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Topic: Job Shop forum / Modified cutting nozzle

Page: 1

Posted: 09-12-2008 16:59 by midtherm

Has anybody had any experience with modifying nozzles? I have seen some that have been made into almost a point, for cutting thin stainless.
Posted: 10-12-2008 10:41 by Microm1

Yes it is possible to modify nozzles and what you modify depends on what you want to achieve. 

In my view nozzle design, gas flow and metal removal are one of the great black arts of laser cutting. There is much fundamental research in universities: Calculations of mind boggling complexity, taking days of computer time to complete can give idealised views of some simplified situations. But in practice nozzle choice is is down to what one has and what works.

Having said that most nozzles supplied with CO2 machines do an adequate job of cutting.

Separate the task into two:-

The inside of the nozzle, a mm or so of the front face around the hole and the shape of the cavity including the lens determines the gas jet. This has to satisfy many diverse and sometimes contradictory needs. Supply N2 with minimum turbulence but at high speed to transfer momentum to the molten metal or supply O2 laminarly but with sufficient volume to react with the metal; possibly cool the cut/metal; possibly not lift any plastic film; probably not waste any with too big a hole.

 The outside of the nozzle is of no consequence to the cutting (apart from a mm or so around the hole) but may have influence the mechanical stability of the nozzle/ lens alignment; if there is a capacitive height sensor then the shape of the nozzle determines the shape of the field and the system's Z response; it has to be strong enough to withstand the (possibly high) pressure of the gas, and one may need to miss some nearby piece of metalwork on the job. 

So, as I said, it depends. Things interact with other things. What do you want to achieve?

Neil

 

 
Posted: 10-12-2008 16:56 by midtherm

Wow, thanks for that Neil. I just thought I would try some as I have seen some very different shapes being used, Especially on thin stainless.

Generally the standard nozzle works fine on most applications, but I feel that we should be able to achieve a better or finer cut when cutting small or complex shapes. I havn't looked at the technical side of this.

I am hoping that any heat generated will be disipated away from the cut surface faster by having a finer "point" at the nozzle. I'll try it when I get a minute and let you know what happens.

Thanks for your comments.

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