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Thread: Shenhui laser and corrugated cardboard

  1. #1
    Join Date
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    Shenhui laser and corrugated cardboard

    Hi,

    I recently got myself a SH-G350 laser machine. It came with an airpump for the air assist and the standard lens, I assume 40 mm.
    When trying to cut corrugated cardboard I find it very difficult to get through the material. The cardboard is 5 mm thick and of the dual layer type (basically a sheet of fine corrugated board on top of a course layer).
    I have to set the head as low as possible (focus almost on the bottom layer, head almost touching the material), but because the cardboard pieces are always a little bended I have to give it a little more room so the head will not touch the cardboard.
    When I do one slow pass I will go through, but the cut is very wide and the edges are very charred. Two or more faster passes result in less charring, but it never seems to go through the bottom layer completely.
    When I do a slow pass I notice flames inside the cardboard that sometimes linger even after the head has passed the area. It seems that the air assist works as an oxygen source rather than a flame suppressor.
    So I have two questions. Will a longer lens work better in cutting (after reading a lot on this forum I understand that shorter lenses are better for engraving)?
    And second, will a better compressor for the air assist result in cleaner cuts? The pump that came with the machine is a rather weak affair. I've read some posts about people setting the air pressure to two bar, the air flow from this pump can easily be stopped by lightly putting your finger over the outlet. No way of telling how much pressure it produces, but it can't be a lot...

  2. #2
    Join Date
    Sep 2009
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    You should have a 50 mm focal in it. Have you checked the mirror alignment.

  3. #3
    Join Date
    Jul 2004
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    Victor, NY
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    Hi Arjen;
    What is wattage of your machine? Offhand I would say your head is too close to the material. Experiment with different heights and speeds.
    Best Regards,
    George
    Laserarts
    *twin 80 watt Shenhui 1280
    *60 watt Laserpro Mercury -42ips
    *(2) 30 watt Laserpro Venus-42 ips
    *whole bunch of woodworking/metalworking machines
    *128 screwdrivers (all needed)
    *wonderful wife (1st) of 53 years who allows me to collect screwdrivers

  4. #4
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    The tube is 50W. And of course I tried a lot of different speeds, numbers of passes and focus heights. When I focus on the top of the material I cut through the top and the 'filling', but never through the second layer. It gets through when I cut at 5mm/sec, but the paper always burns at these low speeds. And then the distance from head to material is only 6 mm, so when I focus lower there is not much room left between head and material. On a flat piece of cardboard, I can leave the head about 2 mm. above the material, and it goes through at 15 mm/sec. But it still burns quite badly. I can see glowing at the edges that flare up a bit after the head moves along. It looks as if the air assist is adding to the fire in stead of preventing it. Like blowing at a glowing stick to get the fire going.

  5. #5
    Join Date
    Oct 2004
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    Cape Town, South Africa
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    Huge fire risk with fluted corrugated , the flutes channel air very well ....
    Shenhui normally comes with a 40mm lens as standard unless you specify otherwise. A lens is cheap , $35 or so , so try a 75 or 100mm one , I don't think you will get much joy...
    I tried corrugated with nitrogen assist and a 4" lens it didnt work well .. we just say no to cutting it.
    Rodney Gold, Toker Bros trophies, Cape Town , South Africa :
    Roland 2300 rotary . 3 x ISEL's ..1m x 500mm CnC .
    Tekcel 1200x2400 router , 900 x 600 60w Shenui laser , 1200 x 800 80w Reci tube Shenhui Laser
    6 x longtai lasers 400x600 60w , 1 x longtai 20w fiber
    2x Gravo manual engravers , Roland 540 large format printer/cutter. CLTT setup
    1600mm hot and cold laminator , 3x Dopag resin dispensers , sandblasting setup, acid etcher

  6. #6
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    A longer lens (70mm) is on it's way from China, so we'll see what happens when it arrives. Do you think more air pressure will help or will it only make things worse?

  7. #7
    Join Date
    Oct 2004
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    With corrugated , you are damned if you do and you are damned if you don't in regard to air assist. Too little and you are guaranteed a flame up , too much and you are guaranteed a blowtorch effect and a major fire.
    Really not worth the risk with this stuff - there are so many other things the laser can do and cut.
    Most guys cutting corrugated and doing scoring etc use something like a flatbed plotter/cutter like this one.
    pl679236-corrugated_flute_cardboard_paper_carton_artioscad_sample_maker_cutter_table_template.jpg
    Rodney Gold, Toker Bros trophies, Cape Town , South Africa :
    Roland 2300 rotary . 3 x ISEL's ..1m x 500mm CnC .
    Tekcel 1200x2400 router , 900 x 600 60w Shenui laser , 1200 x 800 80w Reci tube Shenhui Laser
    6 x longtai lasers 400x600 60w , 1 x longtai 20w fiber
    2x Gravo manual engravers , Roland 540 large format printer/cutter. CLTT setup
    1600mm hot and cold laminator , 3x Dopag resin dispensers , sandblasting setup, acid etcher

  8. #8
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    Abcoude, the Netherlands
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    That is a nice machine, and I agree you should use the tools best suited for the job. But since this is only a hobby so far (I'd love it if the laser would turn into a profitable machine, but I wouldn't know where to start) I'll have to make do with what I have. It's cutting thin plywood (5mm max) quite nicely and it engraves most materials very well, so the things I bought it for are going well. But one always wants more...

  9. #9
    Join Date
    Oct 2011
    Location
    Vancouver BC
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    I've done some cardboard with a 80 RECI and 50mm lens, air assist if I recall (shop air pressure with regulator, don't recall the settings). Cut great!

    Only problem was the cardboard wasn't ever flat and I had to double side tape it down to the table. With a vac hold down like my CNC it would have worked very well. Regardless, I also now turn these jobs away, as it's not the best use of my time......but trying it was neat.
    80 watt RECI 1290 Shenhui laser.
    Chinese Quick CNC 5x10 toolchange
    Unofficial record holder of 6 tubes shipped for one machine. 2 defective and 4 broken. Recommend Coletech for replacement tube!

  10. #10
    I cut a lot of cardboard with 60w at speed of 30 and power of 40 with no fires!

  11. #11
    Join Date
    Jul 2013
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    Changed the lens to a 70mm. This required a bit of mirror adjusting, but after that was out of the way I can now cut 6mm. corrugated cardboard at 20mm/sec and 80% power. And since the head is now 37mm from the cardboard and focus is less critical a slight bend in the cardboard is no problem. Two passes at 30mm. leaves a cleaner cut (less charred) but takes a lot longer when doing complicated cuts.
    Next step is buying a better compressor and experiment with air pressure, but for now this will do.

    Thanks everybody for taking the time to respond.

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