Designing in CAD

Guides and discussions about building water blasters and other water warfare devices such as water balloon launchers.
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Designing in CAD

Post by HBWW » Mon Mar 11, 2013 3:33 pm

Alright, let's face it. PVC Designer kind of sucks and doesn't run on the latest Windows operating systems. I decided that instead of trying to revamp it, I would go with 3D diagrams, but I want it done easy; I don't want to spend too much time if avoidable, which was the point of PVC Designer in the first place. Things may be different for others though, who are well versed in CAD and are willing to spend more time designing homemades there. Plus, I think CAD has an important place in our community's future when 3D printing and fabrication becomes feasible for everyone, including us, to use for our blasters. (The market most certainly isn't going anywhere to fulfill enthusiast blaster needs anyhow.)

What do advanced builder use for designing? I'm a visual kind of guy, so I'm not that great at just throwing materials together to make an awesome Nerf or water blaster. And we all know that basic, bare-naked PVC doesn't cut it anymore if you want triggers and ergonomic design. I want to be able to make blasters that are as close to commercial quality as feasibly possible, in that respect, with nice grips and triggers and what not. Stuff that the best of the best on the NIC do.

Anyway, I'm learning Sketchup at the moment, so I can gather some PVC parts on the web and put them in. Perhaps another tool would do the job better, I don't know. I'm better with 3DS Max, but I use that for models for games; it doesn't seem like the right tool for building water guns at all, except for water guns used in video games and pretty renders. I've also used AutoCAD before, but I have the feeling that Sketchup may be able to work things up faster from what I've heard.

What are others using? Anything crazy like Solidworks?
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Re: Designing in CAD

Post by Andrew » Mon Mar 11, 2013 3:40 pm

3D CAD is probably the best way to go. Not only because of the 3D printer, but also because not all designs are symmetrical.

At the minute I tend to use Solidworks. :P

That's mainly because I've got a student license through uni though. I normally use proDesktop or sketchup. I like the idea of using sketchup, as a base for community designs because it's free and you can easily create and share components.

I still haven't used it enough to get used to it though.

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Re: Designing in CAD

Post by isoaker » Mon Mar 11, 2013 4:24 pm

Unless you really need the 3D, drawing using some sort of good vector program in 2D is probably a lot simpler and just as effective. If you really need to make the two sides different, it's just a matter of drawing a left view and right view. Of course, 3D creations would be easier to port over to a 3D printer if you have access to one. However, I'd still argue it's faster to do initial mock-ups in 2D to get the general idea down, then if it looks promising, spend the additional time to create the 3D version. Starting off in 3D will more likely inhibit one's creative process more than it helps.

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Re: Designing in CAD

Post by HBWW » Mon Mar 11, 2013 5:08 pm

I suppose Solidworks isn't too crazy if you're an engineering student, but I'm not lol. Just trying to get as close to actually connecting PVC parts together as possible to model ideas. Obviously, you don't need this for PVC, but when I want to 3D fab, I will need the PVC as reference. I would much prefer accurate 3D over technical 2D drawings, although with 2D I suppose the fastest way to go is with paper and pencil. I want some reasonable amount of accuracy though, so I went ahead and had a look at Sketchup. I'm not too against 3DS Max though, since I'm most familiar with it.
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Re: Designing in CAD

Post by Drenchenator » Mon Mar 11, 2013 6:16 pm

Sorry for the long post. I'm kinda opinionated when it comes to CAD.

I design everything with pencil, paper, and a ruler. As a medium, it's very free and has no limits or learning curve.

I tend to view CAD with skepticism. I honestly haven't seen an engineering student use it correctly -- or really a professional engineer for that matter -- but it can be done.

I always like to use tools that help me solve the problem I'm trying to solve. CAD is a great tool, but it just isn't for all situations. If I could solve something without CAD, I'd do it that way. If you are 3D printing something, you need to do CAD, but if you aren't you really are missing the true purpose of CAD.

What is the purpose of CAD? Most people seem to think it's a system to help you visualize your design -- to see how it looks and to see how parts fit together, etc. --- but it's much more powerful than that. The point of CAD to help engineers solve the geometry. Underneath all the visual bells and whisels (talk about mixed metaphors), the CAD program is fundamentally about constraining a set of lines, curves, and shapes. You tell it approximately how you'd like it: the CAD backend figures out the rest. I can't tell you how many times I've seen an engineer use Solidworks, and get an "overconstrained" error, and have no idea what it means. It means that the geometry you told it to create can't exist: you have X constraints (degrees of freedom) in the geometry, and you just tried to give it X + 1.

Since I know what CAD's really about (solving a set of geometric constraints), I usually skip the middleman and just write out all the geometry equations, and solve them manually. It's really not that hard, and many times you have to do that anyway to know what you want. I don't really have a problem with this because I'm good at math and can visualize what I want really well (even in 3D).

Another big problem with CAD is cost. It's really expensive. If I remember correctly, a Solidworks license is 4000 USD. That's prohibitively expensive for hobbyists like us. Sketchup is alright, but as I mentioned before, if it doesn't have the CAD backend that solves the geometry for you, you really aren't getting anything except a visualizer. There is hope, though. A few months ago I tried out FreeCAD again. I tried it out a year or two ago and it lacked most of the features I wanted, but now it's started to become more fully featured, though it still needs a lot of work until it's on par with Solidworks. If you are just looking for a replacement for PVC Designer, I'd say Sketchup would work given that it pretty much does the same thing (let you piece together a water gun using virtual pieces).

I also don't like CAD because it has a pretty steep learning curve. Some ideas that I can draw quickly are nearly impossible to get into a computer without a lot of effort. Here's an example: my senior design group project was a donut machine. We were using some wire mesh off McMaster as a cage for the donuts. I don't think we ever figured out how to properly represent it in Solidworks. On paper, it was pretty easy, but in the computer it was a nightmare.

I think that a lot of engineers are attracted to CAD because it offers a deliberate method of design. Design is an art, and it's just too open and abstract for a lot of people to handle. CAD can produce really great visuals and drawings; it can really make anything look good if you put enough work into it. It's kinda like the Powerpoint of engineering. In that sense, it reminds me of Edward Tufte's critique of Powerpoint. Tufte argued that Powerpoint helps the presenter more than the audience, and I think the same thing is true with CAD (the presenter is the designer; the audience is the whether or not the design works). Both are great way to polish a turd when used incorrectly.

Regardless, I do think CAD can help us design more ergonomic and stock-like designs. Nobody has built a reasonably ergonomic homemade without resorting using "exotic" materials or "unorthodox" arrangement of parts. If our current design tools can't represent those kinds of designs easily, then we should move on to better design tools like CAD.
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Re: Designing in CAD

Post by isoaker » Tue Mar 12, 2013 12:41 pm

Pencil and paper trump pretty much anything when it comes to initial design and sketching. Pen and paper is good, too, but pencil offers finer control over line thickness, weight, and even allows for smudging to get smooth gradient fills. That said, small sketches on paper are good, but often hard to share (need to scan or take a picture of it), harder to edit (some hard lines can never be fully erased), and impossible to edit while retaining the original. With digital files, you can copy and edit things, but it is usually more labor-intensive to create things (unless you have a drawing tablet - things get easier again if you have pen input for your computer). The biggest advantage I see to using a computer for sketching is getting the scaling right. With rule guides, I can be sure that when I am drawing a 2" piece, it is 2" diameter and will fit properly against the remainder of the design. Sure, you can also pull out a rule and mock up guidelines on paper as well, but when you want to draw up a large water blaster (e.g. longer than 14"), you'll need to have a larger table and larger sheets of paper to draw on. With a computer program, you can zoom and draw on your imaginary canvas. Moreover, I can still draw a straighter line in a computer program than I can freehand on paper, but then I also have a pressure-sensitive tablet with stylus for letting my sketching evolve more fluidly.

To me, CADs are great, but unless you're building models for a 3D game, the benefits for ensuring how things fit in 3-dimensions are lost to the easy at which one can create multiple 2D views of a 3D object in a drawing program. Until we have UIs that allow us to sculpt and easily manipulate parts in a CAD UI environment, I'd leave using a CAD as a later step after first really fleshing out a design on paper or in a 2D drawing program.

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Re: Designing in CAD

Post by HBWW » Tue Mar 12, 2013 2:03 pm

Good points above, and thanks for the insights. Although I do want to re-iterate that my main reason for this is as a quick and dirty visualization tool; something as close to throwing actual PVC together as possible.

However, there are lots of problems as you guys noted. Lots of parts have to be manually modeled and represented carefully. To get stuff like flexible tubing to work nicely is probably more work in the end than its worth. I guess I'm really just looking for a PVC Designer replacement that's more accurate.

As for 2D, the advantage of 3D modeling is that you can get the 2D views if needed. I think 2D is great for measurements, but you loose a lot of the visual aspects of the item being modeled that perspective views give.

Perhaps its just a matter of preference and familiarity with the stuff. I'm not aiming for anything too accurate, but I do want to be as accurate as possible for the least amount of work possible. :goofy: Perhaps this will change as I learn more on it overall though.
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Re: Designing in CAD

Post by Fishfan » Tue Mar 12, 2013 2:17 pm

3D and 2D. I really need this, because I rarely get to go on an XP computer, so I'm not able to work on it often. Also, my suggestion is you add Sch 80 pipe, and more fittings. This will help a lot, thanks! And do try to get it done soon!
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Re: Designing in CAD

Post by HBWW » Tue Mar 12, 2013 3:22 pm

I haven't started any projects, just exploring. The Sketchup 3D warehouse has a lot of cool stuff you can just throw into your model; I found some PVC parts this way and plan to go from there, but like I said earlier, parts such as barbs or tube (metal or nylon) are missing, which are just as important as PVC.

Anyway, anything you can't find online has to be modeled out. I will do that once I have the time to get proper object measurements, get better at working with Sketchup in general, and what not.
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Re: Designing in CAD

Post by Drenchenator » Tue Mar 12, 2013 4:34 pm

While we are on the topic, I remembered I had a CD with CAD files for all of Charlotte pipe's PVC fittings. I don't remember where I got it from, but it appears to be available online too.

If you want CAD files for brass pipe fittings, McMaster has a lot, though they don't have them for everything.
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Re: Designing in CAD

Post by Andrew » Wed Mar 13, 2013 6:30 pm

In some ways I look at CAD like programming. It's most powerful when you can use it to repeat the same process multiple times (loops with programs, parametric modelling with CAD). With designing a homemade I suppose CAD is not as advantageous, as you probably won't be making a family of similar designs. Multiple different design concepts maybe, but with the number of parameters you'll need to vary, you might as well just build it again.

I don't mind drawing a design, but (unless it's an initial sketch) it's only useful to someone else if it's detailed and easy to understand (hence all the conventions for real engineering drawings). CAD is a bit better in this respect, as it can be much easier to design something that other people can understand. I've seen some pretty indecipherable sketches, of sometimes quite complex geometry/designs. For a community-wide design/presentation tool CAD is pretty useful. Obviously that assumes the person drawing up the design knows how to work with the program, but from what I've seen, most of my colleagues took to CAD much better than they did to drawing.

A lot of the components will need to be built on CAD first. Most of the CAD files available from manufacturers seem to be from autocad or other packages which are not free to use. As a community tool, free and/or open source CAD software would be ideal.

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Re: Designing in CAD

Post by Drenchenator » Wed Mar 13, 2013 7:56 pm

Hmm. I didn't realize Charlotte Pipe's online CAD files were in DWF, which is difficult to open with free software. DXF is the standard and can be easily opened in free software.

I found the CD. It's from 2005 and has about 200 megs of data on it, but no DXF files that I could directly open. It also didn't have any way for me to tell which file was which (nothing was labeled). Instead, it installs this program called PlantSpec. PlantSpec lets you choose a part and make a CAD file from it. Here's a screenshot of me choosing a reducing tee and saving a DXF file.

I was then able to open this DXF file in FreeCAD. Have a look:

Image

Granted, this is a bit slow and tedious, but it appears that a free library of CAD file for PVC fittings is already available, provided off course you have this CD.
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Re: Designing in CAD

Post by HBWW » Wed Mar 13, 2013 10:39 pm

Interesting, a CD they'll mail to you for free? Would make more sense if they just had a download.

I can acquire AutoCAD free via student license, and should do so before my student status goes out. (I graduate in April.) Last time I used AutoCAD was in high school though.

Anyway, I'll explore this farther as I go and acquire the CAD files for the parts/fittings when I find the time.
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Re: Designing in CAD

Post by soakinader » Thu Mar 14, 2013 3:15 am

Hmm I'm an engineering student, and I <3 Solidworks. I have both AutoCAD and Solidworks on my desktop.
I'll have to see about those PVC components. If I can download them and integrate the fittings (specifically the threaded male/female) into one of my pull-valve designs, maybe I could print off some ready-made PC's... in a few years. XP I don't believe I can get away with using the 3D printer for such things yet...
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Re: Designing in CAD

Post by Fishfan » Sun Mar 17, 2013 3:10 pm

That program above looks a little old, but it looks like it might be the basis of what we need. It also looks a little too advanced. For me, I would like something that is simple, but a definite improvement over PVC designer. 3D and 2D, drag and drop visual parts, etc.
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Re: Designing in CAD

Post by Andrew » Tue Mar 19, 2013 6:46 pm

It would have to be a little more complex than just drag and drop, as you'll have to constrain the components to stop them rotating / moving around when you move the other components. Most of the tools in the complex CAD packages are for building new components anyway. If all you want to do is import components, you won't have to use most of the tools. You should only need them (and even then probably a small number of them) if you create your own components if specific pre-built ones aren't available, or you want some bespoke components (plastic sheet casing/triggers).

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Re: Designing in CAD

Post by HBWW » Wed Mar 20, 2013 3:23 pm

The problem is, we'll hit points where custom parts needs to be designed sooner or later. Either with items that have no CAD models available, or for 3D prints in the future. I guess that's part of why I went with Sketchup, although this whole project (for me, anyways) is on hiatus for now as I make repairs and gear up for the community war.
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Re: Designing in CAD

Post by isoaker » Thu Mar 21, 2013 10:22 am

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Re: Designing in CAD

Post by the oncoming storm » Thu Mar 21, 2013 11:15 am

I just make horrible looking designs in paint. (As an exception The Shockwave LPD wan't anywhere but my head till I started get parts for it a few days ago)

I am getting some great performance predictions for it too I expect it to be done by Monday so I can test it.
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Re: Designing in CAD

Post by thelaminator » Fri Mar 22, 2013 1:51 pm

Andrew wrote:3D CAD is probably the best way to go. Not only because of the 3D printer, but also because not all designs are symmetrical.

At the minute I tend to use Solidworks. :P

That's mainly because I've got a student license through uni though.

Which version? I <3 Solidworks. :goofy:

Edit:
Drenchenator wrote: If I remember correctly, a Solidworks license is 4000 USD. That's prohibitively expensive for hobbyists like us.
That's for an over-the-top simulation-all-the-special-stuff version :goofy: a basic license is usually ~$85 USD. Not saying that's cheap, but isn't no $4K :goofy:


Seriously though, I could build 3 SCII's for that price, so like you said, the Pencil&Paper method still does it's job.

Edit 2:
soakinader wrote:Hmm I'm an engineering student, and I <3 Solidworks. I have both AutoCAD and Solidworks on my desktop. maybe I could print off some ready-made PC's... in a few years. XP I don't believe I can get away with using the 3D printer for such things yet...
If you know how to use Solidworks well enough, and your printer allows for Water-soluble-removal, you can quickly make custom PCs with a 3D Printer. Usually a sketch/revolve does the trick, with something of an "arrow" for a connection point,then use the water-soluble substance for the center. Right now I simply don't have the time to show you, so I hope I explained it thoroughly enough.

Oh, and AutoCAD gives me issues. Many, Many issues. :goofy:
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