PPI Expert Wanted

Discussions and help on this commercial controller.

Moderator: twehr

PPI Expert Wanted

Postby iGull » Fri Jun 29, 2012 9:04 pm

Hi

My laser is now getting a heavy pile of use for various projects. One of my main cutting materials is balsa - everything from 0.8mm (1/32") to 12mm (1/2") along with various plys and plastics.

My laser is 60W with a 63mm lens, I decided to give PPI a try with a view to reducing the amount of 'edge burn' on the balsa. It does indeed reduce the burn, but I have to increase power by a huge amount to get it to cut. As an example, 3mm balsa would normally cut at say 40mm per sec with 40% power and 20% cornering. Keeping the speed the same, I need to ramp up the power to about 95% to ensure it cuts through. The edge burn is most definitely reduced, but 95% power seem a helluva lot to cut through balsa as thick as a matchstick ! Reducing the feed kind of defeats the purpose to an extent as the jobs double in time - life is just a compromise :D

Without PPI, I can up the air assist pressure to about 2 bar and that reduces it by a huge margin, but that means using my air compressor rather than the wee hailea air pump.

I was hoping that PPI may have been a magic bullet - any other solutions ? Beam diameter with the 63mm lens is 0.2mm FWIW - I'm wondering if changing lenses might help ?
The 'process' side of things is not my strong point - I used to have 'process engineers' to do that for me :lol:

Cheers

Neil

PS Rather than stick this in a separate thread, does anyone know if the DSP will accept a 'pulsed' signal for the water flow input, or does it have to be a steady value - say a high for flow oK ?
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Re: PPI Expert Wanted

Postby macona » Sat Jun 30, 2012 9:18 am

I always ran about 30-40 psi on the laser cutters we had. Tried the little air pumps that came with the machine and was not impressed. Lenses stay a lot cleaner and less burning and warping with more air, also cleaner cuts in acrylic too.

Of course you need a pretty clean compressor. I have a 5hp Powerex Scroll compressor that is oilless and very clean. http://www.powerexinc.com/products_cate ... ll-product
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Re: PPI Expert Wanted

Postby twehr » Sat Jun 30, 2012 7:38 pm

iGull wrote:Hi

My laser is now getting a heavy pile of use for various projects. One of my main cutting materials is balsa - everything from 0.8mm (1/32") to 12mm (1/2") along with various plys and plastics.

My laser is 60W with a 63mm lens, I decided to give PPI a try with a view to reducing the amount of 'edge burn' on the balsa. It does indeed reduce the burn, but I have to increase power by a huge amount to get it to cut. As an example, 3mm balsa would normally cut at say 40mm per sec with 40% power and 20% cornering. Keeping the speed the same, I need to ramp up the power to about 95% to ensure it cuts through. The edge burn is most definitely reduced, but 95% power seem a helluva lot to cut through balsa as thick as a matchstick ! Reducing the feed kind of defeats the purpose to an extent as the jobs double in time - life is just a compromise :D

Without PPI, I can up the air assist pressure to about 2 bar and that reduces it by a huge margin, but that means using my air compressor rather than the wee hailea air pump.

I was hoping that PPI may have been a magic bullet - any other solutions ? Beam diameter with the 63mm lens is 0.2mm FWIW - I'm wondering if changing lenses might help ?
The 'process' side of things is not my strong point - I used to have 'process engineers' to do that for me :lol:

Cheers

Neil

PS Rather than stick this in a separate thread, does anyone know if the DSP will accept a 'pulsed' signal for the water flow input, or does it have to be a steady value - say a high for flow oK ?


Don't know what your PPI is set at. If it is pretty low (200 ish), you could try upping it a bit to get more power without too much additional charring. I cut 1/8" craft ply with 250 ppi but I run very high power. Upping that to 500 or 700 will give more power.

Don't know about the pulsed signal - try it and let us know :mrgreen:
tim
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Re: PPI Expert Wanted

Postby iGull » Sun Jul 01, 2012 8:09 pm

twehr wrote:Don't know what your PPI is set at. If it is pretty low (200 ish), you could try upping it a bit to get more power without too much additional charring. I cut 1/8" craft ply with 250 ppi but I run very high power. Upping that to 500 or 700 will give more power.


I'll give that a try Tim - I have 60W to play with, I should have thought that would be sufficient :D

twehr wrote:Don't know about the pulsed signal - try it and let us know :mrgreen:


Will do - my own flowmeter died (water seepage into the electronics, insufficient sealing on my part :oops: ) I could make another, but don't have a sensor to hand - I thought I'd try a cheap and cheerful vane type temporarily and wanted to know if they'd work - I'll let you know :D

Cheers

Neil
EMOs are a sign of weakness ...
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