Need way to detect laser

[[email protected]]

What can I use to detect a laser that is being pointed at a point? It
can't be visual. The laser is going to be about 12 feet max from the
point to be aligned. I'm moving a large tank as I try to aligne and
thought if I put something on the closest end to laser with a small
hole this would insure the tank was aligned when the laser was pointed
at the other end.

I am trying to align the seam of 8ft diameter tanks to be welded. they
need to be inline with the travel of the welding unit that is on a
movable track.
I don'tr have the laser yet as I know nothing about this except I am
supposed to accomplish this somehow. Where do I start?
Ken

 

[Wayne]

Sounds like a good transimpedance application using a photodiode.
Perhaps a comparator if it is needed to ensure a proper trigger level.

 

[[email protected]]

I was afraid my description was confusing. I have the seam of the 8 ft
tank but also the automatic welder travel arm which is pivoting as the
tank travels eastand west to where it is aligned. As the tank travels
and the welder arm rotates there is one point where the arm travel and
the tank seam are aligned. once aligned the tank is stationary while
the rotating arm is locked down. Now the arm can move in a linear
motion while welding. But if all arn't aligned it won,t be welding the
seam and I'm in trouble. Clear as mud right?
I had thought to put laser on the rotating arm aligned with its
linear motion, something at front of tank to block laser but with a
small hole. then at rear of tank a detector. That is where I got the
point description. I'l try getting pictures and posting them.
Ken

 

[[email protected]]

I was afraid my description was confusing. I have the seam of the 8 ft
tank but also the automatic welder travel arm which is pivoting as the
tank travels eastand west to where it is aligned. As the tank travels
and the welder arm rotates there is one point where the arm travel and
the tank seam are aligned. once aligned the tank is stationary while
the rotating arm is locked down. Now the arm can move in a linear
motion while welding. But if all arn't aligned it won,t be welding the
seam and I'm in trouble. Clear as mud right?
I had thought to put laser on the rotating arm aligned with its
linear motion, something at front of tank to block laser but with a
small hole. then at rear of tank a detector. That is where I got the
point description. I'l try getting pictures and posting them.
Ken

Ken,

I can't quite visualize your setup. But, could you use a
rotating-mirror laser unit, attached to the welding unit, that would
make a line that is always in line with your welder's linear motion
plane, and then just make sure that the laser line is on the seam
before welding? The rotating-mirror laser units are commonly
available.

Or, are you trying to automate the process? If so, maybe something at
the following site might be helpful:

http://www.contrib.andrew.cmu.edu/~ttrutna/16-264/Vision_Project/

You might also want to ask in one of the "amateur telescope makers"
(aka ATM) groups. They are extremely good at using lasers to align
their telescopes' cylinders with their optics, and might come up with
some good ideas about your problem.

Good luck!

Tom Gootee

http://www.fullnet.com/u/tomg

 

[[email protected]]

I can't quite visualize your setup. But, could you use a
rotating-mirror laser unit, attached to the welding unit, that would
make a line that is always in line with your welder's linear motion
plane, and then just make sure that the laser line is on the seam
before welding? The rotating-mirror laser units are commonly
available.

Or, are you trying to automate the process? If so, maybe something at
the following site might be helpful:

WIll have to check and see what a "rotating-mirror laser unit" is.
I can't automate it with the money restricions I have. Also the
welders travel arm is going to have to be pivoted manually even if I
can get a DC motor to move the tanks which I am sure we will do once
the boss realized how his idea of moving it with a pry bar is going to
take two people and be too time consuming.
I will try and post pictures tommorrow. I know its very hard to
understand without a picture.
Ken

 

[[email protected]]

WIll have to check and see what a "rotating-mirror laser unit" is.
I can't automate it with the money restricions I have. Also the
welders travel arm is going to have to be pivoted manually even if I
can get a DC motor to move the tanks which I am sure we will do once
the boss realized how his idea of moving it with a pry bar is going to
take two people and be too time consuming.
I will try and post pictures tommorrow. I know its very hard to
understand without a picture.
Ken

The rotating-mirror laser units are basically just a small laser
(imagine one of those "laser pointer" keychain things) and a rotating
mirror. The mirror is at a 45-deg angle to the beam. Its axis of
rotation is coincident with the beam. So, it reflects the beam to be
perpendicular to its original direction. And since the mirror is
spinning, the beam sweeps continuously through a plane.

They are used as aids for all kinds of simple alignment jobs, in fields
such as construction, painting, etc. For example, if you set one up
inside a room, with the beam horizontally oriented, you'd see a line on
the walls, going all the way around the room. You could also install a
cover with whatever size opening you needed, so only a portion of the
360 degrees was covered.

At close range, even a cheap one (or a home-made one) might be "good
enough".

- Tom Gootee

http://www.fullnet.com/u/tomg

 

[[email protected]]

geocities.com/clannorm/subarc

I got some pictures which should be much better than my explanation

 

[quietguy]

Not sure if this would suit you, but if you have a number of these tanks
to weld it would be easier to build a cradle for the tank (secures the
tank side to side) and have the cradle on wheels and straddling a length
of old railway line. If the bottom of the cradle has rollers then you can
easily rotate it to put the seam under the welder arm

Little bit of work to set up, but from then on no sweat - and cheap as
chips to build

David - who likes to do things the simple way when possible

 

[James T. White]

geocities.com/clannorm/subarc

I got some pictures which should be much better than my explanation

I must be missing something. Why do you need a laser to do this? Can't
you just drop the welding head down and use it to align the welder
gantry to the tank seam?Also, isn't this pretty much a one time setup to
get the welder gantry aligned to the rollers that will support the tank
while you weld it?

 

[[email protected]]

I must be missing something. Why do you need a laser to do this? Can't
you just drop the welding head down and use it to align the welder
gantry to the tank seam?Also, isn't this pretty much a one time setup to
get the welder gantry aligned to the rollers that will support the tank
while you weld it?

I don't need a laser to do this. I thought it would be easier than
what I have now. It also takes about 10-15 minutes with one person
doing it. Its not a one time setup since we have different diameter
tanks and have to move the rollers for each size. Also the seams aren't
perfectly square so they vary one to the next even on the same
diameter. I did three today and they all varied. Hopefully with a
laser I can get it done in a minute.
Ken