Category: ASME Standards

Drawing Revisions and PDMWorks (Part 1: Letter Revision Identifiers)

Whether using actual drawings or relying on the model, and whether using a highly controlled documentation system or nearly completely uncontrolled, one will find revisions are necessary.   It is important to use them consistently.  It is important to make sure each time another person sees a drawing or model, they understand which revision is in front of them.  It is important not to reuse revisions. If there is a working copy that is incomplete, preliminary or draft, then stating such directly on the document is very important.

Also important is avoiding interpretation confusion.  If using letters to represent revision iterations, avoid using letters that resemble numbers or that can have alternative meanings.  ASME Y14.35M-1997 states that I, O, Q, S, X and Z should not be used as revision letters.  In fact, other ASME engineering drawing standards also forbid the use of these letters for other purposes as well.  The reason is that I, O, Q, S, and Z all can be misinterpreted as numbers 1, 0, 5 and 2.  When X is used, it looks like a field that requires further input.

These rules where written before the Information Age (wiki) and our reliance on computer databases, back when documentation relied on handwriting.  However, these rules are just as important in our current age as they have ever been before.  Many different types of computer fonts exist.  What looks like a 1 in one font will look like an I in another.  Even with my 20/20 vision, I will confuse S’s with 5’s in small sizes in certain common fonts.  Also, transcription errors still enter the picture, as a human who does not have direct access to the electronic database is usually involved at some point.

PDMWorks (soon to be renamed to SolidWorks Workgroup PDM by SolidWorks Corp) automatically assigns revisions to documents when they are checked-in.  There are options for the PDMWorks Administrator to use dumb ranges, or to establish a list of revision identifiers from which to pull.  Unfortunately, when using letters, PDMWorks does not automatically disregard the taboo letters.  So, I’ve made an Excel file with a list of allowed revision letters.  It can be copy-and-pasted directly into PDMWorks VaultAdmin’s Revision Scheme Listing fields.  It is available here: Allowed Revision List.

Part 2 of this article series will address using PDMWorks ability to automatically revise drawings upon check-in.

Drill and Tap (~Part 3)

This entry is part 4 of 4 in the series Hole Callouts

I previously discussed threaded hole callouts in the context of SolidWorks and its calloutformat.txt files (Part 1 and Part 2). As mentioned before, there is a tendency for some to callout threaded holes with too much information. Often, the thread callouts include the drill size. As argued before, including the drill size usually over-defines the threaded hole because the specifications of the thread itself identify the drill size. It also attempts to specify manufacturing processes, which is not allowed by ASME Y14.5M-1994. In fact, including the drill size within a thread callout may actually provide incorrect specification in many cases.

This is particularly true in the case of threads that are in blind holes. These are usually made with forming taps (roll taps). The diameter of the drilled hole for a roll tapped thread is bigger than it is for a cut thread. For example, for a 10-32 roll tap, the drill size is .1762, while a 10-32 cut thread drill size is .159. Once formed or cut, the specification for the ID of the thread is .156 to .164.

On drawings where customary units (inch) are used, the number of decimals places in the dimension usually determines the tolerance for that dimension. Stating a drill size as a decimal dimension applies the standard drawing tolerances to that dimension unless some general note is added.  This means that the tolerance for the drill callout likely differs with that required by the thread.  So, if the drill size is called out, drawing may be providing the wrong information to the machine shop.

Setting up and using SolidWorks Revision Tables faster

I am sometimes surprized by the limited the adoption of the SolidWorks Revision Table.  This is a powerful tool for drawings within SolidWorks.  The Revision Table allows the user to create a drawing template with an easily updateable revision block already included.  The user doesn’t have to use a potentially unstable Excel inserted OLE.  They also do not need a drawn revision block that requires significant labor in order to update and maintain.

The SolidWorks Revision Table is easy to insert in SolidWorks 2008.  With a drawing open, just go to Insert pulldown>Tables>Revision Table.  Within the Revision Table Pane, pick the appropriate revision template.  Choose any desired options for the table. Choose OK.  The Revision Table will automatically appear in upper right corner.  Save the drawing template for future use.  (See Help for instructions to place the Revision Table at other locations on the drawing.  Also, more steps are required in 2007 and prior; but, they are intuitive to follow and provide more on-screen control over the table’s location.)

Custom Revision Tables can be created to suit the companies specific needs.  Right click on the table to use the RMB menu to access functions that provide methods to modify the table.  When modifications are complete, use the RMB menu Save As option to save the new table as a table template for future use.

To add a revision, simply right click on the Revision Table.  Choose Revisions>Add Revision.  A new revision row will appear with the next revision inserted.  Simply double click any field to add or modify its value.  LMB click outside of the table to set the edits.

Of course, there is a simpler way to add revisions to the Revision Table!  I’ve created a macro that provides a form which allows the quick addition of revisions to the Revision Table.  It’s called RevBlockControl.  It is much faster than directly creating and entering all the rows and values.  It has been recently updated, so if you already use this macro, please consider using the latest version.

RevBlockControl Form

Sample image of the macro form

To use the macro, place it in the macros folder under the SolidWorks folder.  If it doesn’t exist, create it.  Within SolidWorks, assign a custom key stroke to the macro and/or create a toolbar icon location for it.

It can be used for a variety of revision table set-ups, including standard recommended ASME types.  It is limited to 5 columns, though it is customizable without editing the code or a complex .ini file.  If editing the code is desired, everything is spelled out with descriptions for easy of use.  In fact, the code can be quickly edited to allow the macro to drive the drawing’s “Revision” custom property.  Additionally, there is a small .ini included in this current version.  It is simply a list of initials used by the Rev By field.  Edit it with NOTEPAD to add and delete names that will automatically appear within the Rev By field.

Even without the RevBlockControl macro, the easy of use of the SolidWorks Revision Table is well worth the few minutes of effort to set it up on a template.  With the RevBlockControl macro, adding revisions to a Revision Table is so fast that it is almost effortless when compared to other type of revision blocks.

Dual Dimensioning and ASME Y14.5M-1994

This entry is part 2 of 8 in the series Dimensions and Tolerances

Dual dimensioning is the drafting practice of using multiple units of measure in a dimension in the same direction of a feature.  SolidWorks and many other CAD programs support dual dimensioning.  This support is usually a little quirky.  It’s actually not  the fault of the CAD application.  At one point, it was a surprize to me (and often is to others too) that no current drafting standard actually supports dual dimensioning.  In retrospect, this makes perfect sense.

My experience is with ASME Y14.5M-1994.  When invoking ASME Y14.5M-1994 (or even ANSI Y14.5M-1982), one will find that rules regarding dual dimensions do not exist.  ANSI Y14.5M-1982 does mention in its appendix that support for dual dimension no longer exists in the standard.  This is apparently because it was mentioned in a previous version.  That said, dual dimensioning has never really ever been allowed by any incarnation of Y14.5.  This is because of very specific wording under the standard’s Fundamental Rules.  The wording may vary between versions, but carries the same meaning in all versions.  In ASME Y14.5M, that wording is as such in 1.4(d), “Dimensions shall be selected and arranged to suit the function and mating relationship of a part and shall not be subject to more than one interpretation.”  (Support for dual dimensions in pre-1982 versions was a mistake that was likely political in nature.)

General practice in the use of dual dimensions is that they are of equal importance to the primary dimension.  This creates issues in that it allows for more than one interpretation of the dimension.  It is nearly impossible for nominals and tolerance ranges to be identical between units of measure.  This means that the dual dimension tolerance range is usually resized to fit within the tolerance range of the primary unit of measure.  This creates a situation where the dimension has more than one interpretation, which is specifically prohibited by 1.4(d).  The conclusion that can be drawn from this is that dual dimensions are actually not allowed by ASME Y14.5M-1994.  This is the hard argument against the use of dual dimensions.  I could end this article right here.  However, I will also explore the soft arguments against their use.

ASME Y14.100-2004 paragraph 4.32.3 uses soft language to discourage the practice of converting inch to metric and vise verse (“should not be used”).  This is known as soft conversion.  This is not an outright prohibition against dual dimensioning by itself. However, the practice of soft conversion is integral to using dual dimensions.  With this practice discouraged, dual dimensioning is also discouraged.

ASME Y14.5M-1994 defines a reference dimension as such,

“A dimension usually without tolerance, used for information purposes only. A reference dim is a repeat of a dimension or is derived from other values shown on the drawing or on related drawings. It is considered auxiliary information and does not govern production or inspection operations.”

By definition of reference dimensions, dual dimensions must be treated as reference dimensions. However, anyone who uses them knows this is generally not their intent. As generally intended, dual dimensions are disallowed unless they are considered reference only.

The final soft argument is gleamed in the wording of ASME Y14.5M-1994 paragraph 1.5.  This paragraph assumes dual dimensions are not in use.  For example it begins one paragraph as so, “Where some inch dimensions are shown on a millimeter-dimensioned drawing…”.  It never then says “Where many inch dims are used on a metric drawing….” This is not a specific exclusion, but should be noted for its wording. It does allow for the use of both inch and metric units on the same drawing, but not multiple values of dimensions for the same features.

With all of these arguments aside, CAD applications do attempt to accommodate users who feel they need this capability.  However, if used, caution must be exercised.  Handling of dual dimensions by CAD (and common practice) can create confusion on a drawing, particularly if the software assumes values for the dual dimensions and its tolerances.

In the effort to avoid issues and violations of the standards, it is my opinion that if dual dimensions are used, they should be noted as for reference only on the drawing.  This can be accomplished by adding a note similar to “DUAL DIMENSIONS IN BRACKETS ARE FOR REFERENCE ONLY.”  This avoids problems caused by multiple interpretations for dimensions.  Of course, over use of reference dimensions is also discouraged by ASME Y14.5M-1994. But hey, who’s it hurting?

For SolidWorks, dual dimensions on a drawing may be employed by going to Tools>Options>Document Properties>Detailing and checking Dual dimensions display.  Also at that location is the choice to display the dual dimension on top, bottom, left or right of the primary dimension.  These are SolidWorks 2007 instructions (other versions of SolidWorks should be similar).

I did make a sample SolidWorks macro that will turn on dual dimensions for a drawing and automatically set them to display on the bottom (default is top).  This example macro can be downloaded here.  It can be modified to use any settings as default.

For the record, this article was inspired by multiple posts on various SolidWorks related forums over the past few months such as these at SW Forums, eng-tips.com, and Pro/E discussion at eng-tips.com.

Create CAD Standards (SolidWorks environment)

Creating a drafting standards within a SolidWorks environment is an important task.  The task may seem daunting to those of us who haven’t done this before, particularly if our company has no pre-existing documentation methods.  These can be new companies, or companies moving from a lack of control into standardization.

Fortunately, there is a lot of help available.  Actual drafting standards already exist.  Also, many of us have been through this before (sometimes multiple times).  ASME provides American National Standards for many of the areas that need to be covered.  ISO provides international standards for these too, however I will focus on the use of ASME since this is what I used myself.  On the other-hand, creating SolidWorks specific standards requires a little more reseach and upfront work.

Here are my very general suggestions for documents and tasks to create a company’s standard.

  1. SolidWorks Templates (basic overview)
    1. Create a basic solid model template.  The setup within this template will become the backbone of everything within SolidWorks. This will be the most used document.  Establish custom properties that detail the part.  (Use of existing properties can be leveraged to simplify this task.)  Creation of this first template does not preclude the creation of other solid model templates. Instead, it will be used to create any others. For details about templates, goto SolidWorks Help and search titles only for the words “document templates”.
    2. Create a solid model assembly template.  Many of the general settings of this template should be duplicates of the settings of the solid model template.  Some planning is required.  Determine the best method of assembly structure for your company.  Several practices exist as guides, such as Top-Down, Horizontal Modeling, Bottom-Up, and Configurations.  It is important to note that there is not one-size-fits-all method for all companies.  Research each and make the determination based on company needs.  Setup the assembly template to support the chosen method.  However, do not become overly reliant on any particular methodology since situations may require flexibility.
    3. Decide how the drawing templates will interact with solid models. This includes deciding to have any pre-defined views, use of custom and other properties, etc.
    4. Create sheet formats and templates for each drawing size that will be commonly used.  Include annotation notes linked to custom properties, such as part number, material, revision, originator, origination date, surface finish number and/or type, etc.  See SolidWorks Help search for “Link to Property”.
    5. If in a network environment, place the templates and sheet formats within a folder where all SolidWorks users will have access.  Point all SolidWorks installs to this location.  This can be done within pulldown menu Tools>Options>File Location>Document Templates and Sheet Formats.
    6. Create a company standard for shortcuts and macros that speed up SolidWorks operations. Set up a network location for the company macros.
  2. Create the following standard operating procedures.
    1. SolidWorks Performancethat covers computer system requirements, Windows settings, SolidWorks installation, working folders, and standardizing files.
    2. SolidWorks Best Practices and Standards
      • Solid models: discussing preferred methods for creating features.
      • Assemblies: cover methodologies (when to use top-down or bottom-up; and what part should be the primary fixed component) and how to avoid circular mating, etc.
      • Drawings: covering how to use templates/sheet formats, shortcuts, common macros, etc.
    3. Drafting Standards, which can rely on ASME Y14.100 (umbrella engineering drawing standard), ASME Y14.5M (GD&T drafting standard) and possibly ASME Y14.41 (3D model drafting standard).  List exceptions to the ASME standards within the procedure.  If relying on these standards, make sure to have copies of them on hand. This will allow the procedure to be short and to the point.  If not relying on a standard, this procedure can potentially be very long.
    4. Source File and Document Control, which covers how to handle file management (SolidWorks files) and documents.  Be sure to cover processes for control of SolidWorks files in folders and/or the PDM application.  This may be a procedure that is supplemental the company’s general document control processes.
    5. Revision Control, which covers how to revise engineering documents.  This can rely on ASME Y14.35.  If the company uses a ERP or PLM, this procedure may be supplemental to those processes.

For references for further research, check out SolidWorks resource links, such as weblinks that can be found here on Lorono’s SolidWorks Resources.  Also, check out Blog Squad sites such as Matt Writes.

SolidWorks World 2008 Day 3 (Jan 23) Breakout sessions

My first breakout session of the day was SolidWorks Sheet metal: Why do I do it like this or that?.  This session went into a lot of detail about sheet metal functions in SolidWorks.  There was discussion covering tears, closed corners, dimensioning preferences, K-factors, when to use normal cut, and the fact that all thicknesses on a sheet metal part need to be identical.  One good point was that closed corners work only when the flanges have the same parent feature.  Like all good sheet metal presentations, miter flanges where also discussed.  One problem I had with the presentation is that way too much time was spent on discussing creation of flat patterns.  When several attendees confronted the presenter with the fact that flat patterns are not often necessary for a designer to create, he argued the point without really understanding why the attendees contested it.  According to ASME Y14.5M-1994, the drawing represents the final product.  Adding intermediate steps (such as flat patterns) are unnecessary since the vendor is responsible for the final product represented on the drawing.  Besides that, most sheet metal shops are much better at determining K-factors and knowing their shop’s limitations than most designers.  I think more information could be packed into the presentation if less time is spent on flat patterning.

After lunch, I attended Leveraging the Design Tables and Configurations….  Many points where covered.  Here’s a few.  It is important to establish a good naming convention for configurations.  Effort must be taken to determine how the model will be represented (drawing, BOM, literature, etc).  Utilize folders in the Model Assembly.  Utilize formulae in the Design Table instead of equations area.  One good point was the suggestion to save backup copies of design tables outside of SolidWorks in Excel itself.

My final Breakout session of SolidWorks World 2008 was Demystifying PDMWorks Workgroup Triggers.  Although I’m not familiar with PDMWorks API, I did learn something about what is possible in PDMWorks.  Also, I learned about the setup required to utilize the triggers. 

I didn’t take many basic how-to Breakout sessions this year.  My main focus was on developing my skills in configuration, customization, more detailed how-to’s, and set up.  I made sure I attended several API related sessions.  Overall, I feel the experience was something that I would not want to miss.  I’m glad I had the opportunity be involved in this experience.Â