Measuring Linear Speed - Sensor Ideas

Bullzi

Lifetime Supporting Member
Join Date
Jun 2012
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Colorado
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Hi Everyone,
Working on my first job that will have some motion functions. The process involves pipe running on a conveyor system. The conveyor drive rollers are set up on an angle so the pipe will spin on the conveyor. I would like to be able to measure the actual linear speed of the pipe on the conveyor without the spin affecting the measurement.

What kind of sensor do you recommend to doing this? I was thinking a encoder on one of the rollers would work but since it is at an angle I am afraid it wouldn't be accurate. Plus there are times that i have seen the drive rollers actually spinning faster than the pipes are moving due to the loading on the conveyor. I was also thinking I could add a roller that is straight but the spin on the pipe would wear it down in no time.

Like I said this is my first time dealing with motion so any ideas that you have would be very welcome. Thanks to everyone for your time.
 
What about using some fast photocells located at fixed distance, so you know space (distance between photocells), then get time from Plc and then you can calculate speed. ?
 
What exactly are your "motion functions", other than learning the speed of the pipe ? Do you have to stop the pipe at a particular location, or perform work on it while it's moving down the conveyor ?

Obviously, workpieces that both slip and spin are not easy to measure or control.
 
One option to consider is non-contact measurement, such as offerings from Beta:

Beta Lasermike

I do not think the spin component will affect the measurement, but it is something to discuss with a sales engineer if deciding to pursue this type of device. There are other companies that offer similar instruments based on the same principle. We have good experience with Beta and predecessors.
 
This might be something for a machine vision system.

Vision sensors fed to controls can determine size and speed. I regularly get emails from Cognex about their vision capabilities.
 
+1 Mispeld
BETA LaserMike LaserSpeed® Pro Non-Contact Length and Speed Laser Encoder
The rotation should not be a problem.

Regards,
 
You can try with some trigonometric calculation,

The speed of advance of the pipe will be around the tangential velocity in the rollers multiplied by the cosine of the rollers deviation angle.
 
Thanks Everyone, The customer did get a demo of the BETA Lazermike so that is on the table but I know the price of it has them a little nervous.

Everything is in the conceptual phase now so everything's on the table.

What about using some fast photocells located at fixed distance, so you know space (distance between photocells), then get time from Plc and then you can calculate speed.

Not a bad idea at all.

What exactly are your "motion functions", other than learning the speed of the pipe ? Do you have to stop the pipe at a particular location, or perform work on it while it's moving down the conveyor ?

The motion function is in the form of a Preheating coil on a moving trolley. It will be servo controlled and will follow the ends of the pipe where they butt together on the line. This is used to preheat the ends (which are thicker than the rest of the pipe. So I actually trying to do 2 different things at the same time, one is detect where the 2 ends of the pipe but up together on the line and two is to follow those ends with the preheating coil to a stopping point.

There are 2 different conveyors one that loads the pipe and the other that feeds it into the furnace. Each one has its own VFD controlling the motors.

I am thinking that if I used a photo cell I could determine where the trailing end of the pipe is on the feed conveyor and if I know the speed of the pipe as it is being feed into the furnace I could then adjust the speed of the loading conveyor and could make the 2 come together where I want. Of course I would need to know the speed of the loading pipe too.

Maybe I am looking at this wrong. Anyone have any other ideas on how I can get the pipe to butt together before a certain point and then be able to detect the exact position of that joint?

This is not a precision application so +/- a few inches wont make a difference but it seems difficult to find a sensor(s) that will help me get the info I need into the PLC.

Thanks for the help.
 
Last edited:
Well, there's always the solution from the Stone Age ...

Have a metal stop come up and stop the first pipe. Assuming you know how long each pipe is, the location of the joint is known when the second pipe runs into it (perhaps detected by a vision system or a strategically positioned photoeye?).

After the pipes are preheated, the stop is moved out of the way and the pipes proceed into the furnace.

One caution: I've worked around furnaces. The high temperatures and contaminants (grit, dust, exhaust gases, etc.) are not kind to sophisticated electronics. I would suggest keeping your devices simple and easy to replace.
 
put 2 proximity or fotocells in 0.2 meter distance and look how long it takes between the cells.
on the road it is done with simple wire in the tarmac to control traffic jam.
 

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