[TheForge] CAD Software

[Andrew Vida]

Hmmm... toughish question.  I would say that whatever you do, get a 
parametric system.  Not all CAD is created equal and parametrics makes 
life a whole lot easier in terms of altering existing designs.  All this 
means is that the precise form of a part is determined by the dimensions 
entered for it.  If, for example, you CAD up a gun barrel for .223, make 
it 18 inches long and decide later that you want it 24 inches instead, 
you should have to alter nothing more than the length dimension of the 
barrel in order to affect the change.  This assumes that you built the 
barrel correctly (CAD-wise speaking here) in the first place.  Too much 
to explain here, suffice to say that there are several ways any given 
construct could be put together in a CAD system.  Some ways will allow 
changes to be done easily whereas others will make the task more 
involved and some may make it very difficult or even impossible without 
starting from scratch.

Another thing you may want to look for is a macro capability.  This 
allows one to build routines that accept parameters for making similar 
parts.  For example, you may want to be able to CAD up different sorts 
of scrolls and each type in different sizes.  If you have macros defined 
for these, you should be able to change the stock size, the scroll 
dimensions such as "OD" and "ID" (just to be conversational) and how 
many times the scroll goes around.  Just plugging in new numbers is a 
whole world faster and more pleasant than having to do each one from 
scratch every time some dimension is altered.  A library of such 
routines for things like scrolls, upset corners, mortise and tenon 
joints, as well as many other common iron elements could be potentially 
very valuable to you if you smith professionally, or even design 
ironwork for a living.

Also, a good CAD system will have various constraint mechanisms 
available to the programmer.  These assure that when some parameter is 
changed that all others which are properly constrained to it will change 
as well.  For example, if you have a baby crib with stiles and rails on 
the gate that goes up and down to place junior in and out of the crib, 
and you constrain all the rails to be the same length and perpendicular 
to the stiles, then when you change the height dimension the gate, every 
element will be altered appropriately without requiring that you 
manually change every one.

As for drawing ability, one of the other advantages of a good CAD system 
is that if you are proceeding in a technically sound fashion (as per my 
point in the first paragraph) you really cannot screw anything up so 
badly that cannot be undone and retried.  As with anything else, it is a 
matter of practice and if you are diligent chances are that you will 
eventually become at least adequately adept.  Do not forget that 
practice makes for good ability.

A couple of years ago I designed a sheet metal anvil in Rhino.  AFAIK, 
and I may be wrong about this, Rhino is not a parametric system, but it 
is really good for some types of work.  It may be good for all types, 
but I just don't have enough experience in it to say whether it would be 
good for smithing design.  You might want to get in touch with Bob 
McNeel at Rhino and ask him.

No, I have not yet built the sheet metal anvil.  No money for that these 
days.  I just want something in the 700# range that I can carry around 
on my back just to make people do a double take.  Yes, I know... I am a 
severe case of arrested development.  Bruce Freeman will tell you this 
readily.

Best luck to you.

	-Andy
Kevin Gallagher wrote:
> Does anyone have recomendations/warnings about CAD software given the type 

of work blacksmiths do?  I can't draw stick men so forget a detailed 
railing or keeping anything in proportion.  thanks
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-- 

	-Andy V.

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