More seriously, converting a 2D drawing to 3D isn't the point.

My tech drawing instruction is far enough in the past that I was able to go straight to 3D. the design process is almost completely different, it's much more like making a real part – you cut bits away and add bits on, although you do make reference to various XY views to check alignments and clearances (it's easy to make two parts and think they are nicely aligned and then realise they are far apart or overlapping when you turn the model! – the answer is usually just a shift in one dimension).

The exception I have found is when creating 'solids of revolution' such as a the hollow spindle below – I drew it as a 2D half-section then rotated it to get the 3d part. Simpler things like bushes are more easily made by extruding two overlapping cylinders, joining them, then subtracting a shaft through the middle.

The 'casting' part of the item below would have been hard (for me) to design in 2D and convert, and almost impossible if I had drawn it exactly as it turned out.

Neil

Hello Peter.

The steep learning curve to 3D is not as steep as you may think. I don't know what software you are using but most are pretty similar once you dig into their operation. There are dozens of similar programs; you draw a line or object to a specific length then edit the line or object size if you need to change it. Many Cad programs work this way. I use AutoCAD.

to make 3D objects you first create an outline by drawing a basic plan of the object base or face, you then extrude the shape to a specific height. creating a crude extrusion.

You can create as many extruded objects as you like, and these objects can be joined to other objects or "Subtracted" from other objects. If you think of this process as a machining process you will soon get the hang of it, Imagine you are drilling holes, (By subtracting an extruded cylinder from another block) or milling out a pocket (By subtracting a rectangular object). You may also wish to join objects think of this as welding, once joined you end up with a single part. In AutoCAD these are called Boolean operations.

You can also revolve a line around a central axis creating a stepped shaft for example. Does the shaft need cross drilling? no problem just subtract a cylinder in the right place.

There are other processes you can perform on your objects for example filleting or chamfering internal or external corners on your 3D object. Not really that different to workshop practice.

Here is a link to a few videos on solid modelling.

**LINK**

Once I started to think of solid modelling as cad machining, I found the learning curve a lot less steep.

Yes there are many commands available in a CAD package however you do not need to learn them all at once. For engineering design you only need a couple of dozen to start with, As you will see in the videos. Once you are fluent with the basics you can extend your knowledge at your own pace learning new commands as you need them.

If you have been working with the one program for the past 12 years that would be a good place to start. You already know your way around the program, a great help.

Regards
John

PS:
There is a second group of CAD programs that work a little differently. Solidworks is a well known example. These programs have parameter driven sketching. You draw a line then enter dimensions to define its properties directly. The solid model editing is really the same as above you just go about it in a slightly different way.

**LINK**

Edited By John McNamara on 22/08/2015 13:53:55

I've 'dabbled' with 3D Peter but discovered it seems to need a very different thought process to the way I normally approach a (2D) drawing. You have to really figure out (imagine) the various major 'blocks' involved and then draw, extrude and join them together. I did manage to draw some simple 3D constructions in the end but it took me a while and I wasn't too sure what I'd really gained in the process to be honest. Of course, I was on that possibly steep learning curve at the time, so it's not an entirely fair judgement. I was also using my existing CAD (TC15) which may not be the ideal tool for 3D (although others seem to have mastered 3D with it).

Most of my drawings are generally straight forward in nature and (these days) I can do them fairly quickly, at least in 2D. I do use my CAD interactively to work out some areas of a design (hole positions, clearances, alignments and such things). Perhaps with more complicated designs than mine are, 3D would be useful to check similar kinds of detail.

However, to answer your question, whist 3D seems to be very useful to some, personally I haven't found sufficient motivation to make the transition to 3D thus far. If I was using CNC (or 3D Print) this might be different of course – but I'm not – and that may be a key difference in the way folk view this particular issue.

Regards,

IanT

I tried several 2D packages and never really got on with them always returning to my trusty drawing board but a couple of years ago decided to give 3D a try and got on with that straight away (Alibre) Originally I only bought it for my hobby model engineering but now use it a lot for work as well

As David says a 3D image is a lot easier for many people without a technical background to understand and easy enough to take a few screen shots of the item viewed from different angles or better still send them an interactive pdf so they can move the item to view from different angles, zoom in etc. Its also just a couple of clicks to show the same thing with a door open or draws pulled out.

The same applies in the ME field, take a look through some of my posts or my album "sketches" many a time a 3D image or two can convey what would take ages to describe or show someone how a part should look if they can't understand the 2D drawings. I think this type of visualisation will help bring more people into the hobby who may not have studied technical drawing or engineering at school. Its also very easy to add a 3D thumbnail of the part to the 2D drawing which again can only be a help to those who have a job understanding drawings and can help with confusing from 1st or 3rd angle projection.

The ease at which a part can be altered and carried through to any assemblies etc is also very useful and would save a lot of time compared to having to redraw a perspective or isometric drawing.

As Neil hinted once you have assembled a few parts its very handy to be able to hold your mouse over the end of a crankshaft or spindle and move in a circular mation you can then watch to see if that conrod, cross head or big end clash with any other parts, can't see that easily being done with 2D

Another usful aspect is being able to overlay parts and alter their transparency. I have found this useful when making patterns, the semi transparent pattern drawing can be overlaid on the finished item to check you have enough machining allowances, shrinkage etc. Then if you want to 3D print the pattern thats only a click or two away.

Is it needed – maybe not, is it useful definately.

J

Speaking as someone who used Autocad 2D every day for 15 years, and now Solidworks 3D for the last 10 years.

If someone told me I had to go back to 2D I would just give up completely, there is no comparison, going onto 3D was like a breath of fresh air and makes my job as a designer of bespoke machinery so much easier.

You need a totally different approach to learning 3D, in fact someone who has never used 2D will probably learn 3D quicker.

Once the models are done, the drawings are just a few mouse clicks away, if any changes to the models are needed the drawings will update automatically as well.

Oh and YES, I do all my model engineering drawings with it as well, even if there is a published design I want to use, I model it in 3D to make sure it will all work out correctly, I only have myself to blame then.

Phil

Edited By Phil P on 22/08/2015 16:59:03

As David said, I can bring up a 2D from any direction, or an isometric, with a couple of clicks, or even set up permanent 'viewports' on other tabs.

I think Jason is right, if you come from a 'building' background then 3D is more intuitive, if you have a drawing background, you will naturally be more used to working in and reading 2d.

Neil

3D CAD is not necessary. It is only another tool that makes it easier and often faster to manufacture something. Most things that are done in 3D could be done with a pencil and paper. But would you prefer to use a slide rule or log tables instead of a calculator or a computer ?

I started my career on a drawing board. Production increased significantly when 2D CAD become available and then again with 3D. Learning 3D in the early days was a long learning curve and to become proficient to create drawings to a comparable standard to ones which were previously created by hand could take 2 – 3 months of training and practice. Modern software is much easier and faster to master. I started with Autocad version 9, then ProEngineer, then Solidworks.

Most 3D models are created by sketching a 2D shape (x and y direction) on a plane or surface and then extruded in the z direction to give it thickness. (eg. To create a part 100 x 200 x 20. Draw a rectangle 100 x 200 and then extrude it 20 in the z direction) With conventional CAD software, the size of the model is controlled by sketching the x,y,z lengths to scale. The size of the model is changed by modifying the sketch. The dimensions for the model are a reference of what was sketched.

Advanced 3D CAD produces Paramertic models where the size of the model is controlled by the dimensions. They are created in a similar way but the size of the model is controlled by the dimensions. eg. To change the length from 200 to 300, you click on the dimension and the model changes. Much quicker !

The 3D models are used as the reference for producing 2D drawings. Projected views, sections, details are quickly made. The models are excellent for checking the compatibility with mating parts and reduces the drawing checking time. If it fits in the model it should fit together when manufactured (if it has been modeled correctly in the first place).

I am building a model steam traction engine from a set of drawings which I purchased. But these drawings are not 100% correct and lack a lot of detail. Also the size of available material is not available and the drawings have to be modified. Therefore I have modeled the engine in 3D before I start machining. There are hundreds of parts which need changing. Much easier and cheaper to fix a problem in the computer model than in the workshop.

The 3D model allows me to check how everything goes together. The model can also be animated to show problems. I can rotate the flywheel and see the motion of the piston and connecting rods and check the position of the slide valve to see where it opens and closes thru the cycle. The drawings are linked to the model and if the model is modified, the drawings are automatically updated and therefore never out of date. 3D models also contain heaps of other information such as its volume, mass, centre of gravity and can be used for determining the stresses within the parts. 2D drawings can be used for profile cutting parts and 3D for creating casting molds and sent to 3D printers.

Paul.

Edited By Paul Lousick on 23/08/2015 01:34:22

As a professional designer and user of Solidworks (special purpose machines like Phil P? ) I have sometimes commented on here about CAD but I wonder how much use my comments are to the other readers. What I mean is; the comments I make are related to my experience of using 3D CAD which is far removed from a spot of laying out for a model engine – you might think. In reality, we all want accurate information tailored to the situation.

3D does this very well, the differences lie in how you get there using 3D. As mentioned above the approach is a little different to drawing in 2D on paper or CAD but the process is the same. You still have to have an idea as to what you want to draw and then you simply do the "fag packet" sketching on the computer instead of scraps of paper etc. The computer captures all the "sketch" data and uses it to create the solid model. What has not been mentioned – possibly as it is not available in the "cheaper" CAD systems – is that the assembled item (engine? ) will have the important features fixed (constrained) in relation to the main arrangement (Master GA) and then subordinate parts are referenced to that. This is known as "in context" in Soplidworks and allows me to make important features "propagate" through the model. This means that if I draw an engine with a 10mm crank pin and 20mm cylinder and then decide I really want 12mm crank and 20mm bore, all I do is change the master part and all the referenced "in context" details change with it. This is especially true of hole locations and such and given that the 2D drawings are linked they are always "current". This means that you will always be able to assemble the thing later (assuming you dealt with tolerances and machine errors first! ).

Whether you would want to do this or not is entirely a personal choice but I like to know that when I make something – it is going to fit/work so it is my default method of working.

Learning the system is easy (for Solidworks) as it is THE most intuitive system you will ever use but also very expensive so you might be forced to use something else. If the Autocad thing is even half as good then it should be relatively easy to learn but I will not use their products for a number of commercial reasons.

Mark

PS. Happy to elaborate if it helps, just ask!

Peter I think you have summed this up well for a lot of readers on this forum.

Basically there are two groups that run together and can be sub divided various combinations, – roughly

One group is age and the other is professional and non professional.

Now take the two extremes, young and professional. These take to 3D like a duck to waters, they have the time, mental agility and more so the effort to achieve knowing that this will make life easier for them in the future.

Now take the opposite end, wrinkly and non professional. Now if they have any CAD experience it will be 2D and probably on old programs that in even the modern 2D world are hard to work. Throw in they do not have the time to learn a very advanced program and take it real slow, in both learning and time applied.

The result is that when they go back to where they had left off they have forgotten how it works and then because it won't do what you want, then it leads to frustration.

There is no easy way out, time has to be applied but they probably wont allocate that time or resent it for what is basically a hobby but a hobby this is making things as opposed to drawing things.

So is it necessary for the hobby? No it is not necessary but neither is a DRO on the mill. However if you can afford a DRO on the mill and this is not just the price of the DRO which is equal to a 3D program, but you have to take into account fitting it and learning to use it which is equal to learning to use 3D CAD although it takes longer.

So if you now have the DRO, you won't go back but if you could have 3D CAD for the same outlay of time you would do it and not go back either.

The stumbling block is the steep learning curve and the time needed to learn it and lets be honest here, as you get older time gets shorter as does the ability to learn things fast.

Edited By John Stevenson on 23/08/2015 21:34:47

John, Peter, I suspect that the amount you pay for the software also plays a big role – you aren't likely to be using Solidworks anytime soon if you only have a few hundred quid to spend, i don't know about the Fusion 360 thing. In the case of Solidworks, using it is very very simple as long as you don't want to do fancy stuff like surface generation or complex curves (helical gears…. ). You pick where you want your sketch to go and everything else tends to follow intuitively. It will flash up the lines pallet and you select pen tool, you then click the start point (akin to putting your pen on the paper) and start to draw. It will initially draw a straight line from the starting point but will automatically make it horizontal or vertical as long as you are close, if you want curves from then on you just move the mouse in a curved direction from the last point and it will generate a tangent curve accordingly. when you move near any intersections (ends, midpoints etc) it will snap to them and close the sketch. The whole idea is to leave you thinking about what you are drawing without messing about looking for commands and buttons. Once you are done the rest follows seamlessly. It's a shame it is so expensive as it would surprise a lot of wrinklies by how quick they could learn it, it really is the easiest way to draw and see stuff you can imagine. Even for simple mods where there is loads of space!

Mark

I f you get profficent on 3D CAD you might actually give up making things in metal altogether.

There is a real feeling of satisfaction when you have designed and 3D modeled a Corliss valve mill engine or a traction engine, and you can turn the flywheel on the screen and watch all the valve gear working etc.

Phil