Need Help Bystronic 3015: Parameters for Cutting Aluminum

[AceLaser]

Hello,


I am in charge of the daily use of our Bystronic 3015 and seeking help with cutting aluminum. Our stock for the laser consists of .080" (2.5mm) , .125" (3mm), and .250" (6mm) 5052 alloy - 4'x10' and 5'x10'. Please refer to the lower part of this post for machine specs.


Currently, we are receiving a hard, "sawblade" burr on all cut edges of .125" and .250". The .080" leaves a smaller burr is the same density. Both burrs are hard enough to shred our strongest 80 grit that we use for debur. The plume is usually tilted slightly away from the the feed direction with white and yellow "sparks". We don't typically get a plasma burn on the top of the material, but it does still happen at points where an axis change will happen on top of a grate. In the past, .250" has always produced a worse result, but we have been succesful in reducing the burr to the same as what we get on .125". The .080" tends to cut clean, only leaving a finger-rocking burr if any.


We use Nitrogen for all of our aluminum work and Oxygen for steel. .250" aluminum requires Oxygen as an assist gas.


Tape shot reveals that we have an oval shaped or "cat's eye" beam path. Main operator claims that this causes a lot of our trouble. I have not found enough information to back up that claim.


Our ultimate goal is to minimize impact on our Spray Prep department with post-laser prep. I'm personally trying to set a tolerance of less than 1mm for acceptable burr.


Here are our parameters:


.080

Head: 5"

Focal Point: 1mm

Nozzle Diameter: 1.5mm

Nozzle Type: HK15

Power: 4K, 70% piercing, 40% Cutting

Feed: 7500 mm/min

Gas Pressure: 3 bar piercing, 8 bar cutting


.125"

Head: 7.5"

Focal Point: 3.5"

Nozzle Diameter: 1.75"

Nozzle Type: Hk17

Power: 4k, 80% piercing, 75% cutting

Feed: 3150 mm/min

Gas Pressure: 2 bar piercing, 9 bar cutting


.250"

Head: 7.5"

Focal Point: 6.9"

Nozzle Diameter: 2.5mm

Nozzle Type: HK25

Power: 4k, 80% piercing, 90% cutting


Machine Specs:

Resonator: BTL 4000 (DOB 2001) - 4200w - 20 mm beam

Chiller: Koolant Kooler - 13HP Compressor - 5HP Pump

Filter: Torit Filter System (Barrel)

Air Supply: Shop Air on isolated line set - 120 gal - 175 max pressure - 1100 rpm - 15 hp motor


Any suggestions are welcome and I will try to respond as quickly as possible. I can provide pictures of the cut quality, if interested.


Thanks for your time.

 

[LaserEd]

"Eye" shaped tape shot would indicate a misaligned nozzle or beam path - that said cutting the direction in parallel with the "thin" direction might be ok but the "wide" direction will cause a lot of difficulty. This is true in most materials. Al I have always used a deep focus (below surface of material) on thicker materials. You may try something around 1/8 or so of material thickness.
First thing I'd look at is getting a better tape shot.
Couple quick questions:
When was the machine last aligned?
Does the machine cut well on CRS or HR materials?

 

[AceLaser]

LaserEd Thank you for your reply.

Our last diagnosis by a Bystronic Tech was Spring 2017. He stated the condition of our resonator was the cause of the beam shape and suggested a rebuild (which is way out of our price range).

We have recently adjusted our power/focus ration to allow the focal point to drop below the material and have started to receive a better cut quality, but not to where we need to be. The laser has always carved through CR and HR steel like butter with zero dross. This was the machine's initial use at the start of its life at another company.

We have the means of aligning the nozzle and that is usually performed on a daily basis.

 

[LaserEd]

The resonator is often the cause of bad beam "shapes". I'd probably say a good optic cleaning and/or output coupler (mirror) replacement would be the place to start - that shouldn't be to expensive. I'd guess 6-8 hours for cleaning and re-alignment (JFYI). Just doing that might be enough to improve performance thus better throughput.

Another quick diagnostic would to be to take a "tape shot" without the nozzle. Here's how: use a small piece of acrylic lay it on table about 7" below tip (twice focal length from lens), remove tip, and do a quick shot - if the beam is round then its nozzle alignment, if lens is clean and in good shape its either a beam path problem or resonator problem (usually resonator).

Hope I helped more than hurt!

 

[AceLaser]

LaserEd - We will try to shoot it without the nozzle and see our result. Thanks for that input!