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HAAS ST25Y X axis ball nut temperature sensor troubleshooting assistance needed

Sparky961

Cast Iron
Joined
Jul 10, 2008
Location
Vancouver Island, BC, Canada
For the year or so I've run this Haas ST25Y, I've noticed up to 0.002" difference on the diameter of a part cut when the machine is thoroughly warmed versus a cold start the next morning. I've learned to monitor and adjust for the first few parts until things stabilize but have recently decided to investigate further.

One thing that is very suspicious is that in the DIAG screen, the X axis temperature sensor doesn't move much from 73 deg F (75 is the highest I've seen lately, and only briefly at that), where I used to be seeing a range between 73 and perhaps 86 or 89 at times?

I'm looking for information on the sensor itself. What type of sensor is used, perhaps the expected values under a test of voltage or resistance? A true electrical schematic or troubleshooting flow chart?

Oh, and don't forget the comments telling me how shitty this machine is and that I should upgrade to _________. That, or that I should call the service technician and let them deal with it. Anything I forgot to head off? Go for it - I'm ready. :-P
 
One thing that is very suspicious is that in the DIAG screen, the X axis temperature sensor doesn't move much from 73 deg F (75 is the highest I've seen lately, and only briefly at that), where I used to be seeing a range between 73 and perhaps 86 or 89 at times?

Can you point a heat gun in that general area, without melting any wires ? If that doesn't show a temp difference then ja, sensor probably shot or there's a wiring problem.
 
Thanks, this is exactly what we did and it turns out the sensor is reading okay.

So, next question: Is a difference of up to 0.002" on an ID or OD from running warm to the next morning cold an acceptable amount for this machine? Like most CNC machinists, I've inherited the care and feeding of this machine but it's history is largely unknown. I do see that all of the thermal compensation settings are at "0", but see little information on how to use these effectively to reduce what I'm seeing.
 
My experience with machine tools in a poorly controlled environment is they tend to heat soak during the day and shrink overnight.
A 6ft long casting will grow ~.001 in for each deg. F in temperature change. It is obviously a much more complicated problem that just the machine base expanding.
On critical parts our guys keep a log of adjustments and change offsets and comps throughout the shift.
In a cold environment a digital submersible heater in the coolant tank can help, sometimes letting the coolant run overnight to keep the iron warm.
 
.002 sounds about right if your compensation isn't set up, one of our DS30s had a similar intermittent issue with the X axis thermal compensation. Operators had decided to disable compensation rather than request help, with compensation turned off they at least knew they would need to check dimensions and adjust offsets frequently.
One day I was paging through diagnostics solving an unrelated issue and noticed X axis was 180*, replaced the sensor and the problem went away.
 
I'm going to experiment with the temperature compensation settings. They appear very simple, being only applied at a proportional rate from startup to a set time. That may resolve the main issue of picking up a job from the previous day of I'm lucky. Otherwise, it's sounding like that amount isn't as unreasonable as I may have thought.

Maybe higher end machines offer better automatic temperature compensation and/or control?
 








 
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