Testing Volume

How big a tube? How accurately? Is there something already in the tube (that can't be removed)?

Without knowing the situation, the first thoughts that come to mind are doing things like filling the tube with water, then measuring the water in something like a graduated cylinder or even something like a graduated pipette or syringe.

Or (still depending on the situation), is the tube straight and of uniform diameter? If so, measure the length and diameter and use math.

Oh, again, if you can empty the tube, empty it, clean it, weigh it (on an accurate scale), then fill it with something with a known density and weigh it again.

Or, write back and tell us more about the situation.

Thank you,

There is no bottom to it to fill it up a water and it has nothing in it. It's about 1.5" tall and about .5" in diameter. I'm testing for wear so simply measuring length and diameter is not enough. Accuracey to a 1000th or even 10000th of an inch would be ideal. I'm looking for a device that can check this.

Let me know if you need any more information.

You want to measure wear on the inside surface of the tube?

That level of accuracy is pretty tough--I don't have any immediate ideas different than what I suggested (with the addition of something temporary on the bottom of the tube to hold water in it, but, naah, that would be pretty tough to get the accuracy you want).

Maybe somebody else will chip in--my next thought is some device that measures surface roughness--with wear the surface has probably changed in roughness (I'm guessing smoother), and maybe a ratio of the before and after roughness would be a means of measuring wear.

I know surface roughness can be measured in microinches--there must be some means of doing it. ;-) I'm curious now, I'll try googling. Yup, google gets 5490 hits on ["surface roughness" microinches gauge]. This is the text of the first hit:

flange face surface finish
Surface roughness of flange mating faces - an explanation of common terms. ... grooves per inch and a resultant roughness between 125 and 500 microinches. ... surface finish comparator gauge, occasionally referred to as a Rupert gauge, ...
www.contractorsunlimited.co.uk/toolbox/flange-facings.shtml - Cached - Similar

If you think using roughness as a measure of wear has any merit, try the same google search and look at some of the hits.

BRAVO!!!

I like that idea.

Thanks! Let us know what you find out re surface roughness gauges.

Lyn's idea in post #9 sounds like it's worth exploring, also.

What is the material of the tube, and what is causing the wear?

There must be a language barrier that is keeping us apart.

This 'Tube' is confirmed as being a hollow cylinder, with both ends open. Other than that, all I see are implications.

It is implied it is a right circular cylinder. The volume of this shape is ∏r²h. For accuracy of volume to .0001 inch³, measure very accurately. "It's about 1.5" tall and about .5" in diameter." will not give you the desired results.

"I'm testing for wear so simply measuring length and diameter is not enough." Testing for wear? The wear on what? What has this to do with the volume? And the thread title; what is Testing Volume?

I think, Eddy current testing will give you the desired result. Eddy current testing is used to measure increase in inner diameter of tubes in shell & tube exchangers with lot of accuracy. Eddy current testing equipment can show you the variation in diameter on its screen, clearly showing peaks and valleys with graphical aids with good resolution.

• Find 2 fittings/plugs to plug the tube ends.
• Weigh these and the tube.
• Set some distilled water out and let it come to the temperature that you will be measuring the weight of the filled tube.
• Record this temperature.
• Fill the tube with the distilled water.
• Weigh the tube filled with the distilled water.
• Subtract the weight of the filled tube from the weight of the tube and fittings only.
• This weight, divided by the density of the water at the temperature you recorded before (find in tables on the net), gives the volume.

The accuracy will depend on

• How accurate the measured values are and
• How much (or less) actual water the fittings/plugs hold/displace beyond/inside the tube and how closely you can use this to adjust to the actual tube length.

I'm having trouble coming up with a reason anyone would need an accuracy to the 1/10000'th of an inch³ for a simple tube. Just out of curiosity, what are you working on?

You still working with playdoh like fluids?

Haha,

The Play-dough was for a buddy. Impact Molding in AA battery manufacturing.

"Impact Molding"? Is this like deep drawn forming for battery cases?

I would think Energizer™ and Eveready™ had this pretty well figured out by now.

It's impact molding the cathode dust in the already molded can. It's that bushing.

Just take a holographic picture of the tube and then superimpose the virtual image with the real image. It might take you hours to accurately replace the tube in the same position but with the diffraction/interference pattern you get under coherent lighting of the two three dimensional images you can sub-micron resolution.

Sometimes I do like to use an overkill approach.

Resolution down to 12.5 Å, if memory serves.

Now with blue and green lasers you can get even a decade smaller.

Wow,

I need to get out more.

That's way more of a process than I'm looking at.

Thank you though.

I expected my proposal would be too precise and tedious. I was just having a little fun with your fuzzy description of "extremely accurate". Now that I've heard more information about what you're doing, I'd recommend visual inspection with image software looking at the battery cap at critical angles. This can operate on your production line in real time and even give you six sigma process control.

Whatever method you use, how will you find comparison results from before?

Figure out the volume from specs of the drawings

Or use your wear measurement system before and after the "weariing process".

A CMM would do the job nicely.

1/2 inch is 12.7mm

10-3 of this is 12.7µm - to be measured with an inner diameter mechanical gauge - TESA will have some fine ones but others too.

10-4 is 1.27 µm - to be measured either by pneumatic gauges or capacitive gauges.

Both need some mechanism to make the gaps from sensors to bore nearly constant around.

First possibility is standard in wide fields of manufacturing. Second possibility is used for measurement of bores in diesel or gasoline injection pumps - these have to be very accurate.

But knowing the diameter your task is not solved.

What about volume resonances? Air in a short tube will have a first longitudinal and a first radial resonance to be excited by a small loudspeaker and measured and displayed by the micro of your laptop. (We measured high frequency spindle rotors at rotation speed between 1000 and 7000 rev/second by this method, no coupling was necessary up to 5m distance.)

Very precise glass tubes with inner diameters specified to 0.01mm are made by SCHOTT as KPG tubes.

RHABE

This is wonderful information.