Laser Straight Edge

[rwa2004]

Does anyone have a good set-up for using a laser for a straight edge? Not looking for the level aspect that you normally see related to lasers. I am imagining something that I can set on a surface and have a traveling indicator to read. I know accuracy will be limited as the laser beam as thickness.

Here is my background - I am asked to check straightness of 9ft aluminum extrusions with a straight edge. My thought is that if I acquire a 9ft mechanical straight edge it will only be good for about 1 week before someone swings it into something. Here is the stupid part, I am not given a tolerance. (Of course, this is a government job). I ignored this requirement for a long time because a requirement without a tolerance is a garbage requirement. I figure the part needs checked with a straight edge and match with +/- 3 ft (I get to pick my own tolerance, right?). However, I think my govt. inspectors are going to tell me I can't ignore it and I have to check with a straight edge even if I do not scrap any parts as a result. For this and a handful of things around the shop, I thought it would be nice to have a laser block and reader block set up and ready to use to set things straight. I have used laser levels, but they do necessarily have a specific beam-to-base height and are made to be adjusted to the level and not to the base. I am curios if there is a laser/reader combination set for the straight edge use I am looking for.

 

[redlee]

Get some 2lb monofilament fishing line tie some weights on each end put .005 shims on each end and you would be surprised how accurate it can be.

 

[Conrad Hoffman]

And, you can even calculate the sag over distance.

 

[CalG]

E920 - Geometric measurement

Laser based system used to carry out all the most common geometric measurements; straightness, flatness, squareness, plumb and level.

easylaser.com

for more ideas, type "LASER surface flatness" in any browser. Like I did

There are even some home brew setups that use video camers

 

[gbent]

Can you orient the part so the checked deviation is in the vertical distance? Lots of laser recievers will display deviation. Mine reads to .050, I have no idea how much better resolution is available.

 

[amaranth]

I used a construction laser with a handheld indicator to mark the height of siding around the house I built. It was accurate to +/- 1/16 of an inch over 300 ft. The indicator will tell you how far off dead center the beam is.

I can thing of easier ways since you don't have a specified tolerance. Get a couple of 10ft 2" x 3/4 pieces of oak, glue them up so the grain is opposed and run it through a planer. With reasonable care you can get something straight to within 1/16" or so. I did something similar when I needed a 10 foot straightedge to align some woodworking machinery.

 

[John Garner]

Hamar Laser is the first name that comes to mind, but WAY overkill for what you seem to need. Pinpoint Laser would be my second thought, but still overkill.

Let me suggest that you look at Pinpoint's website, and browse through their videos and whitepapers. They should give you a better idea of what you're trying to do.

Having done that, I think you'll see wisdom in Redlee's suggestion.

 

[EPAIII]

This is actually a good idea. And if the fishing line saga, remember that the aluminum extrusion is also going to sag, probably a lot more.

The best bet would be to stand them up vertically next to a ladder. That way they should not sag.

If you really want to go with a laser, then I would suggest a laser gun sight. It will have a non-zero beam width but it will be fairly small. Then a shoe to drag along the extrusion with an optical beam splitter (a prism) that sends the light from the laser two ways at a right angle to the laser beam and into two photocells. When the light is equal in both photocells, then the beam splitter is centered on the laser beam. Of course the laser gun sight and the shoe with the beam splitter will both need some adjustments to get things set up correctly. And some circuitry. But you can probably submit a request for quotes. Or use some other official procurement process.

Edmond Optics would be one place that could likely provide such custom equipment. Or perhaps suggest a better idea.

Optics Manufacturer & Supplier | Imaging Lens & Laser Optics Manufacturer | Edmund Optics

Edmund Optics (EO) has been a leading producer of optics, imaging, and laser optics for 80 years. Discover the latest optical and imaging technology.

www.edmundoptics.com

Get some 2lb monofilament fishing line tie some weights on each end put .005 shims on each end and you would be surprised how accurate it can be.

 

[EPAIII]

By the way, in the wonderful world of machining the words "straight edge" has a different meaning than in a hardware store or in Walmart. And a nine foot one will be difficult to find and very, very expensive. Probably a special order item.

Details

www.starrett.com

That one is only 72" long. I couldn't find any longer ones. But it will give you an idea of what a machinist means by "straight edge".

 

[dgfoster]

Without getting into non-disclosure details, what is the general use of the item involved? That would imply a "Reasonable" tolerance for such use. Knowing that, better suggestions can be made.

For instance, in the metrology world, there are various off-the-shelf LVDT levels and optical systems that can reliably check to a few tenths over ten feet. So, it would not be that difficult to qualify and appropriate beam, weldment, casting, extrusion as having adequate straightness to serve as a reference straight edge. And using such equipment, that stright edge could be periodically recalibrated.

Denis

 

[jaguar36]

Grab a laser pointer and a tape measure. Write up a fancy inspection procedure, give it an offical cover page and document number, and make an inspection form.

 

[rwa2004]

By the way, in the wonderful world of machining the words "straight edge" has a different meaning than in a hardware store or in Walmart. And a nine foot one will be difficult to find and very, very expensive. Probably a special order item.

Details

www.starrett.com

That one is only 72" long. I couldn't find any longer ones. But it will give you an idea of what a machinist means by "straight edge".

Yes - this was my thoughts exactly. I am afraid they are going to look the part we are machining and say "where is your straight edge" and expect a real machinists straight edge. And then they would turn around and expect us to use it with no tolerance requirements.