Multi-part assembly drawing

[Nick WheelerParticipant @nickwheeler]

Posted by Nigel Graham 2 on 08/05/2021 10:06:49:

Thank you for your offer Nicholas.

I would find them very helpful – which the on-line "Help" manual is not, to any great extent. Though I managed to create from a copy of its contents pages, a proper, alphabetical, printable index via 'Word' and 'Excel' .)

I think I already have IMSI's guides, or at least links to them, but as you say they do demand already knowing CAD principles – and it's ;lacking that which is my biggest stumbling block.

However I found two primers on the TEE Publishing list. D.A.G. Brown's is fairly old and looks dated by its cover photo of a 1990s-style computer, but still helpful in introducing 2D drawing. The other, by Neill Hughes, is modern and concentrates much more on 3D rendering – though not on how to spell "metre" – but of course neither can cover specific makes of any CAD package and they admit that. Brown probably used AutoCAD; Hughes' examples might be in Fusion, Alibre, SolidWorks – he lists quite a number of CAD publishers.

I like Hemingway's approach with their kits (that's how I recognised your T&C Grinder!), and I saw the same at work. The assembly drawings are in 3D but the parts drawings are orthographic, some with small renderings in the corners to help you visualise them.

My problem with all software manuals is that they're written by people who know how to use the software, and for whom just having the picture on the screen/ability to send files/whatever is their end result. You and I want that representation for practical purposes(although I think our personal requirements show the difference between your technical training and my pick it up as I go along experiences), to send a well formatted 1000page document to someone on the other side of the world who needs it, or to have an entire CD and photo collection on a memory stick to be used in all devices that are available to us.

I have both books you mentioned, and the WPS one is typical of any 22year old computer book – it's so dated to be almost useless, unlike the similar ones on technical drawing or gears that were largely fixed subjects when they were written. If you don't have Hughes book, then I would suggest it is exactly the primer(good description) you need to illustrate the principles you're struggling with. The fork jig and pedal crank are particularly good.

If I'm honest the engine was an academic exercise as I don't have the patience for all the repeated parts, the skills to make tiny fuel injectors or facilities to cast the block, head, manifold and throttle bodies. It uses defined parameter, lots of joints and other techniques to prove to myself that I now have a reasonable grasp of how to use the program. To get to that stage, I've been modelling every part I've made recently. Often that was after finishing them.

I lack the artistic abilities to create worthwhile renders. And I have better uses for spending time proving that again. All of these pictures are straight from the design space, with materials defined to better represent the parts. Fusion suggests that the engine will weigh 3.3Kg….

The grinder is a different matter, as I have a real use for such a thing. You noticed the table is heavily influenced by the Worden, and the grinding head follows common practice. It's in a third iteration that I will build at some point soon. The previous attempts were far bigger(it has to live on a top shelf), chunkier, more complex and had various conflicts that are now worked out. I couldn't have done any of that without the 3D CAD. It's also intended to be very easy to make; the table and tilting mechanism are ideal candidates for laser cutting especially as I would have to buy the material, and the slide rails are standard parts. An evenings simple work(a number of tapped holes along parallel lines is pretty simple, right?) would have that assembly working. The spindle from the WPS book is the only tricky part, and that's only because it needs to be made well. The belt guard is to be 3D printed as it produces a better part in less time than I could make in sheetmetal. Embossing my name into it is a whimsical touch that wouldn't be feasible any other way. I won't be buying any of the kits, because if I spent that sort of money I would expect to take it out of the box, plug it in and start using it.

[Nigel Graham 2Participant @nigelgraham2]

Tom –

I hit the same snag earlier this evening. My first attempt to fit a drawing to an A4 sheet shrank the promised Viewport to playing-card size despite my care with all the settings. I don't know how I did it, but my next attempt approached the quoted 1:1 scale, though still undersize . At least the numbers on the dimensions are as intended – I have know them reflect the shrunken copy.

Essentially I cannot make the system do as I set in those umpteen printing menus.

'

Nicholas –

I like your grinder design. Your comment about price made me look up Hemingway's present price for the 'Worden' kit, and while I agree nearly £400 is not cheap (the motor alone would be a sizeable part of the cost) I don't think you'd find a comparable machine made commercially for that price. There is or was one, resembling a model lunar lander, available for just sharpening vertical-milling cutters, but costing some £800+. I have recently completed the 'Worde,' but I can't recall what I paid, having bought the kit some 4 or 5 years ago now.  

Oh, you know what you mean about manuals etc. being written by people who think we all know the software as well as they do. Indeed, I would say the same about a lot of the software itself I have encountered, at work, from official bodies and in my hobbies. Some of it is downright obstructive.

'

I do have both of those books. I think I bought them together, from the TEE Publishing stand at Alexandra Palace a couple of years or so ago now. (2 or 3 BC…)

I would not dismiss DAG Brown's book out of hand. 3D CAD was probably unavailable when he wrote it, at least for amateur users; but CAD generally has advanced by developing new concepts and functions, not by replacing its basics. I have found it very useful – e.g. it helped me understand a little bit about Layers.

Brown wrote his book as a model-engineer for model-engineers when CAD was just becoming available to us; but since he subsequently designed a range of fine-scale model fittings, no doubt now uses up-to-date 2D and 3D software. Incidentally, the packaging of my copy of TurboCAD is decorated with 3D-drawn images of a bogie and manifold for a miniature steam-locomotive.

Neill Hughes' book leaps that two score years gap by showing what is possible now; but I regard his as complementary to the earlier, not replacement.

Yet I found Hughes more disheartening than encouraging. I have the book front of me now, and though I am allowing for the author using a very different "make" of CAD (and annoying spellings), he still plunges into the deep end in some areas. He seemed to have written for those embarking on a formal apprenticeship or further-education course with a heavy emphasis on CAD/CAM design and production.

Hughes makes the interesting point that orthographic drawing is still very important even at professional levels.

Edited By Nigel Graham 2 on 09/05/2021 23:33:09

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