Rounding of numbers

On most computer systems, decimal numbers that have 5 as the last digit are automatically rounded up when removing a decimal place. This may create a problem.

Some people have a rule that SolidWorks drawings should not have overridden dimension values (Override values).  I generally agree.  Yet, there are several legitimate reasons to use Override values.  One major reason is for proper rounding of linear dimensions for removed digits after the decimal.  Currently, SolidWorks offers no option that allows the user to automatically round dimension numbers in a way that is consistent with current industry standards and practices.

SOLIDWORKS 2015 now has several rounding options that follow the rules below.  More information, please see SOLIDWORKS What’s New Rounding article.

Rounding rule for dimensions

On most computer systems, decimal numbers that have 5 as the last digit are automatically rounded up when removing a decimal place.  For example, the number 1.425 rounds up to 1.43.  This creates a problem.  Most standards require that such numbers are rounded to the nearest even number in the last decimal place.  For example, that number 1.425 should be rounded to 1.42, and 1.435 should be rounded to 1.44.

ASTM E 29 states:

6.4.3 When the digit next beyond the last place to be retained is 5, and there are no digits beyond this 5, or only zeros, increase by 1 the digit in the last place retained if it is odd, leave the digit unchanged if it is even. Increase by 1 the digit in the last place retained, if there are digits beyond this 5.

NASA’s Engineering Drawing Standards Manual states:

When the first digit discarded is exactly 5, followed only by zeros, the last digit retained (i.e., the digit preceding the 5…) should be rounded upward if it is an odd number, but no adjustment made if it is an even number. For example, 4.365, when rounded to three significant digits, becomes 4.36. The number 4.355 would also round to the same value, 4.36, if rounded to three significant digits.  This procedure is known as odd-even rounding.

It is my understanding that this rule helps reduce statistical bias by allowing different numbers to be rounded up or down.  Using the computer default rule (5 is always rounded up) only allows for the upward rounding of such numbers.  This can create greater statistical errors, particularly when compounding rounded numbers to derive further rounded numbers.

Rounding as it affects tolerances

No rule is absolute.  There are other considerations when rounding.  A number should never be rounded so that it increases the original limits of a dimension.  Although this rule mostly applies to inspection techniques, it can also apply to specification.  For example, if there is a feature whose size limits are 1.255-1.275, the specification cannot be rounded so its limits are 1.25-1.28.  In such a case where rounding occurs, the specification limits should be 1.26-1.27.  Fortunately, this isn’t something that often occurs in mechanical design (though it does pop up when trying to apply dual dimensions).

Usually, rounding the limits is something that more often happens in quality assurance during incoming inspection of products.  In such cases, Interpretation of Limits rule from ASME Y14.5 declares limits are absolute.  For example, 12.25 MAX is the same as 12.2500000000000000 MAX.  If the feature measurement is 12.2540, that measurement should not be rounded to 12.25, as it is still out of tolerance because it exceeded 12.25.

SolidWorks should supports more rounding options

Right now, SolidWorks does offer one rounding option for dimensions.  In documents options, there is a setting to round numbers to the nearest fraction, but only if fractional numbers are in use.  I would like to see other rounding options supported, but not a document option.  SolidWorks should have a setting added to the dimension PropertyManager that allows the user to establish a rounding rule for a particular dimension.  For each dimension, users should have a choice to use the odd-even rounding rule, nearest fraction rounding rule (only when fractional numbers are in use) or always round 5 up rule.  This shouldn’t just be for drawings.  It should also be available in the model because they are often used as part of the product definition and because dimensions in the model can be inserted into a drawing.

For now, one can use Override values on the drawing.  The drawback to this is that Override values do not automatically update if there is a change to the associated model geometry.

So, this sounds like this issue should be yet another Enhancement Request.

As of SOLIDWORKS 2015, there are several options for numerical rounding which are available.

  • Round half away from zero, where the only digit being removed is 5, then round the last remaining digit away from zero.
  • Round half towards zero, where the only digit being removed is 5, then round the last remaining digit towards zero.
  • Round half to even, where the only digit being removed is 5, then round the last remaining digit so that it is an even number.
  • Truncate without rounding, where any and all digits being removed have no effect on the last remaining digit.

There is also an option to only apply alternative round methods to dimensions, with the setting Only apply rounding method to dimensions.  When this setting is checked, round half away from zero method is applied to all system and properties values, but the alternative rounding method (round half towards zero, round half to even or truncate without rounding) is applied specifically to dimensions.  Without this option checked, the chosen rounding method applies everywhere in SOLIDWORKS.

To account for dual dimensioning issues, tolerance rounding includes an option to fit the secondary unit’s tolerance range so that it does not extend outside of the primary unit’s tolerance range.  To use this capability, goto Tools > Options > Document Properties > Dimensions and click on Tolerance button. In the Tolerance dialog, check the option Inward rounding of secondary unit tolerance extents

Plug for Enhancement Requests

In past articles, I’ve mentioned some enhancement requests (ER’s) for SolidWorks.  Most (All?) of the enhancement requests I’ve made are now SPR’s, which are slated for some action at some time in the future.  To get the ball rolling on these requests, I’d like to invite others to vote for these changes in the Customer Portal.  I’m not going to provide links to my requests, as they wouldn’t work anyway with the Customer Portal’s java script.   I will mention a brief description of each change, and bold keywords which may be used to easily find the open SPR’s in the Customer Portal.  These are my requests, many of which I’ve talked about prior to submitting them to the ER system.

  • Support new ASME Y14.5-2009 symbols on drawings and models.
  • Option to force captilization (note the misspelling) of annotation notes on drawings (original article).
  • Add CR (Controlled Radius) symbol (original article).
  • Support External Threads as an actual feature similar to Hole Wizard (original article).
  • and a new one (no SPR yet), the ability to auto insert angle dimensions and values in sketch mode, just as we can already do with linear dimensions.  (This was inspired by a recent article by Deelip Menezes, in which he apparently misjudged SolidWorks dimension capabilities in sketch mode, but ended up finding a good candidate for an ER anyway.)

I have other SPR’s, but these are the ones that are actually enhancement related (as opposed to bugs or workflow annoyances).  Please visit the Customer Portal soon.  Choose “Enhancement Requests”.  In the ER search field, enter the bolded keyword(s) for each of the requests above.  Then pick and vote for the associated SPR.

Tutorial: Tag your features

tagsclipartIn this article, I’m covering a topic of tags, which I briefly addressed in my recent breakout session at the SWUGN Summit – San Jose.  What are tags?  This website has tags that are assigned to most of its articles.  Not just blogs, but many types of documents have tags which are used to increase searchability and enhance content filtering.  SolidWorks added tags functionality in SolidWorks 2008.  In SolidWorks, tags can be assigned to documents and features.

Instructions to assign tags to features:

  1. In the view pane or FeatureManager design tree, select any feature.
  2. In the status bar, at the lower right of the SolidWorks window, click the Tags icon.  tagsmall
  3. Tags box will pop up near the icon and will include any tags already in use for that feature.
  4. Type new tags into that field, separating each with a semi-colon.  (Once a tag is typed, it is applied.  There’s no “OK” button to accept.)
  5. (Click on the Tags icon again to close the Tags box.)

Tag Location

Then, to use the tags:

  1. In the filter field (at the top of the FeatureManager design tree), type-in the desired tag.
  2. This will automatically filter out all features which do not contain that tag nor match that text in their description.
  3. To redisplay all features, click cancel x in the filter field.

filterlocation

SWUGN Summit San Jose coming up quick!

If you are in the Northern California area, you’ve may have already seen an email from one of the SolidWorks User Groups about the upcoming SWUGN Technical Summit at the Embassy Suites in Milpitas.  SWUGN Technical Summits are day-long SolidWorks based conferences scheduled about once a month at different locations throughout North America.  Each summit generally offers the choice of 10 sessions within 5 time slots.  Each session offers a detailed look at particular SolidWorks related topics which are geared towards all levels of experience.  The San Jose summit is on March 23, 2010 and will feature presentations by SolidWorks Product Managers, local independent SolidWorks and VAR experts.  Among the presenters are a couple of first-timers, Gabi Jack (Bay Area) and Alex Ruiz (driving up from SoCal).  I’ll be presenting a session on advanced customization techniques.  If you’d like to see a particular customization topic covered in my session, leave a comment here.  Right now, I plan to talk about customization of hole callouts, Hole Wizard holes, Shortcut Tool, Mouse Gestures, and Sheet Metal Gage Tables.  (I’m also thinking about the Custom Properties Tab Builder, but that is a topic all to its own, so I may save that for another time.)

The cost to attend the SWUGN Technical Summit is only $40.  This is a bargain by almost any measure.  Similar types of conferences can cost $800 or more.  Check out the SWUGN Technical Summit website for session details and registration.

OK, and now for some fun.  At the San Jose summit on March 23, 2010, the first person to come up to me and says “SolidWorks Legion is awesome, dude” will earn a free CSWP test of their choice (does not include the new CSWE test).  The second person who says that line to me will earn a free SolidWorks hot-cold insulated mug.  Don’t try to be the first person and repeating the line twice. 🙂  Also, SolidWorks employees, VAR employees and other presenters are not eligable to earn these items.

Deleting a Row from General Table

This question came up on the SolidWorks Forums today and after answering it I thought of sharing it up.

You have inserted a General table in the SolidWorks drawing and accidentally added one extra Row. Now you want to get rid of that line. As usual you’ll right click on the specific Row you want to remove from the table and clicked on the Delete.

But to your surprise, you can only see the option to delete the entire table and no Row. You may feel bit frustrated with that.

Now here comes the trick to delete the Row from the General Table.

1. Click on Table and you’ll see some thing like in the picture below.

2. Click these small arrows to show the Table Header. (Check, the pointer has changed).

3. Your table should like this.

4. Click on the table again.

5. Select/ highlight the Row (by clicking on the number. See the color change). Now right click on the row number, go to Delete and select Row.

6. Hurray, the unwanted Row has gone. If you want to hide the table header, click on the table again. Now click on those small arrows (look at step 2) again and your header will hide.

Drawing: Detail View with blank detail circle

**UPDATE Sept 2016**

As with many old tips for SOLIDWORKS, this old tip is now outdated.  As of SOLIDWORKS 2017, there is an option for detail and crop views within their PropertyManager called “No outline” that allows you to turn off the view outline.  No more need for the fancy workaround below.

 

**Original post, now outdated**

An interesting drawing question recently came up on the SolidWorks Forum.  How does one create a detail view were the detail circle is hidden?  Jennifer Reid gets props for coming up with a great solution for newer versions of SolidWorks (I’ve modified her original post for clarity):

  1. Open the document that will have the blank detail circles.
  2. Go to toolbar Tools>Options>Document Properties tab>Line Style.
  3. Click the New button.
  4. In the Line styles field, name the new line style something like “None”.
  5. Create new line styleIn the Line length and spacing values field, enter “A,-1,-1”.
  6. If desired, Save the new line.  This is not necessary.
  7. Click OK button to apply this new line to this document.
  8. Then goto toolbar Tools>Options>Document Properties tab>View Labels>Detail
  9. Set Circle and Border to the blank line that was just created.  (It shows up as a blank line at the bottom of the line style drop down lists.)
  10. Click OK to apply changes.
  11. On the drawing, ignore the dashed line for the detail circle and detail border.  This is just a guide that does not appear when the drawing is printed.

The full conversation is found here.