Sensors for plasma cutting
lfjill
Posts: 4
I have implemented a plasma cutting solution with proximty inductive sensors.
It works fine until the metal surface reaches about 200 centigrades or higher, then sensors function changes radically, so the system get farther and the plasma fails.
I wonder if your ultrasonic (or another kind) sensors could work with a plasma cutting system (as hypertherm), that is, that heat doesn't affect the distance measurement and neither the electromagnetic noise of plasma affects it. Have someone had an experience with this kind of cutting systems?
Thank you for your advice.
Luis
It works fine until the metal surface reaches about 200 centigrades or higher, then sensors function changes radically, so the system get farther and the plasma fails.
I wonder if your ultrasonic (or another kind) sensors could work with a plasma cutting system (as hypertherm), that is, that heat doesn't affect the distance measurement and neither the electromagnetic noise of plasma affects it. Have someone had an experience with this kind of cutting systems?
Thank you for your advice.
Luis
563 x 463 - 500K
Comments
As I mentioned via email, heat does affect ultrasonic sensors to a degree (no pun intended). :nerd:
It's likely a case of choosing the right elemental materials to construct the probe from. Things like Curie Point will always be a problem but different materials have different limits.
v = 331m/s + 0.6m/s/C * T
So bump the temperature up by 200C for part of the round trip and and you have a substantial change in speed and hence distance measurement.
Didn't someone have a cheap laser range finder posted somewhere?
IIRC, it was using a standard $1 store laser pointer.
Also strangely enough I was just talking to Bill Latino of LeddarTech at the Sensors Expo in San Jose. They have a LED range finder that looks out across a 30 degree or so beam width and reports distances of objects at 16 different angles in that beam.
They have an evaluation kit of this that you can buy on line for 255 dollars.
http://leddartech.com/app/uploads/dlm_uploads/2016/02/Datasheet-Leddar-Sensor-Evaluation-Kit.pdf
All of which is preferable to the laser range finder we bought last year for 2500 Euro!
Thank Merriam-Webster, you done a better job of exsplaining it.
¿What is "C"?. If it would be near 1, and T= 200, the change is .003, wich is not relevant.
I could be wrong. But Google is your friend here.
If someone has been in touch with plasma cutting, could have a hint.
Do somebody have used a laser pointer to know distance in short ranges? In google "IIRC" stands for a "Reporting Council" for financial data of companies.
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Our 2500 Euro laser range finder does much better, but that's hardly what you want.
Is your plasma cutter intended to operate over evenly finished surfaces, like metal sheets or bars, or should it also accept any kind of workable surface, perhaps with coarse and unpredictably distributed imperfections or ondulations?
Henrique
There are many low-cost THC units available.
https://www.hypertherm.com/en-US/learn/articles/torch-height-control-for-plasma-cutting/
That was a very informative link. Thanks for sharing.
C = Speed of Sound
gamma = adiabatic index, typically around 1.4
R = Molar Gas Constant = ~287
T = Temperature in Kelvin
When going from 293Kelvin to 473Kelvin (approximate numbers) the speed of sound goes from 343 m/s to 436 m/s.
Also keep in mind you might be dealing with large temperature gradients, which means you won't have a constant speed of sound between the objects (assuming there are large temperature gradients).