blow-out at end of cut

[459459]

I am having a problem with blow-out at the end of the cut on holes in 1/4 inch hot rolled steel. We use SMP for programing for our 2000 watt Amada laser. Can't seem to get rid of the blow-out unless I pulse the entire hole. I use a 3mm nozzle ..and a clean 5" lens .. and centering is good. Thanks for any help !

 

[msandoval]

What kind of diameter in 1/4" are you trying to achieve?

What is the power, frequency, duty, feed, gas pressure?
When you say blow-out, does it happen during cutting, piercing?

For starters, I think the 3mm Single Nozzle is rather large. I would use a 1.5 or a 2 instead.

 

[459459]

Thanks msandoval for the speedy reply !
Our 2000 watt laser has always used a 3mm nozzle for anything over .125 thickness mat'ls. The blow-out occurs when cut on diameter goes beyond the start point a bit and travels on previously cut portion of the hole.The rest of the cut is fine. Edges and corners are ok also. Would have to get back to you tomorrow to give you the cut data you asked for. This has been a recurring problem unless we pulsed the holes ... and this is not a solution ... too time consuming !
Thanks again !

 

[ScottI2R]

The blow-out occurs when cut on diameter goes beyond the start point a bit and travels on previously cut portion of the hole.

This isn't being caused by the slug falling per chance is it? And cutting into it.

Scott

In a hundred years, it isn't going to matter anyway.

 

[459459]

Thanks ScottI2R,
But, no. The blow-out is too consistent on each hole. I really believe it's as I said in my previous reply: cut goes beyond start point of cut ... trying to cut where it has previously cut. Almost has to be programming ... just don't know how to get around it ! Do you think eliminating the lead-out would help?
Thanks again

 

[ScottI2R]

I've an idea.(first mistake)
This assumes (second mistake) that you are cutting a circle. I am using this as an example only. Start off toward the center of the slug and program a radius into the actual cut path and continue through the cut as normal. When you reach the endpoint of the cut, make a radius move BACK into the slug where no damage will occur in the actual cut. We have sucessfully done this with laser cutting as well as wire EDM cutting.

Good luck and I hope this helps some.

Yes, I know what you mean about cutting in pierce mode, not cost effective.

Scott

In a hundred years, it isn't going to matter anyway.

 

[459459]

Thanks again Scott,
Looks like I have something to try tomorrow ... will keep you informed as to results !!

459459

 

[ScottI2R]

Thanks,
I hope it works out well for you. Man I miss all the laser work I used to do....After all, it was light work.

Scott

In a hundred years, it isn't going to matter anyway.

 

[msandoval]

I would do the following:

Assuming that you are using a straight lead-in (90 Degrees), I would use edge and approach data to the following tune:

Edge and Approach Data: 201

Work Angle: 91 Degrees
Pierce Power: 0
Pierce Freq: 0
Pierce Duty: 0
Gas Kind: Same as cutting condition
Gas Pressure: Same as cutting condition
Vor Rate: 3.5"/min
Recover Frequency: 10 Hz
Recover Duty: 35
Distance: 0.059"

Either use the above, or use a line with an arc in the lead-in, of course this depends on the diameter of the hole.

Assuming the diameter of the hole is greater than the material thickness, use 50"/min Feedrate, Power of 1300 Watts, frequency of 800, and Duty cycles of 85% with a .5 Kg of Pressure.

Best of luck to you

 

[IRstuff]

Is the blowout symmetrically placed on the cut line?

Are you using the recommended backing material, or whatever is supposed to be underneath your workpiece?

Is it possible that you're getting a reflection of the laser?



TTFN

Eng-Tips Policies FAQ731-376

 

[459459]

So,I have some ammo for this morning to try. Much appreciated.
This forum is new for me ... so far I'm impressed with the responses and the speed of response. I don't have access to the web during work so will update you later on results.

Thanks !!

 

[459459]

Thanks again guys for the info. The boss put me on a punch machine today ... back to the laser tomorrow to try some experiments ... including stuff from you. Will update for
for you.
Ed

 

[459459]

Hi again,
I used a combo of your suggestions: a 0 degree lead-in and no lead out ... a little tweaking with msandoval's cut conditions ... and ended up with a good hole with barely a blow-out showing !

Thanks again for everyones input !!
Ed