Inventor Customization - Using iLogic to Raise a Yellow Flag

“Time is the cruelest teacher; first she gives the test, then teaches the lesson.”
Proverb

With KETIV's Autodesk Manufacturing Academy getting nearer and nearer, I've been working heavily on my iLogic class.  As a result, this post is about, what else?  iLogic.

As I worked on developing my iLogic exercises, I found one place that would have been helpful in a past job working with electronic enclosures. 

I did a lot of work with Electronic enclosures that had to meet NEMA enclosure ratings.  We regularly used Hoffman boxes.  I downloaded this file from their website HERE.

Ahh, The Hoffman enclosure.  I know thee well.

If you want to read about the ratings, feel free to follow the link, it's good information.  For the purposes of this post, let's just deal with indoor, and outdoor applications.

I dealt regular dealt with outdoor (more robust, but expensive) and indoor (less robust, but less expensive) enclosures.  Needless to say, you didn't want to mix them up. 

An outdoor rated enclosure in an indoor application is overkill.  It costs too much, and the gains in exposure resistance aren't beneficial.

On the other hand, you don't want to use an indoor rated enclosure in an outdoor application.  The box isn't designed to meet those requirements, and moisture is likely to get inside the box and damage the components the box is intended to protect.

Back when i was in this line of work, you had to check the box part number and be sure.  while this wasn't difficult, it was sometimes a painstaking step, and there were times that mistakes happened.

Fortunately, one of these mistakes never made it beyond the computer, but it did result in lost time as the wrong box was removed from the model, the correct box (which may not have been the same exact size) was placed in, and the components placed in the box again.

So how does iLogic help?  With one, simple line of code, I can create a warning that will tell me the rating for this enclosure.  So I know right away if this is an outdoor rated enclosure, or an indoor rated enclosure.



Yes it's simple, but it can also be effective.  And sometimes little extra warning is all the help we need.

It's Automagic! The Drawing Resource Transfer Wizard

“He's got tools. Something to see.”
 Sid Monge

Necessity is often the mother of invention, and last week proved no different.

I was creating a large number of drawings for someone, and we were faced with something that, while easy, can be exceedingly tedious.

We needed to update title blocks in several drawings.  There were only about ten or twelve, but copying and pasting each one can be time consuming.

So instead, I used a tool to help automate the process; the Drawing Resource Transfer Wizard.  It can be found from Windows Start>All Programs>Autodesk>Autodesk Inventor (version)>Tools

The Drawing Resource Transfer Wizard

So how does it work?  Let's roll some footage and take a look!



This tool really helped me transfer the title blocks quickly, without having to do a bunch of copying and pasting from drawing to drawing. 

One thing to watch out for.   While the Drawing Resource Transfer Wizard will try to match up all the properties in the new resources, but it may not be able to do it in every case.  In other words, it pays to double check when everything is done.

In my case, I had to open the drawings to create final prints, so I checked the title blocks along with he dimensions, views, text, etc. that I had to check anyway.

In the end, this tool saved me the trouble of having to do a lot of tedious work, and let me focus on more important (and fun) things.

Happy Inventing!

Change Model Reference - Making the Switch

 “There are no answers, only cross references”
 Proverb

Every release of Inventor brings many new features.  So many, in fact, that some useful features can get easily overlooked. 

To this end, I've decided to revisit one of those, 'subtle but significant' features; Replace Model Reference. 

Change the Model Reference

This particular feature is actually available from the 'Subscription Advantage Pack' for Inventor 2010.  If you're on subscription, those files are available from the Autodesk Subscription site.  It was made available to everyone with the release of Inventor 2011.

What does this tool do?  It lets you change the model an Inventor drawing is using to generate it's view.

Why would I use it?  If you've ever tried to parts, assemblies, and drawings, in Inventor, you've seen that the drawing you've just copied wants to reference the original part or assembly. 

The old trick was to rename the original files, and force the drawing to ask you for it's reference file.  You'd point it to the new copies, and you'd be off and running (after renaming the originals again, of course).

Effective, but a little inelegant.

But by clicking the Change Model Reference button, you can open up a screen that allows you to select the current reference, and then browse to redirect it.

Choose view, and browse to new reference

Clicking the browse button, you can select a new model.

Choose your new file

Once that's done, the new file will replace the current one.

There it is.  The new reference!

Bear in mind, while Inventor will try to keep the dimensions it can, but it may not.  It all depends on how different the view is.  If it's totally different, all best are off.  But, if you've just created a copy, it's pretty solid.

So there it is.  Give it a whirl.  It's a great help!

Happy Inventing

Obeying the Rules - Enforcing Length using iLogic

“Hopefully my experience can help a little bit. I'm just a small piece of the puzzle.”

 Ed Jovanovski

One simple, but effective case I've see for iLogic is to prevent someone from inadvertently call out a length longer than what can be purchased, or manufactured by the tooling in the shop.  If caught too late, the ramifications of calling out the 'unobtainable' length can cause a lot of rework as the design is corrected.

Fortunately, a few lines of code in iLogic can help with that.

In this video, I describe how iLogic can be used to limit the length of a sample extrusion to 60 inches or less.



There's tons of things that can be done with iLogic.  This is just a small example.  I hope to post more as I go!

P.S. Here is the code that I used to create the rule.  My comments are below each line of code

iLogicVb.UpdateWhenDone = True
'updates part after rule finishes running

If Length > 60 in Then
'The if statement telling iLogic that something is to be done if the parameter 'Length' is longer than 60in

MessageBox.Show("Length cannot be longer than 5ft", "Design Violation")
'Displays a message box stating that the length can't be longer than 5ft

Length = 60 in
'Resets the length back to 60 inches

End If
 'Ends the if statement.

Maintenance Time! Autodesk Inventor 2011 SP1

Flying isn't dangerous. Crashing is what's dangerous. 
Aviation Proverb

It's out!  Last Friday, Autodesk issued Inventor Service Pack 1.  Fixing those inevitable little 'random features'.

I installed it last Friday on my Windows 7 64 bit box, and things are humming along normally.

So go ahead and give it a download from the link HERE!

Happy Inventing.

Construction Time Again - Inventor Sketches

“The road to success is always under construction. Under construction. That means you're always working. So that's what he's doing.”
Chad Epperson

There's a busy week ahead of me, so this is a shorter blog today.

But I wanted to talk about something that is often taken for granted.  Construction lines.


When I'm training, I'll even tell students "They're a good practice, but don't wake up in a cold sweat if you forgot a construction line." 

Construction lines.  Can I just forget they exist?

So why do I say they're a good practice? 

Well, it is good book keeping.  But the single biggest reason is that a construction line is ignored for the purposes of creating a sketch boundary.

Okay, so what does that mean when translated from 'geek speak'.

Here's a rectangle, divided by a line.  About as simple as it gets.  All lines are standard lines.

Nothing special here!

 
But what happens when I extrude the lines?  The line running down the middle splits the profile, meaning you have to make two picks to extrude the entire rectangle

Inventor sees two regions here

But if I make the middle line a construction line, the line is ignored, and the entire sketch can be selected in one click. 

You can make the line a construction line by selecting it, and clicking on the construction line button.

Make the regular line a construction line

Now, with the construction line created, the extrusion only requires a single click to select the entire profile.

Construction line created!

Profile can be selected in one pick

So there's the big difference.  Do I convert lines to construction lines when necessary?  Yes, I do.  I find it particularly useful when I have a complicated sketch with a lot of line geometry.  I find it makes creating the extrusion a lot easier.

That's it for now.  Happy Inventing!

The Random Software Surprise of the Day

“My software never has bugs. It just develops random features.”
Computer Proverb

Before I get started, I'll put in the standard disclaimer that the images I use aren't the actual assembly.  The real assembly was customer data, which I can't post here.  Consider it a 'dramatization'.

Today I ran across one of those little random issues that makes no sense, until you try that 'one thing'.

What was that?  I encountered an Inventor assembly file that was crashing when placing an angle constraint in an assembly.   One time, every time, just like clockwork. 

Could it be that the Angle constraint was broken ?!?

I checked all the initial things.  Cleaned up temp space, checked the video settings.

None of it helped.

I tried reproducing the error in a different assembly file.  That file works perfect.  At least now I know I've narrowed it down to something in that file.


Staring at the file, looking for a culprit, my eyes fall upon two components that were downloaded from a third party site. 

Could it be? 

For the heck of it, I remove the two third party files from the file and try it again. 

I hold my breath for a second.  It works perfectly, just as advertised.  It seems one of those third party components had a corruption in it that was killing the file.

So what's my big lesson?  While I'm a huge fan of third party components, there is some bad stuff floating out there.  I'm certain it's not intentional, but every download can't be perfect.

As Damon Runyon put it "Trust but Verify".  If an assembly suddenly starts 'acting up'.  You might want to remove some of that third party content.   A corrupted file might be the cause of your woes.

Making it up in Volume - Uploading Data into Autodesk Vault with Autoloader

“It's not the load that breaks you down - its the way you carry it”
Lou Holtz

The inspiration for my blogs often comes from the challenges I face in my day to day functions at KETIV Technologies.  This blog is no different.

I was faced with loading a large amount of data into Vault, and we knew that the data wasn't perfect.  So I turned to the Autoloader that's provided with Autodesk Vault.

Autoloader, ready and waiting

Being a bit of a control freak, I tend to have a bit of a distrust of anything that contains the phrase 'Automatic'.  As far as computers go, I tend to go with the 'if you want something done right, do it yourself' approach. 

Needless to say, I approached Autoloader with a bit of trepidation.

But while I did open up Autoloader with a bit of caution, in the immortal words of Obi Wan Kenobi;

"This is the weapon of a Jedi Knight. Not as clumsy or as random as a blaster, but an elegant weapon for a more civilized age."

So I fired up Autoloader, and uploaded some AutoCAD data, and up went the data.  Autoloader found some broken links that needed to be fixed, and put the data in with next to no interaction on my part.

In conclusion, while Autoloader isn't the 'magic bullet' for every situation, the control freak in me had acknowledge that my concerns about Autoloader were unfounded.  When you need to upload a large amount of data, this is a fantastic tool that you shouldn't hesitate to use as part of your arsenal.

A pictures worth a thousand words, so here's a video on the steps to upload data.  Enjoy!

Yielding to Logic - Extracting Drawing Scale with iLogic

“The logic of words should yield to the logic of realities.”
Louis D. Brandeis

Just this Friday, I was posed what I thought was an easy, five minute, question.  "How do I place the view scale into the title block?"

My inside voice said, Pffft!  No problem!  After all, there's a spot right there for it in the title block already!

Scale is already there! 

So I go into my title block definition, and look for the iProperty that accesses the drawing scale. It should be a slam dunk.  All I have to do is choose the property that calls the scale.  But as I look, my stomach sinks.

Here they are.  All I have to do is choose one.  But wait?!?

It isn't there.  Scale isn't available.  I think I know why this is.  In many cases, the scale can easily vary from view to view, so which do you call? 

I puzzle over this a bit.  I bounce it off of Javier Chavez, one of my KETIV team members.  He confirms what my eyes see.  The scale isn't there.

So, now, as they say, it's time to execute 'Plan B'.  Which means, I have to develop a 'Plan B' to execute. 

Now I'm pacing about my little office, rubbing my chin, and annoying my coworkers with my heavy footfalls. 

After a few moments, I have 'Plan B'.... iLogic!

iLogic to the rescue!

So I create a new iLogic rule, and enter the following code below (with comments):

'Forces update after rule runs
iLogicVb.UpdateWhenDone = True
'Extracts scale from 'View 1' on drawing sheet' to a field named SCALE
SCALE = ActiveSheet.View("VIEW1").Scale
 'Writes scale to a custom iProperty named SCALE
iProperties.Value("Custom", "SCALE") = SCALE

Here's the rule in context of the iLogic editor.

In short, the code extracts the scale of the first drawing view via the API, and writes it to a custom property.  With the scale written to a custom property, NOW I have something I can extract for the Title block!

SCALE custom iProperty

With this field added to the title block, I'm in business.

The custom iProperty

With that being done, is the rule perfect?  Frankly, no.  I have work left to do.

This is what's still on my to do list.

1) My triggers don't update completely every time.  Just like Rule #2 of Zombieland, I have to 'Double Tap' the update button once in a while.  I want to go over it and make sure it updates consistently.

Still have to work on the triggers some more

2) The view has to be called 'VIEW1'.  If it's not, or if you delete the first view and place another (now called VIEW2) the rule will bark about not having 'VIEW1'.  So there's a little work to be done to remedy that.

But I think the backbone of the routine is solid, and I'm willing to take a little time to revel in a small victory, if only for a few seconds.  I don't consider myself one of the iLogic 'gunslingers' so sometimes you have to 'Enjoy the Little Things'.

Which by the way, is Rule #32 of Zombieland!  :-)

As I learn more, and improve the rule, I'll post updates!

Happy Inventing!

P.S.  It's back.  Autodesk Manufacturing Academy is back, hosted by KETIV in Cerritos and Oregon.  Come see us in October!   And check out the videos from last years session HERE!

***UPDATE 20-March-2012 ***

After some hunting around, and help from a friend or two, it looks like teh direct update can't be triggered right when the view scale changes.  But if an event trigger is set to run "Before Save Document".  The rule scale will update when you save.  I tried it in Inventor 2012, and it works!

Here's the ticket!

What's Done is Undone - Editing Properties in Autodesk Vault

“My life needs editing.”
 Mort Sahl quotes

In a perfect world, a file would go into Vault once.  It would never be edited, corrected or ever adjusted.  We'd look happily at out Vault, with no version ever larger than one.

Then we'd walk outside to a beautiful, sunny day, and the birds would be chirping, our neighbors would wave, and all would be right in the world.

What a wonderful world it would be indeed, but as we insert the sound of a needle screeching across a record, reality gets in the way.

The truth is, mistakes happen.  You get distracted, you forget, you're tired because you couldn't sleep that night.  The reasons go on and on.

One of the common things I often do in Vault, is forget to update all the properties before I check in.

In a perfect world, I'd enter them in Inventor's iProperties, then check in the file.

This is where I should get them

But I sometimes miss that step when I'm placing these in Vault.

Fortunately, I can change them after the fact.  Vault provides us some property edits that allow us to change the properties once their in Vault.  All you have to do is choose the part, go to Edit>Edit Properties, and follow the wizard.

Salvation.  Editing properties in Vault

There's a couple of nice little tricks to the wizard, so here's a video to follow up those steps!



Happy Inventing!

AEC Exchange - Now More than Ever

“A doctor can bury his mistakes but an architect can only advise his clients to plant vines.”
 Frank Lloyd Wright

AEC Exchange has been around for a little while now.  I've been fortunate to watch it start taking hold within the last year or so, as resources like Autodesk Seek the resources created inside Autodesk Inventor available in a format easily used inside of Autodesk Revit.

Imagine taking Inventor model that you've designed for a building, and being able to easily send those models into Revit.

It's be a dream a long time coming.

Since a picture is worth a thousand words, here's a video of AEC exchange in action.   A special thanks to the guys at Autodesk for providing the data set!



Happy Inventing!

Project Photofly - The Next 'Thing' for You and Your Camera?

“All photographs are there to remind us of what we forget. In this -- as in other ways -- they are the opposite of paintings. Paintings record what the painter remembers. Because each one of us forgets different things, a photo more than a painting may change its meaning according to who is looking at it.”
John Berger quotes

I finally had a chance to try out Project Photofly from Autodesk Labs.  I really wanted to try it out on my own stuff, and not just pull down just the sample data.

Before anything else, what is Photofly? 

Photofly is a software that will allow you to take several pictures from a standard digital camera and stitch them together into a 3D image.  You can even apply a known distance to the image and use that to figure out other dimensions. 

As if this weren't intriguing enough, it's done over the cloud.  That's right, you upload the files to Photofly's servers, and the stitching is done offsite in that ether-world known as 'The Cloud'.

The cool part, is that your computer resources aren't hit for this.  I actually put Photofly on my 6 year old desktop with a mere 2GB of RAM, 128MB video card, and a 3.4 GHz single core Pentium 4.

The hardware didn't matter, it was only a vehicle to interact with Photofly, although I'll admit I was wishing for a better video card after I'd downloaded the image.  Even then, the product was very usable. 

The first thing I did was pull out my BlackBerry and take some pictures of my 3DConnexion SpacePilot Pro.  My results were pretty good for a first time, I thought!

The first 3D Picture I created with Photofly

Next, I thought I'd try something a little tougher.  So I headed down to Planes of Fame again and tried taking pictures of the FJ Fury there.

These were a little tougher.  I was hampered by the fact that I couldn't see the top of the plane, and I really couldn't get good pictures of the back.

And I do think there's still some user error that needs to be worked out!  :-)

First just a regular picture

The FJ Fury sitting at Chino.  I'll give anyone 3 guesses what plane the Fury is based on.

Here's the first side of the FJ Fury

And the other angle.

Side 2

My first impressions?  This is pretty cool stuff.  The ability to take a 3D picture, and possibly even get measurements off it could be a real boon when you've got something your trying to get into  a 3D program.

But there's two of things that I've already learned in just this brief little journey.

1. This shouldn't really be surprising, but watch your lighting.  Bad lighting can cause Photofly to have problems putting everything together.  
2. Get plenty of pictures.  When I took pictures of the FJ Fury, I started on one side, took a picture, walked 3 paces, and took another picture, and repeated.  I only did this at one level (about eye level), I should have taken another 'ring' of pictures at a lower level, to have more images to stitch.  If I could have, I also should have taken a 'ring' higher than eye level.

Aside from the user errors, there's a lot going for this little program.  I for one, hope to see it continue into the future.

For more info, check out Project Photofly here.  There's also some instructional videos I'm going to be going through myself!  I've just scratched the surface.

There all on the link above, but here's the first embedded in the blog! 

Enjoy!

Keeping Your Head in the Clouds - Project Centaur from Autodesk Labs

“A pessimist only sees the dark side of the clouds, and mopes; a philosopher sees both sides and shrugs; an optimist doesn't see the clouds at all--he's walking on them.”
 Leonard L. Levinson quotes

The last couple of days I've been going through my daily duties of installing network deployments (which I refer to as the 'Progress Bar Rodeo') and preparing Vault data for implementation.

But during this time, my Twitter account has been buzzing about something new on Autodesk Labs called the 'Project Centaur Technology Preview'. 

My first thought is, I have no idea what it is, but it sounds cool.

So I took a look, and found out that it looks very cool!  Upload your files to the cloud, let it run optimization over the web.  Then, it'll spit back results when its done.

I'll be the first to confess that I haven't tried it yet.  I haven't had the time to install and try it.  But here's a video from our good friend Rob Cohee who gives a quick run through of Centaur in action.

Take a look! 

 

Searching Your Memory - Saving Searches in Autodesk Vault

“We believed we could build a better search. We had a simple idea, that not all pages are created equal. Some are more important,” 
Sergey Brin quotes

If you've looked at Autodesk Vault, you probably know that it runs on a database that makes searching for data much faster than just standard file searching inside of Windows Explorer.

But it's one thing to search quickly, it's another entirely to recall what you were searching for.

Lucky for us, Vault has a way to save it's searches!

First, I'll open up my Vault Explorer, and search for the word 'Green'.  Vault locates all the files that have the word 'Green' in their= fields.  In this case, it finds it in the 'Description' filed.

A search for 'Green'

 
You can narrow this search by typing another bit of data to filter down the search even more.  For example, if type the word 'Drawer' into the search now, I'll search the data containing 'Green' for data containing 'Drawer'.  Now I've filtered my search even further.

The search narrowed further

Now that I've searched this data, narrowed it (possibly multiple times), what happens if I need to return to it?  Of course I could go through the process, but I can also save the search.  All I have to do is click on the pulldown next to my search box.

Saving the search

Once this screen is selected, you'll be asked to save your search.

Now the search can be named

One the seach is named, it is placed in the 'My Search Folders' section of Vault.

Now the search is saved.

All you have to do now, is click on when you want to go back to the search data, and you'll return to that search in a flash without having to type in the same information all over again.!

On a final note, if you need to edit, rename, or delete a search, just right click on it in the browser, and you can do whatever you need.

Editing the search

That's it for now!  Happy Inventing!

Lost Inventor Tool Ribbon. An Addendum

“Why did you want an addendum to what you had already written and signed?”  
Thomas Mesereau

While reading my previous post on the Vault Add-In, Mike Carlson, KETIV's Data Managment Specialist Extraordinaire, pointed out that there's another Add-In that, if set not to start, can cause you a bit of grief. 

The Add-In is called the EDM Add-In, and if it's not set to Load on Startup, Vault won't work correctly.  It'll try to start, but then shut down again.

Turning it on is the same as in my previous post, but with one exception.

This Add-In is hidden!

So when you go into Tools and choose Add-Ins, you won't see the EDM Add-In unless you right click and choose Show Hidden Members.

Here's that crafty little Add-In!  Set it to Loaded, and also to Load on Startup.

So there it is, another one of those Add-Ins that in the rare case where it breaks, can be fixed in seconds. 

All you have to do is know where to look!

Lost Inventor Tool Ribbon. Answers the the Name "Vault"

“Buying the right computer and getting it to work properly is no more complicated than building a nuclear reactor from wristwatch parts in a darkened room using only your teeth.”  
Dave Barry


Every once in a while, you see a strange little thing come up.  You don't know why, but it's easy to fix once you know where to look.


In this case, a Vault ribbon doesn't show up, even though the Vault client was installed.  


It was puzzling, but the fix ended up being pretty simple.  In the end, it turned out that the add-in for Vault wasn't starting when Inventor was started.  Clicking a few buttons was all that was needed.


The first step was to go to the Tools ribbon, and Choose Add-Ins.  

Choose the Tools Ribbon, and click Add-Ins

After choosing the Add-Ins icon, you'll see the add in screen.  Once this comes up, select Inventor Vault and make sure that the Loaded/Unloaded and Load on Startup options are both checked for that line item.

Make sure the indicated options are checked for Inventor Vault

Once you do this, The Vault Add-In will start, and the next time you start Inventor, the Vault ribbon will be available.

The Vault ribbon found

Granted, this won't fix every issue, but when Vault is installed, and you can't get it to show up in Inventor, many times, this will fix it!

Happy Inventing!

Life Lessons - The Ghost of Engineers Past

“There is a certain majesty in simplicity which is far above all the quaintness of wit.” 
 Alexander Pope 

We live in a world where things we take for granted would have been considered science fiction only fifty years ago.

Today I've updated my Facebook and Twitter pages from my Blackberry Storm (on which I've also received several e-mails today). I also used a GPS to find the coffee house where I'm writing this blog with a laptop that has more calculating power than the computers that flew to the moon and back.

In a world of ever increasing complexity, I know I often forget the beauty and elegance of a simple solution.

Today I was walking the floors of the Planes of Fame air museum (where I saw a great seminar on aerial photography by Paul Bowen), and notice some ingenious solutions created by our engineering forebears.

The first, if you're flying a 1940s vintage aircraft, and need to check to see if you're landing gear had lowered, what did they do? Gauges, sure! They had them.

But what if you wanted to double check?

The designers created a simple tab on top of the wing that popped up when the landing gear was down. Purely mechanical, just a little piece of metal.

The landing gear indicator on a A6M5 Zeke "Zero" Japanese fighter
Yes this is a real, flyable WWII era Japanese Fighter
The indicator is just highlighted, on top of the wing, above the landing gear
(click to enlarge)

A closer look at this simple solution

The same solution on a Russian Yak-3
(click to enlarge)

Another incredibly simple solution, the 'yaw' indicator on the N9MB Flying wing.
'
Considered the B-2 Spirit's 'grandfather', this aircraft tested the flying wing concept back in WWII.

I'm told the airplane has a tendency to yaw (if your looking from the top, the nose would be swinging from side to side slightly). It is however equipped with a yaw indicator.

How does this sophisticated instrument work? It's a piece of string attached to the nose in front of the pilot. If the string is blowing to the right or left, the airplane is yawing. If the string is blowing back toward the pilot, the airplane is flying straight.

That's right, the precursor to one of the most sophisticated aircraft in the world today used a piece of string as a flight instrument.

The flying wing back in May
(click to enlarge)

The back of the Flying Wing
(click to enlarge)

Notice the string between the canopy and the Northrop decals
This is the yaw indicator
(click to enlarge)

So why do I mention this? Because I think we all get caught up in complex solutions involving computer controlled whirlygigs with a galloping rod adjusting feedback loop, that sometimes, we forget that there might be a simpler solution for that.

If anything, seeing things like that makes me appreciate (and look) for the lessons taught by the designers who sat at a drafting board where the sketching toolbar was a pencil, the delete key was an eraser, and the 'computer' was a slide rule.

Chains of Thought - Chain Dimensions in Inventor

“Loyalty to petrified opinion never yet broke a chain or freed a human soul.”

Mark Twain

Chain dimensions in a manufacturing drawing have always made me 'squidgy' (that's the official term for it).

When you start thinking of how chain dimensions can affect tolerances, and how they stack up across a set of chain dimensions, it can get a little bit frightening.

Chain Dimensions
(click to enlarge)

In the sample above, look at how the tolerances stack up, let's assume a dimension of +/- .005

That means that the '3.916' dimension can vary safely between 3.911 and 3.921. So far, so good.

But we start to see a problem with the next dimension, 10.284. The way this is dimension is placed, it's .005 tolerance adds up with the previous dimension, meaning that it can actually vary between 10.274 and 10.294, and still meet the tolerances as dimensioned (even if that's not what's intended.

As we go on, the 7.50 dimension will stack up with the previous two, and so on. The problem compounding as the chain passes the previous tolerances to the next.

This is why baseline dimensions are so popular among the mechanical crowd.

Baseline dimensions. Nice, safe, baseline dimensions.
(click to enlarge)

In this case, the dimensions are all measured from the edge, and totally independent of each other. This eliminates the 'stacking' issue that chain dimensioning has with tolerances, and generally conveys that this part needs to be held to a tighter tolerance.

But does that mean that as a manufacturer, you'll NEVER use chain dimensions?

Not necessarily. The obvious case for chain dimensions is when tolerances aren't important, such as a rough cut, or a series of outside dimensions with loose tolerances.

The other is a case where the dimension from edge isn't as critical as another dimension. Looking at the example below:

I have a stretcher, a common tool in woodworking. There are many cases where the length of the shoulder is critical, and the tolerance of the tabs (known as tenons), is secondary to that shoulder length.

Cases such as this, and also cases similar to this are where I've used chain dimensions to get exactly what I want.

Chain dimensions used to get the desired effect.
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A dieset using chain dimensions. The Center to Center between the pins is critical.
The sides are flame cut a typically only for reference
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So there, you can see where chain dimensions aren't ALL bad. Like most tools, it's knowing when you can make the best use of them.

Food for thought I hope!

Taking a Sampling - Where Did My Inventor Sample Files Go?

“The proof of the pudding is in the eating. By a small sample we may judge of the whole piece.”

Miguel de Cervantes Saavedra

Last week I was fortunate enough to receive my new laptop. 64bit Windows 7, 8 GB of RAM, 500GB hard drive. It'll be a dream for at least the next 6 months, before the next dream box comes along.

Of course with that comes the installation of the software I'm using. To date, I have Inventor, Vault, and Showcase installed. Not to mention Snagit, Camtasia, and several other small programs I usse

After getting my system ready I found that I need to run a quick test on some files. No problem! I'll just grab a sample file! There's sheet metal parts, assemblies, drawings, a slew of flies I can use for a quick test when I don't have the time or desire to build a data set.

Well, when I went to get them, they weren't there! There were some iLogic files, a translator folder, and an html document named 'Where are my sample files'.

The 'Where'd they go file'
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Not to fear, if you click on the html file, it opens up to a hyperlink that takes you to a page where you can download the files.

Found them!
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The link will take you to the download page but if you're reading this blog, you can just go ahead and follow the link here.

It definitely saves the disappointment of finding the location (which can vary if you're on Windows XP versus Windows Vista/7).

If you're a CAD Manager or IT in charge of getting the files, you can also download them and put them on a server instead of hunting for them when you're asked. Then you get kudos for being proactive!

The download page
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That's it for this weekend, just a small tip today, but don't worry. I'm thinking of what to do next already!