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Learning CAD with Alibre Atom3D

Discussion of the series starting in MEW 274

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Alibre Atom3D

Alibre Atom3D

Thanks to the generosity of Alibre, Model Engineers' Workshop Magazine is able to offer every reader of Model Engineers' Workshop a free six-month licence to Alibre Atom3D. Alongside this great opportunity, starting with issue 274 of Model Engineers' Workshop we are running a detailed tutorial series in the magazine. This page will be the 'hub' for links to example files, tutorials and more so make sure you drop in regularly to keep up to date!

Andrew Johnston14/03/2019 16:24:45
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Interesting debate. I've been using Alibre Design Expert for the last 15 or so years. I'm old enough to have started with drawing boards, pencils of differing widths and a copy of BS308. So I've got substantial 2D experience. Back in the 1990s I started using a simple 2D CAD package - can't remember it's name. But it ran under DOS rather than Windows and was lightning fast. I used it to design parts for racing cars at a time where our draughtsman at work was still using a drawing board. He was cockahoop when a CNC machined box came back with some holes that didn't line up. Turned out the the machinists had made a mistake so he had to grovel. I then graduated to a cut down version of AutoCad, which I didn't get on with. It wasn't anything more than an electronic drawing board, for instance lines didn't snap to the nearest other line, so you had to zoom in to connect and then zoom back out. Hopeless. That was the point at which I bought Alibre. I've not really had any problem using it. Sure there are some quirks and things it doesn't do well. But all real parts are 3D so it's completely natural for me to think in 3D and so it's easy to create a part by extruding and/or cutting. For workshop use I create 2D drawings plus an isometric view of the part. I also make extensive use of assemblies. On my traction engines there are several reasons. One, to account for different size materials due to obsolescene. Two, where I'm changing the design to reflect the original engine, and three because the original drawings are poor and full of fundamental errors that mean parts as drawn would never fit or work.

I find 3D CAD invaluable, it's 2D CAD that's a bit odd. I'm idle and I like parts that I make separately, maybe months apart, to fit together. For that 3D assemblies are crucial to eliminate design errors. After that it comes down to my machining.

In a sense 3D is much older than computers. In the "good" old days things like engine rooms on ships where created as a scale 3D model to establish pipe runs and lengths rather than try and do it as a 2D drawing.

Andrew

Edit: Still got my Rotring pens, although I haven't used them in a month of Sundays.

Edited By Andrew Johnston on 14/03/2019 16:26:43

Nigel Graham 214/03/2019 20:35:55
104 forum posts

A rather unusual engine design there, Jason, with that long bifurcation on the connecting-rod and very wide angles in the crankshaft. What was it (the original)?

Two hours work so far... Ah, but such productivity with shapes like those is possible only with considerable operating skill; beyond my realistically achievable level whether I convert to Alibre or stay with TurboCAD. It would take me two hours to draw even one of the simpler components, and most are by no means straightforward.

I like your system for using colour to signify materials. In fact 19C designers sometimes used colour-wash for a similar purpose, and I think a certain standardising came into use. In some cases, civil-engineers at least also to tinted what might have been contract-negotiating drawings, to make them more eye-catching to the client.

My last attempt at a 3D drawing was of my steam-wagon's cross-head. These will use a siamesed casting pair I chanced upon in one of those boxes of lonely and forlorn castings that appear on model-engineering show trade-stands. A bit big for the scale of my steam-wagon engine but as it's all enclosed and their are no surviving drawings and prototypes, I don't think anyone will quibble!

It's similar to your engine's cross-head but with an internal small-end, and triangular cut-outs at the front and back. I think they were originally for a 7.25"g loco, and narrow-gauge at that. I measured the castings to establish possible machined sizes, then drew it as an extruded outline in thickness, with extruded cuboids subtracted to give the guide-bar channels.

As it happens an Alibre "magazine" has just appeared among my e-posts, containing a short (8 minute) video on common sketch errors. For some reason I couldn't get the separate amp and speakers to work so had to watch in silence (well, to the background of the concert on Radio Three!), but it clearly showed the effects of misclosures not apparent until you magnify the image.

That was one of the first things I learnt eventually on TurboCAD and probably common to any similar make of CAD - that closures have to be pixel-perfect (in fact I think their real definition is finer still; numerical not visual).

I think its point was that in Alibre an extrusion won't work and an un-closed or over-stepped joint is the likely cause. In TurboCAD it might extrude but as a thin-walled polygonal "tube".

I've also found in TC and I imagine you can equally unwittingly do this in Alibre: a lot of editing can leave tiny line fragments hidden under the visible lines; and these fragments play merry hell until you find and exorcise them.

Nigel Graham 214/03/2019 20:47:27
104 forum posts

Andrew Johnston;

Re your, "For workshop use I create 2D drawings plus an isometric view of the part."

From what I saw at work (I retired a couple of years ago) it is common professional practice to put a coloured isometric picture alongside the annotated orthographic views to help the machinist see what he's making.

Having bought both their boring-bar and Worden tool-grinder kits, I see Hemingway Kits uses the same principle.

JasonB14/03/2019 20:48:05
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Its just an engine from a Rum Distillery, may have run a small set of cane crushing rolls or been used for something else.

Alibre will analyse each sketch as you deactivate the sketch and if it finds any problems with the sketch such as you mention above it will list them out and you just click on the item on the list which will then be highlighted red so easy to locate, you may very well have to zoom right in to see the problem but at least you know where to look. From other posts in this thread some users have not had this turned on but it is worth doing so and setting it to come on as default.

Neil Wyatt14/03/2019 21:48:23
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Note that when lining up nodes or shapes or centrelines etc. the cursor changes to show when it has 'snapped' to be perfectly aligned. Watch for this and you will rarely get 'open' shapes.

Neil

Neil Wyatt14/03/2019 21:50:20
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Posted by Nigel Graham 2 on 14/03/2019 20:35:55:

I've also found in TC and I imagine you can equally unwittingly do this in Alibre: a lot of editing can leave tiny line fragments hidden under the visible lines; and these fragments play merry hell until you find and exorcise them.

Less of a hazard in Alibre as it doesn't habitually convert curves to multi-segment lines until you export.

Could be an issue with an imported DXF of course.

Neil Wyatt14/03/2019 21:52:06
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Posted by David Jupp on 14/03/2019 09:34:12:

I'd say that there is significant benefit of using something like Atom3D even if you only want 2D drawings - it's often faster than a pure 2D approach once you get the hang of things, especially if you need cross section views, enlarged detail views, isometrics etc. Also when the design evolves/changes, the 2D drawings update automatically.

The vast majority of commercial users of Alibre produce 2D drawings for manufacture of their designs.

Yes if you are happy working in 3D and then producing a 2D drawing, but I think Nigel wants to work in 2D.

Neil

Neil Wyatt14/03/2019 21:53:59
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Posted by Steve Skelton 1 on 14/03/2019 10:49:58:

Here's my experience for what it's worth.

I tried to use the package based on my AutoCAD 2D experience and fell flat on my face.

I then read the tutorials and had a lightbulb moment.

I found I had to forget everything I had learnt about 2D CAD and drawing board draughting and imagine I was trying to make the item from a solid block or adding to it in a solid block as if I was machining it (or welding on to it). I then found it made sense.

I am not suggesting I am proficient at using the package but if I think in terms of adding or taking away material then I seem to be able to do what I want.

Not sure if others are with this??

Steve

I think you are spot on Steve.

Neil

Neil Wyatt14/03/2019 22:02:58
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Posted by Nigel Graham 2 on 14/03/2019 11:02:44:

I never reached the advanced levels of "sweeps" and the like, but I found even with those two basic actions the properties of the generated solids and their reactions to editing tools differ markedly, with no clear rhyme, reason, pattern or manual instructions to help you choose the right type where both will give the same figure (mainly cuboids and cylinders). I assumed this will be common to all 3D CAD packages, because they have to perform essentially the same calculations and routines behind the presentation.

:

You still need to understand both Design and CAD. They are separate. The latter is extremely difficult, and exists to express the former as images.

 

Turbocad has two ways of making 3D from 2D - you can give an object 'thickness', doing this to a circle creates a smooth cylinder. You can also extrude, which leaves the original flat shape and creates a faceted 3D version (typically a circle will have up to 90 facets). These two types do behave differently.

Alibre just has one consistent extrude which does not create a separate, but a smooth one still connected to the original shape, like TC's 'thickness' but more flexible.

 

MY feeling is that DESIGN is the hard bit and which needs lots of experience. CAD is a lot of unfamiliar things at first but the steep learning curve soon flattens out.

 

If you have missed parts of the series you can get back issues at mags-uk plus Mintronics are looking at producing a PDF version of the series.

 

Sorry to harp on, but I suspect that if you were asking 'how do I do this?' rather than 'why should I bother to learn this?' we would have you happily using Alibre by now.

 

 

Neil

Edited By Neil Wyatt on 14/03/2019 22:05:12

Nigel Graham 214/03/2019 23:01:08
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Thank you Neil. I would ask if I do convert to Alibre and need help.

I need decide whether to continue to attempt to learn CAD or give up; then choose whether to stay with TurboCAD or to convert to Alibre.

TurboCAD has a third way to generate solids: "Primitives", a few common solids like cuboids and cylinders you set to your own dimensions. These too, have their own characteristics.

I think the relative difficulty of Design and CAD is in favour of the design to start with but I understand your point.

I see using CAD or indeed manual drawing means acquiring a set of fixed skills, as tools to perform a project. Those tools change only in minor details; but the project is the real variable. In model-engineering, it can be anything from a simple machine-tool attachment to a showmen's road-locomotive or radial aero-engine.

However, I find CAD far harder to learn than I had envisaged, irrespective of what I design; and I can learn any difficult subject only to a random, unpredictable but rigid level. I abandoned CAD for about 6 months within a year of buying it; but having tried again I think I am near or even on my level for it.

John Davies 615/03/2019 10:51:23
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Am just starting. Drawing the 25 mm circle went OK; but after deactivating and going to Extrude, the circle disappeared from the screen. and the Extrude dialogue box "enter box" was greyed out. I am sure there is a simple explanation; but I have not been able to find it yet.

Be very grateful for any help. John

Edited By Neil Wyatt on 01/05/2019 13:54:51

David Jupp15/03/2019 11:10:33
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Circle disappearing - you may have 'sketch visibility' toggled off. There's a button for that on the Viewing & Analysis tab of the Ribbon, or try key combination Ctrl+Shift+K to toggle it. Sketch visibility is not required to be on, it's a preference choice.

Enter box greyed out for Extrude dialogue - some key information is missing - is the 'Sketch' field populated? If not clik in it, then click on the sketch to be used (in Design Explorer).

Edited By Neil Wyatt on 01/05/2019 13:54:57

Andrew Johnston15/03/2019 11:13:59
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Posted by Nigel Graham 2 on 14/03/2019 20:47:27:

From what I saw at work (I retired a couple of years ago) it is common professional practice to put a coloured isometric picture alongside the annotated orthographic views to help the machinist see what he's making.

I don't colour or shade the isometric view. The isometric view is helpful to give a quick overview of the part without having to interpret the 2D views. It is also useful as a sanity check for asymmetric parts to ensure you don't drill, or countersink, for example on the wrong side.

Andrew

Anecdote: In my O-level metalwork practical I countersunk some holes on the wrong side of a part. Fortunately the part was then riveted to another part so the boo-boo was hidden, and I passed metalwork with grade 1. Which was pretty much the highlight of my school career.

JasonB15/03/2019 11:19:21
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You want the one on the left of the pink box "toggle sketches"

Edited By JasonB on 15/03/2019 11:20:00

Edited By Neil Wyatt on 01/05/2019 13:55:05

David Jupp15/03/2019 11:21:40
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Ah yes - Jason has it, I keep forgetting that the simplified interface for Atom3D does a few things differently from Alibre Design.

Edited By David Jupp on 15/03/2019 11:22:10

Edited By Neil Wyatt on 01/05/2019 13:54:46

Neil Wyatt15/03/2019 18:12:48
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Posted by Nigel Graham 2 on 14/03/2019 23:01:08:

TurboCAD has a third way to generate solids: "Primitives", a few common solids like cuboids and cylinders you set to your own dimensions. These too, have their own characteristics.

I forgot those!

I think you might do well to set out exactly what you hope to gain from using CAD, whether 2D or 3D.

Fore some jobs, the back of an envelope is entirely adequate but if you want to design for a 3D printer or CNC tool, 3D CAD is virtually essential. And there's all sorts of things in bewteen.

Neil.

Nigel Graham 215/03/2019 20:43:43
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Thank you Neil.

I can answer that: I knew what I hoped (and still wish to) gain from CAD before I started, and I always knew the envelope-sketches still have a place.

The main points for me were and are:

Orthogonal drawing techniques whose advantages over manual drawing, include:

- copying repeated features or even large parts of the drawing, readily and accurately, to another area or even a new drawing.

- making changes or corrections more readily and less messily than on the drawing-board (I saw parallels with word-processing v. typewriters here),

- accurate dimensioning, as the computer does the sums,

- consistent lines etc, admittedly more aesthetically than functionally important.

Also, Isometrically-based assembly-drawings readable from different sides, to help ensuring Part B will rotate freely on Part A without hitting Part C; or to make building & servicing notes for future reference.

I was vaguely aware of brochure-style CAD pictures, from works drawings having small pictures to help the machinists and fitters visualise the task. This though, was and is of lesser importance to me, and worse, I now know adds only considerable difficulty.

Although not a time-served, professional machinist I do have a general, somewhat sketchy, semi-skilled background in electrical and mechanical engineering trades. So as well as my model-engineering hobby, I already understood engineering-drawings, in both manual and CAD days.

Also, I had some 20 years computer experience: MS 'Word' and 'Excel', and using laboratory instruments controlled by BASIC and 'Labview' programmes.

My encouragement was a perhaps too-ambitious project to build a 4"-scale steam-wagon from the scanty publicity photographs and Commercial Motor magazine trade-reviews remaining of the original, introduced in 1908. It was and is a matter of design a bit, make it, design the next bit, make it... then a few years later find Part B will not only hit Part C, but would obstruct Parts D to H.

So I saw CAD as potentially very useful.

I even hoped that one day I could reclaim the dining-room from its resident, A0-size, industrial-pattern drawing-board!

My reasons for wanting to take up CAD, was clear, and still stands. I knew it is a lot to learn but unfortunately, not how difficult and non-intuitive it all is to learn, nor the lack of useful supporting literature.

Colin Heseltine18/03/2019 15:55:57
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I am drawing up a simple adaptor to connect dust port on a grinder to a vacuum. Once I am happy with it I wish to convert the 3D CAD data into a file my 3D printer can then use to print the required item. I have created my basic shape and changed diameters as required.

What I now need to do is cut the smaller diameter at 45 degrees and rotate the cut piece around to give me a 90 degree bend. What is the best way to achieve this. I have followed the MEW tutorial exercises but not found anything that covers what I want to do.

Any suggestions please.

Colin

JasonB18/03/2019 16:11:23
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Bit hard to say without seeing what you actually have but rather than cut a bit off and try to rotate it I would draw the small diameter as a sketch and then draw another sketch with a 90degree bend, you can then "sweep" the circle along the bend which will give a mitred bend or if you fillet the path you will get a smooth flowing bend.

Draw circle and path

sweep1.jpg

Select sweep, enter the circle as the sketch and the bent line as the path

sweep2.jpg

Result

sweep3.jpg

Here I am editing the path to follow a curve

sweep4.jpg

Which gives this

sweep5.jpg

 

Edited By JasonB on 18/03/2019 16:15:43

Nicholas Wheeler 118/03/2019 16:56:31
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Not having any training in 2D drawing(the 50 minutes a week 36 years ago just made my head hurt), I find the insistence that 3D CAD is counter-intuitive peculiar. Representing a 3d object on a plane requires all sorts of artificial constructions and although I can read them OK, drawing an existing object is really tricky. Designing and drawing that way is a step too far for me.

3D CAD is easier, because you are intended to get to a 3d representation as soon as possible. So you sketch(which is what Fusion calls your first step) a basic sized shape, and extrude it to 3d. Then you add or subtract features directly to/from its planes, faces and axes. This is how you fabricate or machine the intended object, so it gives you a good idea of how to make it too. Being able to design the additional parts is place is another big help, what could be more natural than designing a piston in its bore?

I struggled for years with various versions of Turbocad, yet had a respectable model of a QCTP within a couple of hours of installing Alibre. Then the computer does the complicated bit of forcing the 3d into flat drawings to make the part. None of my stuff is going to be rendered into a pretty picture!

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