Aichi D3A Val

[pickelhaube]

Doing this is a skill all to its own.

I do believe there is no way I could ever do this.

I can't even text off of my cell phone. Tried it, can't do it . So screw it.

This is looking cool

[gburch]

Doing this is a skill all to its own.

I do believe there is no way I could ever do this.

I can't even text off of my cell phone. Tried it, can't do it . So screw it.

This is looking cool

Thanks. In many, many ways, though, it's exactly the same skill-set you have as a scratch-builder: Being able to think in three dimensions, knowing the tools and materials, and building up a big enough bag of little tricks with them.

It's also something that, like scratch-building, requires a lot of patience, a willingness to experiment, and a willingness to fail and start over. Unlike scratch-building, though, I can save the file I'm working on before I try some dumb new idea, so I can go back to exactly where I was before I screwed everything up

[gburch]

Hard to see it in this view, but the last weekend work was devoted to refining the fin and rudder, which has now been cut out as a separate piece:



I'm glad I picked something simple, with lots of straight lines, for my next project.

[gburch]

Found a little more time to work on the stab and elevator last night, and took these shots to document the state of WIP:

[gburch]

The joint between the flat and dihedral portions of the wing has been optimized, ailerons and flaps cut on a rough basis, cowl cut from the fuse mesh and work begun on the first panel detail -- the cowl flaps. Since the latter has some of the finer panel detail, I'm working toward that part of the cowl being the first part to be printed as an early prototype, to see if the ideas I've been thinking about for addressing this major issue have any legs. With any luck, I may spit the first plastic on that part this weekend ...

[pickelhaube]

Will your machine be able to make the wings and fuse smooth ?

[gburch]

Will your machine be able to make the wings and fuse smooth ?

No. There will be "striations" from the print layering process. Note two things about this. First, the layers are between 0.5 and 0.75 mm from "peak" to "peak" and less than 0.25 mm "deep." Second, I've got a full V-2 "beta kit" delivered to a "beta-builder" and one of his first comments on receiving it was that the layering was much less than he had expected.

As I've bored everyone to tears with on the original V-2 thread, I HAVE developed techniques for achieving a completely smooth finish. It takes time and effort, but it can be done. Although this is a subject waaaay down the line on the Val project, the same basic techniques will apply to this product, if and when I ever get to the point of creating a full airplane model. Basically, the same kind of surface filling and sanding will have to be done, and panel lines -- which I now anticipate being printed into the surface -- will have to be scribed out on each pass of filling and sanding. That's how I did the few panels on the V-2 model and it worked well. It's how I anticipate doing most of the panel detail on t he Val right now.

I have another idea -- which is to print all or most of the panels as separate "skin sections," which would be individually filled and sanded, and then applied to a base model surface. That is a back-up plan that I'm going to explore as I work on the Val.

Yes, these methods will take more effort than a traditionally molded model. A big, big question is whether anyone would be interested in going to this extra effort. As I've said before, I don't know if that will be the case. There's only one way to find out ...

[gburch]

Two shots of the mesh work with the first printable part, the cowl, and the front, fixed part of the canopy, after much struggle with the really hard problem of merging the curved surfaces of the canopy frame and the flat surfaces of the glass in that part:




The polygons defining the flat panes are highlighted. I discovered some genuinely new mesh-building techniques working on that problem.

... and the first printing:





The second shot shows the experiments it took to get to a first full printed part. The last pic is a close-up showing the panel details and the scale of the layering from the print process.

I'd hoped to actually work this weekend on surface finishing of the first full prototype cowl to demonstrate how a smooth finish with panel detail would look, but work-work will likely interfere with that plan ...

[flyboy_fx]

[pickelhaube]

That does not look that bad.

Not to sound like a dummy but why do the stryations happen ?

Does the hot point move to slow or fast ?

The more expensive machines get it smooth. This would be a home run if those lines were not to happen.

[gburch]

... well, I couldn't help myself:







Total work time: under one hour, not counting drying time (when I really did some work-work). One slathered coat of putty, sanding, three coats of filler primer, sanding; scribing the panel lines between each step. All tools and materials shown in the pics. The last two show the part as it could be assembled and painted. Real rivet-counters would want to drill the rivet holes ...

If you're willing to do that, some day, you could have a Val ...

[gburch]

Now that I look at that last pic, I see I'd sand some more ... maybe put one more coat of primer (without scribing). But this part was just a proof of concept, so it'll stay like this ...

[gburch]

Not to sound like a dummy but why do the stryations happen ?

Does the hot point move to slow or fast ?

The more expensive machines get it smooth. This would be a home run if those lines were not to happen.

The striations are the height resolution of the z axis. Think of them as "pixels," I guess, and the issue being how much resolution the printer has. My machine MAY have one more notch of resolution in the z axis, BUT, the smaller the layer, the longer the print. This piece took about an hour and ten minutes to print. With twice the resolution (half the layering), it would take twice as long (at least).

The more expensive printers do have higher resolution. They move a LITTLE faster, but still take longer to print. But since they're almost always making pure prototypes, that's not a big deal (except that trial and error takes much longer). Since I'm trying to balance resolution against practical production time ...

[cjg476]

It looks likes it turned out really well...I like it...

[gburch]

Outer wing panel, first pass at getting panel detail into the wings:



Note the "quilted" look is a function of the default rendering settings in my mesh editor. If I took the time to fiddle with rendering at this stage, I'd never get anything done. In fact, the edges of the panels and lines will print crisply.

The big, looming issue is how to chop the wing up for printing. Everything else fits inside the print volume of my machine nicely (as the cowl did). I've got a zillion ideas about how to do this, and I suspect I'll end up trying at least half a zillion before it's all done ...

[pickelhaube]

Outer wing panel, first pass at getting panel detail into the wings:



Note the "quilted" look is a function of the default rendering settings in my mesh editor. If I took the time to fiddle with rendering at this stage, I'd never get anything done. In fact, the edges of the panels and lines will print crisply.

The big, looming issue is how to chop the wing up for printing. Everything else fits inside the print volume of my machine nicely (as the cowl did). I've got a zillion ideas about how to do this, and I suspect I'll end up trying at least half a zillion before it's all done ...

I really like the way the cowling came out. How long did you say it took you to finish it ? How easy is your plastic to sand or are you trying to sand the filler/ paint ?

As far as the wing goes splitting on panel lines is the way to go. I am sure you thought of this already. Maybe do a male / female join between the panels. Although more plotting it could be easier to do the flaps and ailerons as separate pieces.

[gburch]

I really like the way the cowling came out. How long did you say it took you to finish it ? How easy is your plastic to sand or are you trying to sand the filler/ paint ?

Under an hour of actual working time. The sanding is probably 80% of the filler/primer. This is ABS plastic, which is considerably harder than styrene -- and that's a good thing. It makes the sanding of the filler much less difficult, because it's waaaay softer than the plastic.

As far as the wing goes splitting on panel lines is the way to go. I am sure you thought of this already. Maybe do a male / female join between the panels. Although more plotting it could be easier to do the flaps and ailerons as separate pieces.

Oh, I'll definitely be chopping the parts on panel lines. The issues are how to do it in a way that ends up being strong, gets the best use of the print volume, prints quickly (which is a trade-off between part thickness for strength and time) and aesthetics. I'm definitely making the control surfaces separate parts.

I still have only the vaguest ideas about how I'll handle some issues. The prop is just scary stuff in the future. The canopy ... who knows? Hinging the control surfaces? Sheer horror. And the folding outer wing section ... truly terrifying . . .

[pickelhaube]

Yeah the prop may just have to be casted.I have made a few and once the mould is made casting a prop is easy.

Is the prop the same as the Zero ?

Maybe you can cast the wing as standing tapered tubes like you did for the V-2 that way you can do interlocking tabs.

That way you can print out the main spar as you go and it you make that interlock the strength will be there.

[gburch]

Yeah the prop may just have to be casted.I have made a few and once the mould is made casting a prop is easy.

Is the prop the same as the Zero ?

I don't know. I'm having a REALLY hard time finding good technical info on the Val. If I didn't know your plate was so full, I might ask you if you were interested in casting the prop. On the other hand, I haven't even given it any real thought yet. I know the only way I could print it would be to print each blade separately, and probably make the hub from nested styrene tubing., which would have to be drilled to accept the prop blades. Anyway, that's as far as my thinking has gone on it, so far.

Maybe you can cast the wing as standing tapered tubes like you did for the V-2 that way you can do interlocking tabs.

That way you can print out the main spar as you go and it you make that interlock the strength will be there.

That's kinda sorta the idea I have in mind. The problem is that the wing chord at the root and most of the way out to the tip is longer than the longest dimension of my print volume. I'm thinking of doing the wing basically in three sections, longitudinally, the leading edge, the center, and the rear, and then those will have to be repeated out along the length of the wing's span. To increase strength, I'm thinking these won't all end on the same panel cut, if that makes sense.

[gburch]

Panel work extended into inner wing section, and first panels "scribed" on the fuse:



Before I go too much farther, I'll need to print test pieces of some wing and fuselage sections to see if the panel detail is turning out in those areas as well as it did on the cowl. This is a pain in the butt, because I have to "solidify" the test parts for printing, that's a major job, but that work will never make it into the final product. Better safe than sorry, though, before I go too far down the road with panel meshes that won't work in the end.

[nooker21]

Can this model be scaled up and down as you see fit? Like once you render everything, could you churn out a 1/32 version just by adjusting the printer settings? Or is there more work involved than that?

[gburch]

Can this model be scaled up and down as you see fit? Like once you render everything, could you churn out a 1/32 version just by adjusting the printer settings? Or is there more work involved than that?

The short answer is there's more to it than that. Yes, you can scale a part in a couple of ways -- either before exporting it to the printer or with the printer control software. For a completely solid part, that's really all there is to it -- cut the size in half, and the printer will produce a part one-half the size.

BUT. ... there's always a "but." First, the layering Matt and I were talking about above will be more noticeable on a smaller-scale part. Of course, there will also be fewer of those layers and, for some kinds of things, the same surface finishing techniques I'm already using will create just as smooth a part at 1/32 scale as at 1/18. But things like panel lines will begin to shrink down to the point where they will begin to be close to the scale of the layers ... This could be addressed, but it's an issue.

Second, and much more important, is the issue of part thickness on hollow parts. I spend a great deal of time making parts as thin as they can be to cut down on print time and no stronger than they have to be. In some cases (like the body skin parts on the V-2 model) these parts are just two passes of the extruder head thick. Cut the size of the part in half, and they'll be just one layer thick -- basically only slightly thicker than a sheet of paper -- and will become unstable. Other parts are optimized to be three or four layers thick for strength where it's needed. Again, just shrinking the part with simple scaling will kill that work.

Bottom line: Yes, a 1/32 model can be built, but it would take almost as much work as going from the base mesh to printable parts in 1/18.

[grunt1]

It depends on whether you would want to use the same material in each scale. The material I use most often has a .7mm thickness requirement but there are other choices that can go to as little as .3mm. So you could scale down and use a different material.

The trouble with scaling up is the cost. If you have a wall that is .7mm, the thinnest to keep your material and printing cost down, and then scaled it to 2x your cost would be 2x because all of your walls would be 1.4mm. If you drew the model at the larger scale instead of scaling it, you would be able to do it all at .7mm.

This is a very cool, but very new world and for every new trick there are new rules that have to be learned.

The other drawback is that you want everything possible to reduce the material cost, support material cost and and printing time cost. In casting or injection molding it still makes sense to reduce the material cost but given how cheap the material is and that a mold generally doesn't care, ie it just stamps out a part hollow or not.. it's not really an issue. That's why figures are not hollow.

Lot of new amazing things in this new world but there are a lot of new rules too. Crazy times indeed but fun..

[gburch]

It depends on whether you would want to use the same material in each scale. The material I use most often has a .7mm thickness requirement but there are other choices that can go to as little as .3mm. So you could scale down and use a different material.

The trouble with scaling up is the cost. If you have a wall that is .7mm, the thinnest to keep your material and printing cost down, and then scaled it to 2x your cost would be 2x because all of your walls would be 1.4mm. If you drew the model at the larger scale instead of scaling it, you would be able to do it all at .7mm.

This is a very cool, but very new world and for every new trick there are new rules that have to be learned.

The other drawback is that you want everything possible to reduce the material cost, support material cost and and printing time cost. In casting or injection molding it still makes sense to reduce the material cost but given how cheap the material is and that a mold generally doesn't care, ie it just stamps out a part hollow or not.. it's not really an issue. That's why figures are not hollow.

Lot of new amazing things in this new world but there are a lot of new rules too. Crazy times indeed but fun..

grunt1, are you using a commercial service for printing? If so, what material are you getting your stuff printed in?

I did note when I looked briefly at the Shapeways site that they seem to base their charges at least in part on the material involved. But with the technology I'm using material cost is by far the least significant factor, and I mean by FAR. Print time is a much more significant factor. As wall thickness doubles, so does print time (more or less). With even a maximally optimized large, thin-walled part taking between one and two hours, time matters a lot.

The "personal business" I'm envisioning is premised on the idea of having enough time available to print basically one whole kit per week per machine -- that's based on estimates of having time in the mornings and evenings on some weekdays and four or five hours per day on weekends to print. The value of time and the effort to manage this process is way, way more significant than the cost of rolls of ABS filament to feed the machines. ... or so it seems to me as I begin to kinda sorta envision what the economics and effort of a printer-based limited kit personal business might be like.

[grunt1]

I use a variety of printer types and shops depending on whether the goal is cost, detail or repeatability. Almost all of them use the cubic volume of material as the primary cost measurement. At this time, it's the most fair way to align all of their costs with the value of what is produced. The biggest cost factor for the service is the machine time which includes the machines themselves, operators, maintenance, repairs, and support from the manufacturers. The time it takes to print an items is directly related to the amount of cubic volume of material so that works well for them. The other cost factor is how large the item is, but I haven't seen anyone charge a premium for that, yet. The reason being that they try to load as many different jobs into a single "well" to reduce the total amount of printing time cost on their side. A large item that didn't have lot of cubic volume, like a big hollow cube, would eat up the well and not generate the per CU revenue they need.
This is similar to paper printing in that if you have small runs, it's a good thing for the manufacturer or printer to squeeze more similar jobs in with yours if they can so they don't have to reload the plastic type, the inks or whatever their setup materials and costs are.

You really should give Shapeways a try. After your most recent posts I now get that a big part of the project for you is doing it all in yourself in your house and I'm down with that. And it's really cool to watch something you drew take physical form right before your eyes! Anyway, we all have our missions.

At some point though, it ends up more like not publishing a great article you wrote (that we all want to read) because you want to do the layout and run the printing press yourself. I also play with the idea of a printer at home, but at this time the technology is changing too fast for that to make sense. In the near future, you work out your model or get one from someone else, upload it to Kinko's 3D (Shapeways today) and then run down the street if you have one nearby or wait for the UPS guy.

At this point I think you can safely claim, and we are your witnesses , that you can score mission accomplished on the printer portion of your project. If the members here had a vote, they would probably want you to spend more time working on manifold, thickness, and loose shell issues with the Val STL file and not so much swapping motors out of the maker bot. Not to mention working flaps, proper dihedral, and rivet count! Maybe it's worth a poll.