Rotary Laser centre finder

"Tropic of Cancer". [?]

Where's that ? I'm not into astrology

Just over two years ago in **LINK** the idea of a slant mounted laser was discussed, ChrisS then made one and it went on show at AP on the SMEE stand. Sir John's Dambuster pictures were then posted as a "been there done it way before you" but it is not the conical beam idea but two projected lines.

Thanks John McNamara for posting the link, the video series looks very good- something interesting to watch and learn from.

Billy.

So we have to thank Sir Billy for the patent rights to this design.

Just read the linked post and to be honest I had forgotten about it [ or more to the point - not quite understood where Sir Billy was coming from ]

Must admit that my Dambusters centring device has been removed from the router and the 5v supply used to supply a decent LED and I'm back to the old fag paper method [ can't teach an old dog new tricks ! ]

However I can see a use for Sir Billys method on the mill picking up certain features, so where do I send the royalties ?

Hi Michael G

Alas placing the beam on the tropics does not help make it more accurate.

The beam strikes the ball at too steep an angle. It is confirming the beam is close (within .025 inches) but for greater accuracy you need a cone. Dan Gelbart quotes 50 micron typical accuracy. But he does not mention a cone.

The cone is the best way with a one degree or less difference to the beam. Its a bit like; actually the same as the shadows getting longer near the sunset...

There must be a geometer in this forum who can express it mathematically.

Regards
John

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Tropic of Cancer

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Thanks again, John

What I was hoping was that the circle of light would become emphatically ovoid when the ball was displaced from centre. ... But, thinking further; that would only be obvious when viewed from above.

MichaelG.

Thanks for the photo/explanation of the Mk 2 version Michael (Cox). I have a laser pointer approximately 12mm outer dia. I gues a new project is coming up.

Thor

Edited By Thor on 26/01/2014 16:10:14

Good thread, just bought me a lazer from the lanes in meadow hall. Now to make the metalwork.

Excellent concept. Some very useful links as we'll..

Bri

Nuts.

Al.

During my career as an Inst. Tech I have carried out the centering of Lasers through Optical Plumbs. I cannot tell for what reason as it was very hush hush at the time but led to the development of Phalanx. The original requirement was to establish an almost perfect vertical aiming mark, but failed as the physical structure was not stable enough. Wind pressure and thermal heat on one side etc. The measurements were done over 30m and an X/Y sensor measured the deviation. The best I could achieve was 0.15mm over 30m. The optical plumb itself was rated at 1 in 30000, that is 1mm over 30m.The resolution was so sensitive it was measuring the vibration of the element in the illumination bulb which was then changed for an LED.

In general a tube Lasers beam is too big in dia. and any development should be carried out using a diode Laser. These vary greatly in quality of beam and its shape, mainly a lozenge shape which has to be corrected by filter and a collimation system.

Please take care and do not view the Laser beam directly and if working use green goggles. Laser power is usually safe below 0.9Mw for 0.25sec. but NOT recommended. Flashing around is not nice either.

The rotating Laser is a good idea as it gives a static coherant image, the Cone or the ball are equally effective and quite common in aircraft jig setting up with SMART Laser system which is self seeking. This has a theoretical 'jig' in the PC and the measurements are put through the PC in real time and any deviations are measured for correction. All the big aircraft makers use this system and they require calibration quite often. It all has to be traceable.

Clive

Michael, I have made fibre optic light pipes and you need a method of transmitting the beam into the fibre. I did it with a glass tube and a glass window and an oil meniscus. Quite complex to set up but could measure the difference in length of a Fibre optic cable using an EDM measuring device. Used industrially for some time.

Clive

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Sorry, Mike ... I don't believe it works like this

The exit angle from a fibre optic is usually in the order of 60-70 degrees [included], so the spot will be greatly increased in size at 10mm distance.

You would need optical element[s] to collimate the light, and maybe more to focus it.

MichaelG.

With the exception of the marble base , all machining was carried out by using my single spot laser edge finder to find a datum corner to set the DRO and then all dimensions were taken directly from the DRO, not one single piece was 'marked out'.

So I think there is a lot of room for developments of this kind and it will be most interesting to see whats forthcoming.

Just spent a good piece of today watching all 18 videos from this guy - but am having to regretfully accept that I may never have a water-cutting machine of my own....much as I'd like one.

Very much enjoyed watching them all and there were quite a few ideas/hints (that hopefully) I can remember and utilise should the need arise. Never heard of "flextures" before (for instance) but I'm sure they will find a use one day...

IanT

< condensed quote >

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Lofty,

We're in agreement there !!

With a DRO [or on a decent analog machine], and one good datum point, there should little or no marking-out required ... use the Mill more like a Jig Borer.

That's what was underlying my "a very good place to start" comment when I mentioned the Ickey Ball.

MichaelG.

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P.S.

The little Stirling engine looks good ... I hope EDF-man was suitably impressed.

I do not see why you need to introduce a fibre. The discussion is about rotating a source in air to generate a cone then observing the intersection on a cylinder, cone or sphere target. We are not into precision metrology, we don't need DRO's, we are not into absolute measurements or taking gravitational levels. This is about a bloke in a shed with a poundshop pointer lining up a drill, mill or Lathe.

The sensitivity geometry is simple, the shallower the angle of illumination the higher the sensitivity. For cones and rods a Tan term gets in there so the gain increases very rapidly towards infinity around zero degrees. With a sphere the sensitivity function then includes the diameter of the sphere. Although a ball can be placed over a hole as an alignment target we might not need a ball target too often. A hole can be the target, we can set the pointer to cross the axis of rotation to produce two cones, with points touching, the lower cone can then illuminate a bore.

A point that may have escaped- pointers often have non-round beams and fuzzy edges. However because we are rotating the beam, the defects only produces a wider ring when the cone hits something. Say the beam was a small picture of David Clarke, as we rotated the beam it would then appear to be a series of rings but always rotating around the true axis of rotation. Often the spot is so bright that it appears fuzzy, TURN UP the background lighting then you will reduce your eye sensitivity and the spot will appear tighter. Always better to use pointers in the brightest illumination usable.

Billy.

PS thanks Sir John for your comments, Others got there before me.

Hi Guys,

Re the Gelbart video, been there done that. He clearly has some imagination and intelligence and is open minded to new or different ideas, unlike some of those on youtube who fall short in those departments. He does though sound, on first listening, a little too dogmatic but I shall reserve full judgement till a later date.

I can recommend the idea of one size collet usage, ie the TTS system from Tormach but I standardized on 20mm collet instead of 3/4". He could make life easier if he shortened the shanks to about 30mm anything more is a waste as the collet only grips about an inch. Not having power feed on the Z on my mill the extra shank length was a pain.

All this hole location fiddling about, set ABS to 0,0 on DRO on one corner of fixed jaw on vise, if you want a centre hole just dial in radius and hey presto dead nuts on, really simples

Having now spoken it's back to the silent order monastery for me.

chriStephens

PS Hi Billy, long time no see..

Chris,

Re: your first paragraph ... it's worth reading the biographical note that I struggled to link, earlier in this thread.

MichaelG.

Hi All

Hi Michael

You raise some interesting points:

Fibre optics have got me thinking.

And an absolute reference system using micro switches is also a good idea. I was at a factory a couple of weeks ago that made kitchens and the like. Thy had an amazing CNC router, yes I drooled.... The work was fed onto the table by a robot that pushed it against steel pins that popped up as a positive stop. then disappeared again when the vacuum took hold.

Now there is another idea. A spring loaded pin that popped up from a machined base that hid within a T slot the work could be located against that.

It is strange how discussions in this forum lead to other worlds........

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Gee I am glad they invented CAD

A couple of links on cones intersecting.

First for a brush up......
**LINK**

Then if you are a masochist....
**LINK**
**LINK**

Regards
John

Edited By John McNamara on 27/01/2014 10:48:33

Hi Guys,

Got a dispensation from the Abbot to speak again, Only watched half a dozen of Mr. Gelbart's videos so far, he gets my vote for "videos to be viewed watched" for all aspiring machinists/hobbyists. I particularly like the way he questions classic assumptions that have been trotted out as gospel, by the old guard, for generations.

My only gripe is that not all of us have the mega-bucks to throw at our interests the way he has, whether it's his or his company's. Translation, I am jealous!

chriStephens