First, out of left field, Autodesk suddenly announced it was going to resume development of T-Splines for Rhino!  The first news of this came from the T-Splines message board, where none other than Autodesk CEO Carl Bass chimed in and informed the community of the decision.  That pretty much made my jaw drop to the floor.  This means that there will be future releases of T-Splines for Rhino, with new tools and functionality.  Really, I truly did not see that coming.  Also, in the past few days they put out a release candidate for Rhino V5.  You can download that here.  There are some really nice fixes and upgrades in that release – most notably for symmetry and exact insertion of geometry.

Second, it should be noted that Rhino3D V5 is finally here.  I had been using the beta version for more than a year and was questioning anyone who had not taken advantage of the beta as it was more stable, 64-bit compatible, filled with impressive new features, and free to anyone with a V4 license.  Now that V5 is officially here, you truly have no excuse for not upgrading.  If you go to the Rhino3D website before February 26th 2013, you can upgrade fromV4 to V5 for $345.  Also noteworthy is that my friend Kyle Houchens of The Outside will be doing a set of webinars on V5.  I’m going to attend the first four of them myself, and would recommend them to anyone interested in quickly getting up to speed on V5.   You can register for the webinars here.

Third, there’s a new version of VSR Shape that was just released.  I’ve played around with VSR Shape in the past, and I have to say this new version looks very compelling.  VSR hasn’t gotten a whole lot of attention in the past, but I really think with the new V2, that’s about to change.  Check out the demo video here.  The new Multiblend tool looks downright sick – a very very slick solution to a common problem in NURBS surface modeling.  Honestly, I can’t remember the last time I was so excited for a new tool.  The symmetry functionality looks mighty impressive as well.  I’ve just returned from a laser scanning job and will be using the demo version of V2 to model some of the trickier aspects, I’ll let you know how it works.  If you’re a Rhino user you should absolutely check it out.

On the laser scanning front, Creaform recently released a new version of VXelements software, which is the interface that powers their 3D scanners.  The new version includes some fantastic upgrades which I can say really improve the capabilities and performance of their units.  In the past, getting crisp edges was a bit tricky – you would have to set your resolution fairly high to get one.  Now, the software detects part edges and automatically bumps up the resolution of the mesh right along the edge.  Big improvements have also been made in scanned “ribbed” surfaces – very thin extrusions, and also in the scanning of very high resolution objects.  Against better judgement I installed the new software before embarking on a week long scanning job in Montana, and I’ve had nothing but flawless performance from it since.

The folks at Autodesk took the “Egg Man” demo I did at the end of the presentation and put it to some music, which I thought was really cool.  So, dim the lights, crank the speakers, and enjoy!

Pecking away at the Convair 240 radio control model.  This is being done for a contest on the Ezone forums, and so I really need to get moving on this thing to get it in the air by June 30th contest end date.  The wings are getting there – mostly lofted, just have to add the rear spars and ailerons.  Having designed more than my fair share of RC planes in 2D using AutoCAD, boy, is this a better way to work!  The wings are going to be my favorite style – 1/32″ balsa d-tube leading edges with shear webs.  Super strong, super light, and very “stick and tissue.”  I’m going to try to get the tailfeathers and fuselage formers knocked out this weekend.  Haven’t quite decided if I want to do the nacelles out of balsa or vac formed styrene, but I’ll have to make a call on that pretty soon.

The fairing half is on a magnetic building board that I use for building balsa model airplanes, this was very handy because it kept all the magnets in place while I laid them out.  Tucker and Walnut, faithful four legged shop assistants supervise from below:

Okay, really, they’re just watching for that cat that walks by the window from time to time.  Anyhow, moving on – I then broke out the hot glue gun, and just surrounded each magnet with a little glue.

All we’re going for here is keeping them from falling off the tape once we slide this thing off the table.  Then, I simply clamped the two halves together at the edges.  After that, I just took one magnet at a time, placed it relatively close to where I thoughts a magnet was.  Once I felt it pull, I just let go, and the magnet snapped into place.

Well that was easy!  The “hole layout” was less time consuming than if I was using drills/clecos, and more tolerant of edge distance.  Once I bond these together and the resin has cured I’ll simply slide the exterior magnets off one by one, and then pull off the piece of electrical tape that the interior magnets are glued to.  Easy!  Obviously, this will only work in non-blind applications, but it sure seems like a nice method to me.  If your alignment is super critical, I would still recommend using a few holes/clecoes just to make indexing them together fool proof.

I’ve left the peel ply on here, because the parts are still pretty darn soft, but everything else has gone into the trash.  Now, simply get some air underneath the layer of Stretchelon covering the mold, and then pull the parts up, along with the film:

Now, just simply peel the Stretchelon off the parts – if you’ve used mold release, it should come off very easily more or less in one piece:

Presto!  And the molds are totally unharmed – same as they were when we started.  Here’s a closeup of the surface texture of the finished part:

Yes, a bit of texture, but like I said before, a few swipes with some 80 grit to prepare for primer and the texture just vanishes.  Or, if you really want a smoother texture, just get more dense tooling foam.

Okay, granted, it’s a bit hard with the light here to really see what’s going on, but if you look at the post I link to above, you’ll see this is just the CNC machined version of the gear leg tooling.  Since one of these molds is two part, the next step is to join the two parts together:

We usually join them together with some fast setting epoxy and then drive some dowels into them for good measure.  Now at this point you’re probably thinking “well that’s nice and all, but now you’ve gotta spray some sort of primer/sealer onto that thing, and hand finish it.”  But, you would be wrong.  You see, I hate sanding.  Actually, that’s not really true, I like doing body work, but I hate sanding when there’s no point to it.  And now let me show you why there’s no point to it:

This, my friends, is the heart of “The Method.”  The green stuff over the mold is an elastic vacuum bagging material called Stretchelon.  Stretchelon is a high elongation vacuum bagging film.  I hate dealing with bagging tape, and so I’ve routered channels into my work table here, coated them with shelf paper and then used hardware store screen door spline to create the seal.  This method works quite well, but you can just as easily make a tube out of the Stretchelon and put the mold in the tube.  I pull my vacuum for the mold from the bottom of the table.  The mold is sitting on a piece of breather so that the air gets evacuated from all around the mold.  The slight porosity of the foam does wonders to allow the air to travel to the edge of the foam.  Closeup, it’s looks like this:

The Stretchelon pulls down right onto the foam, sealing it for use.  Pretty cool huh?  Yes, there is a bit of a texture to the mold.  If you want a smoother mold, just buy higher density foam.  But what I’ve found is that since the first thing I do when I go to prime a part is to scuff it up, that texture simply vanishes with a few strokes of a sanding block.   The final thing to do is put some mold release on it – the film is polyurethane and so epoxy will stick to it.  I’ve used Frekote in the past, but I like to use another Airtech product called Safelease 20L.   It can be dispensed from one of those hand squeeze spray bottles you get at the hardware store, so I like the fact I’m not using a bunch of aerosol cans.  And it works, so that’s nice.  Anyhow, once you spray your mold down with some release and then wipe off the excess, this mold is pretty much like any other – yes, it’s slightly more ding prone than standard hard tooling.  If you want to make lots of parts (let’s say, more than 10) then I would simply go with a more dense foam, say 25 lbs.  If you get any dings, you can simply patch them with spackle.  When I first starting doing this, I was really concerned about mold wear, but frankly it just hasn’t been a real problem.  Some of my molds have been used 10-12 times now, and for the most part they look just like they did the first time.  So now, it’s just a matter of laying up the laminate, in this case 3 layers of 5.7 oz carbon:

And then, you vacuum bag another layer of Stretchelon (or regular bagging film) over on top of the part:

Your standard peel ply/perf/breather fabrics are on top of the carbon.  The vacuum for the top bag comes from a standard bag tap.   So we’ve got two separate pumps running here – one for the mold, and one for the part.  They’re both around 25-26″ of mercury.  You’ll get a few more inches of mercury with a bag tube made with bagging tape, but the cost and labor savings of this whole screen spline method are nice.

After the part has cured, you simply switch both vacuums off, and remove the part.  The Stretchelon comes off the foam with the part, and as long as you haven’t gone and poked some holes in the first layer (which you’d pretty much have to try to do) the mold is just as pristine as when you started.  Here’s some advantages of The Method:

1. It’s freakishly fast.  On small parts, I’ve done a design, mold fabrication, part fabrication and demold cycle in under 24 hours.

2. It’s very accurate.  With the EXAscan laser scanner, what you’ve got is a fully digital production workflow.  The data goes in on the EXAscan, comes out on a CNC mill, and you do NO hand finishing of the mold.  If you need a tight tolerance, hand finishing can quite easily take you out of that tolerance. Of course the same level of accuracy applies to designs that start off in the computer.

3. Far less sanding.  The first time I pick up a piece of sandpaper with this method is when I go to put on primer.

There are a few drawbacks:

1. Certainly, if you want to make molds out of cheap boat cloth and polyester resin, The Method will cost more.

2. There is SOME limit to what the Stretchelon can do.  Not a lot, but some.  One case in particular – if you have a cylinder that you want to lay up over, the Stretchelon will have a seam somewhere along the length of the mold.  So, occasionally you have to be creative.

So there you have it – this is “The Method.”  I’ve heard rumors of other people doing something like this, but I’m not sure if anyone has taken it to the extremes that I have.  I’m going to be outlining a few of the finer points in a few days, and I’m sure people will have some questions, but that’s really the gist of it.  Happy 1st Birthday to Better Living Through CNC, and thanks for reading.  Enjoy!

Go to Part II

Do you know what tomorrow is?  It’s the one year anniversary of the launch of this blog!  And I’m cooking up a very special post to celebrate the occasion!  Stay tuned…..

-Sky

The fuselage digitizing was our first real chance to use the new MAXshot photogrammetry setup.  I’m happy to report that the MAXshot worked flawlessly.  The through process is very much the same to using the EXAscan, but covers a much larger area more quickly, and more accurately.  Here’s some pics from the scanning process:

Here’s a screen shot of the capture session for the right side of the fuselage:

For the straight lofted panels we just scanned the perimeter – no need to scan every square inch when you can get all the data you need from the edges.  James will be up in Reno again this coming week to scan the wings.  We’re really excited to be working on such a cool project!

Now just run tsBevel, the options I use for something like this are: Segments = 5, Positioning = Distance, Keep on Face = Yes, Retopo Snap = No.  You’ll need to play around a bit with the bevel distance, in this case I found that 0.09 worked nicely, but you’ll have to adjust it for each model, depending on size.  Here’s what you get:

Now select the middle face loop, and set your drag mode to UVN:

Now just push that face loop inwards using the normal (blue) arrow.  I like to do it numerically, so that I can make them consistent.  I used a value of -0.05 here, but again you’ll have to play around a bit for each application.

Now just run tsMakeUniform.  You should do this after every change in topology.  In smooth mode you get this:

It’s quick, it’s easy and it looks good.  Can’t beat that!