Machsupport Forum
General CNC Chat => Show"N"Tell ( What you have made with your CNC machine.) => Topic started by: RICH on April 27, 2010, 11:05:13 PM
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Here something which i made which is different than the norm. Namely a custom collimator, base, and a trivet stand for intruments.
This is a custom colllimator base which allows you to rotate or adjust about the axis, tilt front to back,
tilt about the vertical , and position side to side. Fun thing to level amd have all the targets line up!
Three targets are provided internaly in the colimator such that they appear at 15 feet , 100 feet and basicaly infinity.
Thus a far target distance is provided even when another instrument is located very close to the collimator. Putting the targets into
the collimator was a real pain in the ask to do!
The level on the right can be leveled repeatably to within 1 arc second. The white bodied object on the end of the level is an optical
micrometer which provides measurement to 0.0001". I made the trivet base for mounting of variuos intruments.
When the 100 foot distance taget is viewed ( sorry for the poor picture) you will see the divided scale. The spacing divisions on the scale
are 0.0012" from line to line.
So Tan = .0012" / 1200"=.000012 for an angle of .000687 degrees =2.5 arc seconds
RICH
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Great work Rich.
How did you make the targets please ?.
Tweakie.
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Tweakie,
You can't make those targets as they are glass. They were puchased.
RICH
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Nice looking work there, Rich :)
Dave
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Nice work Rich! And like you say, somewhat unusual.
What do you use the collimator for? Just curious.
Daniel
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The collimator provides you a target at close range. So I can focus a theodolite / surveying instrument at say 100 feet or infinity and check calibration even though the distance between them is only a few inches.
There are actualy three targets in the collimator, one is just a cross hair , the other two have different cross hair scales.
So i can calibrate the micrometer head on the level, or check the adjustments say to bubble movement. That level pictured is extremely accurate.
Resolving to 3 arc seconds, and the level / bubble is maginified and split imaged / coincidence and can be repeatably to 1/20 of an arc second and set to 1 arc sec.
To put it into perspective, say you have a machinst level with a sensitivity of .0005" per foot or roughly 10 arc sec's, well at 100 feet you could be
+- .060" in accuracy ( of course you would need a true reference ) , were as the level will be 10 times more accurate and is it's owne reference.
I leveled out a guys 60 foot long mill bed as he was having difficulty trying to do it. Actualy i spent 12 hours doing it as data was taken along the bed over a time peroid. The concrete was found to be expanding and contracting due to temp changes ( from day to night time). The bed was profiled
and compared to the varient over hours used, and changes as the 10 ton head moved over the bed was noted. Then all the data was resoved to how the leveling should be done and set to the best tolerance that could be had. So he was able to then face a 6' x 6' x 4" thick Al plates to within .003" before grinding was done. But your intruments need to be spot on and known to be accurate.
Just one of the devices used in quickly checking them.
There are more accurate ways ( autoreflection ) but i made the collimator for kicks.
RICH
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Wow! A 60ft. long mill, that's some serious piece of machine! 12 hours for aligning this monster looks like no time ;)
Thanks for the details. Though I am still not sure I understand how you use the collimator to benefit its behaviour :D
Daniel
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OH, and I thought it was a scope for your pistol . ;D
Ed