The Shop > Tools
Anybody build Dan Gelbart angled laser centre finder?
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:
--- Quote from: Arbalist on April 13, 2015, 01:49:23 AM ---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.
--- End quote ---
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:
--- Quote from: Arbalist on April 13, 2015, 04:59:26 AM ---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.
--- End quote ---
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:
--- Quote from: vtsteam on April 13, 2015, 07:07:40 AM ---
--- Quote from: Arbalist on April 13, 2015, 01:49:23 AM ---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.
--- End quote ---
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.
--- End quote ---
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.
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