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Jeff Body
12-06-2015, 3:11 AM
What is causing this? It's a vector file set to cut in RDWorks. 60w lightobject laser and air assist on a SH-350.
It's happening on wood and acrylic. The cut isn't going all the way through in a few spots and when it does it's cutting a perforated line. As you can see some areas are better then others EVEN when they are right next to each other. So I'm not sure if it would be alignment or focus. I've checked the alignment and it's spot on in all 4 corners. The cut itself isn't smooth at all. Does anyone have any ideas?
This is 1/4" MDF

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Here are my cut settings. I've tried it with and without the Laser through mode checked. At 85% I'm running 20mA and I've turned the speed all the way down to 8mm/s with only a very small improvement.

Can anyone help with some ideas?
Thank You!

Neville Stewart
12-06-2015, 3:25 AM
I'd guess your power supply is on the blink, literally. Does it act the same if rastering?

michael croft
12-06-2015, 4:54 AM
morning Jeff just had same problem so this may be the answer http://www.sawmillcreek.org/showthread.php?237975-Chinese-50w-laser-loosing-power

Bill George
12-06-2015, 8:23 AM
First that is not true wood you are trying to cut, looks like some sort of wood particle board using glue to bind it together. Glue can vary and be hard to cut. Has the machine worked fine up until this problem and have you cut or vectored before successfully?

If so I would then guess its your power supply or tube, but if the machine is brand new I would contact the seller to see what they have to say.

Dave Sheldrake
12-06-2015, 9:05 AM
8mm per second with a 60 watt tube on 1/4 mdf isn't going to happen reliably.

Try around 4-5mm per second. The pics are a classic example of the beam only *just* making it through and running out of steam before it gets a clean cut

Greg Knight
12-06-2015, 9:43 AM
For your air assist, try pushing about 30psi to the laser head. Anything more then the little compressor most laser companies seem to send with them. We changed ours to a larger air compressor, and it made a LOT of difference. Remember back to your fire triangle from Chemistry. Heat - Air - Fuel = Laser - Air - Product.

Kev Williams
12-06-2015, 11:28 AM
What Dave said-- All 4 of my lasers when cutting "almost" all the way thru, the results tend to look similar to these. Slow the machine down and let the laser get completely thru.

And this is strictly my opinion, but I've found air assist to hinder good cutting results rather than help, usually in the form of more leftover soot and harder-to-clean-up edges, especially with engraving plastics. The few times I've experimented to see if cutting with or without air is better, I've never found any noticeable difference in quality or depth of cut. When I DO use air it's strictly as an anti-flareup and smoke-moving measure, with the air pointing at least 1/4" away from the beam.

Scott Shepherd
12-06-2015, 6:07 PM
And this is strictly my opinion, but I've found air assist to hinder good cutting results rather than help, usually in the form of more leftover soot and harder-to-clean-up edges, especially with engraving plastics. The few times I've experimented to see if cutting with or without air is better, I've never found any noticeable difference in quality or depth of cut. When I DO use air it's strictly as an anti-flareup and smoke-moving measure, with the air pointing at least 1/4" away from the beam.

I've found close to the same thing Kev. On our Trotec, the air pressure adjustment is inside the right cover, so it's not adjustable without taking the cover off. I ran new tubing from it to a gage and regulator outside the machine, cranked up all the way up, and that would allow me to be wide open or open as little as I wanted. I had a larger cutting job and I experimented over a lot of cutting. I couldn't see a single noticeable difference in any change I ever made. Nothing. Zero. After running it like that for about a year, I finally pulled it all off, put it back to the original setup, and left it alone, never adjusting pressure.

Maybe it helps on something, or maybe it takes a lot more pressure to help than that onboard pump had.

Keith Winter
12-06-2015, 9:04 PM
Two things to consider. You have laser through mode checked, that limits laser power. I never cut with that on. Two, you are probably going too fast.

Bert Kemp
12-06-2015, 9:33 PM
Yep to fast my 60 watt cuts 1/4 but its like slow 6 to 8 mmps ,for me its faster to cut 2 1/8 and glue them together. I have the time and the extra cost is minimal, but I get much better results and less chance of Fire as I had a few weeks back cutting 1/4. Because its slow with more power that fire chance increases .

Jeff Body
12-07-2015, 11:30 AM
Thanks guy. This is the first time I've cut this MDF with the new tube and power supply. I cut it before with the original overpowered 40w tube but I don't remember what settings I used. I through out all my old settings when I replaced the parts and starting over documenting all the setting for the new tube and power supply.
It's been awhile but I don't remember having this much trouble cutting it.

I've been cutting 1/4 cherry and maple at around 15mm/s with 85% power so i figured something is wrong if I had to lower my speed this much for MDF. I also tried unchecking the laser through check box and it made no difference.
I'll try dropping my speed some more and give that a shot.

The tube and power supply are only 2 months old. My stock tube and psu fried on my so I upgraded from a 850mm tube to a 1250 tube from lightobject. I also replaced the power supply to match.

Neville Stewart
12-07-2015, 11:44 AM
MDF is probably 30% glue. It's far more dense than pure wood.

Gary Hair
12-07-2015, 11:58 AM
MDF is probably 30% glue. It's far more dense than pure wood.

The good news though is that it is fairly consistent density and once you figure out the right settings they tend to stay pretty close. Not the same with plywood or even solid hardwood.

Neville Stewart
12-07-2015, 12:10 PM
Very true indeed. You can tell I'm off work today :)

Jeff Body
12-07-2015, 3:31 PM
question about air assist.

I have a HF airbrush compressor. I'm only able to get about 8 psi on the gauge of the compressor and that's if I close to valve on the laser head some to generate the restriction. The pressure valve on the compressor itself is wide open. My laser head just flows too much air to be able to generate any pressure.

How are some people able to get 30 psi.

If I block off the air it'll generate enough psi to shut off the compressor.

Am I missing something?

Kev Williams
12-07-2015, 3:42 PM
On the rare occasion I use the air assist in my LS900, I set the airflow so it just noticeably moves the smoke, which is about the same flow as if I lazily blow thru a piece of 1/8" tubing by mouth.

However, my LS900 uses a hose and copper tubing for the air, NOT a nose cone. A cone is probably going to need a little more air, but not much.

Last summer I was sandblasting my boat with play-sand down to 30 psi, not sure why anyone needs that much air for cutting with their laser, just seems extreme to me.

Keith Winter
12-07-2015, 8:30 PM
I cut quarter inch with 12-14 speed on my 130w chinese laser you need to slow it down more than a little. You're going way to fast for a 60w.


Thanks guy. This is the first time I've cut this MDF with the new tube and power supply. I cut it before with the original overpowered 40w tube but I don't remember what settings I used. I through out all my old settings when I replaced the parts and starting over documenting all the setting for the new tube and power supply.
It's been awhile but I don't remember having this much trouble cutting it.

I've been cutting 1/4 cherry and maple at around 15mm/s with 85% power so i figured something is wrong if I had to lower my speed this much for MDF. I also tried unchecking the laser through check box and it made no difference.
I'll try dropping my speed some more and give that a shot.

The tube and power supply are only 2 months old. My stock tube and psu fried on my so I upgraded from a 850mm tube to a 1250 tube from lightobject. I also replaced the power supply to match.

Dave Sheldrake
12-07-2015, 8:52 PM
On the rare occasion I use the air assist in my LS900, I set the airflow so it just noticeably moves the smoke, which is about the same flow as if I lazily blow thru a piece of 1/8" tubing by mouth.

However, my LS900 uses a hose and copper tubing for the air, NOT a nose cone. A cone is probably going to need a little more air, but not much.

Last summer I was sandblasting my boat with play-sand down to 30 psi, not sure why anyone needs that much air for cutting with their laser, just seems extreme to me.

I routinely run 25 to 40 psi on the CO2 machines under 200 watts and up to 300 psi on the big metal cutters Kev, the standard cones aren't really great designs, to get any real benefit they have to fit in with laminar flow calculations, when they are right, it makes a big difference :)

Dave Sheldrake
12-07-2015, 8:53 PM
I cut quarter inch with 12-14 speed on my 130w chinese laser you need to slow it down more than a little. You're going way to fast for a 60w.

I'd say 3 - 5mm per second to be honest...max @ 85% power on a 60 watt DC pipe

Jeff Body
12-07-2015, 11:12 PM
I cut quarter inch with 12-14 speed on my 130w chinese laser you need to slow it down more than a little. You're going way to fast for a 60w.

Well...................
By the sounds of it my thinking was completely wrong that I should be able to cut it at a higher speed.
Guess I'll have to lower the speed and check it out later this week when I get home.


I'd say 3 - 5mm per second to be honest...max @ 85% power on a 60 watt DC pipe

I'll give it a shot.

Thanks guys. This forum is full of some helpful people.
I'm trying to make a better life for myself. My dream is to work for myself one day so I'm learning all I can.