Did you ever see that 2005 kids movie called “Robots”? Wow. What a great, and I think completely underrated movie. I could sit and watch that with my 4 year old cousin over and over and over again. Robin Williams, Mel Brooks, Ewan McGregor, Greg Kinnear, Paul Giamatti. The premise is that this crazy inventor robot inspires kids to be inventive. But the company that he starts from his inventions is taken over by a greedy robot, who turns the whole company into an evil empire. It shows how even in a fantastic mechanical world, there is still this caste system between old and new. It’s funny in a mechanical sort of way, but it also has a bit of a lesson about modern culture. The main evil element in the movie is a mega corporation making and selling “upgrades” for robots, making you feel bad if you aren’t upgraded. To me, this movie is saying that upgrades (symbol for materialism/consumerism) are just being pushed on you so that someone else can profit, and the benefits to you are pretty hollow, when it comes down to it. Heady stuff for kids, but I think they need to be able to think for themselves rather than letting marketing and advertising (or even cool animated movies) think for them.
Anyway.
I got burned recently by “upgrade-itis” - that uncontrollable urge to upgrade software for no apparent reason - with my recent Wordpress (blog software) upgrade. I actually did hesitate for a moment, and asked myself “is this really prudent?” Frighteningly, I heard the answer in my head say “No”, but I went ahead and did it anyway. Having little conversations with your inner self is one of the scarier parts of being an independent, and not working with an office full of other people all day.
I always lament the new versions, but that’s because I’m driven to try them out as soon as possible. Upgrade-itis? Yeah, I got it bad. New versions always mean a lot of work for me. Still, I can’t avoid them, I’m drawn like a moth to the flame. 2009 is a bit of an exception. I’m so anxious to bury the stinking corpse of 2008 that 2009 could not come soon enough, and after having played with it for a couple of months by now, I think it is overall pretty good.
Still, I think the beta period is WAY too short. Rhino has beta periods that last months. Rhino is successful and powerful software, and they have serious competitors, but they are only on version 4.0. I personally don’t run into bugs in Rhino, but I don’t use it as much as SW either. I don’t think Rhino puts much stock by what panic stricken self promoting marketing people say. Neither do I.
Back when SW first started, they claimed they were doing new releases every 6 months. The release cycle gradually slipped, and now I believe we are on a 12-14 month cycle. How often do you need a new version? Is every year too frequent? Release cycle has a direct relation with product quality (meaning reliability, stability, predictability). Is getting new features quickly more important than getting new features that work?
Brian Benton over at CAD-a-blog set up a little poll and asked AutoCAD users how often they think Autodesk should bring out a new version of their software, and this is what they had to say. Granted, these are AutoCAD users, and are probably more afraid of change than most.
So let’s take a couple little polls, and try out my new poll plugin (that SodaHead crap didn’t work very well).
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Ok, it’s my fault really. It’s my fault for being upgrade happy and not checking to see what else is happening. It turned out that today’s 2.6 upgrade to Wordpress causes a problem if you don’t clear out your cookies - you won’t be able to log in. It keeps saying that your password is invalid.
So if you came to my blog to leave a comment, and you can’t do it, it’s not because I’m throwing a tantrum and have blocked everybody out. Just clear out your cookies, and carry on.
Sorry. This is the second time upgrading to the new Wordpress version has screwed me. Wonder if these guys sit next to the folks writing the SW Install Manager?
So I bought this Xi computer. The experience of working with the company was pretty good, and I have to say it was a lot better than some of the other machines I have bought recently, like Boxx and Hypersonic. They took the time to explain to me why I needed this or that and why I didn’t need this or that. This helped me make a decent decision, I think. They answered my technical questions and gave reasons for their suggestions that didn’t sound like a sales pitch.
The goal of this computer was to have a desktop (tower) that was reasonably economical, and yet reasonably fast for SolidWorks complex parts. I wasn’t out to break any records, and I wasn’t out to skimp, but I didn’t plan on buying stuff I didn’t need this time. In the past I’ve paid $3-4k for a computer with stuff I never wanted or had the opportunity to use, like SLI, Bluetooth, multiple processor sockets, tons of mother board connections for external power, external scsi drives, and lord knows what else.
Processor
I keep hearing that the processor is really the king with SW data. I also keep hearing that Xeon processors don’t really give any advantage, in fact they give a little disadvantage. Also quads (for straight SW) are probably not the best choice, especially if you have to give up clockspeed compared to a dual core, and especially if price has any thing to do with your requirements.
So, from that, I spec’ed the fastest dual core processor I could find, which was the Core2 Duo E8500 3.16 GHz. This only added a very modest amount to the base cost of the machine as spec’ed by Xi. I could have (and maybe should have) had watercooling and overclocking (up to 3.4 GHz) for an extra $300 or so.
Memory
I don’t do large assemblies. I don’t do huge drawings. I do big complex parts, with lots of features (largest had about 1300 features, average parts have 200-400). I never ran out of memory even on my 2 gb laptop. Still, this is a box I don’t want to have to make any apologies about for a couple of years, so I tried to be forward looking with it. I spec’ed 4 gb of RAM, with space for 8. Of course I have to go with a 64 bit OS to do this, so I went 64 bit Vista. Not because I’m a big fan of Vista, but because in a couple of years, new drivers will probably not be written for new devices on XP. Vista isn’t really horrible, but it’s not really compelling either. I had to have an OS, and I couldn’t use OSX or Linux, so there I was.
As to the DDR2 vs DDR3, the fellow from Xi talked me out of DDR3. The difference between 800 MHz and 1333 MHZ sounded important to me, but he explained that due to latency and mobo differences, the difference was not very noticeable. The mobo was much more expensive for the DDR3.
Video Card
This really wasn’t as big a decision as you might think. I knew I was going to go nVidia, I know FireGLs are reputed to work, but I just don’t like seeing that ATI logo on a SW box. I knew I was going to go Quadro, even though I know you can apply a soft quadro hack to a GeForce and get just about the same thing. The choices were the 570, 1700, and 5500/5600. The 5600s just seem ridiculously priced, and the fellow from Xi that I talked to doubted that I would see much of a benefit from the 5600 as compared to the 1700, plus the 5600 adds $2150 - doubling the cost of the machine I wound up with. I didn’t see any reason to skimp on the 570, since the 1700 was only $250 more than the 570.
So, I think I found the sweet spot for what I’m doing, and didn’t have to spend a ridiculous amount of money to get reasonable performance.
Hard Drives
I think hard drives are really a terciary concern in a SW system, unless you are doing a lot of file operations locally. On my little network here at home, I’ve got probably 1.5 TB of storage, about half of which is used. I really didn’t need more space. I wanted fast drives, but the drive speed was not as important as the processor speed. I got 1 10k rpm 130 GB WD Raptor. No RAID. I was going to do a RAID 0, but decided against it mainly because its twice as likely to go belly-up on you. Of all the computer components I’ve had fail, drives have failed more often than anything.
Again the fellow from Xi talked me out of the 15k rpm drives in favor of the 10k Raptors that have been around for a while. If part of his prejudice was because of reliability problems, then he served me well. I want a box I can bang on and forget about the hardware.
DVD
I got a bare-bones DVD reader. With the other computers in the office, I have 3 other DVD writers and an external DVD writer that I don’t use already. There was no reason to load this one up with another. I’ve got an external usb 3.5 floppy drive should I ever need to use that.
And that was that! It came to $1997 before adding Office 2007 Small Business Edition. Not bad. Let’s see how it performs.
Benchmarks
Benchmarks are a touchy thing, especially for SolidWorks. The benchmarks that exist are really meant to benchmark hardware against other hardware, but a lot of people use benchmarks to compare versions of SolidWorks. Some people come up with their own homegrown benchmarks, but they don’t take into account the entire range of capabilities that you can run into. The only real benchmark that has existed for SolidWorks is the Spec.org benchmark for SolidWorks 2007. I’ve heard that SW is working with SPEC on a new benchmark that exercises the processor to the same lavel as the graphics. This benchmark is not available for 2008 or 2009 at this time.
There are two other informal homegrown benchmarks that you can find results for. One is Mike Wilson’s Ship-in-a-Bottle, which comes with a macro that you have to run, and then use Feature Statistics to give your time for 50 iterations of the macro. This one is a simple part that uses some surfacing, and actually makes changes to the model which rebuild with each cycle of the macro.
Of course there is an error with the macro when run in SW09. The files were originally created for 2001 or 2001+.
A second informal benchmark is Anna Woods punch holder. She keeps a spreadsheet of specs and results. The punch holder is a part that could have been modeled differently to rebuild faster, but it’s a single part with a lot of holes and a lot of patterns. My rebuild time for the punch holder on my two older machines was in the 177 second range. At the time when the machines were new, it was a respectable time. The Xi runs this test in 87 seconds. The fastest times I have seen on the SolidWroks forums are in the mid 70s. So 87 is not bad for a box that is not geeked out.
My personal benchmark part is this one, with 263 features, mostly surfaces.
My Boxx box, AMD single core processor, XP32, 3 GB RAM, Quadro 3450 rebuilds the part in 125 seconds, using 1 GB of RAM .
My tablet PC is kind of a strange choice for a CAD box, but I only use it for traveling, and it works fine for occasional simple modeling, user group presentations, and Word docs. It has a dual core 2.4 GHz proc, 3 GB RAM, and mobo based graphics (eek!). Total power mismatch. The processor is far ahead of the video. Anyway, the tablet PC rebuilds the part in 93 seconds. A big improvement over the older machine. The tablet PC also used about 1 gb of RAM for this test.
The Xi rebuilds it in 53 seconds. Now that’s a time savings worth having.
Take a look at the task manager for the Xi rebuilding this part:
This shows that the CPU was between 65% and 100% for the entire rebuild. It never went below 65%, except in the first couple of seconds, as it started. This I think puts to rest the stuff that people say when they claim that SW modeling doesn’t use multiple threads. I think the distinction is that multibody modeling uses mutiple threads more than predominantly single body modeling. The situation was very similar on the tablet PC, although it took almost twice as long to accomplish the same rebuild. Dual processors work for SolidWorks.
Notice the amount of RAM used. This is the difference between XP and Vista - .8 GB RAM. Vista is a veritable RAM hog, but it is also slightly (10%) faster, in other tests that I’ve done side-by-side on the same computer.
The final benchmark I did was to compare the Boxx running Vista to the Xi using the Windows Experience Index. This at least is a consistent way of measuring one set of hardware against another, regardless if it is valid or tuned to SW or not. The results probably require some interpretation. Here are the results for the Boxx and the Xi:
The Xi is clearly ahead in the processor and RAM functions, but the 3450 card in the Boxx makes a big difference. If you discount the Aero interface graphics, the Xi score jumps to 5.3. It is interesting that while the Boxx’s 3450 video card scores higher than the Xi’s 1700 for the Aero interface, the 1700 scores higher for “3D business and gaming”. The fact that they lump these together I guess is Microsoft’s tribute to themselves, or their own DirectX graphics standard which is in opposition to OpenGL, which SW uses.
Access the Windows Experience Index in the Control Panel, System Maintenance, Performance Information and Tools.
So far I’m very pleased with this new machine. It is far faster than what I have been using, and was much less expensive than those boxes were as well. I can recommend both the experience and the hardware. They also have a notebook… It’s not time for me to replace a notebook yet, but when I do, I want to have a look at the Xi offering.
Jessica Rivera, pictured above, of CCNTV, reports that David Weisberg is putting together a 650 page freely distributed ebook entitled The Engineering Design Revolution. Cadalyst reports that the book will be available on July 1 (2008) at www.cadhistory.net. So far, it’s not there.
David is not taking any money for this book, but asks that you donate to a charity specified on the website if you like.
I look forward to seeing the book. I’ve enjoyed the many versions of the talk that Jon Hirschtick and John McEleney have given on the History of CAD at several user group meetings I have attended. To have all of this and more rolled into a book written by one of the guys who helped make the history will be instructive.
Will someone give a holler when this thing hits?
Ok, guess that literary reference! Especially you non-Americans. Just another example of silly wordplay. The Lombards as I understand it were part Welsh, and Wales is close enough to Ireland that I claim free word association to be in the tradition of James Joyce rather than just inane impertenence.
In my mind, Amazon sounds like Absalom, and of course Absalom, Absalom! is William Faulkner’s best known novel, and Faulkner is a relativist - like Picasso (Barcelona) - he liked to show things from multiple points of view. Too many connections to ignore.
Are you lost yet? This is what it’s like to wake up in the morning as Matt Lombard. Weird word associations. (Ever read James Joyce’s Finnegans Wake? Parts of it made sense to me, which I found disturbing.)
To the point finally. Absalom was a son of King David (yes, THAT King David) who tried to overthrow his father. Absalom got caught by his long hair in the branches of a tree while riding his horse and one of David’s generals speared him, as caught here in this photo from the AP. Of course David was distraught over the death of his eldest remaining son, even though Absalom was trying to kill David (I was gonna say “he was trying to kill him”, but even I get lost in the pronouns at that point).
How does that relate? Well, Amazon.com is a great usurper, and would convert all author profits into *.com profits if it could. But at the same time they are probably my biggest source of sales, so if my army were to kill Amazon, I would be sorely distraught. Still, they have done me a disservice. My next book is of course the SW09 Bible, and this is how they have rendered the name:
You know, there are a lot of shenanigans in the CAD books section of Amazon, but something like this is only controlled internally. There is no incentive to give them for doing a good job with your book. They have literally hundreds of thousands of other products, and one book that only sells a few thousand copies is a drop in the bucket of a drop in the bucket.
My recommendation is of course to buy your books directly from the author. You will gain a worth while connection, and the author makes a livable wage (as opposed to slave labor wage). If you are really down and out, you can buy stuff from Amazon.
Anyway, the SolidWorks 2009 Bible will be available after the software ships, but before the end of 2008. I’m guessing the software isn’t going to ship until October. So that narrows it down for you. No, the book is not going to ship in July 2008. I’m not even done writing! How Amazon came to apply this title for my book can only be explained by incompetence, stupidity, and/or malice.
I guess I can’t complain too loudly. Today they sent out a marketing email, and the 09 bible (4-5 months from existence) is selling #2 in the SolidWorks category on Amazon, right after the 07 bible. People are hungry to skip 08.
I learned SolidWorks 12 years ago after having come from AutoCAD and Mechanical Desktop. I started with Mechanical Desktop 1.1, which was only comprised of Designer at that point, I think. I never really got into the “zen” of MDT. I found it difficult to use, and unbelievably crashy.
AutoCAD drafting was simple. It was like an electric pencil. There was no intelligence built into the tool or the workflow or anything. If you got good at it, you were good at brute force drawing lines and placing dimensions, and you had to develop really good skills at visualizing shapes in 3D. Probably the Stretch function was the most advanced stuff in terms of intelligent drafting tools.
I had done a little manual drafting, but only enough to appreciate what sort of improvement the electronic pencil was. In school I had also learned Cadkey, where I first picked up on the differences between 2D and 3D. I remember thinking that the main difference between Cadkey and AutoCAD was that the command syntax in AutoCAD seemed backwards. In Cadkey I did some 3D wireframe work to set up FEA problems. Even with FEA, we started with doing hand calculations, and computing matrices by hand, then moved up to writing simple Fortran programs to solve nodes from a 3D wireframe model. Solving even a simple FEA matrix by hand will give you a new appreciation for the simplest computer automation.
One project that I worked on in 2D AutoCAD was to design a set of plastic pressure sensor housings, and then I had to also design the fixturing to test them. The fixturing was not automated, it was loaded manually, but it was a multiple-up fixture, so we had to have pneumatic and electrical connectivity to 30 or 40 small units (coin sized). I always thought I was good at visualizing 3D shapes from 2D data, but this job really stretched me. It was tough to make sure all of the 2D views were updating correctly with each change, and that there was no interference between parts in your mind represented by different color lines on the screen.
At one point, on a bootlegged copy of AutoCAD 10 or 12, I don’t remember, I started getting into the AME (Advanced Modeling Extension), which was a simple boolean modeler, but it allowed you to create 3D solids right inside AutoCAD. This helped me answer some of my 2D questions.
One night I was working late, and the president of the company was walking past my office door. He looked in, and saw a bunch of 3D shapes on my screen. He stopped and came back and looked over my shoulder to get a closer look, and we chatted about how I was using this to help me solve some spatial problems in this fixture design I was working on. I was the only mechanical guy in a small company with 6-7 office people. The rest of the office folks were electrical engineers or programmers.
The president, an electrical guy, instantly saw the value in this 3D visualization tool in a completely different direction from where I was headed - marketing. “How much money do you need to do more of this?” My initial reaction was “Well, overtime pay would be nice”, being young, and disenfranchised with salary work. Anyway, I settled for the $1000 to buy the first release of Mechanical Desktop. I thought small back then, as a naive hillbilly fresh out of the woods, $1000 sounded like a lot of money to me.
My next job was at a medical manufacturer who was already using HP ME-30 (later became Solid Modeler, later spun off to CoCreate, later bought by PTC). I didn’t know much about parametrics, but I knew that ME-30 was somewhere between the AME boolean software and the MDT primative parametrics. The medical manufacturer was disenchanted with ME-30, and part of my job was to evaluate and implement a new 3D modeler. The early favorites were SDRC and SolidWorks. This was in late 1996.
What followed was less of an evaluation, and more of the new guy simply bowing to scathing political pressure. There were good arguments on both sides, but it was clear that the decision was made before I ever was hired. My main function was really as a scapegoat in case the selection of the new kid on the block software (SolidWorks) backfired.
So by the time the corporate dust settled, we got a copy of SolidWorks 1997. They had agreed to send me to training to learn this new Windows-based, user-friendly, drag-and-drop, mid-range modeler, which is a promise they renigged on. My first project was to take a clay model of swoopy shapes, and to create it on the computer and show it to the marketing people in a bunch of different colors.
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Just a little rant here. Marketing people have difficulties visualizing colors? Here I was trying to visualize complex shapes, and they need my tool to visualize colors?
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Anyway, so here I was on an early release of a populist 3D CAD modeling program, with no training, late at night, learning the intricacies of the loft feature. Fortunately there wasn’t much to learn back then, and the documentation covered most of it. Here was my very first real assembly.
The beige part was their existing unit, and the Industrial Designer had come up with the blue part as an update from a wire-formed cage that held the bucket. It seemed to me that the beige housing was in need of redesign the most, and that the swoopy blue basket didn’t really match anything at all. This unit was a “v-vac” (where the first v = vomit).
Anyway, as theoretical as this seemed, I saw it just as a test of my potential. So regardless of how much corporate BS and personal jealousy was behind setting this project for me, and regardless of how pointless and stupid the whole thing seemed, I attacked it with everything I had. I had to admit, this SolidWorks thing was pretty cool. I was able to design, model, and visualize (in as many different colors as they might require) even a shape like this, which you couldn’t even touch in 2D. I was able to see the thing in cross section almost instantly.
SolidWorks is now infinitely more complex than it was in those days. It’s no longer possible for one person to know everything about the software. The documentation can no longer teach you more than the basics. From the awe that we all experience, and that Devon wrote about his first design, a few of us occasionally grumble about things that are less than perfect with the tool. It has captured our imagination, and when it becomes something other than what we imagine it to be, it’s a little like a kid leaving home for college. You get kind of involved with the product because it touches your imagination. It is rare indeed for a technical computing tool to do something like that.
Here’s something I want to start using on this blog. I tried to set something like this up in my last post, but it turned out to be kind of annoying and conventional. I think this is much better. I really like it when I go to a blog, and they have a youtube video right on the blog site, so I don’t have to go to another window to check things out. I wanted to do that with 3D models too.
So I got a little help from Patrick Cook. It helps to know Patrick Cook from Eric Droukas, a little confusion between a tall skinny guy and a shorter rounder balder guy. Never said I was much good at distinguishing shapes. Anyway, Patrick sent me over to 3D Content Central.
To be honest, I’ve avoided 3D CC because it was always hard to use, and the people running it seemed to think making things simple is rocket science. Anyway, it seems to have gone through a rebirth, because it really is simple now. And now, they have a youtube-like embed code that enables me to put models in my blog posts and have you rotate them right here on my blog! Now how cool is that!
A couple people have suggested that just downloading a set of zipped viewable files would work for them. Hmmm. I was hoping for more imagination from you all. Downloading files is so old-tech. I’m going to pull a SolidWorks on you - you asked for one thing, but I have a different idea, so I’m going to give you something different.
Anyway, you will have to install another plug in for this to work. This time the Viewpoint plugin. By the time I’m done with you, you’ll have a whole pile of internet crap loaded on your machine.
This is truly cool. But not only is it cool, it will also be useful for describing how to make various parts and use different techniques. Now that Patrick has pointed me in the right direction and I no longer look at 3DCC as my grandfather’s download site, maybe we can even get some of the other bloggers to use this stuff! When was the last time you heard me this excited about something? Probably the last time I tried to combine sketch relations with splines and it all worked as expected.
Anyway, what do you all think of this?
A few posts ago I wrote a little about an artificial knee implant that I modeled a few years back, and said later I’d walk through how it was modeled. Today’s the day. This isn’t an example of great modeling, it’s just an interesting model.
The image to the left shows the part with Real View, with edges visible. This is a part for which Real View makes sense, because the part really is reflective stainless steel.
Even with Real View, though, this part is hard to visualize in a 2D image, so I’m going to try something in this blog entry. The image communicates, but it’s a flat image and what it’s trying to communicate is not flat. Since my topic is 3D, I should be communicating in 3D, rather than just in flat images, don’t you think? So I’m going to link out to html based eDrawings documents. .
If you click on a link to view an eDrawing, your browser may try to download and install an eDrawings 2008 plug-in for your browser (IE6,7 and Firefox). If you don’t want that to happen, don’t click on the links. You will also have the chance to cancel out of any installation.
I tried to make the eDrawing viewer appear right inline with the blog text, but I have a little more research before I can make that happen.
Anyway, when I started looking at the knee, there were several ways I could go. I was thinking “loft” since that seemed the only feature, but then there were options when lofting too. Which direction should the loft go? Across the fingers or in the direction of the fingers. And should I try to do the whole outer face in a single surface or should I make it with multiple features? In reality, I tried all the options. Sometimes you just don’t know until you try it.
Because I wasn’t sure where to start, I just started modeling the data that I did have. I had a 2D drawing, so I redrew some of the views in the SolidWorks part. This didn’t get me anywhere because the drawing wasn’t even close to the actual shape of the part. Here is an eDrawing of some of the sketches I started with.
With that, I realized that the part would not lend itself to 2D sketches, because there was nothing 2D about it. So I made some 3D sketches that seemed to more accurately represent the contouring of the part. Drawing 3D splines like this is not fun or easy. I first drew the splines on the default plane in the 3D sketch, then moved each spline to the Z depth that it represented. From there I tweaked the ends of the splines to flow in the same direction as the part. Here’s another eDrawing showing the lofted surface I created from a set of 3D splines. The 3D splines are shown on the surface.
Next I had to make sides. Sides are easy when you do a solid which makes all sides of a body at the same time, but with surfaces you have to think about how to make each individual face. In this case, a couple Radiate surfaces did the trick. The red faces in this eDrawing were created by Radiate. If I had this part to do again, I might now use the Ruled surface instead of Radiate, although for purposes such as these, they are fairly similar.
Because I chose to do this using surfaces, I have to explicitly model each face of the part. So the next task is to enclose the open edges of the Radiate, which is done by simply lofting from one open edge to another. Lofting between segmented edges has been handled differently by SolidWorks over the life of the product. The original way to do it was to make a Composite Curve from the edges, then loft between composite curves. Or you might convert edges in a 3D sketch, and loft between sketches. There was a thing called Smart Selection for a while, which wasn’t so smart, so it was replaced by the Selection Manager, which is the current technique. This part was done using the Composite Curve technique. The red surface in the eDrawing is again the newly created face.
This leaves me with two ends to cap off. Capping off ends is one of those tasks that requires an endless source of inventiveness. One one end, it was easy because that end was just going to be cut off. But the other end was less easy and was actually a complex shape. I got away with a very sloppy modeling job, and was able to cover it over with a big fillet. The red ends are shown in this eDrawing.
Once the ends are capped, the model encloses a volume, so I can use the Thicken and/or Knit features to make a solid from it.
The plan is starting to take shape. The two fingers are modeled as a single finger, and then the area between them is cut away (shown in blue in this eDrawing). Most of the sloppy modeling is covered over by some big red fillets. The 3D flow of the shape is created by lofting a set of 3D splines. Everything else about this model is actually rather easy. Don’t count on fillets saving your project like I did in this model. Again, if I were to do this again, I would have done things differently.
Now I need to cut a geometric shape into the inside. This is again done with a solid feature, shown in red in this eDrawing. This feature matches a shape that the surgeon cuts into the end of the femur. Some additional features are coming to help locate and secure it.
The remaining feature of interest is an inset, shown here in red. This is an area on the geometric cut made in the last step that is inset from the main surface and small spheres (about 0.030″ dia) are fixed in here. I’m not sure how this is done when manufacturing the real part, but it creates a rough, porous surface into which the bone tissue can grow to become intertwined with the implant. I didn’t model all the small spheres. This is the kind of thing that you can take care of with a note, or a texture on the model. To model this inset, I created split lines around the inner faces, knit the faces inside the splits together into a surface, then created a thicken cut feature.
Finally, I added a couple of posts, some undercuts which were possibly used for fixturing during implant or manufacturing, and some lettering. Here is an eDrawing of the completed knee implant.
So the model really wasn’t that difficult. The biggest hurdle is to visualize how you are going to make that complex outer surface. There are many ways this part could have been modeled, and several that are much better than the methods I chose.
As sloppy a model as this one is, I have seen several implant models by other companies using more sophisticated software tools that were not as clean as this model. The reason I point this out is that you don’t have to have Catia or ISDX or Alias or Rhino to make good surface models. You just have to approach the problem methodically, and be able to evaluate your results as you work.
Have you ever heard the saying “done is beautiful”? While I may feel that way about mowing my yard, I at least strive to be more meticulous about CAD models.
Thanks for visiting my blog. Did you find the eDrawings helpful, or did they get in the way? Any other ideas for how to include 3D content on a blog like this one?
I really needed a vacation, and the 4th of July came just in time. For Kim’s birthday, I decided to take her for a short vacation to Snowshoe Mountain, a ski resort in West Virginia. The resort was hosting a bluegrass festival, and frankly, I couldn’t think of a better way to celebrate American independence than by going to a place as independent as West Virginia and listening to something as American as bluegrass music.
My friend Chris send me a link to the website for the event. Del McCoury, one of the living legends of bluegrass, was going to be there, along with some legends in the making like Steep Canyon Rangers and Larry Keel.
I have to admit, I’d never heard of Larry Keel before. He’s a guitarist I’d compare most with Tony Rice, after only having heard him once. His band’s theme was traditional topics with a high energy modern style. Jams can get a bit mesmerizing.
Anyway, the music was great, and the overall experience was, well… an experience to be sure. Here’s a run down. Possibly somewhat dramatized from time to time.
So it all started with the drive between my house and Snowshoe, which is basically 2 hours of twisty mountain roads in the 350Z. Personally, I can think of nothing I would like better to do for her birthday, but Kim is terrified by speeds higher than a hay wagon, so this was a white-knuckle, bag-on-the-knees sort of couple of hours for her. Happy Birthday, Kim! There is a lot of great scenery along the way. The Virginia-West Virginia border follows the ridges of the Allegheny mountains. This was the view from the Shenandoah Mt. pass at about 3000 feet, the site of the former confederate Fort Edward Johnson.
Ride along with us following some bikes through the twisties:
So we disagreed about the ride. I found it exhilarating, and she found it terrifying. I did slow down on the straight aways to ease her mind a little. Anyway, it started to rain as we approached the top of the mountain. Just a light rain. We had a big umbrella and rain jackets.
It’s a ski resort, but it’s summer time. No snow. But they still run the lifts. Before the music starts, we decide to take a ride on the lifts. The resort is at the top of the mountain, with the lifts and trails running down from the lodges. It’s amazing being able to look down from the top.
Beautiful view of the lake down below from the lift. I guess I never realized that I was afraid of heights. So Kim has her revenge. Once we ride down, I realize I also have to ride back up. Ok, I’ll drive slower going home. I PROMISE! Click on the image to the left for another short video clip.
With my feet firmly back on the ground, it was time for the Steep Canyon Rangers to play. If you like bluegrass, americana, or traditional folk-blues styles, you really need to check these guys out. They write a lot of great original material, and each is a master of his instrument. They range from traditional to ridiculous. There’s definitely something for everyone to love with these guys.
So when it started raining, it wasn’t that big of a deal for us to just sit right there. Here’s a progression of photos, ending with a video you have to see to believe.
Ok, in the above, you can see it’s raining a little. The guys are under a roof. The audience is sitting in plastic Adirondack chairs exposed to the elements. You can already see some empty chairs in the front couple of rows.
Now it’s getting foggy, on top of the rain. We are at over 4800 feet in elevation, so we’re getting some low flying clouds.
Finally, we get a closeup of the stage from about 30 feet away. It’s so foggy and rainy that you can’t even see the band. In the video below, you see the really hardcore bluegrass fans. Of course alcohol and Gore-tex go a long way to keep you dancing in the rain…
It turns out that dancing was one of the themes that would get visited again and again at this festival, most of the time with simply ridiculous results. For those of you who aren’t bluegrassers, traditional old-time Appalachian dancing is called flat footing, clogging or buck dancing. Not much of that going on at Snowshoe. When I think of flat footing, I think of an old farmer in his ball cap and cowboy boots tapping his heels and toes without moving his arms very much. That’s just how I see it, maybe others see it differently. Most people were dancing like they were at a Grateful Dead concert. More on that later.
When you say “bluegrass” to people, everybody has a different idea of what bluegrass music is. Some people think Alison Krauss sings bluegrass because she won all those bluegrass awards, but that’s not bluegrass to me. To me, bluegrass means Bill Monroe, Flatt and Scruggs, Stanley Brothers, Jimmy Martin, and a dozen others who wrote or adapted most of the traditional songs from old time folk, country, or blues. Then groups like Country Gentlemen, Del McCoury, Seldom Scene and many others kept the traditions alive but also wrote new songs. New groups bend the genre even more, like the Dukhs, Nickel Creek, Psychograss, Bela Fleck.
These days when you go to a bluegrass festival, you’re likely to hear modern country, electronic folk, or an acoustic country-rock-jazz-folk fusion that’s tough to characterize. Rarely have I gone to a festival where all the music was straight bluegrass. I think promoters want to at least mix in a little of a more pop style to attract a mixed audience and more money. It all can be good music, but when you go to see bluegrass, and they play country instead, well, that’s a line I don’t like to cross. Snowshoe had a couple of bands that had a bluegrass instrumentation, but played a more modern rock-country mix. You never know what’s going to happen. It can be any age range, from a baby:
To a middle aged drunk wearing a Charlie Brown shirt. This guy was dressed as Charlie Brown the first night, and as the Kool Aid man the second night. He was more sober the second night, and left off the crazy hop-on-left-foot-twice-hop-on-right-foot-twice drunken-white-middle-aged-guy dance.
To a young redneck with a wardrobe malfunction:
This guy was hilarious. Unintentionally of course. He was persistent in wanting to dance in front of the stage, but his pants simply would not stay up. I was laughing too hard to get a very steady video of it.
Eventually, and this is no joke, Public Safety officers came and handcuffed the guy, but the audience booed them so loudly that they had to relent. This all happened during one of the acts. Fortunately it was one that I was less interested in, so this little escapade kept my interest up.
Instead of arresting the fellow, they eventually got him a belt and actually physically put it on him. In this pic you can see the cop on the left trying to unlock the cuffs while the lady from the local taste committee explains that this is a family event and they would not tolerate forcing crack on minors.
Enough fun for one night.
Another of the really cool things going on at Snowshoe was mt. biking. In a different life, I used to ride with a group of guys at a ski center in Bristol, NY, south of Rochester. We would ride up the fire trail, and then come down the slopes. Of course we didn’t have suspension or disk brakes or any of the stuff they have now.
At Snowshoe, they were renting out long travel, dual suspension, disk braked, downhilling machines. Lots of guys had the requisite body armor. I guess I was naive to think that some of the guys that rode in our group just wore cut-offs and a t-shirt.
They sure looked impressive. I worked my way through college at bike shops, and I used to ride a lot, both road and off-road.
Anyway, these guys rode the bikes down and the lifts back up. This was pretty posh. They even had someone else put the bikes on and off the lift for them! I’ll bet I could still do this kind of riding. I secretly envy all the stuff on these new bikes. They don’t look like much for real riding, you know, working hard and turning the pedals, but they look like gravity machines to beat the band.
The fireworks for July 4 got rained out. So they moved them to the 5th. They really put on a nice fireworks display. Since we were on top of the hill, and the guys shooting them off were down the hill, some of the fireworks happened at eye-level, and some actually below where we stood. It was a very cool fireworks display. Nicely done. The only problem was the ash raining down on us because the wind was blowing our way.
We got a really strange effect as well, since the last storm was still rolling out, in the distance we could see lightning lighting up the clouds, and adding to the artificial fireworks.
Kim found a setting on my camera especially for fireworks. You can tell Kim took this one because it’s not blurry and off the side of the frame. Maybe I should ask Al Dean if putting pictures on my blog makes me a professional photographer?
So eventually we got back to music. Del McCoury was really the highlight, obviously, but Steep Canyon, IIIrd Tyme Out and Deer Creek were really the music that I came to hear.
Del seemed to be making a game of calling for requests, maybe half of the show both nights was pulled from the audience. The band really has to be on top of things to pull that off. He’s only got 50 years of material to call from, so there are hundreds of songs people could choose. I think Del may be feeling the effects of age, since the last couple of times I’ve seen him he’s had difficulties remembering the words. But then again, I have difficulty remembering all sorts of things.
The Steep Canyon Rangers Saturday show was really unbelievable. I’ve heard these guys several times, and this night they were really on top. These guys have definitely honed their skills over the couple of years I’ve been following them. They were really hot, especially Nicky, the fiddler. He has improved significantly on his ax, and just blew me away on Saturday. These guys are all headed somewhere. You might compare them to an early Country Gentlemen, where individuals (John Duffey, Eddie Adcock, Charlie Waller) went on to legend status.
This may have been my first time seeing IIIrd Tyme Out. There’s no doubt why they are such a respected band. They are just a great live show, and have a great command of their instruments and voices. I could listen to these guys all day.
Fortunately, my local record store has a huge assortment of bluegrass right in the store. I’m out of luck if I want Sibelius or Mahler, but Don Reno, Ralph Stanley or IIIrd Tyme Out is no problem.
The Deer Creek Boys are a young band I have heard before in a local festival. Put these fellers in front of a big audience, and their energy level raises to meet the challenge, but it seemed to wane in front of a smaller rain dampened set of fans. The big guy on the bass is called Sweet Potato. Here, Sweet Potato pulls off a nice Jimmy Martin, Sunny Side of the Mountain:
On the way home, Kim and I stopped by the National Radio Astronomy Observatory, an immense radio telescope in Green Bank, West Virginia. This picture shows a barn in the foreground for scale comparison. The valley that the telescope is located in is nicknamed “The Silent Valley”, because it is supposedly one of the most radio interference-free areas in the country. This thing is huge, out in the middle of no where, with seemingly no effort to protect or disguise it.
Anyway, this was a great 4th for us. I hope you all had a good one too.
Mike Sabocheck is the MidAtlantic Territory Technical Manager for SolidWorks. TTMs are the technical side of corporate sales, and get involved in some of the tricky requirements that potential customers sometimes throw into a sales situation. I was offered a TTM position in California, and reluctantly declined. The job seems like a lot of challenge, but also a lot of fun. If there is any job at SW I would want, it would be the TTM job. I’m sure that sounds ridiculous coming from me, but the part of being a reseller engineer that I really liked was dealing with the customer requirement challenges. Of course TTMs have other duties like dealing with resellers, and interacting with user groups which I would also enjoy.
Anyway, I’ve known Mike since he took over as TTM for the Upstate NY region in the 90s. Mike’s a great guy. He’s the one who wrote the famous quote on the back of my first book, which reads in part “…plus his snappy wit and wisdom make SolidWorks accessible to users at all levels.” It was a very carefully worded statement, but I think it came off with just exactly the right tone. Mike knows I’m sometimes a little over the top, but that I’m also enthusiastic about SolidWorks.
Mike is one of those guys that I go to every few months with a question, hoping he can help me out. He also comes to me sometimes, and his recent phone call is what sparked the idea for this blog entry.
Mike asked me about a part I have up on my (very neglected) website. It’s an image of an artificial knee joint implant. This was my initiation at Trimech. They handed me the part and the drawing for it, and said the guy before me couldn’t do it, so here you are, hotshot.
It took me a couple of weeks of thinking about it, and I started several models before I settled on an approach that worked, but I eventually got something that looked reasonably like the part.
I mentioned that they gave me a drawing. This was the crux of Mike’s question. If you have a part like this, how do you make a drawing of the part? The insides of the part are all straight lines and arcs, but the outside is splines and swoops. What can you do? The drawing that I got was awful. It was done in AutoCAD, and it was all lines and arcs, with a lot of cross sections. It didn’t come close to representing the part. It was obvious that the 2D in no way represented the actual 3D.
I don’t know how they made the part, but I would guess it was cast and then ground. It’s possible that the first model was carved by hand, and then a pattern was made from that for the casting. But this was a highly polished surface. I know they couldn’t have manufactured from the drawing because A) the drawing was awful and B) the drawing was 2D, and didn’t give enough information for any manufacturing process to make the part.
This question about drawings and complex shapes is one I’ve had to confront from time to time. I can’t claim to have any definitive answers, because I think the answer depends on the situation every time. Still, there are some things you can say unequivocally.
First, it is unrealistic to expect to make a fully dimensioned print for a part like this. In the same way that I couldn’t model the part from the drawing, even if you start with a correct model, you couldn’t make a meaningful, fully dimensioned 2D drawing of the part.
Second, you have to answer what you need a drawing for in the first place. No one is going to take a sheet of paper over to a manual mill and start spinning wheels and come back with this part. Not gonna happen. The part (or tooling to create the part) is going to be made by some form of computer controlled process. It’s not going to be someone standing at the controller fat-fingering toolpaths, either, this will require software to create toolpaths directly from the CAD data.
Ok, so you’re not going to use a print to manufacture. Maybe the part has some areas that do not need to have a highly polished surface. Well, that’s something to put on a print. Tolerance on a part like this doesn’t mean much. Even though the outer surface is mirror polished, real dimensions could be +/- 0.030″ without any functional problems.
There are actually some location pins, and the inside shape is all straight lines that have to match a cut in the end of the femur. You can dimension stuff like that, if for nothing else so that the matching geometry cut into the bone by the surgeon has some sort of a reference.
The part has to be inspected some how. How will you tell if a part passes QA? Is a guy actually gonna sit there with a set of calipers and measure this thing? Probably not. A comparator? Nah. How about a CMM? Well, possibly. If you’ve got parts like this to inspect, and they have to be quantifiably measured, you’re going to have to use some sort of a CMM, laser or contact. A set of go-no-go gages and a good procedure might do just as well for something like this where there is a complex shape that doesn’t have to meet a really close tolerance.
So, what do you tell somebody who asks how to make drawings of complex shapes?
- Make sure your drawing has a purpose
- Make sure your drawing can fulfill the purpose you assign
- Manufacturing and inspection are two areas that might require drawings: give those people the data they need in the format they can use. Just “because we always have to make a fully dimensioned print” isn’t a good enough reason to make one. It might turn out to be an immense waste of time, and what you get from it may not be useful in any way.