non-contact measurement

Hi Randyl,

I've no experience with non-contact length measurement but here's one idea that I have:

You install two photo sensors a few inches or centimeters apart (designate distance as "D"). You will also need two timers (T₁ and T₂).

T₁ measures the time it takes to break beam A and beam B.

T₂ measures the time it takes to break and unbreak beam A.

Your length will then be:

L = D ÷ T₁ × T₂

The accuracy will depend on how well you control the speed of the pipe or board. If it's constant, the accuracy will be high.

Vulcan,

Thanks for the ideas! They are good. Our problem is that speeds will vary and sometimes the material will even reverse direction before the final cut is made.

Randy

I use a laser phototcell and a encoder which is in a fixed position on a converyor and with a digital diplay use it to display the length of steel plate in mm to the operator on the line which runs up to 30 meters/min.If you think this could help you then contact the company Banner and ask a sales rep to come and see you.

Thanks...this sounds like what we are looking for. I found Banner Engineering which looks to be the company you referred. I'll check them out.

Thanks again,

Randy

Randyl, is this to measure the length to make the cut, or is it just as the first post suggested to measure a cut length of pipe etc...?

If its to measure where to make a cut then how accurate does the measurement need to be?

John.

Electroman,

It's to measure the length for the cut and which can be anywhere from 8'6" to 41'.

On a lot of the projects it can be sloppy. + or- one inch, although my preference would be .125 of an inch.

OK, I know this sounds sloppy but the cut material will be further processed into a finished product.

Thanks,

Randy

Another one just popped up. Mount your laser emitter at an angle and height such that when the pipe or board breaks the beam, the length of the board is just right for cutting.

<Surface is TOO ROUGH>

How rough?

<moving under it>

-Moving on SOME Roller--take the measurement *off that Roller.

Best way out.* Rubber tyred pickoff signalling out 1 pulse every 1" or 0.1 foot?

Or maybe the <boards or pipe> can be First marked with a paint marker every 1' or 0.1' before loading to this Length-Measured-Cutoff Table . TOO-ROUGH will be now bypassed . Sense-the -coloured-spot system will take over.

Laser Salesman was right.

use a laser sensor length wise looking at the end of the tube. Out put a analouge signal to small plc and use this to cut at whatever threshold required.

Give Keyance a call. They have the non-contact systems you need and the design group to help.

Here is a lot of companies that specialize in what you are asking

http://steellinks.com/pages/Sensors__Gages_and_Measuring_Devices/Length/index.html

Thanks everyone! You got me on the right track. I think we'll have this project under control shortly.

FYI. I got a call from a Keyence rep. Unfortuately... he didn't know they sold what I was looking for. They do as well as several other companies.