proximity/distance sensor narrow beam, inside steel tube

[union7]

Hi I have a CNC lathe type machine with an outboard tube support, that supports 1/2" square aluminum stock into the lathe spindle.

Currently I have my code set to do a number of parts machining loops based on the stock length.

I am considering a non-counting method instead by measuring how much stock remains.

For various reasons I won't explain now, the simplest measuring location may be to have some type of transducer at the outboard end of the support tube,pointing down the tube at the end of the stock.

So, basically what we have is a 40" steel tube with 1.2" Inside diameter.
At the far end of that tube is a steel collet, think of it as a plug at the end of the tube.
The core of that collet is 1/2" square jaws that the 1/2" Square aluminum bar passes through.
There are also some support segments in the tube spaced along the length so that when viewed from the end with no stock loaded one would see a 1/2" square window down the length of the tube..

If 36" of square stock is loaded into the support tube ,after loading a transducer..laser or...? Could be positioned to measure the distance to the end of the stock as it is fed away from the transducer.

The difficulty might be that the transmitter and receiver need to deal with the 1/2" square corridor available to transmit and receive within.

Sinc the square is rotating or at least in a random position during stopped measurement, it's effectively a circular window of only 1/2" diameter.

Can anyone recommend an appropriate sensor or type of sensor to look for?

Laser?.
..Ultrasonic (i doubt because of support segment interference)
Optical (but transmitter and Receiver would have to be really close)

Distance resolution only need to be around +1 1/2" as I'm only concerned the collet has enough grip for the final part, or else it ends the process.
(I don't want to use the method of overpulling the stock and checking if it is long enough and then feeding it back in)
(There is no access to the near-final stock position, collet end..and even if there was, well let's stick to the idea of non contact measurement from the far end of the tube, because it has advantages for me)

 

[itsmoked]

I'm missing why can't you just set an adjustable sensor perpendicular to the tube that will stop further advancement (call a halt) to the process when the remaining length is too short for the last part? This kind of sensor is cheap, reliable, and doesn't require any accuracy what-so-ever.

Before you say 'no' I have to present the mental exercise of: You say 1-1/2" accuracy. Envision 40 vertical light curtains an inch apart. They would give you 'inch accuracy' over the entire length but likely you really only care when the remaining stock is too short so delete the first 39 of them.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[3DDave]

A laser rangefinder can do this measurement, just use a little care in the initial alignment. I have a Bosch unit that does millimeter distance reporting. I think it could look down a 1/2 tube, but that would be tight. I have been searching out of interest and haven't found a factory usage module, just some OEMs for long distance units that certainly won't aim down a tube and some people hacking the Bosch units to talk with Arduinos. There's a bunch of triangulation distance sensors which also won't work well and it's been tough to separate them out.

 

[union7]

3DDave... I was going to pick up one of those Bosch rangefinders today...I am wondering though, how far away from the transmitter, the receiving sensor is..(laterally) because my window is small....

 

[union7]

itsmoked : no access for that kind of sensor, stock is inside a revolving tube. .

stock feeds axially relative to the outside tube

.."let's stick to the idea of non contact measurement from the far end of the tube, because it has advantages for me"

 

[3DDave]

It's a GLM 15, which I think has a 15 meter range. I just shot it through a slightly opened door and it wasn't confused by the slight scattering from dust or dirt on the lenses. It also worked on a high-polish mirror surface as well as visually black surfaces. The laser and sensor windows are about 3/8 center to center, so it's close.

There are a ton of Chinese module makers, but they all seem like ones for surveying with huge sensor windows.

These guys make an upgrade board for a rangefinder to add external serial and USB -

http://www.porcupinelabs.com/lr4/

looks like it would be $300 for the total sensor; figuring out the software and further hardware extra.

This also looks promising

https://www.bannerengineering.com/u...aser-distance-sensor-q4x-series.html#flt/6887

I found these looking for Laser Rangefinder Automation

 

[union7]

3/8" That's good to hear, cool thing is ; I can get one locally to test...thanks for the help.

I'll share what I find.

 

[roydm]

Another approach,
How about a 40 inch capacitance level transmitter with the Teflon insulated probe inside the 1/2" tube.
The aluminum tube will act as the ground
As the tube gets used up the Capacitance (depth) will be less and less.
Standard 4 - 20 mA output