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dr wogz

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Hi all,

With advent & popularity of 3D printers, many are now starting to look at designing their own parts & creations. And, with more & more "entry level" CAD programs out there, it's just getting easier to design & develop your own designs.

But using a CAD program, thinking in 3D, understanding the features, functions, and buttons can be intimidating!

So, let's start a list of ideas & thoughts we have that make our design easy, thoughtful, and generally pain free to modify / manipulate..
 
Be mindful of your start orientation / work-plane selection.

All CAD program have three planes on which you can start your model. Use them wisely. It can also make it less of a hassle when importing your model into your slicer, as it imports 'the right way up'. (Or imports so that you don't need to spin it on 1 or 2 axis..) As well as with drawing creation (if you go that far, to create drawings of your parts..)

When you build a house, you start of the ground, the XY plane, and build up. But building a house in CAD (or at least, to extrude the house shape) you might want to start of the ZY plane and extrude it thru the X direction. This way, your house is oriented 'right side up' but you started on a vertical "right-side" plane..

The same with your Models. Build them "the right way up". I have an idea of what my part is going to look like. (I know how my printer prints.) When I start building my part in CAD land, I'll start on one of the three planes that makes the most sense for the part to be oriented properly.. Sometimes you might even want to create a new work plane on which to start your model, so that it ends up 'right side up'. Then, the part is always 'right side up'.

(The number of times I've started a model, or use a co-worker's model that isn't 'right way up' is .. well.. A little forethought on how you start can go a long way!)
 
when you say "extrude" it sounds like SketchUp, is that what you use? I use LibreCAD for 2d drawings, it has some support for an isometric view.
 
I (currently) use Creo 3 (PTC / Pro Engineer). I have used Inventor & mechanical Desktop in past jobs. (as well as very short stint (1999) with Cadkey) I have over 20 years in front of a 3D parametric CAD station, and over 30 years in drafting & design. I'll also toss in 20 years of technical writing and technical illustration.

I will be listing a 'term definition' soon, as they pretty much all work the same way..

But yes, Extrude is just that: push a 2D shape thru an axis perpendicular to the 2D plane at a set amount..
 
Modelling & the model tree: Keep things simple!

Simple modelling, many steps make light work. When you’re modelling your part, don’t try to do the whole thing in one sketch.. Keep the geometries simple. If you’re modelling a square with mickey mouse ears (a circle at each corner). Make it so. A square, then add the circles. Editing, refining, or trouble shooting your design later will be much easier. Some modellers allow you to rename the geometries in the modelling tree. Do so, it’ll be much easier to navigate and edit the part later..
 
Fillets & Chamfers.

Most decent modellers will have a fillet and a chamfer tool. You pick an edge, ant it’ll give you a radius for a fillet or as for the depth for a chamfer (or ask for the X and Y for an unequal chamfered edge.)

Always try to put your fillets & chamfers at the end of the design cycle. This make it easier to edit the part later. And, doing makes the model less likely to crash or become corrupt.
 
The power or parametric

"Parametric" para = many. Metric= value/variable

Many of the new 3D modellers are ‘parametric modellers. Meaning you assign values to give the model form. You can also go farther and give relationships / equations to your measurements. This can allow geometry to remain the same when a value changes. Supposed you have a hole 1/3 the way along on the side of a block. Your block side will be D1 long by D2 high. You hole can be =D1/3 by D2/2. This way, regardless of what your D1 & D2 values are (the side of your block), the hole will always be 1/3 along, and ½ the height. There is usually a switch to turn on & off the variables, so you can build equations.

With this, you can build something, say a NC, whereas all the dimensions are based off one value, the inner BT diameter.

The more advanced modellers (Fusion 360, Solidworks, etc..) you can build parts form tables; an excel file, whereas all the dimension are listed & read from a spreadsheet. This can help with making equations, and you can see all the variables in one place. You just have to remember which variable is which!

You could build a fin can, and have only 4 variables: BT dia, Fin root dim, Fin tip dim, sweep angle (fin rake), and number of fins around. It would calculate it all for you based on these 4 parameters..

You can then start to really think about your design, and start assigning some rules to all this, to have a really robust design.
 
I use Alibre CAD program. It is very powerful and very easy to learn and use. There Atom version is there cheatist version but still packs a lot of power CADing power.
 
Coming at this from a Solidworks perspective, but, whenever possible, especially with your first extrude, use the midplane option. This automatically creates a centerline plane within your part model, which is extremely helpful when making an assembly.
Use any feature patterning tools available. Instead of painstakingly applying several fins to your model, pattern the part/feature. "Ok, I got this one fin where I want it..." You can either repeat your previous steps as many times as you want fins, or you can say "Pattern this around that axis so that there are x fins, either all y distance apart or else spaced evenly."
 
Top tips I can come up with-
1. Use some form of version control, even if it's uploading a private file to github or onedrive, use version control. It's a basically infinite undo button, so long as you...
2. Control Ess. Ctrl. S. Save all the damn time. Save as soon as you do something. Save after you save. Check the file back into your version control after you save.
3. Consider your ultimate design intent. Always. This sounds strange to people unfamiliar with CAD software, but you're always faced with multiple ways of creating the same result... The number of headaches you create for yourself down the road will be governed by how well you thought ahead when you made each prior decision.
4. Is the software refusing to do something for reasons that don't make sense? Did something goofy just happen with your graphics? Save your work and close the application. A crash is imminent. Trust me.
 
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I use Alibre. From day one found it to be very easy to learn and use. I use the expert version but there Atom version is a good choice for someone or hobbyists
just learning a CAD package. Also, I believe the cost of ATom is less than $200.

It has just about all the functions as the expert vision meaning you will be able to draw some very very complex models. Then you can combine parts to make an assembly, Then you can export the model in STL (other export formats available ) so the model can be sliced and 3D print.
 
Have the Alibre Atom 3D too. On my system, always. No net connection needed. Never expires or has a 'User Usage Rules Change'.
 
https://learnrms.com/
The Resilient Modeling website shows an approach that is particularly useful for parametric CAD software. This is stuff they don't teach in college classes. I've shared this link with a few folks at my job (we use Siemens NX--formerly known as 'Unigraphics'), but most folks just do their own thing (which can be problematic). This is not an all-or-nothing method, but there are various concepts that may be helpful--and just understanding the concepts and goals of 'resilient modeling' may help one's approach to design. The info is probably not for everybody.

Side note on parametric CAD-- For hobby related stuff, I'm a longtime TurboCAD user (since 2001) and continue to be a fan, though with caveats. It is NOT a parametric program, though there are some parametric capabilities, as well as a 'part history' that can be enabled (with limits--for example, operations can be deleted; however they cannot be reordered). I'm definitely interested in considering Alibre down the road, though as a fairly advanced CAD user, I'm concerned about what tools and capabilities may be lacking in the lower-priced options. But I can definitely say the following: while I was designing the Javelin parts for Matt Steele's NCR kit, using a non-parametric 3D CAD program led to a lot of re-work even for seemingly minor changes (such as changing shell thickness), depending on the nature of the particular change. If I had had a parametric CAD package at home it would have saved me A LOT of time and effort.

Josh T.
 
I primarily use Fusion 360 and Inventor. My biggest recommendation to anyone getting started is to pick a program that will grow with your skill set. Many fantastic programs have hobbyist, educational, and trial versions. If possible choose something like Fusion which will do just about everything you could want, has a free Hobbyist or personal license, and has a ton of good instructional content on YouTube. A good community around the software will be instrumental in your success. Oh and one last thing, walk before you run. Start smaller, do basic projects and designs. Don't download software and the first time out decide you're going to draw up a scale Saturn V. You're most likely going to frustrate the hell out of yourself and give up!
 
I have no idea where to start.
Here is the back story.

Since last March, I have been playing with tetrahedrons, and trying to fashion some sort of stable "fly-able" version thereof. I think I have fashioned a successful corrugated cardboard model. It employs 3 isosceles triangles on top, and 3 equilateral triangles on the bottom with 3 very large fins for stability.
After that, I saw somewhere elsewhere, something akin to the tetrahedron, but instead of having 3 sided faces, it used 4 sided faces. The designer said the sides were "diamond" shaped. A parallelogram, each side being of equal length, with equal corresponding angles. My model is made of basswood. It is heavy. It is a prototype. And I have not been able to fashion a workable recovery system. The center tube ruptures when an ejection charge is fired.

So, I am, for the moment stymied.

However ...

Last November, and December, a fellow whose first name is Nick, showed up at our monthly launches. He was flying a 3D printed 10 (ten) sided rocket. He said he started playing with an elongated dodecahedron, but dispensed with the top side so he could have a "pointed nose cone" (it wasn't really a nose cone, but aero-dynamically, it would suffice). I will describe it as having five top faces, and five bottom faces, and the nozzle of the rocket motor emerging from what would have been the 11th side. Five fins emerged from the seems were the bottom faces are joined. The launch lug passes thru the body, adjacent to the center tube and motor mount. It is a light weight rocket for one that is 3D printed.

He explained that he used a special plastic that he purposefully over heated so that it would "foam up," to reduce weight and speed up the printing process. His model was perhaps 12" or 15" tall, maybe 3"or 4" around the middle - and fairly light, considering it was all plastic. I don't recall what motors he was using. I believe they were 24mm D or E motors.

Okay, so here are my questions; Are all 3D printers capable of doing this? What is the special plastic that "foams" when over heated, and prints quicker in that mode? I believe he told me what it was, but it didn't mean anything to me at the time, and now I can't remember what he said it was, and I have not seen him since, and I have no way of knowing how to contact him. I don't remember if he said he was using or had access to a CAD program. I am thinking that CAD program is more likely capable of handling geometric shapes and solids. Or are there other programs that are just as capable, but cost less? I don't recall him referring to the "Thingy verse," which I understand is where most of the 3D print files reside. Or will I have to program it myself? I know nothing about programming.

Carlos/c0c0m0ke
 
He was probably talking about "Light Weight PLA". I've seen several recommendations for using it with rocketry, but I haven't tried any of it myself. Pretty much any FDM printer should be capable of printing with it, you would probably just need to create a special profile in the slicer.
 
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