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Thread: 2500 x 1300 mm flat bed laser Ruida parameters - can someone share theirs please?

  1. #1

    2500 x 1300 mm flat bed laser Ruida parameters - can someone share theirs please?

    HI, we've had our big 2-head, 2-tube laser a few years now, and after a lot of tweaking, I'm mostly very happy with it.
    I saved the vendor settings right at the beginning, although they're pretty useless - the chinese mob who set it up were very good, but things like reverse interval settings etc, and small circle speed limits were not a part of their expertise.

    For a long while I had slight start and end cut alignment issues - fixed by minor tweaks to backlash.

    Engraving is great. Cutting is another matter. For anything say 35mm high or bigger, cutting is great. It's just very small stuff I'm finding tricky:

    I've had 2 jobs recently - diecutting card for a printer - 7000 discs, 3/4" diameter, and 5000 at 1" diameter, set up on A4 sized sheets.
    The problem with our big laser has been at that small diameter, the circles are not perfectly circular.
    They all have a slight flat-spot at 5-past 12, and 35-past, or between 12 and 1, and between 6 and 7 o'clock.
    The start and ends line up perfectly. If I set a seal of half to 2 mm, (or path overlap) it is imperceptible, which is good.

    I did have other issues, mainly being the 'bounce' at the beginning of every cut - a dampened sinewave shape that ceased after about 3 or 4 cycles, which I attributed to the higher acceleration in idle, then slowing down and overshooting the mark as it started each new cut. It did not matter where on the clock the start point was. I had to crank the cut start speed right down low, and the acceleration right down low in order to eliminate the bounce or wobble - read, edit and write to the controller, in User settings.

    That made everything pretty slow though.

    With the big laser, both tubes - W1 and W8 Reci are carried in the extra-big gantry, so there is a fair bit of inertia to have to shift and absorb - much moreso than smaller bed lasers where the gantry only carries the head and the belt for the head.

    I tried turning on and turning off the Backlash Reappy checkmark. All that did was alter the starting place of each new file, and change the total time taken for the jobs due to extra travel time to begin each new cut at the opposite side of the clock. It did not change the flat spot which is like a failure of Y to move microscopically at the direction change time after the head passes 12 o'clock or 6.

    When I tried to go faster, we got the bounce at each cut beginning point.

    I tested this by lasering lots of concentric circles, not by wrecking the client's job!

    IN the end I guessed that although in Vendor settings, Y has a much lower acceleration factor and lower overall speed because it is a bigger Leadshine stepper motor moving a bigger weight, compared with X's stepper which only has to drag the head - that maybe the RD6442 might have problems sending instructions ot 2 different drives with different parameters, and perhaps that's the reason for the flatspot - so I set both X & Y in Vendor settings to the same lower speeds and acceleration as Y used to have.

    It sufficed to run this job acceptably - and the resulting discs look round to anyone else, but I still see the minute flats. And minute overcorrection bounce in the curves.
    No, the belts are not loose, nor is the lens loose. if I laser a 1200mm square on cardboard, the four sides are accurate, as are the diagonals.


    So, I was wondering if anyone else with a machine with a heavyish gantry like ours, might not mind sharing their vendor settings for overall X & Y speeds & accelerations, and User settings for the same, and small circle speed limits please?

    It is great at bigger sizes, but I'd like to be able to have it better at the tiny vectors, at a greater speed than snail's pace!

    Thanks for any thoughts!
    Last edited by Ian Stewart-Koster; 07-05-2021 at 10:54 PM. Reason: typo
    Best wishes,
    Ian



    ULS M-300, 55w made 2002 with rotary. Goldenlaser 130 watt, 1300x700 made 2011.
    Flat bed 2500x1300 150/90watt 2 tube laser, 2018 model.
    Esab router, 1989, 4.5 x 2.0 m, conv. to Tekcel, and modded a 2nd time.
    HP L260-60". Roland PNC-1410. Mimaki GC-130 SU.
    Screenprinting carousel 6x4 and 7x4 ft 1-arm bandit vac table.
    Corel Draw X3, Illy, Indesign & Photoshop CS2 & CS5, Enroute 4
    Pencil, paper, paintbrush, airbrush & dagger-liners & assorted other stuff.

  2. #2
    your flat spots are caused by slop in the drive train, specifically, when one/both stepper motors slowly stops, then changes direction. I've fought this problem for years with my big New Hermes V5000XT engraving machines, specifically the Y axis, these machines move the entire 29x22x 1.5" thick aluminum table with a 1/2" dia. steel leadscrew and cheesy plastic nut, driven from the stepper with a 2 piece coupler with a rubber "X" between them acting as a shock absorber. I tested my backlash with a dial mic just last week on one of them; when turning the lead screw by hand (power off), when I stop and change direction the screw must move 3 'thumps' (steps) before the table starts moving the other way. That's bad. The only way to tighten the backlash is to squeeze the coupler together to reduce it's slop, and to very carefully tighten the lead screw against the end bearing to the point the stepper won't move the table, then gingerly back off the lock nut until it WILL move... all of which does little if the cheap plastic nut is worn out, which mine is

    -- you likely have the same problem, one way or another. You're moving a heavy gantry with belts. Do you happen to know if your couplers have any sort of shock absorption? Also, your Y axis is likely driven with a small belt from the stepper gear to a larger gear that's connected to the shafts connected to each end of the gantry. If so: Is that belt tight? Is the motor carrier fastened tightly to the back of the cabinet, and is the motor fastened tightly to the carrier? Are all the pulleys/cogs tight? Are there any secondary stepper shaft supports, and are they tight?
    My LS900's Y stepper, you can see the shaft support, closest to the camera on the left--
    LS900Ystep'.jpg
    Several years ago that support bearing's end-screw came loose, which caused the 2 lower mounting screws to loosen slightly, which caused similar results to yours. That belt is brutally tight, requiring the shaft support-- and as the screws loosened so did the belt. It took me a few days to find the problem

    ANY cog/pulley with a slightly loose set-screw will have a 'dead space' of cog rotation that's not moving the shaft (or vice versa)...

    As to your speed settings, all I know is what helped my machine a bit, and it was lowering the "space" speed, which is how fast the machine moves between laser fires, and lowering the ACC speeds. One plus I found from lowering the space speed, is when rastering, the over-run distance during the turnaround was reduced...

    Circle speed limits, all I know is, with my 1390 Triumph at this moment I'm cutting silicone gaskets with 41mm holes, at 50mm/sec, which is fairly quick I guess, and they look to be good circles to me --what I have problems with is rounded corners, because my machine doesn't seem to consider a 1/4 circle a "circle", so speed limits don't apply. I have to suffer with slow-straights to keep the round corners smooth.

    Good luck
    ========================================
    ELEVEN - rotary cutter tool machines
    FOUR - CO2 lasers
    THREE- make that FOUR now - fiber lasers
    ONE - vinyl cutter
    CASmate, Corel, Gravostyle


  3. #3
    Thanks, Kev - there's food for thought. I'll relook at the Y stepper belt to the big gear, and check the couplers - if I can get to see them at all - they might be hidden inside square section that supports the gantry. The flat spot is only tiny - but it is enough to irk me.

    One aspect I found interesting was when I got it, a big square was not square. I solved that by changing the tension on one side's Y belt by letting it off about 2mm. I'm guessing that allowed the left side Y teeth and the right side's Y belt teeth to remain more perfectly aligned the full bed length...
    Perhaps the issue lies in that tension changing a tad more over time and I should recheck a big square...

    A Youtube clip I found fascinating when watching it last week, was all about Harmonic drives - it was a characteristic of offset toothed belts and gears that I'd never have thought about.
    12 minute Link here: https://www.youtube.com/watch?v=7QidXf9pFYo
    Best wishes,
    Ian



    ULS M-300, 55w made 2002 with rotary. Goldenlaser 130 watt, 1300x700 made 2011.
    Flat bed 2500x1300 150/90watt 2 tube laser, 2018 model.
    Esab router, 1989, 4.5 x 2.0 m, conv. to Tekcel, and modded a 2nd time.
    HP L260-60". Roland PNC-1410. Mimaki GC-130 SU.
    Screenprinting carousel 6x4 and 7x4 ft 1-arm bandit vac table.
    Corel Draw X3, Illy, Indesign & Photoshop CS2 & CS5, Enroute 4
    Pencil, paper, paintbrush, airbrush & dagger-liners & assorted other stuff.

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