There are some high accuracy ultrasonic sensors if that 2mm repetitablility affects your process.
Regards
Fernando

Also, what I posted was just a quick example. I'm pretty sure you can get some with much faster switching freq.


Brett

Hello,

Where are all of you standing regarding this subject?

It would be interesting to see that feature implemented into mach3

Also, for Flipz, i guess cutting underwater would throw off the ultrasonic height sensor, what kind of sensor are you thinking of using?

Regards
Fernando

we use Linear Displacement Transducers ( LVDT )
made by solartron meterology

one model although an old one which is still available from RS
which with a 12v dc input gives  a + - 9v dc output with 0v at centre of travel
RS 646-482  , but be aware they are expensive !

were you able to get the whole thing to work?

How did you implement it?
Regards
Fernando

Hi.

For laser cutting you need to use ring sensor around your nozzle and the position can be measured with linear potentiometer or LVDT sensor. The measurement can be translated to a analog voltage which can control servo drive directly - or if possible - through Mach.

The better way for metallic materials is capacitive height sensing where you have oscillator that gives frequency (in range of 200 kHz - 1 MHz) to your insulated nozzle. By monitoring the amplitude or phase locked loop comparison you can get out signal that depends of the nozzle distance ie. capacitance between nozzle and plate. This signal can then control your analog servo drive or given to control.

I have some data of capacitive sensors but no time to produce devices at the moment. If someone with electronics skills is willing to continue - I'm willing to co-operate.


BTW. I'm still waiting for faster M03 M05 handling to Mach as this is slowing my applications significantly!! Any news??

BR. Arto

I guess there are quite a few types of sensors that would work. I have been looking into linear pots and LVDTs, and plan to have mach red the analog voltage and control the position of the z axis.

For some applications we are left with contact sensing, for example waterjet cutting where you may cut different types of materials that would behave differently on some sensors, and then there is underwater cutting where welll... it just makes things go out of whack.

Regards
Fernando

I think the electromechanical sensor (ring around the nozzle, linear slide and distance sensor) and capasitive one are those which can work in real life. You can think of optical and ultrasonic ones but how many you need of those as you must sense around the nozzle - just one spot is not sufficient?

I agree the sensor ring is the right one for WJ and AWJ. If you need to minimize scrathes to your workpiece - the sensing can happen when piercing and then only occasionally say once per 200 mm or something.

With thin materials some vibrations may occur. With mechanical sensing these can be damped too.

BR. Arto

we only use one sensor as you can see in the picture in this thread
it works fine on our lasers , we can hold the height position to within 6 - 8um

Hey Dave,
One question... does your foot sensor tend to get stuck when passing over already cut material? seems that if it touches a slot prom the side it might tend to get stuck.