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LB2000EX w/ P 300L

warner

Aluminum
Joined
Aug 29, 2006
Location
New Hampshire
Question for you gurus. How much compensation do you guys have to enter through out the course of a day in the offset page for your finishing tools? This machine is supposed to have thermal compensation through temperature sensors, but I am not sure it works properly. We turned them off and had the same amount of offset change that we had to manually compensate for in the X offset in the control. What is this machine capable of? That is my main question that I have asked Okuma; waiting for an answer. The control resolves to 5 places (.00001). We are holding +/-0.00005 on a diameter in non-ferrous material, but cannot leave the machine alone for more than 20 to 40 minutes at a time without checking on it to verify part tolerance. Usually have to make adjustments that often. We have charted the movement of the machine base on how much we have to change the offset, room temp, coolant temp, etc. The chart looks almost the same from one day to the next, so it is predictable, but not enough to code for it. Ideally, we'd like to run lights out, but until we can stabilize it a bit more, that ain't going to happen. Anyone have similar experience with the LB lathes? Or is my tolerance window to small, ie an I asking too much of the machine?
 
That is my main question that I have asked Okuma; waiting for an answer

hy warner :) i dont think that you will receive an answer about that ...

We are holding +/-0.00005 on a diameter in non-ferrous material

pls, how are you measuring it ? can you share a drawing with the part ? do you measure before finishing and adter ? what tool delivers that tolerance ? are you a lucky guy with 0.1um increment control ? what is the increment of your control ?

cannot leave the machine alone for more than 20 to 40 minutes at a time without checking on it to verify part tolerance.

is this not ok ? or you wish to measure only once / day ? at how many parts do you control the dimensions ? what is the program duration ?

We have charted the movement of the machine

why ? what are you after ? please, can you share those charts ?

The chart looks almost the same from one day to the next, so it is predictable, but not enough to code for it

you wish to code the compensation ? i guess you wish to minimize the number of tool corections :) you are a smart guy / at least you have an idea :)

Ideally, we'd like to run lights out

look warner, as you said, tolerance is too small :) a coordinates measuring machine needs calibrations like this :
... once / week for 0.1mm precision
... once at 2..5 hours or once/day for 0.01mm precision inside a medium with controled enviroment
... before every measuring, if 0.001mm precision is required, again, inside a medium with controled enviroment


what do you think about this :
... use droop control*
... aproach not in rapid, but rapid+feed*
... reduce rapids speeds, or remove them*
... maybe reduce turret indexing speed
... reduce chuck size
... reduce tools size / shunk
...... * means : at least for the operations with tight tolerances :)

those will help a bit, but wont deliver lights_out :) kindly !
 
Anyone have similar experience with the LB lathes? Or is my tolerance window to small, ie an I asking too much of the machine?

one more thing : you wish to boost the stability of a setup, with a tight tolerance ... is not easy to run lights-off at such precision, and the few places where you may insist, will add a bit of more stability, but the final result is far from lights-off :)

however, enhancing a setup will give you real experience, helping you understand better what you need to do to achieve lights-off :)

you are not the 1st guy trying to make a huge step on ice :)
 
Licensing and NDA's prevent me from sharing prints here, but is is a simple 2 axis turning with tight tolerances on the diameter. Ideally, we'd like to increase production buy running unattended at times, so having to chase offsets prevents that. We were lead to believe that the control resolution, with the thermal comp, should allow us to do that. But since it isn't working to the degree (no pun intended here) that we need it to, we are questioning the tolerances of the machine to begin with. We are measuring with snap mics calibrated with certified Deltonic gauge pins. Part program is less than a minute. I have started looking into in-process probing, but am not sure if it will resolve to the numbers we need it to.
 
I have started looking into in-process probing, but am not sure if it will resolve to the numbers we need it to

why dont you measure automatically near the cnc ? if durations is <60, you may only measure the final part once is out of the lathe, thus there is no problem if a part will be crafted out of the tolerance :) if durations is longer, than i guess you would consider measuring before finishing, thus to avoid trashing parts :)

how are you taking the parts out of the lathe ?
 
try a laser system near the lathe; however, you may hit the fact that +/-0.00005 means +/- 1 corection, if one corection is 0.00005, more precise 0.00004

if you wish to be more comfortable on the setup, i think you need a lower increment control, and there are few guys with experience on such lathes :)
 
Hardinge T series lathes are the only machine I would want to try that with, they tend to put more thought into that realm of accuracy than most. assuming you didn't add an extra zero...you are pushing the limits of the hardware I would say. If someone asked me if production machining, lights out, to 50 millionths was possible...my first reaction would be "no". Followed by, maybe if you want to spend the $$.

does the lathe version of the p300 show you the thermal comp pages? The mills will tell you how much the machine has grown and how much it's comping it. I believe there is also a page to adjust the microns per degree for each axis that it adjusts it, if the growth is consistent/linear maybe you stand a chance of adding to the comp adjustment ratios until you find stability as it warms up. It could be as simple as this piece of iron has slightly less carbon in it and grows at a different rate. I would imagine that Okuma has a standard table that they put in the control, I doubt they do a thermal study on each machine they ship.
 








 
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