Mike,
My understanding of laser cutting is that the surface finish deteriorates
with thickness of material. What sort of thickness of steel were you still
getting a good finish on ?
My guess the reason they only do stainless for intricate work is that it
doesn't oxidise to the same extent as normal steels. Wire wool will burn
quite happily on it's own, so I guess a similar result happens with small
components when heated too much with the laser.
For brass, there are some places that will mill very small or complex
components out of a sheet. There was a 5" guage GW 51XX 2-6-2T at a
previous Donnington exhibition with a few hundred rivets in each tank side.
At 0.5mm per hole, I can't think of another way of doing this sort of thing.
Appearently it sounded like a old machine gun when banging out the holes ;-)

Simon.

----- Original Message -----
From: Mike Williams <mikewilliams4@...>
To: <halfinchlivesteamforum@...>
Sent: Thursday, October 14, 2004 5:24 PM
Subject: RE: [Half inch live steam forum] CAD projects



Simon / David,

I'm using CAD for laser cutting in 2.5in Gauge too - but only small wagon
components. I agree with all you've said. I am impressed by the quality of
cut possible with the laser, but the limit to the size seems to be the heat
generated by the laser on small pieces which can burn or even melt
completely.

Having said that, I've just had cut some stanchions for the bolster of a
wagon in 7mm scale (14mm long) and the finish is perfection. There is a
hole for a pin which is less than half a millimetre in diameter, through
steel 1mm thick, and it is half a millimetre from the edge. The reason this
is possible is that the parts are stainless steel, and for cutting stainless
they use an argon shield around the laser which prevents the build up of
heat. Sometimes stainless is not suitable, so I asked my cutting firm
whether they can programme the machine to cut stainless, but insert mild
steel. They laughed and said it doesn't work like that, but can anyone tell
me why?

Incidentally, the firm I use is in Leighton Buzzard and charges £100 per
hour of machine time, plus the cost of the metal. I assume that's about
market rate? Of course, calculating how much time it will take to cut is
just down to experience. The stanchions mentioned about take about 6
seconds each.

One other little point is to avoid square corners if possible because the
laser has to stop, change direction, and start again. This causes a delay
(time = money) and local build-up of heat, so try to put a radius on every
corner you can, even a tiny one.

Mike Williams
www.williamsmodels.co.uk