hello...ive been in the machinist / fabrication / industrial maintenance / automation fields since 1995. i have no formal college degrees, all on the job education so please keep that in mind.
im currently building cnc automated machining centers for the window **********. im trying to find a way to accurately measure a distance of approximately 30 feet .... ( 30.000 ) any help and ideas will be greatly appricated
thanks in advance
let me also says that ive come here looking for a " think tank" type place to talk about some of my work related ideas....just looking for like minded people, smarter than me. i need to keep my mind stimulated.
i have much respect for everyone here and the knowledge and experience they have..
Laser measuring devices are going to your bets bet. I don't know if the accuracy is enough, maybe you'll get +/- .015" max unless technology has improved.
the machine has a feeder with multiple tracks....a gripper in each track on a long arm that grips the tail end of material and feeds it thru the machine. gripper assembly moves back and forth on a extruded aluminum rail that has a linear rail and bearing setup. timing belt and idler pulley at one end and servo motor driven pulley at other end.. this rail is roughly 250 " long. the material is being fed thru a cnc saw , multiple tracks of material at a time.
the issue is that if the linear bearing rail is not PERFECTLY straight and the movement of the assembly thru the length of the rail. it causes a steering effect at the gripper end at the material. . basically this makes the cut lengths of material vary too much in length.
the linear bearing rail up inside the aluminum extrusion rail can be adjusted to keep the the grippers and and material moving squarely to the saw blades. im just unsure how to accurately do this.. on one of our high tolerance machines we need to keep cut lengths in the .018" variance range in order to pass testing. thats between the shortest and longest parts
we have had laser alignment done on the rail but desired results werent acheived. looking for a cheaper and easier method of doing this. it needs done after assembly before run off and once installed at customer locations
1. What accuracy do you need?
2. Done after assembly? Then what? Can you adjust or are you just verifying conformance?
3. Cheaper than laser is unlikely..
Originally Posted by atopper33
Tell me and I forget. Teach me and I remember. Involve me and I learn.
end goal is to keep the gripper line always in a 90 degree relationship to the saw blade thru out its roughly 20' range of linear motion. this would probably just be need for initial setup and adjustment.. something somewhat simply quick and easy to use. i was thinking possibly a Keyence measuring laser mounted both of the outside tracks measure the distance to the blade in the saw. you could move the gripper carriage and make adjustments to the linear bearing rail say every 6" thru out its linear range of motion. basically every 6" or so adjusting the bearing rail to maintain a right angle relationship to the saw blade. this would have to be very accurate. right now you can see the variances in length in parts after measuring many runs and cuts of parts. if you change the starting length of parts you can also see change in part lengths.
possibly a measuring laser on either side of carriage or a cable potentiometer , but that would probably not be as accurate as the laser method
1. .015" - .018" range in variance from longest to shortest parts in a test run.. more parts ran = more forgiving range..
2. max swing of .018" in order to pass our testing study then the accuracy must be replicated out in the field at the customers site
3. i agree .....guess i would need to contact xxxxxx and see if they offer measuring laser and the accuracy of those lasers at our required ditsance.
thanks for any and all ideas
or possibly even ultrasonic measuring sensors to measure the distance to the blade. one issue is the blade is at a 45 degree angle . im sure a setup fixture could be made to overcome this if its even an issue
i need to research the limitations and accuracy of precision triangulated laser measuring
That's fun - if we worked together, I would require that you convince me that is actually required...015" - .018" range
As far as your application as described - I doubt anybody reading this thread knows what you are talking about...
Tell me and I forget. Teach me and I remember. Involve me and I learn.
material averaging 150" is fed thru a dual blade 45 degree saw....( think picture frames ) the feeder has multiple tracks and the ability to say feed 6 , 150" lengths of material thru the saw. lets say it pushes 6 lengths at 150" and is cutting parts at 30". so 6 30" parts then another and another till its out of material. the issue is , the material is gripped by air accuated grippers at the tail end then it feeds it thru the saw. as the gripper carriage moves along the linear rail and feeds the material thru the saw , it doesnt move in a precise linear motion. this causes a steering effect of the material and part lengths vary.. the gripper point is roughly 4 feet out in front of the center of the linear bearings. so the carriage and gripper assembly is pushing and pulling the material thru out its linear motion. which results in variances in length.
6 lengths cut up into 30" parts , i would get 30 parts total . i measure all 30 parts and i need to maintain no more than .018" between the shortest part and the longest part in order to pass our required qualification testing.. if i can figure out a way to keep the grippers in a square relationship to the saw blades , i think it will improve the cut length accuracy.
the outter most tracks are the furthest from the center of the linear bearing so they see the most deviation in part length. if during setup adjustments i could accurately measure the distance between track 1 gripper and the blade and track 2 gripper and the blade at the same time and adjust the linear bearing rail as i go along the length of the rail. this should keep the line of 6 grippers moving squarely to the blade and improve cut length.
I have had good experience with this line of cable-actuated position sensors, commonly called "string pots". IF they are properly applied, they can provide repeatable and accurate results. Get the manufacturer's assistance to make sure you're using the right product, and in the right manner.
http://www.te.com/usa-en/products/se...?tab=pgp-story
Yes, that's what I thought you're trying to control tolerance structures at the machine/part level. You should consider a different manufacturing approach such cutting (manufacturing) those interfacing parts in a fixture that cuts them as a set or together. The surfaces are then aligned and as good as the fixture.
If you can't do that consider a corner interface design that allows for the variations in length and angle and allows a proper fitup.
Summary: I suspect that the manufacturing process and/or design needs a rethink.
Tell me and I forget. Teach me and I remember. Involve me and I learn.
thank you all for your ideas and help. i thought of the cable pot method. it would have to be something thats installed and setup for intital machine setup then have the ability to put it on the machine again out in the field for install and setup. or redesign the entire process with something that produces accurate results with less headaches...if its even possible. im still exploring ideas
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