Warning, Modern Methods in Use

When the subject of CAD, CAM, CNC and 3D printing come up there is often the comment of "what use is it in the home shop" maybe this post will give you an idea of how all these new technologies can come together to produce a model.

Don't worry they will mostly be machined on manual equipment

From etching to finished part

May not be for everyone but shows what uses these things can actually be put to.

J

I am an amateur machinist and consider the use of a CAD software a great tool for making models.

The old, imperial (inch) drawings which I received for a traction engine have to be re-drawn to suit metric steel sizes. This could be done by hand drawing (~0.2mm accuracy) and calculating the dimensions with a calculator

or use CAD (0.00000001 mm accuracy). More accurate.

3D CAD models allows me to completely build my model on the computer before I make it in the workshop which is much quicker than re-making mistakes on a lathe and mill and far cheaper,

Paul.

Plus it's extra nights inside to do your hobby without having the ration book stamped.

Good article but made me wonder why they didn't 3D print the patterns.

Word processors have replaced the typewriter.

CAD has replaced the draughtsman's easel.

Neither of these have replaced the value of a pencil and paper for getting you thoughts down or sketching out an idea.

But I must admit I'm itching to get a 3D printer, and if someone can start offering an affordable "casting from your STL file service" I'll be in the queue (and I bet the foundry will be in China!).

Neil

I use a calculator to transpose imperial to metric and visa versa to four decimal places imperial and three places metric, nothing in the home workshop needs to more accurate than that. I don't understand where the 0.2mm accuracy by using a calculator comes from, perhaps a new one is required.

Hi Mick,

The scaled accuracy of drawings made by hand is only as good as you can draw a line and 0.2mm is about as accurate as I can measure by eye. Measuring the overall length of something with a rule is only as accurate as the drawing. Therefore to get an accurate overall length of multiple parts you have to use a calculator to add up all of the length of all parts. (this is how we did it in the old days on a drawing board before computers. And used slide rules before calculators).

With CAD you can draw something which had hundreds of parts and measure the overall length to 0.00000001.

Many of the old drawings of machines which we model are drawn in inches. CAD can draw these using inches and display duel dimensions in mm without the use of a calculator to convert the inch measurements

CAD is only a tool that makes it easier to draw.

Paul.

Wrong end of stick grasped on this occasion, but scaling from drawings (sometimes unavoidable) is a practice not to be encouraged. There should always be enough information on an engineering drawing to allow the machinist to produce the component drawn. The only time its acceptable to scale a drawing is to ascertain dimensions that are for features in fresh air, such as the profiles of castings. In my experience any un-dimensioned detail on any imperial drawing, should scale to a preferred fractional size and therefore easy to convert to metric. As you might have deduced I don't have a CAD system.

My initial reaction was, "No CAD is Computer Aided Design not Drawing", but then I remembered that "to draw" in French is "dessiner" so perhaps there is not much difference.

I do find, however, that 3D CAD definately helps the design process. I still prefer 2D CAD (DraftSight) for quick sketches.

Russell.

I thought CAD was Clown Assisted Doodling ?

Mick, My comments about CAD where in response to the original question about "what use is it in the home workshop".

CAD is just another tool that can be used in manufacture. It is not necessary to make anything, just assists to make it easier. Similarly, we do not have to have a digital readout on a milling machine. Just makes machining easier. We can produce models just as good by using the standard vernier scales.

I have been producing drawings all of my working life. Firstly on a drawing board, then on computer and use CAD because I have it available. There are good, free packages on the internet and it is worth the effort to learn to use one. Saves a lot of mistakes in the workshop.

Paul.

Without modern methods I would not contemplate some of the projects I do, don't get me wrong, I could make most of the parts on manual machinery, in fact I used to do just that, I simply would have run out of time before anything got finished, for me CNC and Cad modelling etc just increase production, additionally it adds another set of skills and allows for more consistency in parts manufacture, be they for a bike or my 9F........

Technology holds no fear for me, I've faced down far greater demons.......

The equipment available has always and continues to be a limiting factor whether hand drawing or CAD, its only the tolerances which have decreased(?) to a point where they are almost irrelevant.

I've just checked my Pentel drawing pencils, these were in common use at the board even in the 70s and 80s. The smallest I can find is 0.3mm PS523.

The Rotring pens seem to go down to 0.2mm, when unblocked.

That being said all the drawings I have and do see clearly state 'Work to dimensions only. Do not scale from drawing' or something along the same lines.

Jerry

With modern methods I would not be able dothe tasks involved or compete in a global market which I do alright out of and don't need to advertise.

Understand modern stuff has its advantages namely batch production which is no use what so ever in small batch or one offs.

In fact just gone through process of having a part made that I can do manually in 86 mins. CNC 5 axis at 100 off a time come in £3.50 each dearer with a greatly simplified drawing to follow which would save me 8 mins. Reason for cnc palm out is I don't want to put all my eggs in one basket and do myself.

I have no problem doing one offs in fact prefer that way with above simplistic part, to me anyway. Which leads me on to what use is cnc produced hence term 'produced' for one offs and small scale production. Drawings have to be made, converted over, machines specifically setup before job starts. Its the recouperation of this that bangs the price way through the roof.

In fact some of the stuff I do will take an experienced 5 axis setter/operator a full day and a half to draw and setup. Run a full days production and end up 55% dearer than manually produced and be in debt for 12 months of sales sitting on the shelf doing nothing.

Cost outrageous for one offs on cnc seen people pay £600 for a part I couldn't charge more than £50. Time to make by cnc around 17 mins = £600 thank you very much, no better than manually produced which just about sums cnc up.
Throw large scale repetition cnc comes in to its own or where the skills cant be found to produce manually.

Edited By Jon on 18/09/2014 13:48:32

Jon,

You need to shop around a bit more.

Literally this morning I asked a local CNC firm to quote me on some thick washers. 40mm O/D, 15mm reamed bore, 7 mm wide. Bar is just EN1, stock size, only the bore matters.

I do these at present by drilling a short length from both ends, reaming and parting off at just under 8mm then surface grind to get a clean face. I reckon these cost me in labour about 70p to 75p each, no material cost

They will run the whole 3 metre bar in one go, drill with a U drill which does both the drilling and reaming in one go, part off to 7mm, minus 0.00 plus 0.02 guaranteed flat finish and good surface.

Again no material cost and they have quoted 15p each to run a whole bar which will make 330 washers. Their estimated run time is 50 minutes which equates to about £60 per hour which I think is very good for an expensive machine.

Now the break even point is 66 washers. At 66 the costs are identical, after 66 it's free stock for next time.

While reading this thread I was reminded of trying to learn to play an instrument.

A while back I tried to teach myself the Piano, I am sure a number of the members of this forum can. Well I failed. The pressure of other interests and work, and yes a lack of will, kept me away from the necessary practice. I was not a complete failure being able to play the simple tunes that were part if the beginners course book I was working from. However it was clear to me that unless I practiced a lot harder and longer I was not going to progress further.

I believe learning Computer Aided Design is like learning to play the Piano, you get out what you put in. Luckily I did persevere with CAD.

Yes a sharp pencil, rubber, ruler, square, protractor, dividers, compass and some good paper on a board is a great medium for drawing and thinking. In fact its all you need to define almost any object. Some of the greatest inventions of our time have been drawn with nothing more. Using these simple tools is the way we all start drawing, maybe along the way with a little help from a drafting machine at work, or if we were lucky we got one second hand for home. In their day they were expensive.

Of course you can not just sit down and create a masterpiece. Learning to draw properly takes time. Learning to conceptualise an idea, then design a practical representation of it that can be produced economically takes a lot longer.

Now back to CAD.

In 1988 the Macintosh computer was released, and gee was it expensive! No way could I afford one at the time. Anyway a good friend did get one and on it was a program called MacDraw, a very simple 2D CAD program. I played with it and was hooked.... Being able to edit the design and refine it was so quick. You could even make things move in a limited way using blocks? Well that is what they are called now I cant remember what Apple called them.

I never did get a Mac but a few years later did get an IBM PC AT from a place in Watford... cant remember the name. I managed to get a 5 inch floppy of a well known CAD program and started drawing. not very well and it was only 2D but it was fun. The old AT was a beginners primer, the program was simple, and very frustrating to use but the results were worth the effort.

Today's Cad programs are a lot easier to use than the one I started with. via the Net you can get help on just about any question you can type in regard to the particular program you are using, via dedicated CAD forums or from the manufacturer. There are also hundreds of eBooks on the net. and books from bookshops.

You will still have to learn the basics of your program, once learnt maybe 40 or so study hours later. you are about the point in time where you can draw simpler projects, This is the point where I got frustrated with the Piano, but not CAD. It is also a point where using a Pencil and Paper for simple work will be just as quick. I think this is why many people stop using CAD around this level or sooner.

If you watch a great Piano player you can see that the persons hands have become one with the music and the brain. The process of playing has become secondary to the music. Design with a Pencil or CAD is a similar situation They are both output devices putting your thoughts and ideas on paper. You probably don't think much about the pencil you should not think much about the CAD program you are using.

CAD however can do something that is a lot more difficult with a pencil. It can create 2D and 3D objects the can be viewed from any angle, objects that can be linked to each other forming complex mechanisms. Possible with a pencil but it is very laborious, and editing your drawing can mean redrawing it entirely. This is where CAD comes to the fore, you can redesign and redesign your project until you are satisfied with the implementation. And today you can convert your drawing into machine readable code that can be manufactured on a CNC Machine. impossible with a pencil.

Once you break through the learning level and are able to forget the drawing process, and just concentrate on the design you will find it is a wonderful tool to express your thoughts. Getting to this level can take time, a lot longer than getting to stage one but it is worth it.

Edited By John McNamara on 18/09/2014 15:58:38