Had Another Go

[Nigel Graham 2Participant @nigelgraham2]

Edited because I missed your previous post.

 

I think I started the drawing using XZ. When I reached the stage of making the holes through it spotted that I had no way to form the cavity.

So essentially I started again but now making the block half-thickness so I could sink half the cavity into it, place a plane on the surface and mirror the existing extrusion on it.

 

I wasn’t assembling the covers to the cylinder as I don’t have a model for that. I was trying to assemble one to its own copy by the flat faces, and I did anchor one of them. I didn’t keep the assembly drawing – it was only a CAD exercise with no practical engineering value, and was too far gone to do anything with.

I’ve not tried drawing the cylinders, though since I have changed the design from compound to simple, and it is basically a rectangular block with two big holes through it and some recesses (the ports) in the ends, I might be able to do so. I could not plot the steam-passages if they slope through the block, and I don’t know how to represent hidden details in Alibre anyway, but at least I can place their entrances so the passages and various fasteners don’t collide.

.

Just tried making a pdf copy of one drawing but I have no idea where, if anywhere, it has gone because the system offers no way to name it nor to select its directory path. It just offers two or three pdf variants and what appears to be a printing option, and no information to help you. I have never previously created any .pdf file, from any application, and really know nothing about them, or even their point.

.

Huh! No sooner posted that, then what happens? A Chinese manufacturer of industrial electronic PCBs sold in US$$, has plastered a blooming great advertisement straight across the thread itself, in the block usually taken by Amadeal. Has Mortons cynically sold it the space and prominence or is this another PRC business of little or no relevance here,  insinuating itself onto here, as they do in the site’s classified ads section? I wonder if this being a thread about CAD has attracted it?

[Nigel Graham 2Participant @nigelgraham2]

David –

I imported two copies, anchored one, and tried fitting the other to it.

While “Undo” will reverse several previous moves, it doesn’t tell me what I had done wrong to need its services.

[Mark EasingwoodParticipant @markeasingwood33578]

Nigel,

Click on pdf icon.

 

Box selected as highligted in Green.

Click OK.

 

 

Then name file in box highlighed in Green.

Click Save.

In the above example the file is saved in “Documents, Alibre_Atom, Elbow_Engine.”

(Note folders on LH side and top address bar.)

This is Windows 10, but 11 is pretty much the same.

Edit: If you haven’t already created a folder for your files, you will need to create one first, or from the above, by clicking “new folder” and then naming it.

 

[JasonBModerator @jasonb]

No need to make the part half thickness. Just like doing the solid extrude mid plane you can also do a cut extrude the same way and cut out the cavity equally each side of the central plane ( or if you choose duel then an unequal amount)

OK if you just had the two covers and one anchored you could right click them and select “show reference geometry” which brings up the three planes for each in brown and you can then constrain those planes and mate the two flat edges. Depending where you anchored the first it may only need the ref geometry of the unanchored one.

[JasonBModerator @jasonb]

As for the advert, you would not have this forum without them. Amadeal just moves around with any others in rotation

If you actually looked at the advert you would see that PCBWay are one of the companies that a lot of hobbiests use, not only for PCBs but also 3D printing in both plastics and metal. I’ve an article due to come out in MEW at some time and that will show an example of an engine crankcase printed by them, less expensive than a similar size one can be bought as a casting. They will price in other currency.

Other forums where people get on and make things feature items printed by them and other similar companies, I’ve a couple of engines that will probably have a metal printed part or two in them so watch this space.

No affiliation with PCBWay or Mortons just not a biased view and an open mind to how we may source parts for our hobby.

[David JuppParticipant @davidjupp51506]

Mark – and anyone else using Atom3D or Alibre Design.

I strongly suggest that you DO NOT use Microsoft’s Print to PDF for making PDFs from Atom/Alibre – when the models get a bit more complex it really does not work well.  It also has a badly thought out file save dialogue which makes it all too easy to overwrite the model you just spent ages on, with the PDF that you are creating.  You can lose work that you’ll never be able to recover.

Atom3D / Alibre Design includes a ‘built in PDF writer’ that avoids both the above pitfalls – it should be set as the default in System Options -> Drawings -> PDF   (use the check box for Built-in PDF Writer).

[Nigel Graham 2]

On Nigel Graham 2 Said:

While “Undo” will reverse several previous moves, it doesn’t tell me what I had done wrong to need its services.

True Nigel, I suggested it as a simple way to ‘back out’ and try something else.

Actually assembly constraints and the like offer a preview before you finally commit, so the Undo should rarely be needed.

In terms of ‘what you’ve done wrong’ – most commonly there are 2 possible ways round that an assembly constraint can be solved.  Murphy’s Law dictates that the one you didn’t want will be tried first – there is a ‘flip’ button available that allows you to reverse the application of the constraint.

If you still can’t work out what went wrong, consider saving the file anyway – then create a ‘Package’ from it to send to someone who can diagnose the issue.

[Nigel Graham 2Participant @nigelgraham2]

Thankyou – given that I know virtually nothing about .pdf files, having seen them only as e-post attachments (so I thought that their purpose) I may be safer not using them!

I can save Alibre images and drawings in .jpg format, just “photographs” I can use directly without opening Alibre itself, rather than trying to push them into a document of unfamiliar type.

 

I tried various bits of the drawing as constraints, having to Undo each step. None would work. The Constraints menu evidently didn’t have enough evidence because its type options stayed faint. Each move just threw the mobile copy randomly anywhere.

So far, most of my model steam-lorry’s CAD drawings are of parts already made, so everything else needs fit them. There are still only six exceptions of parts drawn first, of many more to go. Some can still be made from direct measurements of existing metalwork, but that informal approach is not really sensible and feasible for the engine and transmission. They need proper design drawings.

….

Jason –

PCBWay might have private customers but its own web-site suggested otherwise, that it is a large-scale company relying on trade accounts.

So do many other firms. For example, I want my model lorry’s leaf-springs heat-treating, but have found no heat-treatment company whose advertising attracts informal, one-off enquiries from private individuals. They boast about “aeronautical” customers and that “ISO9001″ racket – all very costly.  I will probably have to heat-treat them myself, difficult as they are up to 14” long.

And PCBWay is on the other side of the world – very useful. It also displays its prices in US dollars although Chinese, so introducing all sorts of trading and money difficulties. It is also common for Chinese companies to blanket the world with unsolicited advertising e-mails – I normally report those as “phishing”.

Amadeal – fine. They clearly want our custom. PCBWay? Really? Besides, I want the ads down the side or always below the discussion, not within them.

[Mark EasingwoodParticipant @markeasingwood33578]

David,

I bow to your greater knowledge of Alibre, so I have ticked the box. I was tho’ only refering to saving a PDF of an already saved drawing, not making a PDF of a model. I would use, File, Export etc to save a model, is this correct?

Wouldn’t it be better if Alibre made this setting the default option?

 

Nigel,

PDF files are very commonly used, easy to email, share and open without special software. You can save word documents, drawings, and even this page, or any other web page as a PDF.

Using the recommended route you should get this dialogue box, just check where you are saving it in the highlighted box/browse button.

 

Mark.

[JasonBModerator @jasonb]

As David has said the PDFs will be a lot better quality particularly if enlarged than a screen shot or image taken from Alibre. Even if just printing at home it will be clearer and should save you some ink/toner as the printer is not trying to do a photo but just black lines.

As I said real model engineers use PCBWay, etc not just companies. click the Euro button if Dollars are  a problem for you. What is the problem with buying from other parts of the World? They are a legit company and add our VAT on at source just like any of the other far eastern companies like Banggood, Aliexpress etc. Pay with paypal or similar and they will do the exchange rate for you. You simply drag the file onto their web page, select your options and they post it to you and you have your part in a couple of weeks. A lot easier than dealing with some UK companies.

A Few examples of other hobby users prints from them and other similar sites who will all take orders for individual items or batches if you want

[David JuppParticipant @davidjupp51506]

I tried various bits of the drawing as constraints, having to Undo each step. None would work. The Constraints menu evidently didn’t have enough evidence because its type options stayed faint. Each move just threw the mobile copy randomly anywhere.

 

The Assembly constraint tool highlights only those constraints which are mathematically viable for the entities selected by the user.  You have to select 2 entities to have any constraint types highlighted – this only means they are mathematically plausible – it doesn’t mean they are what you want, and at that stage there is no validity check as to conflict with existing constraints.

If the options remain feint, then you haven’t selected 2 valid entities to constrain OR there is some other issue.

As to the ‘random movements’ – I suspect that’s usual, as per below.  After fixing one cylinder cover completely, I’ve chosen 2 flat faces to make coincident – note that the initial preview has both faces pointing in the same direction (not what I want).

 

So I use the Flip button – that only solves the condition, anything else about orientation is left random.

So I have to apply another constraint to get the cover facing the right way again….  but again it assumes the opposite of what I want, so have to Flip again

And after flipping – add yet another constraint to do the final alignment

 

 

[Nigel Graham 2Participant @nigelgraham2]

Well, I tried it..

and tried it…

and tried it…..

With your instructions open (though it’s a bit awkward switching back and forth between Alibre and the forum).

This was the nearest I reached: no nearer but basically round and round in circles with one “over-constrained” error after another no matter what I do. As I said, I find this Assembly system very hard, probably the most difficult area of Alibre, where it should be fairly straightforwards.

[David JuppParticipant @davidjupp51506]

Nigel,  that’s nearly there.  If you save a package file from that assembly, e-mail it to me.  I’ll check out the conflicting constraints, and can advise on next steps.

[Nigel Graham 2Participant @nigelgraham2]

Nearly? I feel like one of those caterpillars in the Lewis Carroll story – probably part of one of the two Alice novels – who are nearly at the sundial but circling it without ever reaching it.

I’ll try as you suggest…

Well, I did try, in this Forum’s message page, but could not see how to attach any file.

 

(The simile was deliberate. Prof. Carroll’s day work including developing the weird mathematical abstractions called Matrices, which are totally incomprehensible to me.)

[JasonBModerator @jasonb]

Here you go, three constraints is all it needs, I tried to do it slowly for you.

[David JuppParticipant @davidjupp51506]

Nigel – you have my e-mail address at Mintronics.  Send the file there.

[Nigel Graham 2]

On Nigel Graham 2 Said:

…
The simile was deliberate. Prof. Carroll’s day work including developing the weird mathematical abstractions called Matrices, which are totally incomprehensible to me.

I share Nigel’s pain.   I struggled so badly with matrices at school that it altered my career.  Abandoned science and any form of engineering that demanded higher mathematics.   Partly my fault – being young and foolish I assumed that anything that didn’t come easily wasn’t worth the effort: I didn’t know then that I was capable of hard work!   Partly the way maths was taught – advanced stuff was presented with no obvious application, and seeing no value in it, I turned off.   No-one ever said, “Patience Young Grasshopper! At this stage of your learning journey, we’re teaching basic rules, not applications.  What this stuff is for comes later. Meanwhile, shut up and learn the rules. ”

Forty years later, matrices returned.  The application was computer graphics.  Everyone on the forum benefits from matrices, more so if CAD or Photoshop is used.   Not necessary for users to understand matrices, but a software engineer might have too.

There are 13 graphical transformations and the maths for all of them can be expressed by plugging values into a 3 x 3 matrix.   When an XY coordinate in a 2×1 matrix is multiplied by 3 x 3 matrix the transformation is a new 2×1 matrix.  The transforms are:

3D transforms are done the same way with 4×4 matrices.

The plug-in simplification provided by matrices is handy, but there are more advantages.  Due to a hardware quirk, turns out matrix maths is faster than applying the underlying formula sequentially as one would do manually.  Also, matrix maths can be supported directly in hardware.  A Graphical Processing Unit, present in all modern computers, sets up the display in a matrix, does any maths necessary in parallel on the millions of numbers representing pixels and colours before writing the result to the display.

The matrix capabilities of a GPU are available for other purposes, not easily, but hey!  Good because there are plenty of other applications speeded by matrices:  laminar flow, FEA, cryptography etc.  Thankfully rarely necessary for me to understand matrices cos I struggle.  But once in blue moon matrix maths is exactly the right tool!

Dave

 

[Andy StopfordParticipant @andystopford50521]

A non-obvious implication of the fact that all the objects in a 3D computer graphics scene can have any of the transform matrices listed by Dave applied to them, is that points (defined as a one-dimensional object at co-ordinates x, y, z) can be scaled.

Huh? How can they be scaled, they don’t have a size to scale?

Indeed, but if other 2 or 3 dimensional objects are set to be children of the point, they will inherit its transforms, including scaling – this is, for example, useful in CGI animation where you have to set up a sort of skeleton to control a character’s movements with many hierarchies of elements in the skeleton.

Completely irrelevant to Nigel’s problems, I’m afraid.

The Caterpillar in Alice in Wonderland just sat on its mushroom smoking a hookah – I don’t recall anything about a sundial, a different story perhaps? It did advise Alice that one side of the mushroom would make her taller, and one side make her small – I suspect it would have been quite comfortable with scaling one-dimensional points…

[Nigel Graham 2Participant @nigelgraham2]

David –

Thank you for the offer. Just posted the file.

 

Jason –

Thank you for the demonstration, but I am not sure I followed it properly. I knew it should be easy, but the more I tried it the worse it became.

Earlier I tried drawing the crankshaft, another part already made. Not as an Assembly of course, but a single Part. I took about an hour laboriously plotting one throw. I could mirror it to make the second, necessary anyway because the outer webs are a bit thinner than their companions.

The two throws are at right-angles. I could not turn that copy through that right-angle. So I tried copying it radially but that gave a four-way mass, not four separate images. I returned it to 2-throws pointing the same way, to try to delete the copy and plot the correct replacement. Then totally lost its orientation. Knackered and disillusioned, I closed Alibre without saving the drawing.

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Dave –

LOL!

You tell us you struggled to understand matrices then go and show us Degree-level ones so we who need our Tracy Tools charts to see how many “thous” make 17/64-inch, remember our innumeracy!

Essentially what you’ve quoted means absolutely nowt to us who were only taught to add or times two boxes of innocent little numbers and the answer has a fancy name – without ever being told the fancy name’s meaning, what you have really done and why, nor any link to any other branch of Hard Sums. Let alone any real use.

Right, so we now know Matrices are now used in Finite Element Analysis (as by my work colleague), computer graphics programming and a few other specialist fields that didn’t exist in the 19C. Fields so advanced I am surprised Matrices are in the secondary-school maths syllabus, albeit in splendid isolation untouched by lowly Trigonometry and Algebra.

So I wonder what, or if, Professor Charles Dodgson thought Matrices could be used for. Or perhaps that was the point: would a 19C OxBridge type want his Pure Mathematika to be used by anyone? Except perhaps for calculating the safe speed at which a girl can fall down a rabbit burrow.

The Alice connection struck me as apt by their fantasy element, as I suppose in Carroll’s day Matrices, I think called Determinants then (one of the Fancy Names with Meanings and Uses never spoken in polite society), were pure number puzzles.

Indeed, simply arcane boxes of easy or Extremely Hard Sums, as innocent as a Victorian spinster Sunday-School teacher; a Century before mere trades like Finite Element Analysis and Computer Programming sullied them way beyond Oxford’s ancient stone Dreaming Spires and Latin-speaking Pure Academics. And yes, I have spotted the accidental but rather appropriate double meanings there….

 

All of which doesn’t help me design a model of a steam lorry introduced only a few years into the reign of Queen Victoria’s successor – but it’s just as well that doesn’t need more than fairly simple, real-world arithmetic.

Just CAD skill on a par with understanding Matrices.

[Andy Stopford]

On Andy Stopford Said:

[…] points (defined as a one-dimensional object at co-ordinates x, y, z) can be scaled.

Huh? How can they be scaled, they don’t have a size to scale?

[…]

Permit me a moment of ‘topic drift’ please, Andy … but then tag it as irrelevant

This put me in mind of the classic jibe about Angels on the head of a Pin

… which basically goes to demonstrate a lack of comprehension of the question that was pondered by Thomas Aquinas and others.

The best answer, so far as I am aware, was that Angels [being non-corporeal] occupy no space and therefore an infinite number of them could be in the same place.

.

Euclid, of course, effectively covers the matter nicely in his definition of ‘a Point’

MichaelG.

[duncan webster 1Participant @duncanwebster1]

I remember sitting through a lecture about Laplace transforms. Unfortunately the maths lecturer was not an engineer, he was a pure mathematician. At the end he turned to us (first time) and said ‘any questions’. Someone who had been listening completely stumped him by asking ‘why?’. If he had started by saying ‘this is a typical engineering problem, and this is a neat way of solving it’ I might have listened. As it is, in an engineering career lasting over 40 years, Mr Laplace has remained untransformed

[JasonBModerator @jasonb]

Back on topic, specifically the crankshaft.

You only got a “4-way mass” as you left it on the default 4. For a job like that you would want to do it by angle so again change the default from equally about the ctr of raitation to angle and enter the angle, in this case 90deg. This would give you two throws and you can then trim th elines of teh first away. However unless it is a very complex counterbalanced one then just sketch the second one.

I have  afeeling I did a video of the crank before fort you will have a look

Looking at the image you posted of your assembly attempt on the covers the “concentric” constraint is likely to be what is stopping the others working. I would right click that and delete then see how you go. But wait for david’s analysis of what is in the file

[Nigel Graham 2Participant @nigelgraham2]

I tried to use a simple rotation by angle but that just did not work. It did not give weird answers. It just did nothing. So that’s when I tried using the Copy tool.

Copy with just 2 objects gives the original and copy 180º apart. Copy with 4 objects gives 4 at right-angles as a single unit.

I’ve looked again and realised “rotation”, is one of the extrusion types so it would not work.

In fact I cannot see any method simply to rotate any object through a set angle. I can’t imagine there is no such tool, but it is very well hidden.

Entering “Rotate” in the search box says it means rotate the view.

“Revolve”? Adds or removes material.

“Angle”? No result.

These in both Sketch and Model modes. I don’t know if you can copy a sketch entity by that rectangular array tool, but surely you must be able to move and rotate it too?

Otherwise, drawing something like a multi-throw crankshaft or a set of Tee-slots needs each iteration plotting individually.

On this shaft, each web rim and root is rounded on radii from the shaft axis, so constructing the outline needs three circles, two lines, and much trimming. So even without mistakes, each web entails quite a lot of work, and there are four of them. Very inefficient and risking errors for a relatively simple entity repeated three times in the same sketch.

……

 

Laplace Transforms?

I’ve heard of ’em. At work. Someone apparently thought I could understand him telling me they were part of the signal analysis in the laboratory. Well, the electronic signal analysers did all the analysing, but I could not have understood how M. Laplace (he was French) had Transformed whatever he transformed. I tried to look them up but the computer had never heard of them, and just stared blankly back at me.

However, at least his work subsequently found real engineering uses!

I helped assemble and test sonar transducers the company designed. Sonar combines the sciences of acoustics and vibration, materials physics, underwater physics, electronics, computing and mechanical engineering, so is extremely mathematical.

Dave (SOD) misses an important point about hard work. Learning Mathematics is sheer drudgery, but hard work will not overcome physical inability to learn it. Not by disability or illness, simply individual nature, presumably physiological – the individual brain’s “wiring”.

So, naturally, physically incapable of learning Mathematics above the Trigonometrical Volcano, I could never understand Laplace Transforms, Finite Element Analysis and Matrices.

CAD is very difficult too, although not mathematical to use. So does it demand much the same physiology?

[JasonBModerator @jasonb]

Some confusion. I was referring to the “circular repeat” or pattern tool.

Here you can see I have selected the four sides of the original vertical web and do a pattern by angle of 90deg which is giving the new red outlined crank web. After this trim the black lines away so you are just left with the new ones

 

[Nigel Graham 2]

On Nigel Graham 2 Said:

…

.

Dave –

LOL!

You tell us you struggled to understand matrices then go and show us Degree-level ones so we who need our Tracy Tools charts to see how many “thous” make 17/64-inch, remember our innumeracy!

Essentially what you’ve quoted means absolutely nowt to us who were only taught to add or times two boxes of innocent little numbers

Did you not say you’d done A-Level maths at school?   I don’t believe Nigel is innumerate, I think he’s stubborn and misguided.

 

…
Indeed, simply arcane boxes of easy or Extremely Hard Sums, as innocent as a Victorian spinster Sunday-School teacher; a Century before mere trades like Finite Element Analysis and Computer Programming sullied them way beyond Oxford’s ancient stone Dreaming Spires and Latin-speaking Pure Academics. And yes, I have spotted the accidental but rather appropriate double meanings there….

 

All of which doesn’t help me design a model of a steam lorry introduced only a few years into the reign of Queen Victoria’s successor – but it’s just as well that doesn’t need more than fairly simple, real-world arithmetic.

Just CAD skill on a par with understanding Matrices.

Nigel’s choice of words suggests a bad attitude to learning.  What’s this tripe about “ancient stone Dreaming Spires”?

Whether or not Nigel understands Matrices, they’re a tool much used in science and advanced engineering.   Though not good at maths myself, I understand the enormous value and occasionally get good results by applying it.  Matrices are the right tool for solving a large class of problems.

Who is it on the forum who can’t get CAD to work?  I suggest it’s the chap who refuses to approach learning methodically, ignores advice, and, when challenged writes an amusing essay rather than change.  Unfortunately the ideas in Nigels erudite asides are irrelevant!   Is my example of matrices as applied to computer graphics keeping billions of users happy really trumped by Nigel’s imaginary university town full of puzzle solving Victorian spinsters?  No.

Before Lewis Carroll, the mathematician George Boole formally defined binary maths, for which at the time there were no practical applications.  Unlike Nigel, Boole persisted, and Boole was right because our world is built on Boolean Algebra.  We are digital.

Maths is vital to engineering, and shouldn’t be rubbished by those who don’t want to understand it!

Back on topic, my plan today is to explore Jason’s layout idea in SolidEdge.  Won’t do any harm, but, because Alibre and SE are different, it may be that what works well in Alibre isn’t needed in SE.   Worth a try though because “tricks of the trade” improve perfect tools.  If Jason’s method adds advantage, I’ll pinch it, even though I hate change!

Dave

 

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