Understanding Backlash & Scanning Reverse Interval (2018)

[@13hubi13]

Finally someone who actually knows about the mechanics of lasers, I have the problem that I saw when I wanted to set the scan offset. When I fill with about 200mm/s every second line where the laser head moves from the right side to the left it is wobbly. I checked everything from lense to mirrors to belts, every screw is fixed so I don't know why that occurs. When I fill with the mode that it engraves only in one way from left to right I don't get wobbly lines but it takes much longer to engrave.

[@domesday1535]

you'll also want to consider your step resolution for stepper motors or your encoder resolution for brushless servo motors. Ideally you would code a multiple of this angular resolution divided by 360 degrees times your pulley tooth count times your belt tooth pitch as your offset to avoid any rounding errors causing inconsistent results. Great video, and very good point about the belt rise. Definitely something that can easily go unnoticed but have a real effect on the end product in some circumstances!

[@peterwetton2655]

Excellent video thank you, I'm having trouble with backlash on a very large machine, now I need to determine wether its mechanical or internal and now I know its both.

[@SmellyCatCreations]

Really great video and well explained

[@Gizm0Gizm0]

I have found this video to be very useful and have added it to my next process of setting up, thanks Russ, you do an amazing service for us less knowledgeable folks. I have a pressing problem at the moment where, if I cut a circle, it is a perfect circle but if I scan/engrave a circle, it is coming out as an oval. I have tried different software and get the same results I have tried other files done by someone else same problem. I have increased the current in my drivers, I have slowed the scan right down but still the same. Any help or suggestions would be greatly appreciated folks

[@rusolinio121]

PWM rising value box for both and x and y needs ticking in 'vendor settings'.

[@vaughanza]

Excellent Video Russ, thanks

[@b.w.oostdam8875]

That is very very interesting. I am new to the Hobby lasers but am used to using CNC machinery all my life. Never owned a belt driven machine up to now and I am experiencing precision problems with small circles. Which btw are at the moment all made with a G3 command. (GRBL). Would it help or even be a good idea to put some dry lubricant on the flange of the timing-wheel and on the side of the belt to try and diminish the 'climbing'of the belt on to the timing-wheel flange?

[@esmirhodzic981]

you sir are a boss. thank you. Great video

[@AliGhane-ek8xe]

thank you man🙏👍

[@philo24]

Top quality video, thank you

[@Poonyas]

Video made it very clear how to set the scan reverse interval for the X-axis. But after you set this correctly and rotate the drawing 90 degrees and scan Y-swing, the Y lines are offset... How to fix this because there is only one setting for the offset and scan intervals??

[@fyrstorm2010]

Very interesting video as always.

[@Thinklaser]

Hi James, Thanks for the kind comment. Gareth@ thinklaser

[@bengmo64]

Man I wish I had your backlash problems lol, I'm fighting to get my machine to make circles that are round to the eye!

[@CAM-kg2ic]

Where do I find the setting to adjust backlash in Lightburn?

[@Thinklaser]

To adjust the backlash settings in Lightburn, Turn on your laser machine and start up Lightburn. Go to Edit> Device Settings Click on Enable Scanning Offset Adjustment Then add your line shift values for your standard speeds. You will need to work these out yourself for your specific laser machine. E.g. Speed 050 | Line Shift 0.000 | Initial Offset 0.000 Speed 100 | Line Shift 0.020 | Initial Offset 0.000 Speed 150 | Line Shift 0.040 | Initial Offset 0.000 Speed 200 | Line Shift 0.060 | Initial Offset 0.000 Speed 250 | Line Shift 0.080 | Initial Offset 0.000 Hope that helps!

[@zachofalltrades6116]

my machine is making circles like this but on the top right and bottom left making circles look kinda like a lemon, I noticed the back stepper motor belt that is the small belt is kinda loose how can i tighten it up.

[@caseygriswold8617]

Thanks for this super informative video. Truly appreciate it. I'm assuming everything gets handled the same for the Y-axis, correct? If I have very long engrave jobs, for example many coasters, nearly full of engravings. It will take a couple hours to engrave everything, which is done from left to right along the X-axis. When it's done engraving and begins cutting, the cuts aren't centered around the engravings. It cuts them just a bit higher than it should. Leaving more margin at the top, and less at the bottom. Which is confusing to me, the laser head is moving left to right, and slowly making it's way down. Is this a backlash issue or a scanning reversal issue? I appreciate any advice.

[@geeperjane]

Check your belt tension. If it is loose you'll get misalignment like this

[@jameswares4469]

Very good video 👍 can you show how to setup special mode and explain how it works . Thanks James 🥃🥃👍

[@Thinklaser]

Hi James, Open up RDWorks and go to the right-hand side or the screen where you will see the Work/Output/Doc/User/Test/Transform tabs. Open up "User" and scroll down to Sweep Parameters. In this section, you will find both "Scan Mode" and "Facula Size (50~99%). With your PC attached to the laser machine, click "Read" which will read the settings from your machine. In Scan Mode choose "Special Mode" and change Facula size to "50". Click "Write" to send these settings to the machine. The Special mode is effectively pulsing the laser beam so at 50% Facula the beam is on for 50% of the time. The benefit of this is that it allows you very fine control over the engraving parameters at the bottom end of the power settings. Normally a glass laser tube starts to fall off at 9~11% so using Special mode will allow you to work at 18~30% instead (outside the pre-ionisation mode). This is also great for people with higher powered lasers (80~150 watts). I've used it in applications such as engraving onto foam where you don't want to get too much heat into the product and for a special engraving finish on black acrylic where the mark looks like it's been gently scraped onto the surface for an almost silver finish. Russ has used it for getting very fine detail onto anodised aluminium.

[@antoniolamarca6094]

@@Thinklaser congratulations on your videos. always very interesting! I have a question: what is the right tension of the belts? I am always afraid of pulling them too much and ruining something. in particular, I think the main belt of the Y axis motor is too tight in my machine

[@wazwuz205]

This is very good information, thank you for sharing your knowledge and experience

[@user-dw6gv2hs3f]

Thank you!!

[@Thinklaser]

You're welcome, hope the videos help. Gareth @ Thinklaser

[@yvanvalenzuela6509]

Hello my friend, very good video. I have a problem: when I have a job with many cutting lines, maybe about 10 minutes cutting, when that job finishes and I want to repeat it, the starting point of the job moves approximately 1mm in the Y axis (vertical), what can be the solution? A second problem is: when I outline for several minutes and then the shapes are cut, they do not coincide with the outline, they get out of phase, what is the problem there? greetings and thanks

[@channel-ri8cu]

driver start on rising or falling edge, seek driver user manual

[@bewokking11]

nice vid but i have one problem. when Im doing the scanning reverse interval test, I noticed that my line become shaky and wobbles. what does that mean please help me.

[@geeperjane]

Check your belt tension

[@andyfaulkner_GLTS]

This might fix my exact problem. But How do I draw the line at the origin and what was the file used to com back to the line from the other side. sorry if this is so simple but unsure on how to do this many thanks in advance.

[@geeperjane]

Set your origin and press pulse as you hold the down arrow button on the laser. This will give you a line on your set point. Press the reset button on your laser so it comes in from the right, then press pulse again to mark a dot on your line. To come back from the other side just frame any file you have. The laser doesnt need to turn on and frame will always make the laser come in from the left.

[@andyfaulkner_GLTS]

@@geeperjane many thanks

[@MrBrettStar]

Does the backlash affect the scanning reverse interval?

[@MrBrettStar]

Just tested and yes it does, whatever adjustment that you have made to the x you will also need to make to you scanning reverse interval

[@channel-ri8cu]

@@MrBrettStar oh gosh