Cutting part longer than my bed size

Community Laser Talk
1

I have been trying to cut a piece of material longer than my bed size without success. I am fairly new to laser cutting but I am successfully cutting many parts that fit on my cutting bed. I am running Lightburn Version 9.24 on a Windows 10 machine. My laser cutter is a Boss Laser LS-2440 150 Watt with a Ruida 644xs Controller. I have watched the youtube video that cuts the mermaid no less than 8 times trying to find any details that I have missed.

I am trying to cut a part that is basically 72 by 1.25 inches.
I have logically created 2 parts with the following steps:

  1. I loaded my original part.
  2. Created a box on the same layer as my part and it is around my part and the size of the box is 72.44 by 1.88 inches so it surrounds my part completely.
  3. I grouped my part and the box around it together.
  4. Next I created two boxes on a different layer that are 36.22 by 1.88 size. Half the size of the original box
  5. I over laid these two boxes on top of the box that is around my part. I snapped them in the corners.
  6. The finished view is these two smaller boxes completely cover the larger box around my part.
  7. I created a circle that is .275 inches, put a vertical and horizontal line in the circle and grouped them together. I then put the circle on another new layer. I then copied the circle so now I have 2 circles
  8. I moved both circles to the middle of my part where the two smaller boxes join together and snapped them to the smaller boxes accordingly. I did move them in about a 1.4 of an inch from the edge so they would cut on the material. I set the cutter so it would only engrave these circles for reference.
  9. Next I selected one of the smaller over laid boxes and selected my actual cut part and then went to cut shapes and the smaller box dis-appeared. I then went to the other smaller box and repeated this process. It also dis-appeared.
  10. I then save my work to a file and then saved it two more times as filename1 and filename2.
  11. I opened filename1 and deleted one half of the drawing which gave me half of my cut.
  12. I opened filename2 and deleted the opposite half of the drawing which gave me the other half of my cut.
  13. Both of my files have the registration circles in them.
  14. I sent the first file to my cutter and it prints just fine with the registration circles.
  15. I then open the second file in Lightburn. I move my material in my cutter to get ready for the next half and jog my cutter to the center of the first registration circle and then select my first registration circle and then select “print and cut” and then I select “set first target position”.
  16. I then jog my cutter to the second registration circle and then select “print and cut” and then I select “set second target position”.
  17. My start from location has changed to “Absolute Coords”. I saved the file in Lightburn. I then send the file over to the laser cutter.
  18. I start the laser cutter. The first thing it is does is engrave the registration circles over the top of the original set. Then it begins to cut my part.
  19. The reprint of the registration circles are about .03 inches off from the first set of circles.
  20. My part gets cut out but the the overall length is at least .25 inches longer than my original drawing which is not good since the part I am trying to print has other interlocking components that need to have the notches in a specific location.
  21. The first half of my cut is correct in length but the second is not correct. I have noticed in my part where I have notches being cut that as the cutter goes down the cut the notches progressively get further off.
  22. I can print 36 inch parts that come out at 36 inches repeatedly so I think my cutter is accurate.
  23. I believe my problem lies in the process of joining my two files together with the registration circles but for the life of me I do know where the problem lies.

I am attaching the following files for reference:

  1. girder-innerwall-72.lbrn2 = the original part to be cut
  2. girder-innerwall-72-sheet.lbrn2 = the original part plus the two smaller cut boxes and the registration circles.
  3. girder-innerwall-72-sheet-1.lbrn2 = the first half of the part
  4. girder-innerwall-72-sheet-2.lbrn2 = the second half of the part

If anyone has any insight it would be helpful. At this point I am making a lot of expensive firewood.

Thanks;

girder-innerwall-72-sheet-2.lbrn2 (13.7 KB)
girder-innerwall-72-sheet-1.lbrn2 (17.0 KB)
girder-innerwall-72-sheet.lbrn2 (21.0 KB)
girder-innerwall-72.lbrn2 (11.3 KB)

2

Before I got a big laser, I used to cut parts out of 8’ sheets on a bed 24" deep. Here is what I did, and it worked famously.

First, I got a piece of 3/16" thick aluminum angle, and through painstaking alignment, and re-alignment, I got it as straight as one could hope, from front to back, and bolted it to the bed. This gave me an “absolute” Left alignment reference. so as long as I slid the piece down the left, and it was butted against the aluminum rail, it would be straight.

The next thing I did, was install a pop-up dowel pin into the “zero” position of the bed, so I could puch it, and it would pop up. I created a file that cut 2 registration holes 23" apart from front to back, and I’d cut that file before raising the pin. Once the holes were cut, I’d raise the pin, and place the plastic so that the pin went through the hole, locking it in place.
I’d use a copy of that exact file, so that the holes were still in the file, and I’d slice the file at 23", and cut it one section at a time. When the first segment was done, I’d move the plastic down, so that the pin was in the second hole. At this pint, the next segment should pick up EXACTLY where the first one left off. I’d cut the next hole 23" up the sheet, for the next move, then cut the next segment (or rest of the file).
If you’re following me, It’s an extremely accurate way to keep the files in perfect alignment, and if for some reason, you move the plastic, or you get a crash, or tip-up, all you need to do, is push it back up against the left rail, and it was back in perfect alignment.

It sounds complicated, but it was extremely simple once you established your rhythm.

And EXTREMELY ACCURATE!

:+1:t3:

1 Like
3

Hi, I am relatively new to laser cutting but my woodworking requires that I cut 8’ long pieces of marine plywood. The cuts are simple, basically a single, long sweeping curve but it can’t be cut in sections. (these are internal frames for wooden boats and SUP’s).
Question:
What laser cutter should I invest in that will 1) consistently cut 1/4" marine plywood and 2) are the any that are already designed to accommodate step-wise or continuous cutting?
I could spend $10k and would like to explore more consumer-grade options and use the step-wise (registration pin method described in this thread)

Thanks for any insights!

4

C’mon, anybody got any thoughts on this?

5

Well, given that it arrived necro-posted on a two year old thread, it arrived pretty far down on the list of things to look at.

In round numbers, you need:

  • COâ‚‚ laser
  • At least 50 W
  • Pass-through access to the platform

There’s likely a conflict between four-sided passthrough and good exhaust handling, but that’s in the nature of fine tuning.

I routinely use the front passthrough hatch on my 60 W OMTech for long pieces of stock, although I haven’t match-cut large items.