I often have adjoining parts, say a grid of squares. I make touching edges to save on material and cut time, but I’ll often end up with a situation where the laser will cut out a grouping of the objects which then fall and the inside cuts separating them sometimes get messed up because of the fall.
I’ve tried grouping everything as 1 object or keeping it separate, it doesn’t help.
Thanks for the advice!
The algorithm makes a reasonable assumption that the material won’t move while cutting, which causes trouble when the interior pieces fall out or tilt. Unfortunately, there’s no way to control the exact laser head path, so there’s no way to avoid unpredictable situations like that.
IMO, the design must have a thin border between the pieces with a few tabs holding them in place until the cutting finishes. Perhaps if you regard that border as a fixture holding the parts in proper alignment it won’t seem quite so “wasted”.
My game (picture below) currently fits in exactly 1 sheet that my bed can take.
Adding even 1mm between each of those pieces would waste a considerable amount of material. I’m thinking of just having to use different colours, but then I have to break all my lines apart and make it very layout specific which is going to be terrible. And then cut time would also be significantly affected, which also means wear. This type of board density is pretty normal for me and a normal game will have 4-8 sheets. This one only has 2.
As you can see I even make use of the cutouts for pieces.
And honestly 1mm isn’t enough, my laminar flow is strong enough that my small pieces do move by 1mm easily if they fall just right.
I would think strategic placement of tabs would solve the problem.
It’s a tradeoff between wasting material on a built-in fixture and wasting material on scrap parts that fall out. I’d favor doing a layout that optimizes success, rather than trying to save a few slices of material.
It might be possible to lay the pieces out to fill one full sheet and one half sheet, so you could produce two complete sets from exactly three sheets, with only thin frames remaining as scrap. Your material cost goes up by 50%, but your reject rate drops to 0%, so it might be a net win.
Maybe two millimeters, just enough for tabs holding the pieces in place. You might need only a single tab for each piece, perhaps cut halfway through from the top to simplify snapping the piece out.
Would it be feasible to do the cut on a honeycomb bed to prevents the pieces from falling through? That might produce unacceptable smoke / fume accumulation on the bottom surface without a masking film that would be annoying to peel off.
It’s a nice compact layout and I admire your ability to pack things in place, but … if it doesn’t work, you must try something different.
Yeah with a good sheet and bigger pieces it’s very efficient, but I think will have to learn tabs for small pieces.
I do use a honeycomb + a fixture to hold the sheets flatter. That’s why parts have a chance to move, the gap. But it’s worth it for not having flashback or as much smoke damage.
I had not thought of partially cutting tabs, that actually makes it very reasonable in terms of post processing… I guess it’s time to start changing my approach! I guess I hadn’t thought of the fact that they can still touch on most sides too so the concern about multiplying my cutting time significantly could be mitigated that way.
I guess you guys just sand the edge after a tab is removed? I tend to leave the dark edges so that’s going to be annoying as well.
Good point. Perhaps you could surround a two-column set of squares with a frame and one tab apiece, so they’d abut along the middle with the tabs keeping them in place on the frame.
I don’t make anything where the edge appearance matters very much, so I don’t have any recommendations. Maybe you could just embrace little imperfections? 
Haven’t tried but I would think you could touch them up with a soldering iron to blend them with burnt edges.
My thought exactly. That or set up a jig to use my laser as a chop saw lol
I’m also wondering if I could make really pointy connectors instead and have them on each side so it doesn’t need to be as strong because there’s no leverage.
Can you make the gap underneath the material?
If it only has a couple mm to fall, it can’t fall too far astray…
I don’t cut puzzles, but I move my material up 5mm.
It’s 2mm elevated above a honeycomb
I set my material up so that it is no more than half the thickness of the material above the honeycomb so that anything that drops will stay in place.
Yeah I know it’s a bit high, 2mm on 3.2mm material, but it’s because I made a steel frame that braces my sheet so they don’t bow which is very common for me with the size of my sheets and the amount of unevenly localized heat I put in with all those small pieces.
2mm with 3,2mm material should be fine as they can only drop straight down unless you have a massive kerf.
The honeycomb under is the wildcard. Depends on edges hit the honeycomb.
I don’t know if this helps in this case: of course, you need to do the engraving layers first. For the cut layer, try to enable “remove overlapping lines”. This will also reduce the time needed to cut, but my experience is that LightBurn then cuts objects close to each other one after another. So you might not have the effect of pieces falling out too early. But this is just an assumption, I never tested this for this use case.
Small addition: if your edges are too dark, try to increase speed. The faster, the less charring, usually. I can at least state this for diodes, I don’t know if it applies similar to CO2.
Yeah the problem is that I’m already at 100% unfortunately so I keep slow
Honeycomb sounds like the cat’s meow for cutting but it’s the worst thing you can use… I pitched mine and use a sheet of rolled steel… Easy to clean and support the material over a sheet of steel.
A good cut on my co2 means I can use a napkin to wipe the edges and virtually nothing transfers to the napkin. This is the proper speed/feed.
Alright, clearly I need to rework my cut settings. I did settle on this speed and power when I was having feedstock quality issues so… yeah.
As for the honeycomb, good point, I only used it before I had my brace that elevates my material! It’s superfluous now that I already have a 2mm gap and that I modified my vents for laminar flow instead of downdraft!
