Alibre - A First Attempt

Jason -

I understand that, but could not make the Constrain tool work fully (the most it did was align things on invisible axes), and failed to make Flip, flip anything at all.

As far as I can see I was using the "book" way, which seems either

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Case 1;

Bating faces looking in the same direction, outwards:

1) Rotate the images so both faces, on anchored part A and adding part B, are visible. Highlight these faces.

2) Open Constraint, select the A face then the B face as the tool's entry values.

3) Flip B by the double-arrow sign, so its contact face is now towards that on A.

4) Select 'Apply' and B should move onto A......

OR, Case 2

Both parts the right way round; only A face visible (image rotated if necessary, by a different isometric view).

1) Highlight the A surface.

2) Open Constraint, add that face to its entry form.

3) Rotate the image to show Part B's mating face.

4) Highlight that, add it to the Constraints form.

5) Select 'Apply'.

- and in either case, Apply makes B move onto A.

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Shouldn't it? If I have that right, what stops it working?

I can't see any other way. Escher would have had great fun exploiting 3D CAD's propensity to create very strange effects by the slightest operator-error, but that doesn't help us put a simple engineering project together.

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A further complication is shown by that scribing-block's clamp, pin and thumb-wheel. They need meet so the correct faces meet without combining the parts, and the holes and pin are all co-axial. So two constraints simultaneously, surely: 'co-incident' and 'co-axial'.

Assembling the scribing-block's thumb-wheel to the pin placed it centrally, inside the clamp and apparently part of it unless I managed to Undo it immediately. This centering works on something axially symmetrical like John's car wheel and tyre; but here we need an unsymmetrical result.

I tried to correct the misplaced thumb-wheel by dragging, by something I saw on the tool-bar, and called "Component Move" (I think), and by Undo. All failed but I was probably using "move" for the wrong purpose. This was where I closed the file to clear the mistakes, and re-opened it.

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Some of Alibre's moves are not at all easy, and certainly not intuitive. As with a lot of advanced programmes, if you go wrong you obtain digitally-legal but totally wrong results, no change to the displayed data but an error-message comprehensible only to its programmer; or nothing happens at all. With no clue as to why.

3D CAD would be a lot less frustrating for new users if it didn't allow you to MOVE, DRAG or ALIGN parts by wiggling them about randomly with the mouse. Then you'd have to learn to constrain/join/mate them properly using the relevant features in the parts. Like using the centre of the flat part of the thumbwheel, joined to the centre of the hole on an outside edge of the clamp - the two surfaces that on actual parts would bear on each other.

And turning off the display grid and its snaps should be the first thing to do before using the program.

Assembly of all the parts.

There is a lot more pulling about of parts, zooming in and out and flipping them about than is actually needed but done to show that although an initial constraint will set say the base hole and column co-axial they hand slide up and down and could be anywhere on the screen until the position of the end of the rod is constrained to the bottom of the base.

You will also see that when I add the screw to the block I can flip it from one side to the other and then set the hole to one side of the block it defaults to the hole ctr line so I use the offset option to set it half the hole dia away.

hen it comes to adding the thumb wheel that can be flipped but you can see it is also flipping the screw so I then fully constrain that by setting its end 5mm from the block's side.

Note Cosmetic screw threads as I used are not part of Atom but added to make it easier to see the parts being flipped about. Parts were drawn off the top of my head so may not be exactly as shown in article but have all the features needed.

Edited By JasonB on 04/05/2023 13:30:31

Constraint limits (handy for letting clamp slide, but not beyond ends of column) are also not available in Atom3D.

The assembly bit makes all the grind worth it Nigel, especially since you have credible movement

Stick at it, keep your chin in and keep swinging

One thing I do find helps both during assembly and earlier when 2D sketching is to try and click the item you don't want to move first and then the second one will move to it. That way even if the first item is not fully constrained it will generally stay put.

Fusion works the other way, think join this to that.

Now don't go and confuse things even further, Mr. Wheeler!

Finally took the plunge and had a tutorial with David Jupp today, so thank-you for that.

To see how much had sunk in I tried drawing a nut and bolt based on ones I have sitting on the kitchen window-sill, obtained for I forget what! I thought from quick measuring by rule that they are M25 but the standard size is really M24 - I am not going to worry about that here!

I set out to try to crack that Revolve Cut thing to make the top chamfers on the nut and head, helped by going right back to Jason's video. It worked, but I still found it difficult. The underside chamfers are just that, Chamfers.

I tried the threads, using values from the Zeus book that I keep by the PC, but they defeated me.

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I realised the less efficient way is to draw the nut with hole in one go. By drawing it with no hole then making a copy on its own file, one can become the bolt head and then you can turn the other into the nut, but never mind. It was a second go at the Revolve Cut tool!

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The two are separate Parts so if I feel up to trying to give them threads, I can. I forgot about aligning the two sets of planes and had a bit of a fight with that Flip tool to make the nut face the right way on the bolt, but then constrained the two together by end faces. I see the two are slightly out of angle, by the hexagons.

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I am now fairly certain that new mouse I tried was giving me gyp, but the Escape key is also a bit slow at times, needing two or three goes. David showed me the view-cube but is there a way to keep it on the screen? It seems very fussy when it will be available when going back and forth between Sketch and Model, and I couldn't determine when.

Making progress Nigel.

Apart from your progress I am also impressed with the amount of attention your post has attracted, and the help offered. I have visitors coming to stay this week, but when they have gone home I will download the trial of Atom 3D so I can assess it for myself. I must say I am looking forward to it.

Once turned on the View cube which was not available at the time of the article should come up on any new part modelling screen and stay there until turned off via the view tab. Once turned off it will not come up again on any file new or old until turned back on.

The only time you may not see it is is a dialogue box like constrain, mirror, circle pattern is opened and happens to obscure it. All you need to do is hold the right mouse key down on those boxes and drag them to somewhere else on the screen

Nigel,

To get angular alignment of nut and bolt head, one option of several is to use 'show reference geometry' for the nut - then you can use its reference planes to constrain to assembly planes.

Another option (if nut and bolt head are same AF size) is constrain 2 flats to be aligned.

If they are not the same AF size, constrain flats parallel - that is 'offset' with the 'free' option chosen.

Or set an angle between 2 flats (be that zero, or some other).

Edited By David Jupp on 05/05/2023 07:41:29

Modelling physical threads. This can be done either by cutting material away (as shown in the MEW series) or by adding material on.

The most common problem I see is that the profile sketch used for the thread is wider than or equal to the thread pitch. For the helical tools to work well, the profile width (along the helix axis) should be less than the pitch (only needs to be slightly less). If needed, rounding of thread crests can be done afterwards using a fillet.

Another common issue getting helical tools to work is if the profile sketch is not on an appropriate plane, or difficulty selecting the axis for the helix.

If a particular task eludes you - open a support ticket with Alibre (and attach your file) the team at support will be happy to help.

Thank you.

I seem to find the View Cube a bit more elusive than that. It seems to be on or off depending on which screen you are on, sketch or model, and I've not fathomed out what switches it off again.

I also spent a while this evening trying to put a thread on that bolt shank.

I tried using the instructions in the tutorial, with the dimensions adjusted, but kept failing to make the profile. This seems very hard for any sort of revolved cut, and threads just add more complexity. Often I cannot even make the Line tool draw a line.

Perhaps I'll leave threads and concentrate on more important aspects. I don't usually draw threads fully for standard fasteners anyway, though it is important to consider the sizes of nuts and bolt-heads, and room for spanners. I would rarely if ever need design a thread or a spring; but there are many possible uses for the revolved cut tool.

Nigel,

It isn't just you - view cube is disabled for me in sketch mode. I can maybe see why that could be 'by design' but I'm not certain about that. I'll check with Alibre QA.

If you are still having problems with revolve cut, for thread or anything else, send me a part file where you have failed (don't delete your attempts) and I'll take a a look.

I assumed that the view cube was unavailable in sketch mode

So you have to right-click-hold to check your aspect once things get more involved

It's one of the programs weaknesses, you ask for a surface, click sketch, and it flips and turns into a totally different aspect

It's not just you Nigel, its one of those things all users have to learn to deal with

Totally the way to go, I just bang in holes, 6mm 8mm 10mm whatever, and focus on the main job

At assembly time I line up the holes

Threads just consume CAD memory and do nothing useful

Edited By Ady1 on 06/05/2023 10:27:36

Ady - if the plane or face 'flips' when you enter 2D sketch, click the 'reset view' button on the Ribbon. That will flip the sketching plane around. Clicking it again will flip it back. If the workspace has been rolled away from 'head on' to the screen, reset view will bring it back to the head on orientation.

All faces/planes have a 'front' and 'back' so there is a default orientation for sketch mode - but that isn't always the one that is most convenient or comfortable for a particular task.

I know that bit thanks, and if you change the aspect to figure out which way round you actually are, then click reset-view it returns to the first position, which IS useful

Nigel

One of my "homework" jobs was a scale drawing of my arbour press which is a relatively simple tool

Now I use that drawing for building all my modifications and for solving any problems

no need to go scrabbling about in the workshop trying to build stuff any more, just sip a cup of tea and ponder the task in comfort while at my computer desk, then draw the idea-parts, bring them in and check for fitments and build issues. I've already been saved from a few wasted jobs/ideas.

When I go back into the workshop I know exactly what's needed (well 90% of it anyway)

The time spent learning to use Alibre now really does save you huge amounts of time and effort later on

In this example the square adapter on the nose of the ram for holding the former is too big and fouls the sheet metal being folded to 90 degrees in the die press, so that's a dead plan but Alibre meant I never had to make it to find out it was a failure

Edited By Ady1 on 06/05/2023 10:59:40

Threads - in Atom3D your only options are to model them physically, or to not bother with them. You'd have to add any note to the 2D drawing manually.

Alibre Design Pro & Expert have 'cosmetic thread' options with the Hole tool which

• maps a thread texture image (or a plain colour) onto the relevant face of the model to show it is threaded
• provides callout data for the thread in 2D drawings
• uses traditional methods to show thread in 2D drawing
• has inbuilt data for many thread types - which can be added to by the user

The Hole tool doesn't slow the display down to the extent that modelling physical threads can, and it makes downstream drawing production much simpler.

I agree that modelling physical threads is rarely actually needed - you are more likely to use the helical tools to model a spring, an oil groove in a bearing, or some sort of feed mechanism.

I thought I'd grasped just enough to try something of my own instead of just blindly following an exercise in the hope my results match it.

The cylinder covers for my steam-lorry seemed simple enough. The basic shape is a disc with a shallow recess on the outer surface, shallow register on the inside; a ring of 5 or 6 stud-holes. I can work with either when I've established quite how big the steam-passages need be.

However, it's not that simple. The cover flanges share a narrow web between the HP and LP cylinder walls. So each cover has a segment sliced off through one hole around the web's central stud.

This proved a nightmare in CAD for what should be easy manually. It took me a long while to establish how to size the two covers so the cut line is at right-angles to the block and central to the web and shared stud. I needed, but found it fairly easy, to use TurboCAD in 2D mode only, to generate and print a dimensioned outline. Key was finding a crucial radial measurement, not feasible in Alibre, certainly not at a basic level.

So I could now draw the things in Alibre.

Oh Aye? 'Oo sez?

I tried to transfer the basic drawing to Alibre as a standard CAD file, but it gave me only a 2D drawing I could save as a static Alibre ".DWG", not an active "PRT" type.

So I started a new Part, using the paper print as my reference: as I had expected needing anyway.

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The most I found I could do fully was create the outer circle.

I planted the seed circle for the bolt-holes but it obstinately refused to be sufficiently "defined" (whatever that means) so the pattern tool cannot work. I tried everything, mainly dimensions, to find what the wretched thing wants. This also created a confusing mess because I cannot stop the dimensions all lying on each other along the axis. That's when it dimensions it at all - if it doesn't it says something about a "parametric" dimension. I've no idea what that is.

Alibre is good at telling you you've done it wrong, but not how to do it right. It seems to need a lot of hidden conditions, and if your drawing does not meet them, nothing works.

I tried adding lines as construction-lines, and one anyway will become the cut-line, to give the little circle a centre location. That failed: either any drawn line starts at the origin and goes off to the right or vertically instead of crossing the base circle; or I cannot make the line tool work at all.

The Undo arrow revealed a heck of lot of failures. Sometimes I'd raise that analytical tool that shows where the faults are. That was useful to a point, unlike the manual's entry on Circular Repeats, showing how to Assemble a pretty picture of a stack of balls. (Much as I was saying by now....)

Nor does the manual help you solve all these "Undefined" problems. It assumes you can already understand everything - so you won't need the manual and your drawings always work straight away.

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In the time it took to find I could not analyse the covers' geometry in Alibre, but used an alternative approach that proved quite easy; then failed to model them in Alibre from the printed dimensions; an expert would have drawn all four, printed them off and be half-way through machining the physical parts. Before tea...

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[Signed]

Disillusioned of Dorset