Planes and Moves/Rotations in Alibre Assemblies

[Nigel Graham 2Participant @nigelgraham2]

I assume it is possible!

With several hours and false starts, I created an image vaguely resembling my engine’s two-throw crankshaft.

It has four identical webs but I had to make three separate web drawings, pointing up, left and right; because four copies from just one gave one correct pair and one handed pair! Anyway I needed one pair at right-angles to the other.

So I drew some simple extra parts to try to understand basic Assemblies. Nothing fancy – just basic, rather symbolic shapes to easy sizes.

 

Assembling:

1) Call up the crankshaft and anchor it.

2) Call up 2 copies of the Connecting Rod, 4 of the Eccentric drawn as a plain disc with a little keyway to indicate orientation*, and 4 of a rather unrealistic, one-piece Eccentric Strap+Rod.

A vertical engine so I had drawn the eccentrics and their rods in XZ, hoping it might open in the assembly drawing in the same orientation. Sometimes Parts do, but usually they open in random orientations, and stay like it.

How do you make the planes consistent between Parts and Assembly, and the Parts transfer in their drawn orientations?

Can a copy of a Part pointing one way, be rotated to point another? (I can’t make that Constraints ‘Flip’ work but it’s not necessarily always what is wanted – even if I make the Constraints work. I probably tried use it for the wrong things.)

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Eventually I managed just a single eccentric on its right part of the shaft but could not rotate it to some nominal angle of advance. I abandoned the exercise, and don’t think I saved it.

So…… :

 

Although “Help” showed I had been using the tool correctly to rotate the Part, something stops it working (the “Apply” button stays grey). The translation part of the same tool (dx, etc.) is the same: enter the values etc. and nothing happens. I don’t think I’ve ever made it work!

– Is it blocked by already-applied concentric and face constraints?

– Is it because copying a Part to an Assembly loses its original planes and axes?

– The rotation tool asks for an axis. Which axis? All the three displayed axes might be nowhere the part and hinge-line in question.

– What conditions need exist in the sketch or model for it to work?

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Clearly, I might be able to assemble an image of the crankshaft with just one connecting-rod, that on dead-centre, and for a horizontal engine, as that is how the rod’s drawing opens; but that’s all. Anything further is too hard!

I also managed a separate Assembly of connecting-rod and cross-head, although the rod was not properly centred across the width of the block. As with the exercise above, the face constraint prevented axial symmetry. Oddly, the rod also parked itself at some angle about the gudgeon-pin as if at about third-stroke. Since I’d drawn them about centre-lines I’d expected the two parts to assemble in line, as on dead-centre.

”’

*The seed rectangle for cutting the keyway took long enough, working entirely by lines and dimensions. I can’t make those constraints work for them.

 

[Ady1Participant @ady1]

The site has been very weird tonight

No captchca box so you cant get in… lol

a strange slow grey page instead of a visible thread…

Don’t be offended if no-one replies atm, it took me 4 hours to get in here

Anyway

Sometimes things won’t line up so you have to do a 3 stage lineup

Stage 1 Get your object into a better simpler position using the main planes to turn it around

stage 2 DELETE those constraints in the listing, the object will stay in position

stage 3 Do your original object constraints again

also

I often lock the main/core part of an assembly into a fixed position and jiggle the other stuff around it

assembly is a bit of a black art but it makes Alibre an exceptional package for the money and all your hard work well worth the effort

[JasonBModerator @jasonb]

I have told you about this before.

If you right click on the part you wish to orientate to the main X, Y and Z planes a drop down list appears, towards the bottom is “Show reference Geometry” Click that.

You will now see the part has its own X, Y and Z planes in brown. You can then simply use constraints to align one of the brown planes with the main green plane or if two parts are clicked you can align brown with brown. Right click the part again to get the dropdown and click the ref geometry again to hide the brown planes when done.

As for something like a conrod or eccentric they should line themselves up as you assemble more parts. The conrod will rotate around its length ways axis if you constrain the big end to a crank journal or an eccentric strap will move to line up with the eccentric even if they seem to be on the wrong plane when inserted into the assembly window.

To get them to load into th eassembly screen in th eright orientation is mostly forward thinking when you draw an item, the more you use Alibre the easier this will become. The assembly should bring the parts to the correct alignment even if they are not drawn that way, again just a case of using Alibre regularly and becoming familiar with how things work.

I have also mentioned sub-assemblies before which can simplyfy things for example assemble the strap, rod and clevis to get an assembly of the eccentric parts or the conrod, bottom half of the big end, wrist pin, etc. You can then bring that assembly into the main drawing which then needs less work in what can become a complex assembly.

[Ady1]

On Ady1 Said:

 

Sometimes things won’t line up so you have to do a 3 stage lineup

Stage 1 Get your object into a better simpler position using the main planes to turn it around

 

Or much simpler – hold down the Shift key whilst dragging cursor on the part in question, this rotates the part freely.   You only need to get it ‘closer’ to desired orientation, no need for ‘spot on’ – the assembly constraints will do that bit.

 

 

Nigel – even when things don’t turn out as you wish, SAVE the file.  We can use this to see what you’ve attempted, and as a basis to show you how to fix things.

[Nigel Graham 2]

On 18 November 2023 at 00:02 Nigel Graham 2 Said:

– The rotation tool asks for an axis. Which axis? All the three displayed axes might be nowhere the part and hinge-line in question.

Nigel, you can use any straight edge as a rotation axis for that tool.  If you have previously activated ‘show reference geometry’ for the part, you can use axes from the part.

 

[Nigel Graham 2Participant @nigelgraham2]

Thank you Gentleman.

I have summarised your replies in a ‘Word’ document to live on the Desktop alongside the Alibre starting symbol.

Regarding making up sub-assemblies, that’s what I did for the crankshaft and the connecting-rod; drawings of physical components I have made. The other bits I tried to add were quick-&-dirty representations, not very realistic and highly simplified, just for the point of the ‘Assembly’ exercise.

[Nigel Graham 2Participant @nigelgraham2]

Just had another go. Found the Reference Geometry tool as you say. Found from it you can constrain two planes to co-incide, but that’s about all.

Oh – apart from discovering that combining two planes also flips the image gracefully round or upside down. Is that natural?

The Move & Rotate tool still does nothing, so it’s clearly an advanced function not for beginners.

It’s all so untuitive, confusing and difficult.

[Ady1Participant @ady1]

Told you months ago to do it properly… or you will flap your wings about on the ground forever

To start with you draw an easily available plan that everyone can follow, there are no shortcuts

Then you do another, and another, until you can fly on your own

[David JuppParticipant @davidjupp51506]

Graham,

For the component placement tool see

https://help.alibre.com/articles/#!alibre-help-v27/assemblies-working-with-parts-in-assemblies-manipulating-a-part-or-subassembly-with-precise-placeme

I know you don’t like videos, but this one is very clear though rather old.   The user interface has been updated since this was produced, so it looks a bit different but the functionality has not changed.

Ignore all the stuff about toolbars – you don’t have those in Atom3D.

 

If you are still struggling – create a Package File from the assembly and e-mail it to me, along with a description of what you are attempting to move.

[Nigel Graham 2Participant @nigelgraham2]

David –

Thank you.

Actually you’ve managed to lose me even there. I do not know what is a “package file”. Is it the type the software itself creates for the data?

I find videos difficult because they don’t move at my slow speed and I can’t usually see what the cursor is pointing at. Even when the demonstrator does not waggle the arrow all around the screen, as some do. I can enlarge the display but even though a high-grade screen it loses definition before the words on a screen-shot are big enough to read.

…….

Ady –

That’s exactly what I am trying to do – simple exercises.

The problem is the big gap between the published .pdf tutorial, and my own, simpler exercises.

I know the published ones work if I follow them correctly, but from your analogy, you need to fly across the gap before learning to fly. And once there, it’s much more than just wing-flaps: which flaps to use how, and vitally, which and how not.

.

The published tutorials lead you A… B… C… and Hey Presto!, a wonderful 3D image of a fairly complicated assembly you could make physically. So in a fit of optimism, you invent your own examples, perhaps measuring real items or copying from a plan set; but simpler and containing nothing not in the tutorial.

So start well…. then fail completely.

Why?

Even if the main tools seem more or less clear, you don’t understand them and their requisite conditions fully, can’t understand the error messages, cannot know what stupidly simple mistake you made somewhere perhaps far back but “legal” to the computer. The official guide will not always help you: different software edition, or information too basic for inclusion. You don’t like to ask the experts (all other users) what they’d think obvious.

So, you realise you might throw together a few simple or simplified parts, possibly not very accurately; but cannot imagine being able to create 3D CAD assembly-models to any really useful level even at what the experts find easy, as shown by what they publish.

 

[David JuppParticipant @davidjupp51506]

Nigel,

Package file created from the assembly collects together all the files needed to re-build it, and saves them in a compressed archive.  You don’t have to worry about which files to send.  Just send the single AD_PKG file to me, it will include the assembly file and all the part files.

https://help.alibre.com/articles/#!alibre-help-v27/product-fundamentals-opening-and-saving-files-package-file

 

That video I linked is particularly well paced, it concentrates on the use of just the tool that you were complaining about, nothing else.  You can pause and re-start it, or just watch it multiple times until things are clear.  I hope you did actually look at the video before giving us your usual anti-video speech…

 

[Ady1Participant @ady1]

It won’t just be you that wants to do this stuff, so the benefit is for all

Pick a model engineer plan, a basic widget that moves

Imperial is fine, Alibre does that ok

I can stick the plan jpegs up in here

Alibre moves us up onto the next level once we “get it”

You’ve tried your way.

Now try ours.

[JasonBModerator @jasonb]

Nigel I’ve said it before and no doubt will have to say it again but you can adjust the speed of Youtube videos. Click the Cog shaped icon to bring up “settings” and then click “playback speed”

 

Ady1 It may be your way but not mine so “ours” is a bit dubious, I just draw the things I wanted to design from the outset.

[JasonB]

On JasonB Said:

Nigel I’ve said it before and no doubt will have to say it again but you can adjust the speed of Youtube videos. Click the Cog shaped icon to bring up “settings” and then click “playback speed”

 

Ady1 It may be your way but not mine so “ours” is a bit dubious, I just draw the things I wanted to design from the outset.

Another thing that’s not helping is making up your own exercises to teach yourself something you don’t understand. You wouldn’t expect to teach yourself  to drive a car because you understand how to ride a bike, would you?

 

For instance, why bother moving parts so that they sort of align before actually using the correct assembly tools?

[David JuppParticipant @davidjupp51506]

Nigel,

Regarding unexpected ‘flipping’ of parts when you apply a constraint…

It may help to know that mathematically at least planes have a ‘direction’ – the direction is normal to the plane, Alibre can display an arrow to show the direction.  This is ‘Show plane normals’ – accessed from System Options -> Design Viewing ->

If you constrain 2 planes, or 2 faces, or a plane and a face, they can either have their ‘directions’ pointing the same way, or opposite ways.  This is the reason for the ‘flip’ button in the assembly constraint tool – the initial application of the constraint may often be the ‘wrong’ one of the 2 possible orientations, the flip button lets you reverse it if needed.

[Nigel Graham 2Participant @nigelgraham2]

Thank you.

 

I have just viewed that video. I was using the Place tool nearly correctly but had not realised it is so bound up with all the constraints that one stops the other – or worse. Nor that you can’t type in a value but have to use the little up and down arrows. Or so it seems. That held me back for a long time and I still don’t know if one affected the other.

I have also found the Show Reference Geometry tool and how to make it fit the default planes, but it hardly helps when you draw all the Parts the right way up with Z pointing up then when you open them in Assembly, Z points downwards.

Though I found you can turn something through a right angle by constraining the appropriate planes. I think.

I’ve also sort of nearly got the hang of being able to modify an assembled part by going back to its sketch mode.

 

I have just spent nearly three very frustrating hours trying to get to grips with it. Every time I think I’ve found one thing something else goes all to pot. I think I’ve sort of worked out how to use the Placement tool but not how to stop it breaking constraints elsewhere in the model. Well, something does, and I was unable to repair the damage.

Perhaps best not touching Alibre for a few days or weeks before trying again. I still don’t believe I’ll ever be able to produce functional assembly drawings in any CAD form for real projects with it, as I had hoped when I started it all.

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Nick –

Sorry – I don’t see what you mean. I can practice Alibre Atom only by trying to draw things with it. I need find something to try. Whether an object I have made, or want to make, or copied from some drawing or other; but I do try to keep it as simple as possible.

As is obvious to you, I will never be able to draw my model steam-lorry, or even “just” its engine, completely in 3D CAD. I know that; but might manage simplified versions of some of the simpler engine components.

[David JuppParticipant @davidjupp51506]

Nigel , you CAN type values in to the fields.   If you are having problems typing into fields that is a separate issue.  Do you have Grammarly installed on the computer?  It interferes with the field entry.  There is another possible thing which interferes with field entry – it’s a bit more involved.

Are the fields flickering when you try to type in?

[David JuppParticipant @davidjupp51506]

Personally, I never bother with the precise placement tool.  Ultimately you’ll use assembly constraints anyway to fix positions of parts.  I don’t feel any benefit in using precise placement except perhaps when trying things with parts that aren’t yet finalised.  For getting things ‘a bit closer’ in order to make applying assembly constraints easier, I use the Shift key + drag combination.

[Nigel Graham 2Participant @nigelgraham2]

Sorry – I got that wrong.

I could type in the angles but the Accept (I think – it’s not open at the moment) button was off. Using the arrows instead worked.

No, I don’t have Grammarly. (I’ve not even heard of it but I did examine the programme index to make sure it’s not sneaked in!) Nor does anything flicker.

I think it’s more likely how I was using everything that was causing the problem.

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I was trying to use Precise Placement to rotate parts through an angle: eccentrics on a shaft. I’d placed them on the shaft by constraints then wanted to tweak them round a bit without pulling them off-centre.

[David JuppParticipant @davidjupp51506]

If Apply is not available, it is probably waiting for something to be defined/entered.  This could be as simple as tabbing out of the field, or maybe some other needed field hasn’t been filled in.

[Nigel Graham 2Participant @nigelgraham2]

No, it was all there but the tool would not act. I could not see what was wrong, at all. I’d told it the part and the axis and the angle, and something greyed Apply out. Using the arrows woke it up! What I don’t know if this was a direct effect or the result of something else like too many constraints.

[Nigel Graham 2Participant @nigelgraham2]

One hell of a Struggle……

Though based on my actual engine this is entirely intended as Alibre Atom practice. It is not accurate to the actual machine in all dimensions, and is considerably simplified in detail. The con-rod centres are correct but the blocky appearance of the stem is because I could not generate the rather involved real shape.

I did discover how to centre the big-ends along the pins by planes (though I’d not thought to make their extrusions mid-planar to help that); and the way to place the half-stroke small-end’s location above the centre line.

Placing the eccentrics was err… “fun”, hampered a bit by optical illusions.

I found it sometimes safer to place the multiple bits one at a time rather than as copies of one call to the library.

The eccentric-rod are standing up simply for appearance: I think plotting their real locations in Alibre would be too much for me. It would probably be easiest manually!

….

Incidentally, I made the real crankshaft from the solid.

[JasonBModerator @jasonb]

Once you have constrained the strap to the eccentric you can just plave the mouse over the strap, hold down th eleft key and position the eccentric simply by moving the mouse while still holding the button down.

You do not need to plot the rods final position, once the valve rod and it’s clevis is in place you simply constrain the hole in the end of the eccentric rod with that of the clevis and Alibre will take care of the rest keeping the rod end moving in a vertical plane while the strap moves eccentrically.

[Nigel Graham 2]

On Nigel Graham 2 Said:

No, it was all there but the tool would not act. I could not see what was wrong, at all. I’d told it the part and the axis and the angle, and something greyed Apply out. Using the arrows woke it up! What I don’t know if this was a direct effect or the result of something else like too many constraints.

As I mentioned – could be as simple as tabbing out of the field (or in this case clicking elsewhere in the dialogue to move focus from the previous field) – something has to tell it that you’ve finished entering the angle.    This is an aspect that many have trouble getting used to, and it isn’t the clearest thing in Alibre.

[Nigel Graham 2]

On Nigel Graham 2 Said:

 

I did discover how to centre the big-ends along the pins by planes (though I’d not thought to make their extrusions mid-planar to help that);

You can go back and edit the original extrusion of the part and switch it to mid-plane.  In most cases there won’t be any negative effects, but you should always ‘generate to last feature’ and check carefully that nothing else has been disrupted by the change (that might need further edits).

If there are disruptions and you feel it’s too complex to tackle, just don’t save the edited file.

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