From: tan@lynx.msc.cornell.edu.UUCP (David Tan,Box 219 Baker Lab,54810,2720402)
Subject: Re: TECH:LASER welded frames
Originator: tan@msc2.msc.cornell.edu
Organization: Cornell-Materials-Science-Center
Date: Wed, 19 Aug 1992 18:33:13 GMT

From article <1992Aug19.171911.25500@news2.cis.umn.edu>, by Groenke <kevin@ssc.space.umn.edu>:
> My Bro and I were recently discussing the construction of bike frames. 
> He's a process engineer and some of the techniques used in his current
> project are LASER welds.  I hadn't heard of these but I'm told that they
> are stronger than TIG welds and brazing.  They also do not weaken the
> tubes by heating them up during the welding.
	   ^^^^^^^

I don't mean to cavil, but is "LASER" the same as "laser", or something
proprietary?  Welding, by the way, is welding, whether you use an acetylene
torch, a laser, or sunlight and a huge magnifying glass, and that means 
heating metal to its melting point (the whole idea behind brazing is to 
"cement" steel tubes together with metal having a much lower melting point
than steel, thereby avoiding heating, and thus weakening, the steel too
much.)  Did your bro mean that a laser can be focussed more precisely than
a flame or arc, thus possibly (with enough heat sinks) reduce the area 
subject to intense heating?  This kind of welding presumably also has to
be done under inert gas (the IG in TIG) to avoid incorporation of oxygen.

I have the (mis)fortune of using lasers regularly in my line of work, and
can assure you that they are expensive, complicated, and require quite a
bit of maintenance, especially compared to an arc or torch!  Since many 
of the finest frames are still handbuilt, the expense of a big laser (and
you'd need a big one to weld with) as well as the expertise to keep it 
running, may be too much for an individual or small framebuilder.

Moreover, unlike a torch or arc, there is a problem with reflection of the
beam.  Not all of the beam will be absorbed by the metal; this mean that 
you have an enormously powerful beam (probably in the infrared, which you
can't see), powerful enough to melt chromoly (or whatever you're using),
scattered everywhere. The stuff is dangerous, and, of course, difficult
to contain.  Presumably you can take people out of the picture
altogether, and use robots (as high-output companies like Univega do)
but that would entail massive retooling costs for uncertain benefits.
It maybe that lasers will be used for bike construction in the future,
but if so, it will (IMHO) be because of economic reasons (just like TIG-
welded steel frames), not because laser welding is a technically superior
method of construction.

Just my 0.02...:)


> 
> We wondered why nobody is LASER welding frames.  My Bro suggested that
> the equipment is too expensive and bike co.s didn't want to invest the
> $'s.  I quickly dismissed that notion knowing of the $'s that go into
> R&D.  Is it a technical problem?  Could the LASER head be too large to
> rotate within the frames triangle's, it doesn't seem likely, but what
> else could it be??  Perhaps the jig and proper alignment were the
> problems.
> 
> Has anybody heard of attempts to LASER weld frames?  What were the
> results??
> 
> Just wondering.
> ***********************************************
> Kevin J. Groenke	
> Student Lab Services Coordinator				___			o		 					_	o
> Shepherd Laboratories							_____		( 		\-						(  	\-
> University of Minnesota						___		(*) \ (*)			(*) \ (*)
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