Need Help!- how to control height with laser cutting.

[webcruiser8]

Hi all, We have waterjet cutting machine, and we want to add laser cutting.
The problem is how to add height sensing and control. I have searched
on line and seems the widely discussed capacitive or ARC control of
plasmar may not apply here. I'd really appreciate if someone can
shed some lights on what type of height sensing we should use.

John

[keebler303]

I think height control is the least of your problems. Have you thought about beam delivery, exhaust, contamination of the optics from the waterjet, etc.?

The big guys use a non-contact inductive or capacitive sensing method to determine the height above the workpiece.

Matt

[askjerry]

I have an Epilog 35w laser engraver... unlike a plasma or other cutting system, the laser is focused with a lens. This means that the focal point will not change from job to job... so as long as you have a flat surface, you set the distance once and run the job.

In the system I have there are two ways to accomplish the focus... automatic and manual. In the automatic mode, the table starts to rise until a probe touches the surface... then the table lowers by a known amount leaving the lens the specified distance above the part.

In manual mode, there is a magnetic gauge that attaches to the lens assembly, you raise the table until the gauge touches the surface than remove the gauge and start the job.

Hope that helps,
Jerry

[keebler303]

Jerry

I suppose it would be useful to know what he is planning to cut, but I assumed it was thin metal. With thin metal the heat makes it warp and you have to move the lens to keep the focal point on the surface of the material. If nonmetallics are used, then you are quite right, no high control is needed.

Matt

[askjerry]

That could be problematic... but it would depend on the thickness and the amount of warp. The system I have wouldn't cut through aluminum foil... but will go through 1/4 plywood. The focal point (at least on my system) can be +/- about 1/16 inch.

[webcruiser8]

Waterjet is good for cutting thick metal, but it is slow. So for sheet metal, we hope to use laser. My understanding from surfing the net, it seems in order to keep focused for a good cut, height control is very important to be with in 0.01". For people with experience in Laser cutting please comment on this, and most importantly, how to sense
the height? What do commercial laser cutters use for sensing? I heard a rumer that some laser machines use
gas pressure at the exit of the nozzle, is this true?
Thanks in advance. John

[keebler303]

We run a 100W Kern and a 30W Vytek here. I have run Kern's metal cutting height follower and it uses a capacitive sensor, as I mentioned previously. A change in the distance from the copper nozzle to the workpiece produces a change in the capacitance. Measure this capacitance and you know your height. Now the controller will move the focusing assembly up or down to maintain said capacitance.

Matt

[webcruiser8]

Originally Posted by ASTECH_CNCTools For metal cutting, both plasma cutter and laser cutting machine can do, but plasma & laser are in different application and work demand. If for thick metal, waterjet, plasma are more suitable, but plasma without high cutting precision; If for sheet meal, laser cutting machine will be good choice. They’re both easy operation, but if want higher work performance, some operation knowledge & skills are necessary. And for laser cutter, don’t worry, the automatic focus system is also available.

Are you just here for advertisement??? The info you provided here are just basic knowledge!!!

[lasfoc]

Hi, We use height control system on our industrial co2 lasers is this the application you are looking for?