Anybody build Dan Gelbart angled laser centre finder?

[vtsteam]

I'm just kind of curious -- at the distances we're talking about, small spot size, and using lenses, etc., why does it have to be a laser?

Unlike an ordinary light source a laser beam is a single essentially parallel beam of light.  The light from an incandescent bulb is scattered in all directions.
 

Baron I appreciate that, but it no longer holds true once you add a filter (which scatters to some degree) and a lens (which converges light).

Also it's entirely possible to make a dot with conventional non-coherent light at a 12" focal length. Every kid knows this when he focuses a spot of sunlight with a magnifying glass on a leaf. Collimators, focusing lenses for ordinary lght -- these have been around forever. I can see the advantage of a laser's coherent beam (no lens or filter) for a long distance dot. But not for a short distance dot. At least not for this relatively crude purpose.

Also, if you want the dot smaller (or rounder) with an overly bright laser, can't you just use a pinhole?

[Arbalist]

Have another look at the video in post #1. Dan moves the laser up and down to achieve the required pattern on the workpiece. This clearly wouldn't be very practical if you had to keep refocusing. The filter I used didn't appear to scatter the light at all, that's not to say it didn't but I couldn't see it. Others are already using a pinhole to reduce the dot size and make it more round.

[PekkaNF]

Uuh...

Semiconductor laser beam from the chip is not round and even.
http://www.thorlabs.de/tutorials.cfm?tabID=38696

I'm using the laser module that has regulator, laser diode, optics and all that stuff to keep stuff simple and compact. I have no interest to mate regulator and laser diode (and for the same reason I don't want to use cheap laser pointer because they might have such a bad regulator that it fry laser if you change different size/type of batteries).

There probably would be a way of using normal HIPO LED, condencer and all that stuff, but it's not for me. Looks too involved and bulky, even though underlying principles are simple.

This laser approach has very complicated physics (and specially the laser diode regulator electronics) but it's all in a small and cheap commercial componenet.

All this talk about the lense is when laser pointer or a laser module that has no "adjustable focus" is chosen.

I have tested this unit with a prism and it seems to work also....it would bring some complication but it would also produce more compact unit as per original Dan design.

If I'll mange to get out of work early today, I'll gobble up something and borrow my daughters camera. My camera got dust on imaging sensor and it has been on shop two weeks allready.

Pekka

[Fergus OMore]

Have another look at the video in post #1. Dan moves the laser up and down to achieve the required pattern on the workpiece. This clearly wouldn't be very practical if you had to keep refocusing. The filter I used didn't appear to scatter the light at all, that's not to say it didn't but I couldn't see it. Others are already using a pinhole to reduce the dot size and make it more round.

But this is 're-inventing the wheel' or worse. I recall Peter Rawlinson writing in Model Engineer- years ago- getting there.

Again, CentreCam was there. Part of it is still on the 'net. Trethewey WAS going to have another go- but for reasons unknown, hasn't.

I was going through the video again. There is something similar to what 'we were doing in production' in the early 1950's. We'd got to screw threads and spinning the threads- and they were not only sealing against liquids but air- and could vent.  It was long before lasers! We used, if my memory is lasting out- a hacksaw, a file  and an old M&W  0-1" Mike to test.

I'm simply left wondering.

Cheers

Norman

[Arbalist]

It's just a centre finder Norman.

It's something most of us can make for a few pounds or dollars though rather than the $125+ that the commercial ones cost. If the commercial ones were a bit smaller and cost £20 I'd probably already be using one.

[PekkaNF]

Oranges and apples.

Optical centering microscope is fiddly to make and fiddly to use ocassionally. And requires removal of the drill/mill whatever tool you have. And takes up a lot of space in the spindle. Ok. if you like cranking the knee on the knee mill or aligning round column mill.

Centre cam et all. USB-cameras are whole lot worse...laptop, program all that. Maybe a cup of tea on the keyboard to go? Only benefit to optical one is that USB camera is shorter. Both suffer from illumination etc. Also USB camera has limited resolution, "dot" size is not that great. Like if the resolution is 650 "dots" and FOV is 6,5 mm, then it's only on 0,1 mm/dot and "optical" resolution is twice that no matter how big screen you have. Then all initial aligment and accuracy is not much better than 0,5 mm. I call it poor overall system efficiency.

Sticky needle or mechanical cetrefinder is whole lot usefull and faster here, probably whole lot more accurate too.

Now, this rotated laser gizmo does not need removal of the drill/mill and is a small complete unit that is simply clamped/clipped over spindle end. Not much knee/quill movement is needed. Because of the principle it centers also round and odd size objects.

When utmost accuracy is needed, "coordinated" drilling is way to go, displaces the marking out too and probably carefull use of old fashion centre finders.

That's my take on it. I just want to see how useful it is before jumping on conclusions. There is so much misinformation that sometimes you just need to DIY some experimentation....

How easy/fast it is? If it beats eyeballing, it's good for me.
Do you need any preparation? I don't like lugging PC or spray paint. is the glare real problem.
Is 5mW laer too bright? Night/day?
Etc...many things can be calculated, some guestimated, but best/fastes is to try.

Pekka

[vtsteam]

Have another look at the video in post #1. Dan moves the laser up and down to achieve the required pattern on the workpiece. This clearly wouldn't be very practical if you had to keep refocusing. The filter I used didn't appear to scatter the light at all, that's not to say it didn't but I couldn't see it. Others are already using a pinhole to reduce the dot size and make it more round.

Sorry to ask so many  questions, but my aim is to simplify, if I can, what you're trying to do.

Wouldn't a lens with laser light require re-focusing as much as a lens with ordinary light?

A CD laser lens would seem to have an extremely short focal length. Has it been tried over the distance needed by a spot of this type?

Why use a lens at all instead of a pinhole with a laser, if this is already commonly done?

For US based experimenters, one source of inexpensive optics is Surplus Shed.

[Fergus OMore]

It's just a centre finder Norman.

It's something most of us can make for a few pounds or dollars though rather than the $125+ that the commercial ones cost. If the commercial ones were a bit smaller and cost £20 I'd probably already be using one.

Oddly, I made one from a couple of bits of rod and a spring and it is surprisingly accurate because it - multiplies the error.

Not new- and someone made something from modelling clay( plasticene) and a sticky pin. Now 'sticky pins' have to be bought in bulk but you can eat winkles with them. Again, I buy cigarette papers. Don't smoke but they work. I share them with my wife's addition to saxophones.

I'm real high tech.
I have a set of mikes and clock gauges in tenths and Jo blocks and a book on Statistical Control and a 'guessing stick' somewhere.
Cheers

Norman

[PekkaNF]

Have another look at the video in post #1. Dan moves the laser up and down to achieve the required pattern on the workpiece. This clearly wouldn't be very practical if you had to keep refocusing. The filter I used didn't appear to scatter the light at all, that's not to say it didn't but I couldn't see it. Others are already using a pinhole to reduce the dot size and make it more round.

Sorry to ask so many  questions, but my aim is to simplify, if I can, what you're trying to do.

Wouldn't a lens with laser light require re-focusing as much as a lens with ordinary light?

A CD laser lens would seem to have an extremely short focal length. Has it been tried over the distance needed by a spot of this type?

Why use a lens at all instead of a pinhole with a laser, if this is already commonly done?

For US based experimenters, one source of inexpensive optics is Surplus Shed.

Laser optics is a bit involved, simple pinhole must be very big to remove just "dirt" on really nasty cheap laser pointer or so.

Small "pinhole" to clean up the "dot" is called spatial filter:
http://www.edmundoptics.com/technical-resources-center/lasers/understanding-spatial-filters/

Here it what happens if you use only pinhole to clean laser dot, lowest picture please:
http://laser.physics.sunysb.edu/~wise/wise11/spring2001/reports/PortJefferson/pjpage2.html

Therefore I much prefer laser module that has all the necessary parts and design to produce clean enough beam of light. In principle well colimated laser beam does not require much "focusing". The unit I have shows clear need for focusing between 5,0m and 0,5m. I should take a picture to make this clear.

I'm not too worried about exact dot shape or size, because it is spun on inclined axis, I'm pretty sure this is not very important aspect on real life situation.

First order of business is to find out if the widely recommended 5mW laser module is too powerful, produces too much glare etc. I would be happy to get away with whole lesser power and danger to vision. Put the proof of pudding is in eating.

I have one really nasty laser "module" that was removed from this kind of device, different color and probably cheaper too:
http://www.quarton.com.tw/laser_level_laser_chalk_laser_chalk.html

I dug out the "module" and light is spraying out of it in every and each direction. Beam on the back is about as strong than beam forward, beam is really fuzzy, even more than laser pointer. It has no good optics and beam size about dime in 5 metres. I tought I could use it because the module is really small, it has battery box for two AAA and a small switch. Seemed fine, but the beam let me down.

Pekka

[vtsteam]

Well it seems to have run far afield of something simple and inexpensive, like just attaching a $10 laser pointer to a mill spindle and you're good to go.

Not that there's anything wrong with getting deep into specalized laser optics to make something useful as a project -- that sounds interesting to read about, but not really the same thing.

Cigarette paper works simply and inexpensively for edge finding, and wigglers. etc as Norman said. But the point here was to try to achieve what seemed to be promised by a simple laser pointer. So a laser finder is the premise of the thread.

So far, it doesn't seem simple or easy....... unless someone can come up with a specific off-the shelf pointer that is suitable.

btw, re papers, wiggler etc. This type of finder (if it worked) would be able to find edges, locatons, and centers quickly, with a single tool, and would not require changing anything in the collet of the mill. So it's different than other tools which do some of those jobs mechanically.

[BaronJ]

Hi Guys,

This one seems to be very similar to mine.  All the same specifications.

<http://www.quarton.com.tw/laser_pen_infiniter_ap.html>

[Arbalist]

Well it seems to have run far afield of something simple and inexpensive.

This is what Pekka's bought, I'd hardly call that expensive.

http://www.ebay.com/itm/121212852782?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

And it should be a simple job to mount it.

It may need the addition of something like a ND filter but these are inexpensive as well and hardly difficult to fit.

I'm in agreement with Pekka, it may or may not prove to be an effective device but it certainly need not require a great investment in either time or money to give it a try. I'm encouraged enough by Dan's video to want to at least spend a little time on it.

[vtsteam]

Sorry arbalist, I missed that one. If itworks, that would be great. I found Pekka's post and sounds like he already has a small spot size with a filter.

[RobWilson]

Just a thought here lads , what about using a laser that mounts to an air gun scope  ?


Rob

[PekkaNF]

I did not got any garage time today, not that much progress today.

I got battery holder for two AA and a small swich. I rigged two different lasers to try it out.

5mW cross hair unit is much more nice to eye on white wall. Pretty natural, because the light is streched whole much further. This laser module was about same price. It would be usefull on some ocasions, specially considering the price. Clearly not as nice line quality as 100€ complete brand units. They have selfleveling and all that stuff.

5mW focusable "dot" unit is whole lot more involved, dot is very much more obivious and definately I would not like to stare into that beam. It's funny how much bigger and glaring the same dot appears on white surface - compared to a miniature dot agains black matte surface.

This cheap "focusable" laser is not ideal, but it could be good enough. Hope I'll have chance of rigging it on arbor tomorrow or latest thurstday.

Pekka

[PekkaNF]

Little progerss today, I got a tad over 1 hour of garagetime and that was time well spent.

I made a POC (E.G. quick and dirty) test.

I desided to use plastic cable gland to insulate laser from metal, I read somewhere that some lasermodules have one polarity on body. Also rubber grommet holds the laser pretty well.

Body was made from sheet metal, I tested 20 degree and 10 degree angle. Easy to change angle and fast to make.

I used plastic batteryholder, lashed with wire.

5mW laser was way too bright with ambient light. Glare/diffration was disturbing.

I would prefer very much smaller and dimmer point. Has anybody tried 1mW and/or green laser?

Right now it looks very usefull on round/slatend surface and round hole/boss, but not that usefull on flat surface and scribed mark. Pretty sure weaker beam would help. I don'ät know ti what degree.

What do you think?

Pekka

[RobWilson]

The results look just like that of the video Pekka 



Rob

[PekkaNF]

I just made a test rig. mechanically it's still all wrong, my only goal was to test 5mW red laser. Very tempted to order lower power module, but it would be nice to find unit with smaller beam diameter.

baby steps

Pekka

[vtsteam]

Make the holder solid instead of sheet metal? Machine vibration may transmit to the sheet, and that might be causing a thcker line than you'd get with a more solid mount.

[Arbalist]

looks pretty good to me, just need to reduce the brightness.

[PekkaNF]

It is actually pretty stable, least at 200-600 rpm, much smaller rpm is a bit more problem, because eye does not "make" the dot track continuous. I first put the drawbolt only on finger tight and because this unit is not balanced it would shake it loose and I could see it it on the laser beam. Hmm...wonder how small dynamic runout (imbalance) it could show........ It might make better dynamic balancer fixture

I'm just trying prove here the concept and figure out what it is for me.

My first attempt is flawed, because I want to dispense with the arbor. It should be mounted over the bottom part of the spindle or such to allow drill/mill bit to coexist. It also has sharp edges and design is dangerous. I was thinking of using a holes saw to make a disc out of plywood and drill few holes to different angles to mount the laser. But it would have been slower to make.

But sheet metal is easy to fabricate, easy to bend to try out different angles and such.

Now I have to try it out with whole lot more ambient light to proved myself will that simple askew mounted 5mW laser work for me or not. Lucily this 5 mW laser is probably way under nominal value, but it's not the problem here.

If it doesn't then I have to look for 1mW unit or start thinking of attenuating it with ND filter or polarizing filter. If I choose filter approach, then I'm very tempted to fold the optical axis with prism or two. This would have a whole lot more involved structure with mounting the prisms and other optics, but it would be easier whole lot more versatile.

I took the collimating lens of the laser and the exit beam from the laser diode was really really wide and oval. Collimating lens has really big impact on dot quality. Not sure how deep I would like to get on this one.

Pekka

[rotorhead]

Hi Lads,

I have to admit to agreeing with Rob and the Sheriff of Nottingham, telescopic gauges, wobblers and a coax indicator are all I've needed, mind you I don't make owt needing tooooo much accuracy...

[appletree]

I am about to undertake the building of one, I bought one of those ones like chronos sell made by SDA manufacturing. I wanted it to use as an edge finder but the dot was to big, I bought a polariser (spelling?) which made the dot dimmer/smaller. For the current project I bought a 5mw red focusable laser the dot is a bit big/bright I tried the SDA polariser to v good affect, to that end i have ordered a phone repair sheet polarising sheet from that well known auction house, sheet is about 80mm x 55mm. 

[Arbalist]

The Laser I ordered arrived yesterday so I've just tried it out to see what sort of image it produces.
First shot shows the setup with Laser about 150mm from the bench and powered by a single CR2032 button cell. The unit itself looks very similar to the one Pekka bought. I paid £5.20 for it. You can get them cheaper but this one came from a UK supplier so arrived in only a couple of days and the vendor checks all units before sending them out.



When first powered up the unit produced a short "line", after rotating the lens you can get it to produce the oval shown in the two pictures below. Without the lens it produces a very dispersed rectangle shape with a bulge in the middle. I thought all lasers produced a beam but this one doesn't without a the lens, the light is spread about a lot!

This is the focused "dot", which stays pretty much the same shape over a distance of perhaps 150-200mm so quite useful but clearly too bright.



This is the same setting but with a ND10 filter (very dark) held in front of the lens. Too weak for practical use but it clearly shows how small the "dot" is without any flare. It may be possible to make it smaller/more round over a short distance.



The lens is in a threaded plastic mount which is not very tight in the barrel, as a result when you tighten the metal cap to lock it in place it rotates the lens altering the focus point! There is a spring behind the lens but it doesn't stop it rotating. I expect that some type of loctite will hold the lens in place so perhaps it's not too much of an issue?

Not sure whether to make a mount for this or try another type of laser first. The other type I've seen are only available from China so it could mean a 3-4 week wait. In the meantime I've ordered a cheap ND4 filter to see if that yields a useful output.

[vtsteam]

If using an elliptical dot, you could arrange the minor diameter of the dot parallel to the axis of the fixture to minimize the line width when spinning.

I was thinking that maybe two lenses at 90 degrees would make a round dot, but then realized the above would take care of the line thickness problem as well.

In use, these things are always spinning to get a target, right? You don't stop them to find a scratched mark after finding the right quill height to minimize spot size. Or do you? Because if the first is true, then a round spot isn't necessary. The second would maybe benefit a little from a round spot.  Just askin....