Is CAD for Me?

[Nigel Graham 2Participant @nigelgraham2]

Andrew Johnston:

Your point and its sample drawing didn't appear until I'd posted the above.

I wonder though, and have thought this of other contributors who swear by what I see as the long way round … did you start learning engineering-drawing with isometric-first CAD?

If so, I understand how you'd visualise your designs that way.

I didn't, so have no problems with orthographic drawings and maps. Further, I see viewing a solid item one face at a time as just as natural as seeing it in 3D. We do that all the time, knowing the sides recede from view somewhere even if we can't see them. Viewed across the room, my long-case clock is obviously 3D because I see it at an angle; but face-on, the crowded shelves of books form a two-, not three-, dimensional image.

Consequently, is needing a 3D model to ensure components fit together without fouling others, an instinctive result of being taught to work what I think the long and hard way round? You can still assess fits etc. in orthographic drawings. It's correct shapes and dimensions that matter, not views!

Converting a 3D model to the necessary 2D workshop drawings means advanced knowledge of your particular brand of software. It's probably there in TurboCAD but like forming 3D assemblies, hidden. I can't speak for Fusion, Alibre etc but TC's maze of solid-generation types and snap methods, co-ordinate systems and work-plane types, all of different properties; makes 3D assembly-drawing a baffling mass of unspecified combinations of which only one will work in each situation.

So it's really a matter of how you've been taught, or have taught yourself, technical drawing. If you have been introduced to 3D CAD by someone who can explain it properly, or can learn this extremely difficult subject yourself, and right from the start, then I can understand you'd work that way.

If you are used to seeing 3D items in 2D, you have not missed much if you cannot learn 3D modelling. It is disappointing intellectually to spend hours on the challenge only to find it impossible; but it's not essential to putting on paper a design whose physical reality will fit together and work as intended.

You can't though, work backwards, turning a multi-part orthographic drawing into an isometric assembly. CAD is not designed that way.

Edited By JasonB on 04/06/2019 16:07:51

[David JuppParticipant @davidjupp51506]

Quoting from Nigel above…

You can still assess fits etc. in orthographic drawings. It's correct shapes and dimensions that matter, not views!

You can – but not in a single click with clashes higlighted automatically. It's also easy in 3D to check for interference in multiple positions of a mechanism.

 

Converting a 3D model to the necessary 2D workshop drawings means advanced knowledge of your particular brand of software.

In most 3D CAD, to get from 3D model to 2D drawings takes just a few mouse clicks (hardly 'advanced'. Making sure all dimensions are arranged nicely and to preferred format can take much longer, I agree.

 

You can't though, work backwards, turning a multi-part orthographic drawing into an isometric assembly. CAD is not designed that way.

You can! It isn't preferred, nor best practice, but it's perfectly possible (except that assemblies are not isometric – views can be isometric). I will sometimes use this approach if someone has already created 2D CAD drawings, but a 3D model is needed for other purposes (though it can be faster in some cases to start again from scratch).

 

Don't worry Nigel – I know you won't be persuaded. There's nothing wrong at all with sticking to 2D should you prefer that.

The odd thing is that most 3D CAD modelling starts with 2D sketches anyway.

 

 

 

Edited By JasonB on 04/06/2019 16:08:13

[David JuppParticipant @davidjupp51506]

That damned winky again ! Only noticed now it's too late to edit.

Edited By JasonB on 04/06/2019 16:08:35

[JasonBModerator @jasonb]

[SillyOldDufferModerator @sillyoldduffer]

Posted by Nigel Graham 2 on 04/06/2019 13:10:03:.

…

View of CAD, as SillyOldDuffer describes? None of us are mind-readers! Apart from my preferring you talk to than about me when discussing how I think, I don't agree with your analysis anyway. …

…

Sorry Nigel but you weren't my target audience. My comments were aimed at anyone reading your well-written CAD-negative posts who might be accepting them as valid insights. If your observations were correct then 3D CAD would be impossible to learn without professional training. That's not true.

I'm certain you're not daft or stupid – just the opposite. I reckon you're a clever chap who's been super-glued to the wrong end of the stick by circumstances. I think you're mistaken about why you happen to find learning CAD so difficult and I'm concerned your critique will put people off who would otherwise have a go themselves.

The Alibre offer is a glorious opportunity if you want to learn CAD modelling and need assistance. It's supported by a series in a print magazine that you can study. Any questions you have can be put to an Alibre expert on the forum. There are more than a few forum members who can help as well. Everything else you've tried doing to get into CAD has failed. Why not try a new approach?

Dave

[Nick WheelerParticipant @nickwheeler]

Nigel, you have the procedure back to front: the 3d models are not pretty afterthoughts, but are what enable you to produce renderings, analysis or 2d drawings. To use 3d CAD, you have to get past the 2d drawing first mindset.

I think this is what makes it easier for those of us who don't have 2d training. Although I can read a 2d drawing, learning how to make them is not a good use of my time when 3d is more intuitive for ME.

[Enough!Participant @enough]

Posted by Nicholas Wheeler 1 on 04/06/2019 18:15:21:

To use 3d CAD, you have to get past the 2d drawing first mindset.

+1

[Nigel Graham 2Participant @nigelgraham2]

Thank you Jason, for the move. I admit it was rather hogging things. The Tea-room would need a Carnforth-size urn and whole collection of Rachmaninov!

+++

Thank you Dave for the clarification.

Thank you too for your compliment – but I was always a slow learner in anything, up to random levels I cannot exceed.

I've just sent the geological article and its 3 TC-drawn diagrams for peer-review, so some good's come of it! One is a simple 2D cross-section. The other two are 3D extruded sections, coloured even; but might be printed in grey-scale at the editor's judgement.

My other 3D TurboCAD efforts are all engineering-related, but not useable. Most are pure exercises but include an unfinished design for an (x, y, angle) jig-table for the bench-drill, of far wider range but lower profile than those cross-vices.

'

I take your point about a new start, but I stayed with TurboCAD not just by price. Alibre is so different I thought it illogical to start all over again after managing to overcome TC sufficiently to produce fairly simple, if rather rough, orthographic drawings I can use.

Also, Alibre looked no easier than TurboCAD despite its support article in MEW; though it seemed friendlier than Fusion, which I'd tried cold and without any support.

[HOWARDTParticipant @howardt]

I went from manual draughting in the 60’s to 2D CAD in the 80’s and finally 3D CAD in the 90’s. I found the best way to produce a 3D model was to start with a block and take shapes away, as you would machine a piece. In the real world I found that modelling from nothing, adding shapes together often created difficult or impossible machining.

[Anonymous]

Posted by Nicholas Wheeler 1 on 04/06/2019 18:15:21:

To use 3d CAD, you have to get past the 2d drawing first mindset.

+2

Andrew

[Anonymous]

Posted by Nigel Graham 2 on 04/06/2019 14:23:09:

Andrew Johnston:

Your point and its sample drawing didn't appear until I'd posted the above.

I wonder though, and have thought this of other contributors who swear by what I see as the long way round … did you start learning engineering-drawing with isometric-first CAD?

I'm afraid I don't understand what isometric-first CAD means? Nor do I understand why isometric drawings seem to be promiment in this thread? To me an isometric projection is a nice to have on a 2D drawing, but is by no means essential.

I'm not a professional draughtsman and am largely self-taught. As a kid I started creating 2D technical drawings at home beginning with various widths of propelling pencils and then moving on to Rotring pens (birthday present). All drawings were done on a small drawing board (another birthday present). No computers in sight; the concept of a PC didn't even exist. During my post-school training, and at university, we did some technical drawing, but all 2D and all by hand on a drawing board.

When I started working in motor racing I bought my own simple 2D CAD package that ran under DOS. Can't remember what it was called, but I rang rings around the draughtsman at work who was still using pencil and paper.

Later, when self-employed, I bought a cut down version of 2D AutoCAD. It was ok but not really anything more than an electronic drawing board. In order to design tightly packed electronics I needed something much more capable. That was when I switched to 3D CAD. I didn't really have a problem learning it, at least for the basics. I've never had a problem knowing what I want to design, but it can sometimes be an issue getting the CAD package to create the model the way I want it.

While I use isometric views on 2D drawings generated by the 3D package I don't remember ever using them when drawing by hand or with 2D packages.

I'd agree with Nicholas, using 3D CAD is natural, not a long way round. Parts are inherently 3D so it makes sense to create models in 3D and let the computer do the grunt work of creating the projections needed for a 2D drawing.

Andrew

[Jeff DaymanParticipant @jeffdayman43397]

Another + from me re forgetting about a 2D mind set when doing 3D CAD. The trick is to think "I want to create a part" rather than "where do I have to put that line to make sure I can project the next line bla bla bla….". For 3D If you want you can model a big block and carve it away with cut features just as you would machine it. Many other ways to start a model too. If you want to see 3D in action there are thousands of youtube video tutorials about getting started all the way to advanced techniques. I started on the draughting board but also trained in CAD at the same time, starting in 1981, the pioneer days of it. Very happy Solidworks user these days after many years of ProEngineer CAD.

[Nick WheelerParticipant @nickwheeler]

I struggled with TurboCAD for ages, Alibre was a breath of fresh air until they massively increased the price.

Fusion is currently free, more capable, and mostly easier to use.

One of the best things they did was to name the first thing you do to model a part a sketch. This suggests that it's just a step, not a finished item.

Then there's the top down approach to assemblies; it makes a great deal of sense to create a piston in the bore it's going to run in, than on a completely separate sheet.

As you work with the program, there are lots of useful features that save a great deal of time: using an existing part to create the matching features on an ajoining one; sectional views wherever you want them; moving parts to develop linkages etc etc

 

I had no training in this, besides watching some of the videos and reading forums

Edited By Nicholas Wheeler 1 on 04/06/2019 22:21:50

[Nigel Graham 2Participant @nigelgraham2]

I can see you find it natural to draw something in 3D because it is a 3D object, but I rarely have much difficulty seeing a 2D representation of it.

Maybe it's what we are used to, but no-one yet has really explained why necessarily-orthogonal workshop drawings have to me made from a pictorial original. Especially as the 3D relies heavily on extruded 2D figures.

Instead, they all say what they prefer, have been taught, or what the CAD publishers intend.

I see 3D CAD's advantages for very complex shapes or assemblies, for the expert; but I still do not know why it is intrinsically wrong to bypass the process.

'

For example, a simple hollow cylinder like a bearing bush.

In 2D (any method) it's two concentric circles and a rectangle.

In manual isometric it is 3 or 4 plotted ellipses and two lines.

In CAD isometric, the computer plots one of several complicated forms: umpteen-sided polygons of individual facets that result from extruding circles, stock "primitive" cylinders modified to size, a solid cylinder subtracted from another… All with specific properties and reactions to further operations; no offered clue which to select. You are assumed to understand it from the start.

By the time I've drawn it in 3D I could have drawn it in 2D and (if I'd managed to print it), made it!

'

Experts naturally find hard things easy; and assume it is easy for anyone. How and why? Why is my approach, my natural and only option, wrong?

[Nick WheelerParticipant @nickwheeler]

In 3d CAD it's two concentric circles and an extrude; quicker than it took to type that sentence. And I would have 'drawn' it in the hole it fits, using those dimensions for both the diameter and length so that any changes, that might be necessary later, cascade through all of the parts.

I don't care how the program does it, in the same way that I don't care how the graphite got in the pencil.

 

And once again, what the hell is 3d isometric?

You only have to learn a technique once. Then it becomes a massive time and effort saver.

Edited By Nicholas Wheeler 1 on 04/06/2019 22:56:12

Edited By Nicholas Wheeler 1 on 04/06/2019 22:57:43

[Kiwi BlokeParticipant @kiwibloke62605]

Anyone here got any experience of Linux CAD packages – FreeCAD for example? I've installed it, and some of the supporting literature, but it looks completely baffling (where are the nursery slopes?). FreeCAD is also available for Windoze and Muck operating systems.

[Frances IoMParticipant @francesiom58905]

Linux Magazine July 2019 carries a brief intro + tutorial to FreeCad (the 2 previous issues had been intros to OpenSCAD

Edited By Frances IoM on 04/06/2019 23:21:51

[Kiwi BlokeParticipant @kiwibloke62605]

Thanks for the info, Frances. Blimey! Linux now enables time travel? Here in backward NZ, it's only just June. I used to see Linux Magazine in the shops, but no more. We have a woefully narrow range of mags here.

[Nigel Graham 2Participant @nigelgraham2]

Nicholas:

Prices:

I looked at Alibre's web-site. No price given, but it does refer to hobby users, though no direct sales in this country. Instead it directs you to its UK agent, Mintronics.

Mintronics' site is clearly aimed at industry and does not mention cost or private-buyers. Now, the Alibre Atom 3 ad in ME, is from Mintronics; but selecting the Atom 3 name on the agents' site deleted the link. So, I was unable to ascertain the price, but now wonder if Mintronics really does sell Alibre to hobby users directly, or only via further agents, as it did with MEW? And if so, by single-cost or expensive subscription?

'

What of Fusion?

Its site originally revealed clearly, free issue to hobby and student use, with obvious protection conditions. (It had an ulterior motive of course.) Several months later, the same offer was noticeably more discreet.

So I looked again, just now: still "free" for educators and students, but the cagey text hints the licence is short-term for possibly stripped-down software.

'

Other software is turning to costly subscription models – WinZip and Adobe's pdf-converter are immediate examples – and it would not surprise me if Alibre and Fusion, if not also TurboCAD, follow suit.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Nigel Graham 2 on 04/06/2019 23:32:48:

Nicholas:

Prices:

I looked at Alibre's web-site. No price given, but it does refer to hobby users, though no direct sales in this country. Instead it directs you to its UK agent, Mintronics.

Mintronics' site is clearly aimed at industry and does not mention cost or private-buyers. Now, the Alibre Atom 3 ad in ME, is from Mintronics; but selecting the Atom 3 name on the agents' site deleted the link. So, I was unable to ascertain the price, but now wonder if Mintronics really does sell Alibre to hobby users directly, or only via further agents, as it did with MEW? And if so, by single-cost or expensive subscription?

.

Seems to be pretty clearly stated here: **LINK**

https://www.mintronics.co.uk/webshop

MichaelG.

.

[Just a disinterested Mac user]

[VersabossParticipant @versaboss]

Aah – after reading all that stuff and shaking my head in disbelief I decided to 'design' Nigel's bush in Onscape.

I have to add my comments above as I don't know how to write something below a .jpg
And the two pics are not in the correct succession…

So the second one is the result as it is shown in Onshape. The dimensions are in the (now invisible) sketches.
The first one shows the automagically generated 2D-drawing, with some embellishments added on that stage (hidden lines, cutout) The dimensions can be placed where one wants them, and their values come from the sketches!

[David JuppParticipant @davidjupp51506]

Nigel – your idea of how 3D CAD works seems to be driven by TurboCAD as far as I can tell. That is rather atypical when compared to many of the packages others have mentioned. I won't criticise TC as I know some people get on really well with it – a few other less well known packages have similarities with it

In most 3D CAD packages your bush could be produced from 2 concentric circles (or even 1) and an extrusion length. That's it, model done.

[JasonBModerator @jasonb]

Posted by Nigel Graham 2 on 04/06/2019 23:32:48:

Nicholas:

Prices:

I looked at Alibre's web-site. No price given, but it does refer to hobby users, though no direct sales in this country. Instead it directs you to its UK agent, Mintronics.

Mintronics' site is clearly aimed at industry and does not mention cost or private-buyers. Now, the Alibre Atom 3 ad in ME, is from Mintronics; but selecting the Atom 3 name on the agents' site deleted the link. So, I was unable to ascertain the price, but now wonder if Mintronics really does sell Alibre to hobby users directly, or only via further agents, as it did with MEW? And if so, by single-cost or expensive subscription?

'

Easy enough to find the prices on Mintronics site, I just clicked "Atom3D, Overview" and at the bottom of the page it gives prtices click here . If you have trouble finding things like this maybe it is just a problem with you and computers not getting on. Prices for the more expensive versions are there too.

Edited By JasonB on 05/06/2019 07:06:14

[JasonBModerator @jasonb]

Nigel, another version of your "complicated" bush

I will describe the process from your 2D mindset of looking at one side and then another.

First look at the end and draw the outside circle and then the bore.

Then looking from the side you can see it has a length so simply give it that length, here I have entered 10mm

Then click OK and I have your bearing which I can move about and look at from whatever angle I want, there are tabs to click for looking square on from all six sides if you prefer that or any isometric/perspective angles.

Want a 2D drawing then just click drawing and select the part and what views I want, eg front, side and plan then click OK and I have a dimensioned drawing.

Any other part can really just be treated in the same way, first operation is a sketch in 2D of one elevation and then cut/extrude or push/pull is like adding the second elevation.

All I have done is drawn a couple of circles and entered a length, nothing complicated for me to enter, the computer may show it a elipses etc but it does the work and not me, old outdated software may show a series of facets but unless you zoom in massively up to date software will look round to the eye.

Now if I also wanted chamfered corners and say an oil hole they are easy to add, no deleting of previously drawn lines at the corners, no need to alter each of the three views as the part is altered and the computer will automatically alter the 2D drawing to show the chamfers and holes on any elevations. Could even go as far as adding a bit of colour but that is a personal choice and really more use on assemblies on the screen than for actually making the part.

 

Edited By JasonB on 05/06/2019 07:34:25

Edited By JasonB on 05/06/2019 07:38:39

[Anonymous]

Posted by Nigel Graham 2 on 04/06/2019 22:36:39:

Why is my approach, my natural and only option, wrong?

Nobody is saying your approach is wrong; whatever floats your boat. But since you say it's your only option I'm rather puzzled as to why you started a discussion on 3D CAD only to denigrate it and, by implication, those who use it.

Andrew

[Author]

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