Customer Use Drawings

It happens at every manufacturing facility I’ve come across.  A customer or potential customer calls up and wants an engineering drawing of some part of a larger assembly so they can design their equipment to interface with it.  The general assembly drawing you’ve created specifically for customers isn’t detailed enough.  The catalog only shows a picture of the part in question.  Their application is something you’ve never encountered before (if they will even describe it to you) and now you’ve got a decision to make.

Company policy states, “Thou shalt not send proprietary engineering data to anyone outside the company.”  This is, of course, for good reason as your engineering design data is what differentiates you from every other competitor, it’s who you are, it’s your life blood and deserves protection at all costs (within reason).  Enforce the policy and you upset the customer or worse yet, lose the sale.  Send them the production drawing and you slowly erode the value of your intellectual property and run the risk of your competitor or customer stealing your design.  Non Disclosure Agreements (NDA’s) can help, but they are a pain because you have to get lawyers involved and they’re difficult to manage.  Some customers just will not sign them – what can you do?

The solution:  Customer Use Drawings.  Customer Use (CU) drawings are just what they sound like, a drawing made for a customer to use.  They are different from production drawings that contain every detail needed to manufacture something.  The information they offer is sufficient for the customer to make proper use of your product in their application.  The level of detail will vary widely, but you can always expect a CU drawing to have less detail than a production drawing.

Companies handle CU drawings in different ways.  Some will assign a completely different drawing number to a drawing that is designated for customer use.  This can be challenging if you do not have an efficient way to link CU numbers to production numbers.  Initial drawing creation is fairly simple as you can just take the production drawing and do a Save As to the new number.  Then add, delete or change the drawing for customer use and you’re done.  As you can see, one major limitation of this method is that now the production drawing and the CU drawing are no longer linked to each other.  They might be driven by the same part or assembly so major design changes will carry through, but they will now have independent revision histories.  The engineer/designer assigned to make changes at some future date needs to be careful to update both drawings separately.  This doesn’t always ever happen.

Another method for creating CU drawings is to use the same drawing file for both.  With this method, everything comes from one file so updates are simple.  New drawing numbers do not need to be created and managed, making the search for the CU drawing the same as the search for the production version.  Drawing creation is even easier than a Save As because you don’t need to delete anything.  The only drawback that I can see is that if you revise a production part from A to B and change a feature that doesn’t show up on the CU drawing, you may still want to output a revised CU drawing to be consistent.  I recommend hiding the revision history on a CU drawing so this change may be nothing more than renaming the file (if you have the revision level in the filename).  Having a different drawing number for the CU drawing enables independent revision histories.  Most cases for the application of CU drawings, however, involve special one-time circumstances where a customer is asking for something out of the ordinary like the dimensions of the “small thermal exhaust port right below the main port”.  A typical configuration drawing of the entire assembly would never include such inconsequential dimensions as no customer would need them (except yours).  A CU drawing could be quickly made of just the “exhaust port” so the customer could be sure their “product” will fit inside.  These cases are usually one-time requests that vary from customer to customer making separate revision histories unnecessary.

The tool that makes it possible to create production drawings and CU drawings from the same file is Layers.  If you have a 2D CAD background like I do, you have probably worked with layers before.  At WDI, like most firms that design products that fit inside buildings, we would design an entire themed attraction in one 2D drawing file using a different layer for every discipline.  Each drawing sheet would have only certain layers showing and all the others hidden.  In the 3D realm, this seems foreign to some, but the old rules still apply and layers make CU drawings possible.

In SolidWorks, the first thing you might consider is to turn on the Layer toolbar.

This gives you easy access to all of the layers and the button that brings up the Layers dialog box.  Things you can control with the Layers dialog box include layer name and description, layer visibility (on/off), object color, object linetype style and object linetype thickness.

By default, SolidWorks places all objects on a special layer called –None-.  This layer is special because it doesn’t really exist.  It cannot be turned off nor changed.  I mention it as if it were a real layer because it can be selected from the Layer toolbar when you are choosing what layer to place an object on.  Placing an object on the –None- layer makes it always visible.

I created a few standard layers in my drawing templates.  First, a layer called NOSHOW which is a dumping ground for important information that may be needed to make a drawing but you don’t want to show when creating output.  Currently on the NOSHOW layer are dimensions used to define the titleblock.  SolidWorks lets you hide things at will but it’s not always easy to unhide them if you do not know they are there.  The NOSHOW layer makes it easy to see what’s there but meant not to be shown.

In addition, a layer called FORMAT where I put the drawing format (titleblock, border, etc.) enables me to turn off the sheet format when I want to print a copy of the drawing with just the drawing views and no titleblock.  Having a titleblock implies officiality, completeness, design verification, drawing checks and approvals, assigned part numbers, etc.  No titleblock implies a quick sketch, a negotiable design, a work in progress, not complete nor official, open to discussion, etc.  There is a time and a place for both making the FORMAT layer a valuable tool.

The other two layers I created are CUSTOMER USE and NOT FOR CUSTOMER.  Placing data on these layers and turning the appropriate layer on or off makes creating CU drawings a reality.  To create a CU drawing from a production drawing, simply select the items that are not for customer (CTRL-Click to select multiple items) and place them on the NOT FOR CUSTOMER layer by selecting the layer in the toolbar.  Turn off that layer by launching the Layers dialog box and clicking the light bulb icon beside it and click OK.  Change your current layer from -None- to CUSTOMER USE by selecting it from the pop-up list in the toolbar.  Add any details that are customer specific including a note that says CUSTOMER USE DRAWING.  Any items left on the –None- layer will show up on both the CU drawing and the production drawing.

By hiding the CUSTOMER USE layer and showing the NOT FOR CUSTOMER layer, you can see what the production drawing will look like.  I usually place some text on the NOT FOR CUSTOMER layer somewhere outside the printable area that says, “THE ANNOTATIONS ON THIS LAYER ARE NOT FOR CUSTOMER USE”.  This helps the user to know what layers are turned on or off.

The final step is output.  It is always a good practice to save engineering documentation in a neutral file format, preferably one that is difficult to edit.  Many companies use PDF files for their released documents.  The Save As tool in SolidWorks includes a PDF option, making creating PDF’s easy.  I typically recommend using a filename that captures the moment in time for the file.  For example, a drawing 84848.slddrw could be saved as 84848.pdf but the next time it is revised, a new PDF would overwrite the old.  How would you know what version of the file you had?  Saving it as 84848 Rev A.pdf creates a snapshot in time at Rev A for this drawing.  A revised drawing would become 84848 Rev B.pdf thus preserving the older version.  If your revision system doesn’t include revision tracking, you might use the date instead, as in 84848 07Jul10.pdf.  For a Customer Use drawing, I recommend appending CU to the end of the filename so they sort next to each other in your file system (e.g. 84848 Rev A CU.pdf).  Adding “CU” to the end makes it clear what the file is intended for.

My drawing templates are setup to include both the CUSTOMER USE and the NOT FOR CUSTOMER layers but they are both turned off.  All drawing is done on the –None- layer.  The CU features lie dormant until I get that call for some obscure question about the size of my exhaust port compared to the size of a womp rat.  Since I’ve never seen a womp rat and I’m not sure what the customer really needs, I send them a CU drawing of the exhaust port and everybody is happy (for now).

For your convenience I’ve created a detailed printable tutorial that you can download here:  AVSITUT-0017 CustomerUseDrawings Rev B.

SolidWorks 2010 files for this tutorial can be downloaded here:  CustomerUseDrawings.

Update:  Special thanks to for the idea of placing a downloadable pdf tutorial at the end of this post.  Her tutorial on Modeling a pair of scissors is an excellent example.

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Sunday, July 11th, 2010 SolidWorks Comments Off on Customer Use Drawings

New 80/20 Weldment Profiles

On April 15th I received an email from 80/20, Inc. announcing new smooth profiles.  I have always believed the sole purpose of the grooves that adorn most 80/20 extrusion profiles was to differentiate their product from others in the marketplace. I have tremendous respect for 80/20, not only because I love their product, but because their service is excellent.  You truly get what you pay for and their fast, efficient service has helped me meet many deadlines on time with a superior quality product.  Most of my customers do not mind the grooved profiles so I’ve had no need to try other company’s products.

In the design phase, however, the grooved profiles drive me crazy.  I use SolidWorks to design my frames because the weldment tools make it so easy.  But, when you make a drawing of an 80/20 frame, it looks like a big blob of thick black ink spilled all over your page. Every one of those grooves creates 2 lines and the standard single-width profile has 4 grooves per side.  A view which would normally have a few lines per stick of 80/20 has many.  What a mess this makes if your views are small because your frame is large (and who makes a 1:1 scale drawing of something as simple as an 80/20 frame?).

Smooth profiles to the rescue.  Thank you 80/20. I just completed a design for 3 new frames and they are going to look so nice with the new smooth profiles.  In addition to the improvement on the drawings, working with these in 3D is also much improved. The big black blob thing is also a problem in 3D but more importantly, it is much easier to mate other parts to your 80/20 frame because you do not need to zoom in so far to pick the correct face to mate to. All of those grooves always had a vertigo effect on me forcing me to pan/zoom/rotate my model to reorient myself. The smooth profiles are much better.

But wait, there’s more! The title of this post implies more to be discussed. So, here it is: I downloaded all of 80/20’s new profiles from their website and did some work to convert all of them to SolidWorks 2010 weldment profile library features. They are all available for individual download at 3DContentCentral. Also, for your convenience, they are all here in one chubby zip file. Place them in your weldment profile directory and you should be able to enjoy all of the benefits of smooth profile frame creation that I’ve mentioned above. Special thanks to Van Graves who provided quality control on these. I finished them late last night but had to fix them all this morning after he pointed out some missing critical features. Working as a team is always better than going it alone. -Amos

SmoothProfiles (3MB)

Update: if you’re looking for all of 80/20’s old profiles (the groovy style or the metric products), I’ve already made those available here.


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Friday, May 7th, 2010 SolidWorks 2 Comments

Spirograph Design for CSWP Contest

I’m going SolidWorks World next week and I’ve been told that the CSWP event on Monday night should be a good time. I remember seeing details about last year’s event where everyone got to play with the iCoaster. It looked cool. This year everyone gets to test drive an RC car.  I’m not very good with RC cars, but there’s a design contest too.  That’s something I can do.

The Problem:  design a new wheel in SolidWorks for the SC10 RC car.


The Rules:  Points will be awarded in these key areas:  1) Is the wheel designed and supplied in SolidWorks format? 2) Is the wheel rendered and/or animated in a cool way? 3) Is the wheel construction feasible? (decided by Team Associated engineers/designers)

The rules seem a bit awkward to me – the company obviously wants some free design work, but I want to have some fun. My best designs come when I ignore the Rules and just get creative (notice I said “ignore” and not “forget” – eventually you need to come back to the rules, but if you can ignore them for awhile, your creativity will not be limited.)

My wife still has her childhood Spirograph!

My wife still has her childhood Spirograph!

The first idea that comes to mind is an old toy – the Spirograph. What if my RC car wheel had spokes that looped around in a continuous weave that looked like one of those designs you can make with a Spirograph?

There must be a mathematical equation to describe the path made when a point on one circle is plotted as it rotates around another circle. If I can plot the path mathematically, maybe I can create a 3D path in SolidWorks to describe a sweep for the spokes of my wheel.  After searching for “spirograph equation”, I discovered David Little’s page at Penn State University. As it turns out, the path of a Spirograph is called an epicycloid.  It’s described by a pair of equations:

x(t)=(R+r)cos(t) + p*cos((R+r)t/r)
y(t)=(R+r)sin(t) + p*sin((R+r)t/r)

R and r are the radii of the 2 circles, p is the position along the radius of the first circle (the hole you put your pencil in on a Spirograph).  Mr Little’s website has a cool Java applet that draws epicycloids based upon your input. If you experiment with this tool, you can discover all sorts of interesting geometry.  After a few iterations, I found a combination that I thought might look like the spokes of a wheel using the values R=72, r=66 and p=67.Applet

Where would engineers be without the spreadsheet? I remember seeing a documentary on PBS called Nerds where I learned that the first spreadsheet was called Visicalc and it was for accountants.  Excel is the tool that I am most familiar with – version 2003 being most preferred. The Excel version of these formulas seems a bit more complicated. First, cells are made for all of the constants (R, r, p). I added a few extra for scaling – the final goal is an equation of a curve that will intersect the hub and rim of our wheel. Examination of the formula quickly reveals that t is an angular variable. I made a column for t in degrees because I know this is a cyclical function that will repeat every 360º (remember, it’s a circle rotating around a circle). I also made a column for radians (degrees times pi divided by 180) because Excel evaluates sine and cosine in radians. I probably could change this default somewhere, but that is something I would probably forget later and it’s easy to remember how to convert degrees to radians.

I know I want X and Y coordinates for the entire path and that they will eventually return to zero. I wasn’t sure how to know how many points to plot so I made some check formulas that subtract the current X and Y values from the original X and Y values – when the check columns both hit zero, I know I’ve returned home. The last step for X and Y is to plot a curve using Excel’s graph tool. The Excel graph matches the epicycloid plot so I know I’m on the right track. (Actually, I’m thoroughly appreciating the same feature that the original users of Visicalc appreciated, Excel’s power to iterate until I get it right.)GraphXY

Some interesting observations: my epicycloid has 12 loops and the equation to describe it requires 3960 points at one degree increments. If I made another with 22 loops, I would expect it to take 7560 points to describe it (360 x 21). For some reason, my check equations did not exactly return to zero until I placed a round function into my formulas – I added a variable for the number of rounded decimal places as well.

What about Z? The equations for an epicycloid are only in 2 dimensions, but I want a 3D path for my wheel spokes. The options are limitless, but a sine function would make a nice smooth equation and it would behave in a similar way as the epicycloid equations. Some constants are necessary to vary how often the equation returns to zero and vary its scale. Graphing the function over the same range gives a clue how the path will vary in Z.GraphZ

PointsExcel’s worksheet functionality makes it easy to create formatted output. It turns out that the way the wheel was originally created, I need my X and Z data points to be swapped. By creating a new worksheet with only X, Y and Z values, I can swap the values very easily. The final result is a text file with 3960 points of X, Y and Z data.

Now to SolidWorks! The Insert Curve Through XYZ Points tool quickly creates a 3D path.

CurveMenuAs a point of interest, I believe it was because of this tool that Walt Disney Imagineering chose SolidWorks as it’s 3D design tool – they had 3D points to describe the path of a rollercoaster and needed a tool to model the track. I created a second sketch on a principal plane perpendicular to the path. I started with just a sketch point and some dimensions tieing it down to the path.

CurveThen I made the geometry for my sweep all tied to the sketch point. This way, if I want to change the profile from a circle to a square, I don’t lose my dimensions when I delete the circle. The Sweep tool turns all this hard work into an effortless expression of mathematical beauty. A few features to tie the spokes to the wheel and I have my entry.

Of course, I must return to the rules. I already know I will not win because, although my design is interesting, it cannot be molded which is the intent of rule 3. Rule 1 is easy – SolidWorks makes the whole thing possible. So Rule 2 is the only one left to satisfy.

AEA DesignI’m running out of time so a quick assembly with a cut-away view and a few minutes of rendering in PhotoView 360 and, at last, I have an entry.

Here are all of the files I used to create this design.  -Amos

AEA Entry 1 of 2
AEA Entry 2 of 2

Followup:  SolidWorks World was great. The CSWP event was very fun even though I am a very poor RC driver. CarI did not win the design contest (for obvious reasons). I did, however, win one of 40 SC-10 RC cars, which is VERY cool!

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Wednesday, February 10th, 2010 SolidWorks, Swell Ideas Comments Off on Spirograph Design for CSWP Contest