Air compressor lines for stationary air compressor.

[5030]

I looked at the ad. 200 psi at 73F and 160 psi at 140F.

My shop maintains 75 (f) year around. Heated and cooled always. I have to, to maintain a steady RH so my precision machines and tools don't rust or lose tolerance.

 

[WinterDeere]

My shop maintains 75 (f) year around. Heated and cooled always. I have to, to maintain a steady RH so my precision machines and tools don't rust or lose tolerance.

I used to work in precision robotics, designing pick-and-place robots and precision laser welding systems with picometer encoders (±0.000,000,000,7 inch), nanometer servo stabilities, and overall placement tolerances for our pick-and-place machines in the sub-micron (±0.000,004 inch) category. We did indeed have to keep our facility at a constant temperature, for those levels of precision.

Having worked in that field for several years, I have more than a few thoughts on this, but the first among them are:

1. We studied the cost of heating versus cost of cooling, and when crunched against our average temperature, building heat loss, solar gain, etc., we always found the most cost-effective constant temperature was around 63° - 67°F for our various buildings. This was great for working on your feet, the production folks loved it, but it made a cold environment for those of us spending much of the day at a desk.

2. Your climate might be even colder than where we were operating (Allentown PA), and 75F is awful warm for a shop, so you might do well to find a new lower constant temperature, if a constant temperature is even needed for your machinery.

3. Most of the major components on most machinery are either steel (11 - 12 ppm/°C) or iron (10.5 - 12.0 ppm/°C). So on something like a Bridgeport with a 30" center-fixed table, your total growth/shrinkage for a change of 20°F (10°C) is going to be only .0016 to .0018 inches at the extreme ends of the table. Moreover, if the shop were on a timed thermostat that got it back to near standard temperature during working hours, it'd be much better than that.

4. You don't really need constant temperature to keep rust at bay, you just need to ensure dewpoint always remains below temperature. This is matter of course in any air-conditioned shop, even my own where temperature is left to swing 50F - 85F while it's not in use. No rust here, because it's always dry conditioned air.

If you wanted to save some heating/cooling costs, you could probably get away with letting the temperature fall off as much as 20F at night, assuming your system has the horsepower to get back up to temperature in a reasonable time each morning, on a timed thermostat prior to working hours.

Even if temperature at opening time is 10F below nominal, you're looking at only a .0008" error at the extreme end of a 30" fixed-center cross-slide table assembly. That's usually not going to blow anyone's machining tolerances, unless you're doing precision optics stuff.

 

[CalG]

I used to work in precision robotics, designing pick-and-place robots and precision laser welding systems with picometer encoders (±0.000,000,000,7 inch), nanometer servo stabilities, and overall placement tolerances for our pick-and-place machines in the sub-micron (±0.000,004 inch) category. We did indeed have to keep our facility at a constant temperature, for those levels of precision.

Having worked in that field for several years, I have more than a few thoughts on this, but the first among them are:

1. We studied the cost of heating versus cost of cooling, and when crunched against our average temperature, building heat loss, solar gain, etc., we always found the most cost-effective constant temperature was around 63° - 67°F for our various buildings. This was great for working on your feet, the production folks loved it, but it made a cold environment for those of us spending much of the day at a desk.

2. Your climate might be even colder than where we were operating (Allentown PA), and 75F is awful warm for a shop, so you might do well to find a new lower constant temperature, if a constant temperature is even needed for your machinery.

3. Most of the major components on most machinery are either steel (11 - 12 ppm/°C) or iron (10.5 - 12.0 ppm/°C). So on something like a Bridgeport with a 30" center-fixed table, your total growth/shrinkage for a change of 20°F (10°C) is going to be only .0016 to .0018 inches at the extreme ends of the table. Moreover, if the shop were on a timed thermostat that got it back to near standard temperature during working hours, it'd be much better than that.

4. You don't really need constant temperature to keep rust at bay, you just need to ensure dewpoint always remains below temperature. This is matter of course in any air-conditioned shop, even my own where temperature is left to swing 50F - 85F while it's not in use. No rust here, because it's always dry conditioned air.

If you wanted to save some heating/cooling costs, you could probably get away with letting the temperature fall off as much as 20F at night, assuming your system has the horsepower to get back up to temperature in a reasonable time each morning, on a timed thermostat prior to working hours.

Even if temperature at opening time is 10F below nominal, you're looking at only a .0008" error at the extreme end of a 30" fixed-center cross-slide table assembly. That's usually not going to blow anyone's machining tolerances, unless you're doing precision optics stuff.

My lab machines are NOT temperature controlled, but I keep the humidity to less than 55% rh.

More than that and I see rust.

A difference of 200 nanometers is the difference between blue and red .....;-)

 

[WinterDeere]

A difference of 200 nanometers is the difference between blue and red .....;-)

Yep. I used to get into endless arguments with mechanical guys over tolerances, as the numbers they were requesting and sometimes claiming they would catch on inspection, were too small to even see at visible wavelengths of light. All of this equipment was aligned and tested using laser interferometers, and even very special ones at that, there were PhD guys who spent their whole careers just on measuring things like the optical encoder accuracies on those machines.

Because the only way we can see an object, or a change in an object's placement, is to reflect light off of it into a microscope, there is a physical limit to how "small" you can see with optics. Because our eyes can only detect down to about 400 nm, and you need to reflect about 1/2 wavelength of light to actually see something, that puts a lower limit of about 200 nm on the smallest object or positional change we can detect with a microscope.

Now compare that to an encoder with a resolution in the hundreds of picometers, literally 1000x smaller than anything we can see with the best visible-light optical microscopes ever made, or servo stabilities in the tens of nanometers... maybe 10x smaller than anything we can see. That's the sort of robotics I was working on 25 years ago, although I was more on the controls side, not designing the encoders or servo motors.

 

[CalG]

Yep. I used to get into endless arguments with mechanical guys over tolerances, as the numbers they were requesting and sometimes claiming they would catch on inspection, were too small to even see at visible wavelengths of light. All of this equipment was aligned and tested using laser interferometer, and even very special ones at that, there were PhD guys who spent their whole careers just on measuring things like the optical encoder accuracies on those machines.

Because the only way we can see an object, or a change in an object's placement, is to reflect light off of it into a microscope, there is a physical limit to how "small" you can see with optics. Because our eyes can only detect down to about 400 nm, and you need to reflect about 1/2 wavelength of light to actually see something, that puts a lower limit of about 200 nm on the smallest object or positional change we can detect with a microscope.

Now compare that to an encoder with a resolution in the hundreds of picometers, literally 1000x smaller than anything we can see with the best visible-light optical microscopes ever made, or servo stabilities in the tens of nanometers... maybe 10x smaller than anything we can see. That's the sort of robotics I was working on, 25 years ago.

Accuracy, precision, and repeatability.

The inexperienced flounders with these concepts.

I'm a "file to fit sort of fellow these days. But my stuff is still sending back images from Mars and from the HST! So I smile when considering "stuff"

Imagine:

I have fourteen components in a n optical train.
They are all made of different materials with different refractive index, with dispersion. That is, light propagates through them at differing velocities, and varies with wavelength.
They also vary in thickness across the surfaces i.e. lenses, prisms etc.

Optimize the assembly with the goal of having all photons arriving at the detector at the same time., over the broadest spectral range, UV-NIR.

It's a task, I'm not sure what it was all worth. may take some temperature control ;-)

 

[5030]

All way too complex for me. In my situation not only controlling the ambient temp in the shop contributes to my employees comfort it also keeps my RH at acceptable levels which equates to stable machines and recently, a growing mouse population...lol I don't much care about the technical aspects, I do care about precision machine stability as well as a comfortable enviroment for my employees and obviously, for my mice as well....lol. Precision measurement is all about temperature stability and corrosion is all about a dry atmosphere in the shop.

 

[5030]

The other issue I had but don't now is, if the ambient temp is too low and the RH is excessive, the dew point or whatever it's called becomes excessive, them my compressors (I have 2, one large reciprocating Quincy and one screw type (Sullaire) produce excessive moisture which has to be removed or it causes grief downline for the CNC plasma table and why I run a point of use 2 micron cannister filter on the inlet of the plasma cutter that provides the cutting action to the torch on the plasma table as well as one on each of the handheld units, not so much for the moisture effect but any moisture present in the compressed air supply to the plasma cutters severely degrades the consumable (expensive) torch components and can cause a malfunction of the air to electrical relays inside the machines. In my situation, it's a matter of balancing the enviromental conditions in the shop with the cost of consumables for the machines and to a greater extent, the stability of the precision machines, especially the surface grinders and the precision measuring tools.

What I employ works fine in my situation and has for years actually.

Entrained moisture in a pressurized air supply is always detrimental to any tool or process that uses compressed air to operate, why my compressors have automatic condensate drains and I also employ an IR refrigerated dryer on the outlet line side of them. Every little bit of condensation removal helps and what I do and how I built my compressed air system works for me and has for many years. Did I really want to build out my system in black iron pipe at great expense versus much cheaper and easier to install plastic? Certainly, but because I have employees, I had to make it compliant to existing safety rules. All has to do with liability.