used in a way that is not defined by ASME Y14.5-2009, a manufacturing vendor will not know how to properly interpret the custom use of the symbology.  ASME does not allow ambiguity on drawings.  However, if a company wishes to continue the use of a few of its own custom symbols and abbreviations, these need to be fully defined on each drawing or in an internal document that is referenced by the drawing.

In my opinion, this is the bottom line: leverage the ASME standards to save time and work (both in the creation and interpretation of drawings).  Try to adhere to ASME as much as possible.  Allow deviations that are necessary, but clearly state such exceptions within the company’s drafting standard or on the drawing itself (whichever works best for the situation).

How to dimension feature patterns on drawings

This entry is part 3 of 8 in the series Dimensions and Tolerances

A couple of days ago, I briefly covered the mythical specification “non-accumulative tolerance” (or “non-cumulative”) as it is often applied to direct dimensions on feature patterns.  See the example in Figure 1 where the dimensional callout attempts to simply dimension a pattern without considering tolerance stack-up.  However, this attempt fails since any two non-adjecent holes cannot avoid accumulation of tolerance due to the dimensioning scheme.  The problem gets worse if three or more positions within the patten are compared to each other.

Non-accumulative tolerance dimension on a pattern
Figure 1

ASME repetitive feature dimensioning scheme

ASME Y14.5-2009 actually provides a linear method to detail feature patterns, called repetitive features and dimensions.  See Figure 2. Unfortunately, the standard does not provide any tolerance rules for its prescribed scheme. Presumably, this leads us to interpret a repetitive feature dimension as though it is shorthand for chain dimensioning.  Chain dimensioning accumulates tolerance as the pattern departs from the dimensioned start position.  Sometimes this is OK, but often this is unacceptable since the accumulation of tolerance can quickly lead to features that do not align to mating features on other components.

Figure 2
Figure 2

Disorganized direct dimensions

Another dimensioning scheme that I’ve seen involves a complete disregard for the fact that a pattern exists.  See Figure 3.  Directly dimensioning each of the positions within the pattern to each other may be acceptable in some scenarios, but likely isn’t a very clear choice for larger feature patterns.  The problem with this scheme is that it can be very difficult to determine the true accumulation of the tolerance stack-up.  It may also be difficult to determine design intent.

Figure 3
Figure 3

Baseline dimension scheme

To avoid the issues associated with other direct dimensioning schemes, one may choose to use baseline dimensioning, which may also be called rectangular coordinate dimensioning in some scenarios.  The advantage of a baseline dimension scheme is that it limits the accumulation of tolerances to the stake-up from just two dimensions.  This is because the total stack-up between any two positions within the feature pattern are related through a common baseline.  The problem with baseline dimensioning is obvious in Figure 4; its take up a lot of space on the drawing.

Figure 4
Figure 4

Ordinate dimensioning

A common alternative to baseline dimensioning is ordinate dimensioning, also known as rectangular coordinate dimensioning without dimension lines.  This scheme also relies on a baseline, referred to as zero (0), from which all of the features are dimensioned.  The advantage of ordinate dimensioning is that it takes up far less space on a drawing, as shown in Figure 5.  Tolerance stack-up is limited to just two dimensions between any two positions within the pattern.

Figure 5
Figure 5

Using GD&T for best results

The best way to avoid accumulation of tolerances is to use a methodology that does not rely on any form of direct dimensions.  ASME Y14.5 actually suggests that GD&T should be used instead of direct dimensions to locate features.  I have discovered the hard way that many individuals in the engineering field have an irrational fear of GD&T.  Even still, GD&T provides a far superior method for the location of positions within a feature pattern. The example in Figure 6 shows a less cluttered drawing.  With the addition of MMC to the feature control frame, this method could provide even better results since it would make use of bonus tolerance.  The position of each feature within the pattern has an optimal tolerance zone that more closely matches design intent.  One more added benefit is that all features controlled by a single feature control frame are automatically considered as a pattern.

Using GD&T to locate features
Figure 6

Since the tolerance zone is optimized, using GD&T may help reduce costs by allowing the manufacturing process to vary in a way that is more in line with design intent.  In turn, this can reduce the number of unnecessary part rejections.

Conclusion

When detailing feature patterns, one may wish to avoid the use of direct dimensioning methods or shortcuts like the mythical “non-accumulative tolerance”.  The best choice to detail a feature pattern is GD&T.  However, if GD&T is not desired, the next best method is prolly an ordinate dimension scheme.  It should be noted that for each of the dimensioning and tolerancing schemes shown within this article, there are a variety of ways to implement them.  This article is meant to present general examples.  Actual tolerancing requirements are guided by design intent and other considerations per individual cases.

Mythical Specifications: Non-accumulative tolerance

This entry is part 4 of 4 in the series Mythical Specifications

Mythical specifications come in many forms.  One realm they seem to haunt is that of repetitive features, also known as patterns.  Many attempts to shorthand pattern callouts are continuously made.  Bad habits die hard as old mistakes are passed down from one generation of engineers to the next.  One particularly bad habit is the use of linear dimensions with the term “NON-ACCUMULATIVE TOLERANCES”, or something similar.  There is no such thing.  Trying to use this shorthand leads to tolerance issues.

Pattern non-accumulative tolerance callout

In the example above, the dimensional callout attempts to simply dimension a pattern without considering tolerance stack-up.  However, this attempt fails since any two non-adjecent holes cannot avoid accumulation of tolerance due to the dimensioning scheme.  Tolerance stack-ups on linear dimensions have accumulation.  There’s no way to avoid it without dumping linear dimensions.

I had originally planned on a short article about this topic.  However, once I started delving into it, I found out that there is a lot of ground to cover.   So, this topic will be addressed in detail within a future article (Feb 23, 2011) where examples of different pattern dimensioning schemes will be explored.

Also see How to dimension feature patterns on drawings.

Breakout Sessions at SolidWorks World 2011

Because of my concerted effort to keep my schedule under control, my experience at SolidWorks World 2011 was a little more sane.  I was able to make more time for breakout sessions. 

I enjoyed the informal format of Devon Sowell’s presentation, Demonstrating Workgroup PDM to Enterprise PDM Migration.  In his session, he involved the audience in the discussion.  Questions from the audience where frequently fielded, along with suggestions and ideas.  The presentation talked about utilities that simplify the migration process, including one that is only available from a VAR.

Other sessions I attended include information on VB.NET programming, ASME Y14.5-2009, and other PDM topics.

I also encountered a couple of breakout sessions by individuals that did not seem as prepared as they should’ve been.  There seems to always be some sessions like this each year at SolidWorks World, unfortunately.  Of course, it’s not completely unavoidable.  Sometimes things just don’t seem to work during the presentation, even if they did work flawlessly during practices.

Overall, I had a fruitful experience at this year’s SolidWorks World.  I’ll talk a bit about my own presentation in a later article.

SolidWorks 2011 official launch

SolidWorks 2011 launch is now official.  The funny thing about launches is that this doesn’t necessarily mean the product will ship right away.  That comes later.  For this launch, SolidWorks Corp invited a panel of bloggers and journalist to their headquarters in Concord, MA yesterday and today to get a first hand look at SolidWorks 2011.  As a matter of disclosure, my accommodations, travel and most meals for this event are covered by SolidWorks Corp.  No one has made any requests regarding article creation nor content in connection with this event.  Some material (such as images and basic information) was derived from the SolidWorks 2011 What’s New (beta) file.  The content of this article is solely of my discretion.

As with each year, there are a number of enhancements in SolidWorks 2011.  Here are a few, briefly covered.  More detailed articles will follow over the coming month.

Assemblies

Chamfer and weldOne area of note is that SolidWorks now supports fillet and chamfer features within an assembly.  Though these new features can be useful by themselves, their is another feature enhancement that helps set a theme.  Fillet welds will no longer be necessary as components within an assembly.  Instead, simplified weld beads is a new feature that is a simple representation of a weld contained within the assembly itself.  These additions and changes will give users more abilities in adding welds and weld specifications to assemblies and drawings.

Design Checker

Design Checker is one of those functions that has a more stealthy existence in SolidWorks.  Well, maybe not stealthy, but under-utilized.  It is a function that sees incremental improvement each year, but without much fanfare.  In the past, I’ve been a little critical of this function’s lack of functionality.  SolidWorks 2011 has eight enhancements for Design Checker.  The enhancement that I feel is most important is the ability to create standard files (.swstd) from existing SolidWorks file formats.  This is step beyond the Learn Checks Wizard currently available.  This allows the user to create a new set of check rules based on an existing file.

Drawings

Scale on viewFor some reason, SolidWorks never had an automatic way to add a scale label to orthogonal views.  There is a macro (that I helped create) which gives the user a non-dynamic method to add scale.  The limitation of this macro is that if the scale of the view changes, the macro must be re-run.  SolidWorks 2011 now gives the user the ability to add a true scale label to orthogonal views.

The macro may still be of use if there is a need to add pre-established labels to drawing views.  For example, if view is pictorial or isometric, the macro provides a quick way to add that label.

ASME drawing standard

ASME Y14.5 2009I’m not really sure why SolidWorks still calls ASME by the other name ANSI.  The switchover to ASME happened like 20 years ago.  Either way, SolidWorks 2011 claims that it now “supports some of the requirements of ASME Y14.5-2009”.

One of the important areas of support is geometric tolerance symbols.  ASME Y14.5-2009 expanded the role of the ALL OVER modifier to a Profile feature control frame.  With this expansion comes a new symbol (the double circle leader).  Also included are the new Independency symbol (encircled I, which declares an except to Rule #1) and the Continuous Feature symbol (oddly boxed CF, which applies Rule #1 more broadly).

Parts and Features

More end conditions are now available with the Revolve feature: Up to Vertex, Up to Surface, and Offset from Surface.  These can be specified separately in each direction (clockwise and counter-clockwise) of the revolve.  These new end conditions are available in Revolved Boss/Base, Revolved Cut and Revolved Surface.  This allows for better control and more flexibility in the use of Revolve features.

New Revolve end conditions

More enhancements available

These are just a few of the enhancements available in SolidWorks 2011.  The What’s New file for SolidWorks 2011 has a fairly impressive list.  However, none of the improvements this year seem monumental.  I am impressed to see minor improvements continue on the Workgroup PDM product.  There are improvements to Sheet Metal functionality, Motion Studies, and a new Walk-through function to expore or create a video of 3D geometry in large scale designs.  More details will be discussed on later dates.