lathe thermal growth mitagation solutions?

[EKrol]

EKrol,
30 to 60 minutes of non-productive warm up time?
On a 8 hour shift? That would hurt.

Better to scrap a expensive part because the tolerances are off? I used to set a timer so when i started my shift the machine is already warmed up. My warmup program first slowly starts to move and keep increasing the speed. Also slowly starting the 3 spindles. When reached the temperature it keeps the axis at a certain temperature. Then the axis move only when the temperature is to low. So its not constantly full rapid all axis. That's bad.

 

[Ox]

B axis milling spindle?


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Think Snow Eh!
Ox

 

[Stirling]

One thing, as mentioned before, we run a warm-up cycle in the morning, or when the machine is idling for a long time.

The best way we have found, is to also get the all the axes moving, not just warm up the spindles. So for example I will travel almost the full range of Z back and forth, and then go to around the middle of the machine (G53 Z-320) and do some XY movements, we do them in the middle just to make sure we do not hit anything because the tools change all the time... The nice thing is that you can write a relatively short program, and use the memory restart function to loop it for as long as you need. We also load and run this if the machine is idling for a prolonged time, just to keep it warm and moving.

Well still, that is a big deviation, I am really surprised. I also have one and it is sub 10 micron machine all day long. Which I consider really good given that this is the "cheap" Nak.

We regularly do some bronze bushings on it which have an +0.0005 to + 0.0010 inch OD tolerance, and after a proper warm-up we adjust the X offset just about 3-4 microns during the whole shift.
And at that point it somewhat hard to tell for me if this is thermal drift, or insert wear, since the inserts practically last the whole batch of 1000 pcs. We rarely change them, usually only if we cannot get the required Ra 0,8 surface roughness requirement.

Correct on the AS200 there is only one option for thermal compensation in the NT Nurse setting 32, which works based on coolant temperature. Still your mileage may vary according to the workload, we have this turned off, seems more stable that way.

On the higher-end Nak's with 30-series Fanuc, you can get the NT Thermo Navigator AI, but on the WT or MX it has not really been a be all end all solution to all of our problems at all times.
First, you really need to feed the system with a lot of data, if you don't, the compensation will be off. This means a lot of measuring and data input.
Second, since we do usually only do high-mix low volume, some parts are running just a couple of hours at a time, which is not a big enough sample size, to get the compensation working reliably, or I should rather say as good as on the parts where we have run over extended periods of time.

A third option, on the higher end Nak's you can also get scales, but I have never seen them anywhere in the wild, the machines seem to run well out of the box even without them. At around 16k for scales on XYZ, it might be an option for someone.
I also think you can order them just for the X axis for example at a reasonable price. However the difference between scales and no scales seems to be around the one micron mark, and I do not see a point in that for our workload.

One question regarding your AS200, what size is your coolant tank? I have noticed that for some reason, Methods delivers these with a "standard" coolant tank, which is quite small.
Over here, you can get one with an extended Coolant tank which is over 600l, and it has done wonders for thermal stability, compared to other small lathes we run with smaller tanks.
We have considered a high pressure system with coolant chiller for the AS200, but as it costs around quarter of the total machine cost, we have decided to stick with the standard Brinkmann 25bar pumps without coolant chiller for this machine, and it works really good as long as you have the extended coolant tank.

Probe repeatability

Ran some basic checks today



Removable probe repeatability

0.0004”

Jingle x axis back and forth and remove/install probe to prove repeatable. Touch off 20 times doing this.



Next test.

0.0001” indicator mag based to turret touching main spindle chuck.

Wiggle x axis back and forth and bring controller back to 8.000” each time.

0.00005” repeatable on dial.

(0.0001” mitutoyo indicator with magnetic base attached to back of dial, not on any type of arm to avoid flexing)



Shop is at 10 deg. C

Set dial to zero @x8.000 on controller.

Ran at 50% rapid.

X1 to x8 for 20 min.

No rpm on chucks



Bringing dial to zero read 7.9982 on controller after 20 min of x rapid 50%



Motor after 20 min was mildly warm to the touch.( 30deg?)

Motor to ballscrew coupling approx half as warm approx (20 deg?)

Upper length of ball screw (where I could reach from the machines backside) approx 18 deg? (Slightly cooler than the coupling. But warm. No longer “cold steel)

Ship temp remained at 10deg for the test.



Placed fan inside enclosure for 20min to cool the x axis assembly and will retake readings on dial indicator which is still mounted to turret and referencing off the chuck



Retake measurement

Dial at zero, machine reads 7.9998



10 min. 25% rapids.

7.9992” on controller dial at zero

25min 25%

7.9989” in controller

40m 25%

7.9986” at controller



5 min cool down

7.9992” at controller

10 min

7.9994” at controller

15min

7.9996”

20min

7.9998”

50min

7.9999”





I’d be more than happy to run any other sorts of tests that are applicable if you have any recommendations fello pm’rs



As it stands I would say I have found where most of the thermal expansion is effecting my diameters.



Question is is there any concerns I should have with these results???

Nothing sounded bad, nothing was striking me as abnormal heat. Stethoscope did not pickup and abnormal bearing/sliding noise, all parts where well oiled.



Any way to reduce this? (Only think that I can think of is a fan to move a bit of air in that area.

Knowing what it is helps mitigate and reduce its effects of course, but it’s better to reduce an outcome rather than learn to work around its extremes

 

[Stirling]

Sorry it took so long to get back to this thread.
But it’s the weekend and I got some time again to post here/test things

Truck unloaded a 5000lb for me to play with too. So I can run lots of parts and try different things. Get to know this machine!

 

[Ox]

Seems ligit to me.

The thing with a lathe is that all errors in X are doubled, so it always seems worse than it is.


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Think Snow Eh!
Ox

 

[SND]

I find my Lynx 2100LB moves about .0015" from start up to operating temp. I run at 25% rapids most of the time.
Shop is always at 68°F.
I debated adding a coolant cooler but meh.

 

[Stirling]

I find my Lynx 2100LB moves about .0015" from start up to operating temp. I run at 25% rapids most of the time.
Shop is always at 68°F.
I debated adding a coolant cooler but meh.

The “coolant cooler” I plan on installing will just be a pond pump pushing through a car transmission cooler I place atop my mist collector outlet.
$100 solution to help keep the coolant closer to ambient shop temp.

 

[Stirling]

Seems ligit to me.

The thing with a lathe is that all errors in X are doubled, so it always seems worse than it is.


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Think Snow Eh!
Ox

Would you say this is a common expansion range for an x axis?

I’ll need to measure my old lathe. But in practice all I would do was run the chuck at 1500 rpm for 30 min while I ate breakfast and it was locked in.
Leave the chuck at 1500rpm furring breaks and it would be within a few 10ths. Even if I left an hour. So c must not have been bad??

That being said this particular program on the new Nak does have a lot of x rapid for tool changes. I’m using the sub as a tailstock so I’m doing a lot of rapid to tall x to swing the tools.