AC went out

[[Me...]]

Hello all,
Our lab AC unit decided to not work. We have left it off and have been observing the temperature and humidity more often. on average our humidity stays around 45% but the temperature swings around 22­°C~25°C. The swing in temperatures is one of those "its always been like this" thing but our usual temperatures are kept within 20° +/-3°C, usually on the low end.

My question is, should we leave it or repair it? Its currently unknown the cost of repairing the unit.

Thanks!

[[Ro...]]

I would fight for repairing it just because summer is coming and you don't want to be hot all day do you 🙂
But as for accuracy.......... realistically it kind of depends on what you are machining and the tolerances you use and the conditions your customers CMM room is in their receiving inspection.
Its all about the coefficient of linear/volumetric expansion, will 2º,5º,10º make a difference?

If youre holding a 2 inch hole to +/-.001 inch then you cant do that without AC, if you got +/- .010 all over then you should be fine, maybe come to an agreeance with your manufacturing supervisors that you're going to "running at risk" and to not run to the low side of tol as the parts will contract when they get to a temp controlled environment.

But yeah, fix your AC.

Go on youtube and look up how to recharge an AC unit, you can buy a pair of "bullet piercing valve, line taps" for about 10 bucks. then get an AC manifold gage from hazard Fraught for 60 bucks, and a can of green dye r134 for about 5 bucks, and between you and your maintenance guy and some of your more curious engineers you can figure out how to recharge your own AC.

[[Ro...]]

Here you go, don't let anybody tell you you cant refill a window AC unit, or a fridge.
https://youtu.be/C2dh1BFeULw

[[SH...]]

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You should not run the machine,coefficient of thermal expansion is very important concept in CMM machine.every material can expand or contract with respect to temperature, if run at high temperature the CMM granite surface plate may get a curvature due to the thermal expansion , this will ruin your machine efficiency . So be careful, follow the machine supplier instruction...

[[Da...]]

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That depends highly on what your Machine is and what you are measuring
You have temp comp for most Zeiss CMM's and the expansion coefficient are set right for your scales in Calypso.
I calibrated a Zeiss DuraMax CMM that temperature changed over 10 C during the calibration with temp coefficient for the Gage Material it didn't even see more then a .0002 mm change during that 6 hours.

As a side note I use a Moore step gauge
If you can get your hands on one they are amazing cost about $1000 per inch.
The gauge I use is accurate on all 12 steps to the inch with in .000000" to .000003"

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[[Me...]]

I have a Contura 2014 in the room, our tolerances are usually around 0.01mm (electric motors) so nothing too terrible but as of right now, I'm at 23°C and 24% humidity...this may be a hard argument if without the AC the room meets our standards.

[[Da...]]

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Just keep an eye on the temp, If you are using long probes on an XT or XXT head calibrate them if the temperature changes that is where you will see the most change as the temp goes up or down. As the temperature changes the relationship between probes tips change as they grow or shrink. This will not have an affect if you are only using one "probe tip" to check the part. (Not Stylus system with more then one tip)