Cad Programs - revisited

OK, I'll try to get this subject back on line.
Cad programs fall into two main flavors 2D and 3D.
Examples of the 2D ones are early Autocad, Turbocad, Autosketch, Draffix,
Easycad, Fastcad and plenty more like this.
Examples of 3D are later Autocad, Turbocad, Cadkey and others.
Next up the list are the modeling programs often called 3D but there is a
difference. Classic examples of this are Solidworks, Solidedge, Alibre etc.
The reason these are different is that instead of working with lines to
produce a drawing you are working with shapes to produce a model.
Any drawings needed are taken from this model. These except Alibre are all
high end programs as regards cost.
Going back to basics here and addressing 2D only as a starting point.
Many books will explain how to start off drawing but they all assume no one
has ever drawn before and start off teaching the relative method of
That's where you start off from a given point, usually 0,0 and draw using a
series of relative points something like X0,Y2 will draw a vertical line 2
unit tall, X2,Y2 will then draw a horizontal line 2 units to the right etc
What no book I have read takes into account is that a lot of us have had
years of experience on drawing boards and we are used to CONSTRUCTION
lines, shades of 6H rubbings etc.
The obvious conversion for such people as this is to set a layer up called
construction and use that layer in the same way.
Swapping later on to the main or outline layer one can draw in the true
shape and either delete or preferably just hide the construction layer.
A classic method to suit these people is to set this layer up, draw one
horizontal line and one vertical line starting at the ref point of your
part, called 0,0.
From these two lines by selection a common command in CAD systems, Offset,
you can quickly and accurately off set the two lines to produce the main
parts of your drawing.
This method doesn't always suit everyone and it pays to take a little while
to try the two methods to see which suits the best.
John Stevenson
Nottingham, England.
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John Stevenson
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We still use Autocad V11 for DOS as it covers all our requirements and is still a reasonable sized programme.
Learning to draw again is not so bad if you had a good basic education in Tech Drawing to start with, and had a very good teacher. Most of what you learned comes across onto CAD, but as John says, using a programme is different to using a pencil and ruler, and I bet that few people draw the same way once they have got their short cuts organised.
The other huge advantage of CAD is the ability to store blocks of drawing parts so you just call them up from your library when required, saves hours and each one is always right (unless you made it wrong to start with!)
Autosketch used to be a good little programme, and quite cheap. A version used to be given away with graphics tablets.
-- Peter & Rita Forbes Engine pages for preservation info:
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Peter A Forbes
I must admit that I use Micro$oft's Visio (wasn't theirs when I started using it). It could barely be classed as a CAD program, but it is quite intuitive and allows me to produce 2D engineering and architectural drawings.
Mark Rand RTFM
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Mark Rand
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cheap as chips 2D cad package :)
not complex but great for those 2D scribbles :)
cheers Dalt
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