Beginners Help

Hi all,

I am new to lasers. Just bought a k40 used but with most all of the upgrades I wanted including a cohesion board and air assist. I downloaded lightburn yesterday and have been going through the manuals they have to try and learn as much as possible.

The machine worked when I bought it.

A few things I am having issues with off the bat that I can’t figure out and can’t seem to find through search is the following:

  1. my laser seems to be inverted with regards to how I see it on my laptop. This means when looking at the laser, the back most left side is actually the bottom right of my laptop. When I Have the machine run a program it goes in the reverse of what I expected. How can I correct this?
  2. When I have the laser “form” the area. Sometimes it only runs half the cutting area rather than the whole thing.
  3. If I set the image in the middle of the work space and run it, the laser seems to want to run it in one of the corners instead of the middle.
  4. How can I control the power output of the laser in lightburn? Is there a setting? (I have the dial on my machine that I will keep under 15ma

The board originally came with grbl ltc but I just upgraded to smoothie firmware (what a nightmare as I thought it was just download and go.

Looking for a little guidance and some readings. Lots of the starting stuff has been around safety, I got that all down pat.

Thanks in advance!

The guy gave me a drag chain that I want to install too that I need to search as well.

the CAM software you are using to do your laser layout needs to have the coordinates set correctly. And your home position should be your back left side of the K40. you should always trigger the HOME process which should move the laser head to the switches in the back left corner.

You also need to setup you CAM software so it knows the size of your working area. A stock K40 had a tiny 5" x 3" working area in the middle of the machine. But when you remove that clamp and put in a full size bed the working area can be 12" x 9"( 320mm x 230mm ) and your firmware installed needs to know that and your CAM software needs to know that.

There are lots of software options for the K40, some are GCode senders which don’t do any design editing but flipping and centering like bCNC, LaserWeb and a few others. Some others like LightBurn do both design editing, GCode generation and GCode sending.

if you look on the K40 section in this forum you should see some FAQs which are really required reading. You are in the right place!

I have read setting your homing and origin positions, I can’t figure out how to do it. I used the radial buttons to move the position in one setting, but it didn’t seem to make much difference.

I believe my work area is bigger than 5x3 as sometimes I can get it to frame right out, and I can manually move the gantry no issues across the whole workspace.

I had setup my camera before I updated my firmware, I’ll need to do it again now that I updated the firmware.

When I setup the camera it asked me to do a lens calibration afterwards. After target area number 2 the laser and gantry would stop not allowing me to complete my calibration. I feel this is all user setup error, again just don’t know where to look

I really have little idea what you are talking about, radio buttons, camera, etc etc. Please read this post and try to explain what’s going on and especially what you are working on. This link explains how people can help you.

Here’s the easy-to-read version of my quote of Paul’s advice:

How to ask for help

Paul Stoffregen, of Teensy fame, wrote How to get technical help from strangers on the Internet. Please read it before asking for help, here on Maker Forums, or on any other forum. From his summary:

  1. Good first impression ⇒ Humans will want to help
  2. Explain context ⇒ Humans will understand your needs
  3. Share details ⇒ Humans will be able to help

He really put a lot of thought into writing that in a way that can help! :relaxed:

In the top bar of this site is a link K40 Intro that is full of useful information; you may have already noticed but I wanted to be clear. I wouldn’t run a K40 without reading it; it has information both about safety and about not damaging your laser. I know you say you got the safety stuff pat, so that’s great, but for “dial on my machine that I will keep under 15ma” — is that measured with an analog ammeter?

For lightburn-specific help (how to make lightburn work with your machine), we recommend the Lightburn Forum — there are plenty of people here who use Lightburn, but for how to configure lightburn for your system, that forum is more likely to be immediately useful. It’s still worth keeping Paul’s excellent advice in mind there, of course!

In general, it’s probably worth posting any questions that are about the laser rather than about how to configure lightburn as new threads here, and posting pictures to show what you see. Pictures really can be helpful.

Smoothieware is extremely reconfigurable and the developers expect you to read the documentation in detail to use it at all. It’s intended to be extremely flexible but “download and go” has never, as far as I know, been their intention. What capabilities or performance were missing from grbl-lpc that caused you to choose to change to smoothieware? This isn’t a “better/worse” situation; they have different goals and are friendly with each other.

For problems like “Sometimes it only runs half the cutting area” I really don’t understand what you mean. Pictures and details are helpful. If it displays communication errors, be aware that lasers are electrically extremely noisy and very high-quality USB cables, perhaps with ferrite cores to reduce EMF, can help with some cases of jobs that just stop partway through. You wouldn’t believe how many complaints have been resolved by replacing the USB cable! :smiley:


Thank you for posting the Tip O’ The Day video. I think I have maybe started to narrow down some of my issues to the origin. I set my origin to the lower left now. However, when I use my laser position tool, everything is still inverted (up is down, down is up, left is right, right is left)

My red and green square are at the very bottom left.

I think this setting here may have factor into what is going on as in the video tip of the day video he sets the job origin to the lower left. Mine seems to be greyed out and showing upper right.

I think once I figure this out it will solve a number of my problems. I plan to check the mirror alignment tomorrow and then retest some laser stuff this week.

If I swap the origin to the upper right, then the bed responds as what you see is what you get. I.e, if I position the laser to the top left on my screen, it goes to the back left on the laser bed, so on and so forth.

I then copied the Line test where I drew a straight line and used absolute coordinates and moved it to all areas of the work screen then ran the program. The laser followed as expected.

The problem comes when I draw a giant letter “2” 200mm height x 131mm wide. I place it in the center of the work screen. When I do this, the laser then goes off the rails and does this:

The laser doesn’t appear to make a 2 at all.

If the laser is unplugged I can move the gantry side to side and up and down with ease and smoothly.

Where I am referring to the machine only framing “half of the work area” this is what I mean. In this image you can see that I have drawn up the # “2” in the middle of my work space. I am using absolute coordinates. As far as I am aware, it should print that #2 where I have placed it.

When I ask the machine to “frame” the area, it does this and only frames half of the machine. It should be framing the middle of the work area should it not?

Lastly, I apologize if some of my questions maybe belong on the lightburn forum. This is my first time using a laser and I am not sure what problems are lightburn related, K40 related or both. As I get some help I will maybe be able to decipher things a bit better and direct them to the correct forums/subforums for help.

Much appreciated to those who can assist.

I think you really need to stop trying to cut or engrave anything and FIRST, get your machine setup correctly. Create a new machine profile, set the working area and the origin(Left,Rear) correctly. Then select and connect to the laser cutter and click on the HOME button.

If it does not go to the left/rear then you have your motor wires connected backwards.
Get it to go the the HOME switches first.

ONLY THEN, use the movement arrows to move the laser head to the right with the right-most arrow and it should move to the right. Move the laser head forward using the lowest most arrow on the LightBurn screen and it should move towards the front of the laser.

Now you can create things to etch/cut etc.

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Thanks - I haven’t been trying to cut/etch anything yet minus the setup stuff for the camera. I have only had the water in it once since I have bought it, everything I have been doing is with no power to the laser and just running some patterning so I can see what it is doing. I figure it is safer this way especially since I haven’t learned what speeds/output etc to run.

Right now it appears that after setting the laser to the top right, measuring the approximate size of the bed based on where the laser stops in all 4 corners (and using a pencil to mark some paper) - I shrunk the size of the bed. The laser now appears to do all the motions I asked of it, where I asked for it which is good.

Next up is likely cutting out a portion of the bottom to fit my lab scissor lift (this scares me)! But I can’t see another way to make it fit and have adjustability

After that I am going to check mirror alignment. I don’t know what each knob is for yet on the mirrors or on the laser tube itself. So I am trying to find a guide for which way the adjustment knobs turn things (I have found guides on how to align the lasers themselves with the painters tape etc).

After that I will look to do a ramp test and then maybe make a jig to quickly measure and set the height relative to my piece (something like a stopper block).

As for why I went to smoothie from GRBL…I’m an idiot. I read it is a good idea to update your firmware. I saw the newest firmware was smoothie and that GRBL stuff was older, so I acted like I was updating my Iphone… My plans with this machine are to do portrait engravings, cut acrylic signs for some projects around the house, make some keychains, some dog tags and then go from there. I am pretty good with woodworking (slow but good), so we’ll see what I can supplement in my work.

Please just get your origin and bed size correct and THEN start messing around with other stuff.
Why do you even care where it’s putting stuff when you don’t even have your home switches and origin setup? The machine has no clue what your are telling it if you have not homed the machine so it knows where 0,0 is…

And since you are not familiar with firmware or anything else related to laser cutting you really should have purchased a Cohesion board for your machine. With the price of the board comes support from the developer and specific configuration files for the K40.

BTW, I run a Smoothieboard clone( MKS Sbase v1.3 ) in my K40 and had no problem setting it up but it did require knowing what steps/mm are, what acceleration is, what jerk is, etc etc. Cohesion developer will support you in getting your board working even if you don’t know what a text editor is.

He did. That’s in the OP. :relaxed: (And to receive direct help from Cohesion3D, just post in their forum and their support team will be happy to assist you.)

When you screw the screws in, they push the stage that holds the mirror. The screws are technically called “stage maintenance screws” and are very fine pitched to give you fine control. You can download STEP files for various laser optics sets from grabcad. They are fundamentally quite similar, and you can load up STEP files in FreeCAD or most any proprietary CAD to get more of a sense how they work. Three points determine a plane; the three screws set the mirror plane.

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I missed that and yes it is ALWAYS best to go to the seller first for support. Ray provides excellent support for Cohesion products.

I got the mirroring part of the problem figured out. Looks like my origin is top right (don’t know what determines that or why).

New problems and I don’t know if this is a laser issue or a lightburn / cohesion board issue, so I will be posting on those forums too:

  1. When I start a job sometimes the machine randomly goes to a completely different location. For example, I wanted to do some test burns for a dog tag I would like to make my new puppy. I ran the word MILA in the middle of my work space. The K40 goes to the bottom right and writes MILA with all the letters on top of one another (See first photo below). Without adjusting anything, I hit the start button again. This time the K40 goes to the top right and spells MILA out properly. I made no adjustments, I didn’t touch the program or the work piece.

I have coordinates set to absolute. Why is it randomly going where ever it wants?

Same thing when I went to do a dog tag, I did it on the wood first in one spot to give me a reference point. Slid a dog tag over top of the wood in the same spot, the k40 decides it wants to go somewhere else entirely. I can’t reliably fire my laser in the same spot to do repeat jobs.

  1. I try and do the calibrate camera alignment in lightburn. It gives me a grid it wants burned into a piece of wood, similar to above, the laser tries to burn it in a different area every time I try to run it. A lot of the time it tries to run half of the grid right off of where my gantry is. When I look at the file, it is dead center set to my machine

  2. I was doing my laser alignment. I think I have it setup pretty good for the most part but I want to tweak things a bit more after running a few more tests at the end of today. I am seeing 3 dots come from my laser tube to the first mirror at every push of the button. Am I in TEM-01? with a dying laser? I tried doing 3 passes at 10ma and 20mm/s and I am only scratching the surface of 5mm plywood. It burns in images, but nothing crazy and I can’t see this cutting anything. I also am not ruling out it being a focusing issue.

The guy I bought it from included a new laser tube, so I am thinking it may have been on its way out…

Without a picture of the dots it is hard to speculate exactly which mode, but unlikely to be in TEM00 any more. So yes, tubes don’t spontaneously return to TEM00; it’s on its way out.

This is what I am seeing off the first mirror directly from the laser.

If it is pooched that is fine, I will have to google how to install the next one. My only issue is I am moving in about 1.5 months and I would of rather installed the new laser after I get to the new place and the thing won’t get bounced around any…

See the K40 Intro linked from the top of the page. That category includes tube replacement info. In particular, the hard part of replacing a tube is splicing the high voltage cable.

I think the shot you posted for the ‘size and positioning’ area is not doing what you think. Here’s the windows of Lightburn. Here’s the documentation on that area.

Don’t know if this helps, but in Lightburn you need to go to edit->device settings and set the ‘origin’ to where you device homes on power up. This isn’t very clear, it’s one of the four corners. From what I understand of a K40 it’s the back left (top left,) same as mine.

Good luck :slight_smile: Take care…

Thanks, I thought this too, but it seems to mirror how the machine spits out my work when I set it that way.

I will look at it again, are the homing switches big red squares? Is there any way to edit where these are or would reversed wires causes these to make the machine act opposite of the way it should?

Mcdanlj is it confirmed my tube is no longer any good?