I am trying to make a memorial project on black slate, 8X10 or 295mmX195mm. I get it all set up on the screen the way I want it but when I tell it to frame the project the laser trace will not fire on the bottom of the project. As the frame starts up the sides the laser turns on then turns off again after going down the left side but before reaching the bottom. Any text or graphics that I put within 1/2" to 3/4" of the bottom edge of the slate will not engrave, the laser will not fire. I have to move all text and graphics up until I get a laser response. This upsets the balance on the layout. The top is not an issue, I can engrave to within 1/4" of the top of the slate with no problem. Is there a margin setting? I drew a box the size of the slate and centered it on the page - shutting it off so it would not engrave. That seems to be the line that the framing command follows, except the laser trace won’t work on the bottom line and part way up both sides. What am I doing wrong???
I betcha:
- The cable to the laser head is dragging on something and
- It’s pulling a connector just enough to disconnect the power or
- There’s a break in a wire inside the cable that’s getting pulled apart at the bottom and pushed together near the top
It’s not a software problem, fer shure. 
Until you get find the problem and know you’ve fixed it, run tests on cardboard instead of spendy stuff.
OK, checked all the connections, they all seem tight. The funny/frustrating thing is that the laser will not fire until it reaches 131mm on the X axis from home. If I move the spoils board and the project board up it lets me do the engraving but I can’t find any wires hung up anywhere. I haven’t used the unit a lot so I don’t think I broke it yet…but it’s possible. I’m using a Tronxy U20 laser that I’ve only done half a dozen projects on since I got it.
@ednisley seems to have the right idea. You need to check for loose connections or broken (and intermittent) wires. Set it up to make a huge square at low speed like 50mm/m and low laser power like 1%. Run the program and watch very closely (with laser safety glasses) to see where it is cutting out. It should not cut out during commanded motions.
Unfortunately, it’s also possible to pull a defective laser right out of the box, so you’re deep in “Trust, but verify” territory.
Judging from the pictures, the laser head cable just sort of bends in mid-air without a drag chain, which means when you move the board upward, you must also raise the laser head to maintain the proper focus. In doing that, you’ve changed how the cable flexes and what forces it exerts on the tiny connector in the head: there’s your problem.
Set up a low-power test pattern as @MikeyH suggests. While it runs successfully, gently pull & push the cable at the laser head until you find the spot where you make the laser flicker.
If you can do that, then you should be looking right at the problem.
Edit: From the manual, that’s your problem, right there:
Every time the assist air tube moves, it jerks the connector around. That is a Bad Thing™ in terms of reliability.
As a start, make sure that connector is firmly plugged in …
I found that if I moved the cable near the frame on the right side of the unit’s outside frame it would work. I had to hold the cable down slightly and it would fire where ever I wanted it to. So, I limped my way through and got my project done for the memorial service yesterday. Next step will be to pull the wire harness from the laser head plug back to the main board and check it with my multimeter to find the break or weak point. There’s only three wires so I’m considering getting some good silicone wire and just replacing the wires completely to avoid future issues. The only roadblock is the plug end, but I can leave an inch or so of wire sticking out of the plug and solder the new wires to them covered with shrink tubing. I’m thinking that it looks to be an 18g wire. Way too small for 14 or 16.
Highly recommended!
AFAICT, they use the smallest wire gauge that doesn’t get too warm, with PVC insulation because it’s cheap. Given what I’ve found inside some wires & cables, the conductors may not even be copper.
Although this is not the place for a hunk of 10 AWG electric stove cable, going up a gauge or two with some nice silicone wire won’t do the least bit of harm and will definitely improve the results.
Add enough length for a much better job of strain relief on both ends; this won’t be difficult, because it has none right now. Secure the wire before it gets to the connectors so it cannot wiggle them around.
Frankly, if there’s no other way to do it, anchor the wires to the laser head with a blob of hot melt glue and accept the fact they’ll break right there: at least you won’t have the connector failing at the PCB inside the laser head.
OK, got the unit apart and got the part of the wire harness out that has the three wires for laser. I connected my multimeter to both ends and moved it all around on each of the three wires. I couldn’t detect a break in the wire. But, I’m still going to replace the three wires with a heavier 18 ga silicone wire then put that wire inside a plastic wire loom to help support it adding another 6" or so to the length to give it some more slack. We’ll see how that goes.