I am a hobbyist experienced in model rocketry, and am trying to cut fins and centering rings for mid/high power rockets. I have created a template for centering rings for a 29mm motor tube to go inside a BT-80 (66.04mm) body tube. Basically a circle centered within a circle that creates a disc that is 66.04mm in diameter with a 29mm diameter cut out circle in the middle. I am having trouble getting my Ortur LM2 S2 LU2-10A to cut a perfect circle. I have tried calibrating using an 80mm square to Calibrate X/Y axis and I can get a good calibration setting with an 80mm x 80mm square.
When I try to cut the centering rings using a 12" x 12" 3mm baltic birch plywood with a speed of 460 and power of 95 with 4 passes, the circles aren’t perfect, and the further away the laser head travels from the home position, the circles look more like very wide ovals with each circle closing, but not perfectly in line. The first row seems to be very close, but not perfect.
Any help in making these circles as perfect as possible? Am I using too much power too fast?
Template Lightburn file is attached.
Are there other settings I need to check, like focal point? How is this done with my laser cutter? Anything I should check on the physical hardware of the laser cutter? I’m completely new to the world of laser cutting and the hardware involved and need step-by-step directions.
I also notice that when the laser is returning from top left to bottom left (home), it appears that the cable chain seems to lag/hang about halfway causing the laser head to not return to home completely but very close, so I have to click the (Home) button in order for it to completely be at home position. For this, what do I check on the laser cutter? Remember I am a complete newbie and need to know what and how to check whatever screw tightness or any other physical aspects that would cause this. If needed, I can take a video of what I’m talking about to demonstrate/illustrate what it’s doing.
I realize these are a lot of questions compiled into this one post, so any help (even step-by-step instructions) would be tremendously helpful and appreciated.
I suggest you go back to default values for this as those are usually pretty accurate for Ortur machines.
You can revert settings to defaults by issuing $RST=* in Console.
The root cause of what you’re dealing with is likely a mechanical issue. Specifically, check your machine for squareness. Based on what you’ve indicated it sounds like your machine is out of square and may not be symmetrical.
Additionally, check all mechanical linkages for backlash and eliminate where possible. Check pinion gears that they’re properly secured with grub screws. Check belt tension. They should be taught with no visible slack but without being overly stretched.
If none of these things are apparent then please take a video of what you’re seeing, publish it to a 3rd party site, and link here making sure the permissions for the video are publicly visible.
Ok, thanks for your help!! I found out the bolts on the laser head were dragging against the wiring chain, so I raised the laser cutter frame up about an inch, and raised the cutting bed up about an inch. The circles still aren’t PERFECT, but I think that when I was calibrating it before raising the frame/bed, I was calibrating it with the incorrect dimensions and the difference/average between those incorrect dimensions was incorrectly calibrating it. I will try another calibration to see if that corrects things.
Also, the Y axis belt had a bit of slack in it, so I tightened it up to remove the slack, and it seemed to improve things tremendously. The frame appears to be square, it is solid with no give or wiggle.
Do you think a calibration will make the circles come out more perfect/accurate? Or should I also check other things? Should I also revert settings to defaults by issuing $RST=* in Console as you suggested?
Are these two independent statements or are you suggesting that since it’s solid that square comes along with that. If the latter then don’t make that assumption. The machine can be appear rigid and solid and still not be square. This only matters if the level of accuracy on your burns is still not to your liking. Then every tiny bit counts.
Resetting will revert the calibration. It’s possible that recalibrating manually could theoretically get you even better than factory since it will be tuned to the actual components of your specific machine but this depends on how well you do the calibration. The approach is up to you. If you decide to do it manually then I suggest you create as long a square as you can manage. Then measure length, width, and both diagonals. Both length and width should be equal as should both diagonal measurements. If diagonals don’t match then your machine is likely out of square or you have other issues worth exploring.
Ok, so how do I check the squareness? By using a physical square? I just assumed (yeah, I know) that since it was solid with no give that it would be square based on when I assembled the laser cutter.
I will try resetting using your suggestion, and then do a test cut again. If that doesn’t work then I will try re-calibrating it by cutting a 6" x 6" square and using calipers to measure 6 points on Y axis and 6 points on X axis, take the average of each axis and use the calibrate option to try and set it as close as possible to “exact”.
Yes, you can use a square or anything else you know is 90°. You can also measure the diagonals of the frame. Any discrepancy in the two values indicates out-of-squareness. Bear in mind though that frame squareness isn’t necessarily that important and can be affected by manufacturing tolerances of the frame members as well as misalignment at assembly time and doesn’t necessarily affect the accuracy of the machine. The important things are that the Y axis rails are parallel to each other and that the X axis rail (the one that the laser head is mounted on is 90° to the Y rails. This can be difficult to measure directly so you might be able to cut a square out of some material then measure the corners with an engineers’ square (or similar). If you determine that it is out of square then you can adjust it by loosening off one of the pulleys and rotating it until you achieve acceptable squareness. Of course this will only work if the grub screw clamps down onto a round shaft, not a flatted one. Loosening off one of the belts and moving it one way or the other to bring the X axis rail into square would also achieve the same effect. I hope this makes sense.
Rather than cutting, burn the square in Line mode on cardboard, then measure the center-to-center distance between the lines.
A cut piece will be smaller than the nominal size by half the width of the focused laser spot (the “kerf”), plus-or-minus any tapering due to the beam shape, plus-or-minus any effects from a tilted beam.
For a diode laser, there’s a bonus error due to the rectangular spot size: the kerf will be different along the X and Y axes.
When I made the second statement that it was “much improved” but still not perfect, I was looking at second test cut - not the last (third) test cut. I still have not checked the squareness yet, and will save these posts to check if needed.
After the confusion of what I had already cut, the third test cut turned out perfect. When I made that statement that it was much improved but not quite perfect, I was still looking at the second test cut, and not the third test cut which I performed after receiving your instructions on squareness. Basically I was looking at the wrong test cut, which was MUCH improved, but not quite perfect. And then I found the third test cut (that I got confused with the second test cut) and could tell it was more perfect and was what I was wanting to achieve. Hope that makes sense.
So I think I have the final output that I was originally looking for and everything looks quite “perfect” for my centering rings. After test fitting them in the body tube with the motor tube in the inner circle, I discovered that they fit like a glove.
Thanks again for all your help guys, I certainly appreciate it. And while this is a big learning curve for me, I’m getting the knowledge I need to be much more efficient and productive in my projects and the final outcome.
