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Thread: Chinese laser purchase/Shenui/Laserworks tips and tricks thread

  1. #46
    For alignment, the final mirror in my testing was only useful for getting the beam central through the tip of the cone. Very little further adjustment is possible without causing reflections and off center beam. So when you drill holes in acrylic and find that you have an angle, you have to go back to the laser mounts. I found that a full turn on one of the plastic screws at the high voltage end of the tube (probably only 1mm movement) was enough to change the angle to fix it (after the further necessary resetting of mirror 1 and 2.

    I could curse the narrow nozzle, but it greatly improves the efficiency of air assist.
    Shenhui 1280 100W RECI

  2. #47
    Join Date
    Mar 2011
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    Olalla, WA
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    If the beam is centered on the final mirror, as it should be, and you adjust the final mirror so that the beam is centered in the cone and your cuts are at an angle then the problem is the alignment of the laser head itself.

    On neither of my machines was the laser head aligned perpendicular to the table in either the left/right or fore/aft directions. An easy way to check is to fire a dot, lower the table quite a ways then fire again. The latter will be out of focus but it should be centered on the first dot.
    Shenhui 1440x850, 130 Watt Reci Z6
    Gerber Sabre 408

  3. #48
    The beam was centered on the final mirror and it was adjusted to center the beam in the cone, but moving the head on its mounts in any direction (including straight down with a spirit level in both axes) always resulted in the dot when the table was lowered being down and to the right. Still trying to explain this except that perhaps the angle on my head between the center of the final mirror and the cone isn't straight??
    Shenhui 1280 100W RECI

  4. #49
    Join Date
    Mar 2011
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    Olalla, WA
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    I use a square to determine if the laser head is perpendicular to the table.

    If the final mirror is adjusted out too much (or in too much, not sure if that is possible) then the beam will have to be steered towards the center of the lens, which then can make it come out at an angle. I generally start with the mirror turned in all the way, then out a quarter turn to give the mirror room to move.

    Someday I want to replace the head with something similar to what Epilog uses.
    Shenhui 1440x850, 130 Watt Reci Z6
    Gerber Sabre 408

  5. #50
    Thanks, I took the time to go over it all again today and decided to lower mirror #2, tweak the head further to get it square, adjusted the #3 mirror to get it straight, got it central in the cone and got the cuts all straight in all corners of the table.

    Following that, because my new air compressor was too noisy and cracked (it is going back), and following an idea on the oplaser forum, I made an acrylic insert (3mm thick) to go into the nozzle, and found that a 2mm central hole with 4.7mm outside diameter worked well for a really tight push fit. I tried to use kerf width compensation, but narrowed down a crash and problems with the processing window hanging when simulating or sending to the laser was due to using this and nested items, I checked this on Windows 7 and XP and they are the same, so I won't be using kerf width compensation.

    The result of the new nozzle insert was much higher air pressure at the nozzle, like a free compressor upgrade so that there is not really any clean up required on untreated wood after cutting now most of the time. The results are comparable to running 29 PSI on the big noisy compressor, except I'm only running 5 PSI.

    I tried using a blank insert and let the laser fire its way through, and that worked but produced reflections/ghosting on the cuts, as did inner diameters smaller than 2mm.

    However, with 2mm requested, with kerf compensation off I got 2.15mm, which is less than a quarter of the cross sectional area of the original nozzle, and you can tell from the way that it hits the knife blade table or your finger. The earlier alignment work paid off because the beam is central in the nozzle all around the table which is necessary for this mod to work and not keep melting the entire insert.
    Last edited by john banks; 03-11-2012 at 4:06 PM.
    Shenhui 1280 100W RECI

  6. #51
    Join Date
    Jun 2011
    Location
    Markham, Ontario, Canada
    Posts
    260
    This is really interesting. I am sick of cleaning my lens all the time specially when running the compressor. Can you take some pictures and show what this mod looks like?

    Regards
    Khalid
    Shenhui 80W RECI (600mm x 900mm)
    Corel X5

  7. #52
    Like this: oplaser.co.uk/opsupport/viewtopic.php?f=20&t=211 but mine is actually central. Will see how Jane gets on with it today with some work and report back and photograph etc.
    Shenhui 1280 100W RECI

  8. #53
    Join Date
    Jun 2011
    Location
    Markham, Ontario, Canada
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    260
    How do you get the beam to be central to the cone? I have tried using the method suggested on Rabbit Laser site and I think I have got it right but I would like to know what you are doing to ensure that the laser beam is coming out from the center of the cone.
    Shenhui 80W RECI (600mm x 900mm)
    Corel X5

  9. #54
    I stick tape over the end of the cone and then fire the laser. It leaves a mark and if you didn't have the power too high or pulsed for too long you can see from the mark on the tape where it is in relation to the mark that the edge of the cone made when you applied the tape.

    Still need to upgrade my compressor because with the 75mm lens we cannot use this insert method since the beam is quite wide at the cone. In fact, I gained performance with the 75mm lens by being sure the beam was central in the cone because it is so wide so far above the focal point.
    Last edited by john banks; 03-14-2012 at 2:30 PM.
    Shenhui 1280 100W RECI

  10. #55
    Join Date
    Mar 2011
    Location
    Olalla, WA
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    I use thermal paper. Since I use a pin table that is about 3" high I can jog the laser head off the pin table where there is about 6" distance to the table. The thermal paper is on the table. Firing the laser should make a nice filled in disk on the thermal paper. If it is half moon or pie shaped then I adjust the final mirror until it is a disk.

    It'a also a quick way to check for alignment across the table. If you get a nice disk in all four corners of your table, you know your alignment is perfect.
    Last edited by Rich Harman; 03-14-2012 at 3:31 PM.
    Shenhui 1440x850, 130 Watt Reci Z6
    Gerber Sabre 408

  11. #56
    Kerf width compensation "sew width" fails to work with jobs not downloading to the laser and the progress bar getting stuck.

    Offset Polygon allows the same to be done. There are a few options to allow the original vectors to be deleted, and whether the direction of movement is to always make larger, always make smaller, or to contour inwards or outwards. I've used it to make some push fit parts in wood and acrylic.

    Might be handy if you're not using CorelDraw's contour function or just want another way of doing it.
    Shenhui 1280 100W RECI

  12. #57
    I still haven't worked out a good way to stop the air hose hitting the panel behind the lid hinge except to move the head to the right of the machine before turning off.
    Shenhui 1280 100W RECI

  13. #58
    Join Date
    Jul 2011
    Location
    Rustenburg South Africa
    Posts
    16

    Cutting speed

    Any idea why my machine would not go lower that a 17 mm/sec speed setting via software but will go as low as 1 mm / sec from the control panel.
    I need to cut some thick material and have to do 2 passes on the software settings before the cut is completely thru.
    Help would be appreciated.
    Shenhui 1280 80 watt RECI

    You may never know what results will come from your actions, but if you do nothing, there will be no results..
    . Rudy Malan † 05/03/2011

  14. #59
    Join Date
    Mar 2011
    Location
    Olalla, WA
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    Here's an issue that I discovered today. Laserworks has a nice feature (preview) that will tell you how long the work will take. It is very useful when working up a quote. The problem comes when there are different speeds.

    If you have two identical items, one above the other with the top one set to 5mm/sec and the other 10mm/sec, the estimated time that it reports will be as if both pieces are cut at 5mm/sec. If you swap them around then the total time will be reported at 10mm/sec.

    The workaround is to make sure that you get the times on each speed setting separately.
    Shenhui 1440x850, 130 Watt Reci Z6
    Gerber Sabre 408

  15. #60
    Join Date
    Jun 2012
    Location
    Bellevue (Seattle), Washington, USA
    Posts
    16
    Yes!! Thanks. That's exactly what I was looking for.

    Scott Moore
    24x36 100W Morntech laser
    Corel Draw X5, PS CS5, Illustrator CS5

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