New To CAD? No, but....

This is the TurboCAD drawing I was experimenting with trying to copy it to SolidEdge, as a jpg copy. #

I cut with the "Slice" tool - I think it's called.

The pin is yellow simply for contrast, not to indicate being of brass! It's actually one of my steam-wagon engine's crossheads, made from a raw casting pair I bought from the waifs-&-strays tray on M.J. Engineering's stand at a show. Of cast-iron, they were probably for a 7-1/4" g. locomotive originally, and a bit over-large for my engine, but since the engine is fully-enclosed I won't tell anyone if you don't!

One modification I have made, not on the drawing, is to drill a sloping oil-hole down each of the ramps flanking the piston-rod spigot, and cutting into the edge of the guide-bar channel, to scrape oil from the bar and feed it to the pin. (The engine is vertical.)

The drawn body is an extrusion, vertically in this view, with the channels and cavities made by subtracting appropriately-shaped blocks infiltrated into the main extrusion.

ordon -

I can't find any "Export" command anywhere; not in TC, not in File Explorer.

Lee -

I was rather hoping it would be "fun", or certainly rewarding, too!

A lot of my exercises to try specific tools are not of anything special at all, just simple geometrical shaped to work out how to use some command or other.

Seems a shame to have made those flywheels then broken them up. Use them as hand-wheels perhaps?

Dave -

I realised trying to draw the wagon in more than an sort of "artist's impression" would be too difficult for me, though perfectly possible for an expert user. Really, it was exercise to see how far I could take it.

TurboCAD does not use the "sketch" term and concept. Instead it allows creating 3D images from a mixture of library solid images and generating from plane figures. So I suppose it is like other CAD systems in that regard, but perhaps less streamlined.

The lines problem Pat describes applies in 2D as well as 3D. One of my first stumbling-blocks was in trying to represent a cross-section by the conventional hatching. It needs the shape to be a closed polyline to work; but as Pat describes this problem is often easily cured by trimming extended lines.

TurboCAD's 2D/3D blur may lie behind what is known to trap many beginners. It is very easy to switch between the two modes in mid-drawing, deliberately but wrongly, or accidentally by mis-selecting the command symbol. Unfortunately this can create havoc!

A .jpg is no good as that is a photo file.

Use .step, stl or igs

If you click "file" top left and then "save as" you get a drop down of about 20 file types, use one of the above to open in SE

Edited By JasonB on 10/05/2022 18:55:41

I noted the comment a few posts ago about how careful you need to be to make sure that a sketch encloses an area for extrusion to a 3D body with no gaps, and suggesting over-length lines which are trimmed back. I would suggest that this indicates someone coming from a non-3D background and who is not yet up to speed with using the 3D tools. In particular, using constraints to control things like lines meeting at a point and using dimensions to control line length rather than drawing correct length lines.

I have done some tutoring for local club members amongst others and one thing that quickly became clear is that it is probably more difficult to transition from years of 2D engineering drawing experience to 3D CAD than it is from a position of ignorance! For example (from among many) on a drawing board, a line is a line and while it might be possible to lengthen it, position and angle are fixed. On a screen, a line can have length, position and angle changed as you wish. It changes the way you approach things. I often create an object - line, circle, rectangle - of roughly the right size and in roughly the right position, but deliberately not exact. I then apply constraints and specific dimensions as required to tweak it into the right place/size. It's a mindset thing, and it's the thing that is often missing from Internet video tutorials. A quick whizz with the mouse and a "that was easy" doesn't always explain the underlying principles!

Edited By Nealeb on 10/05/2022 19:11:23

Edited By Nealeb on 10/05/2022 19:12:29

May be hidden in plain sight. Try 'Save As'. It might allow a choice of different file types, providing export by a different name.

Dave

Using simple tools like Offset and Boolean Intersection I made a Crosshead model.

MoI isn't a Parametric modeller but it's still quite nifty.

Video here, including a very basic mistake.

Martin.

Jason, Dave -

Cor! It works!

Thankyou. I know a jpg file is a photo. I made that version simply to show here.

The types you list are new to me. I've just opened TurboCAD and SE, found TC includes STL files, and tried it, using the Desktop as a convenient carrier. Though the route to doing so is not immediately obvious, I found how to open the file in SE, and save it under a modified name in what I take is SE's default type (name.asm).

All I need do now is find how to make SE work.....

One thing SE revealed is that the spigot for the piston-rod is not quite on the cross-head's axis. This is not apparent on TC's images, but it shows in SE's rendering. I hope my machining of the two real cross-heads was a bit more precise - well, nowt a bit of shim under the guide-bars won't sort out.!

Nealeb -

I know the trap you mean although not the word "constraint". TC has them, as the word appears in the "Help" index I made, but I don't use them at my level. I use its other ways to avoid the problem of lines not meeting, including snaps and "primitives". If I need draw a rectangle or other polygon I use the rectangle or polygon tool.

I may have a rather ironical advantage over your students in having never been a professional draughtsman, so although used to orthographic drawings their methods are not ingrained.

As I do not know what "Constraints" are, I have just opened TurboCAD to gain some idea from its on-line 'Help' errr, manual. The Contents said page 863, of well over 2000. So I selected Page 863 and the word does not appear on any page anywhere near it.

The book's page number is not necessarily the pdf display number. If so, any given entry could be anywhere in that mass of very scrappy information.

Also of course, the Help manual does not tell you what the terms mean, only how to control them in TurboCAD - and whether they are available in the edition you have.

That point would apply to learning any make of CAD. You need understand the concepts and terms before you can learn how to choose them appropriately and use them correctly, in the particular software you have. That background information is not at all easy to find.

Nigel,

I am following this discussion with interest, as I have some empathy.

Allow me please to offer this: **LINK**

https://www.turbocad.com/content/parametric-constraints

MichaelG.

I was also a TurboCAD user and went through a number of updates of the product. I spent quite a lot of time trying to get the 3D bit to work, carefully followed the manual to try to learn it, and eventually gave up as too difficult! I then moved to OnShape, then Fusion 360, then Solid Edge. I still use both the latter two although I have given up OnShape.

Briefly, constraints are a bit like snaps, except that because you can generally move things around and redimension them in a 3D CAD package, they are more than just a snap as they define a permanent relationship between two objects. For example, if you constrain the centre of a hole be on the midline of a component, it will stay on the midline even if you change the size of the object. It's a very powerful technique, to the extent that the mantra "don't dimension if you can use a constraint instead" is generally valid. Failure to use constraints properly is where a lot of models fall apart when you try to modify them later.

I see from MichaelG's post (arrived as I was typing this) that TurboCAD is now using the same core engine as Solid Edge and other products, so perhaps they are actually moving away from a 2D drafting package to a 3D modeling package.

But we all bring different baggage to the table and the fact that I'm more a software than mechanical engineer is probably a useful attribute!

Edited By Nealeb on 10/05/2022 22:26:27

I created 2D drawings daily for 18 years before I decided to try and learn 3D modeling.

I think "3D modeling" is a more accurate term, in lieu of "3D drafting" or similar terms.

You are no longer drafting per se, but rather created these solid models.

I have to agree that a long-term knowledge of 2D CAD is a detriment to learning 3D modeling; it was for me at least.

I had to create the graphical maps of information flow, which I posted in my other post, to clarify the differences in information flow in 2D CAD and 3D modeling (I will copy them below).

In 2D CAD, you created drawings that are isolated views.

In 3D modeling, you create individual models, and everything else emenates from those models, such as assemblies, 2D drawings, bill of material, motion studies, exploded views, etc.

I understand computer programming, and so I was simultaneously trying to figure out what the 3D program was doing from a computer program standpoint, and what equations it was using.

I found a good Solidworks tutorial book, but as mentioned by others, a tutorial video or book can be of limited usefulness when beginning to learn 3D.

The book I had stepped you through one feature at a time, and many of the features where ones that I would never use. The examples tended to be simplistic, and they did not address my specific need, which was how to model antique steam engines.

There was no guidance about how to combine the most useful and effective features together in order to efficiently make a 3D model.

When drawing in 2D, either on paper or on the computer screen, you basically lower the pencil, drag the pencil to create a line, and then raise the pencil. The end result is a 2D drawing.

My greatest difficulty is obtaining a broad overview of exactly what the 3D program was doing, and more importantly, understanding what it was that I was trying to make the program do, so that untimately I could produce a 2D drawing.

Understanding of the 3D modeling process gradually crystalized in my head over about a 1 year period, and once I understood the fundamentals of how a 3D program operates, and the various features they offer, then I could begin to figure out how to start creating steam engine models.

My first 3D models were absolute junk, but with each model there was experience gained, and I would learn a few more tricks and features.

It took me a solid year to learn 3D modeling as it applied to steam engines.

The green twin oscillator engine that I made originally started as a test to see if I really knew how to use 3D modeling. Much to my surprise, I was able to finally make quality 3D models for the green twin, and assemble them into an engine that would function virtually.

It was at that point that I said "I finally get it".

Not that I will every know every aspect of 3D modeling, but I can hold my own.

It was a triumphant point to reach, because my frustration level with trying to learn 3D was off the charts.

One tends to think that if you have mastered a 2D CAD program and used it for 18 years on a daily basis, then learning 3D modleing should be a shoe-in.  Not so !!!

I basically had too much money invested in a 3D program to let it go to waste.

It was a matter of learning Solidworks, or die trying.

Edited By PatJ on 11/05/2022 02:13:31

3D modeling is parametric-style design.

I recall asking the question "What the heck is parametric design?".

The beauty of parametric design is that a change to any 3D model automatically propogates to its related drawing(s), and thus every view (such as left, right, top, bottom, side, and isometric) in a 2D drawing automatically changes when the associated model changes in dimension.

The power of this one feature cannot be overstated.

It would be the equivalent of changing a front view in 2D CAD, and having the right, top, side, bottom, and isometric views automatically change in a corresponding fashion.

The individual 3D models that you create are the "base" of the design.

Changes to any model not only automatically reflect in the 2D drawings, but also reflect in related assemblies, bill of material, motion study, expoloded view, etc.

Parametric means that everything is linked together in a web of interrelationships.

.

Edited By PatJ on 11/05/2022 02:23:49

I have written my own tutorials with the intent to help others perhaps avoid some of the grief I experienced when learning 3D modeling.

Writing your own tutorial also forces you to reach a deep understanding of what a 3D program is doing.

If you can put it into words, you are generally forced to much better understand it yourself.

.

A word about constraints.........

I initially paid close attention to constraints, and tried to use them.

Untimately I found constraints to be very counterproductive to what I was trying to do (create 3D models for steam engines).

Constraints too often caused unintended changes in the model.

These days, I avoid constraints, and avoid them like the plague.

Without constraints, I can make changes to the model and sketches, and avoid the dreaded "3D model implosion".

I know some will howl with derision at someone not using constraints, but it is what it is, I don't use them, and I find them counterproductive.

.

Edited By PatJ on 11/05/2022 02:31:47

My first questions with 3D modeling were very fundamental and basic:

1. How do I make a 3D model?

2. How do I create a 2D drawing from that 3D model?

It took me a while just to figure this out.

.

One of the last puzzles that I figured out with 3D modeling was how to insert planes, and manipulate those planes.

Without mastering the insertion and manipulation of new planes, you will not be doing any sort of complex 3D modeling.

Again, the tutorials showed how to insert planes, but did not really explain when/where/why I should do this, or how to do this to the best advantage.

When a model is first started (in Solidworks anyway), three planes are visible (if you have plane-visibility toggeled on), which are the front, top, and right side planes.

Any of these planes can be copied and offset out some distance from its original location.

I always start my 3D model centered on the origin of the front, top and side planes.

A new plane can also be rotated, and it took me a while to master this trick.

You can create a sketch on an offset plane, and then extrude back to the rest of the model.

An example of using an offset plane is the creation of the fuel inlet on a Lunkenheimer carburetor body, as shown below.

I had to sweep the interior cut again after I added the boss, so perhaps there is a better way to do it, but you get the idea about planes.

.

Edited By PatJ on 11/05/2022 02:55:43

The video I did some time back of your cylinder "casting" is a good example of what Nealeb says about sketching a rough shape and then constraining it by setting lengths and positions which is also how I tend to work. At the start you can see I draw a basic rectangle then constrain it's size and then it's position relative to two axis/planes which makes subsequent mirroring possible.

Nigel - be careful using STL files to transfer designs between systems.

STL is not a CAD format, but was developed for 3D printing. It represents the design as many triangular facets, so it ends up being 'not quite' what was originally modelled. Some precision will be lost, and many CAD systems can't usefully edit STL.

If available STEP (or STP) , IGES, or others should give more robust results.

I can understand why printed tutorials for particular makes of CAD are rare or non-existent, but there is a paucity of even the more generic ones. I own copies of the only two I have encountered, both written for model-engineers - one at least by a model-engineer too, D.A.G. Brown, but quite some years ago.

Ah, so Constraints are not quite what they are cracked up to be? Well, I can't judge that as I've not advanced that far.

I am grateful to PatJ for explaining what Paremetric modelling is. Though again beyond my present level and probable need (advanced CAD systems are intended for industry after all), at least it avoids confusing me I can see it value when designing complicated machines or system intensively - as in industry.

I see your (Pat's) point about Planes. I suppose the TurboCAD parallel is that of placing the work-plane, by default the "floor", on any facet or section of the object being drawn; but its work-plane system can lead you into all sorts of difficulties.

David -

Thank you for that tip. I did wonder, because the TurboCAD file-type list helpfully says what the abbreviation means: in this case "Stereo Lithography". That suggests it was originally designed for map-making.

What you say about it also suggests why my cross-head became mis-aligned. I am pretty sure I had verified the item's axial alignment when I added the spigot to the body.

.

Having found a way, if not the best way, to transfer the file I spent a while just exploring SolidEdge to get some feel of how it works.

I succeeded after some experimenting, in drawing a rectangular block, drilled two holes through it then gained some idea of how the dimensions work.

I like the way they are active - controlling the object itself. Before I twigged that I was baffled by no obvious way to locate a feature across a surface.

In TC, dimensions "associated" with the object follow changes to it, but they are still otherwise passive. I think I've found how to define the dimensions themselves in SE to give datum points - after I spotted that trying to move the holes altered the size of the block itself. The holes' locations were leading the size of the "metal" around them, though I am not really clear how.

With TC's 3D in similarly symmetrical objects I glue a little sphere to the leading corner, to help me orientate myself to the object when seeing it from a different direction; and to give it a home position. (I have found the "home" control on SE, next to the view-direction control, that does much the same thing.)

My best bet if I want to make any progress with SE might be similar informal exercises, but in 2D first so simpler. My usual approach - developed with TurboCAD - is to create a couple of very simple shapes and play around with them.

It might be worth me writing notes as I go so I build up my own "operating manual".

Word of warning - transferring files between CAD packages is an advanced topic. A beginner might get lucky, but unskilled imports usually have peculiar consequences. For example, even if the correct file format is selected, and both packages understand the dialect equally well, a faulty model imported from TurboCAD will thoroughly confuse Solid Edge. Import/Export is a good way of creating problems that baffle experts.

Better to save import/export for later. Get Solid Edge working from scratch and understand the basics before attempting anything complicated. No good tackling locomotives before you can do a Cotton Reel! Same is true of learning any CAD package - they all depend on a reasonable understanding of the basics.

Dave

In order:

DAG Brown's book is hugely out of date for 2D CAD, and largely irrelevant for 3D. Referencing it is reinforcing your misunderstanding of the different requirements for 3D. Put it on a shelf where you can't see it, and won't be tempted to read it again. Mine is in numerical order with other Workshop Practice Books; I haven't opened it in ages.

As you've discovered, it's very easy to draw figures that look connected, parallel or whatever, but aren't. That doesn't matter (much) on paper, but it's deadly in CAD. Constraints are used to ensure the geometry you've drawn is and remains what you want, as their names demonstrate: perpendicular, concentric, symmetrical, parallel, colinear, coincident, mid point etc etc. They're vital, and are normally used before dimensions.

Informal exercises are important, but inventing your own will lead you down frustrating paths. Try simple parts that you already understand. A T-nut, simple split clamp then a U-bolt would be a good start for many of the processes. There are several ways of creating these, as a few minutes in front of the computer for each will prove. Some are much better than others even though the end part will be identical.

Dave,Nicholas -

Thank you for that advice.

I had assumed transferring a file from one type of software to another might lead to details like some of the formatting being lost, but I'd not realised it's much more than just the data.

Ah. I'd not known that "constraints" include those controls I'd already been using under their own names! Normally I would expect to add the dimensions afterwards, and TC certainly works that way. SE perhaps does too but in a different way, as the little menu-video I found on auto-dimensioning shows.

When I invent an exercise I do keep it as simple as possible, often not even depicting an object like a T-nut, just two or three basic shapes.

Mr. Brown's book looks out-of-date even from its cover photo - but I don't think it covers 3D at all.