Laser Cutters

All,

I'm thinking it might be time to pick up the art of laser cutting. I have a design in mind for a new KAP rig and rather than nibble all the pieces out of aluminum, as I usually do, I think a laser cutter might be faster and more accurate.

I did a little research and found a maker space nearby where I could rent time on one, so equipment shouldn't be a problem. But before I go in there and spend the money, I thought it might be good to do some homework.

So who has worked with one of these machines? what software would you recommend for designing the shapes to cut? Any thoughts on materials suitable to KAP rigs and laser cutters?

Dave Wheeler

Comments

  • edited March 2016
    Dave

    as you can see from my posts here lately, I've been using a laser cutter quite a bit to cut ply and acrylic sheet. The laser cutter in question belongs to a local secondary (high) school. It's quite old (they are hoping to get a grant to replace it) and has a bed roughly 3' square. Like most of the equipment at the school, it uses software written for educational establishments (2DDesign see here on the righthand side of the page) which is expensive to buy for a single user (all Windows only stuff unfortunately) . However the file types accepted are pretty standard.

    I design my pieces using Adobe Illustrator (I have an old copy I got for nothing years ago) and save them as wmf (windows meta files) which the laser cutter software accepts (and turns to dxf files I think). The actual laser cutter is treated as a special type of printer and you set things like cutting speed and laser intensity via the printer properties dialog.

    There are two sorts of cutting such machines will do - cut lines or 'engrave' areas (where the head moves to fill in a shape). By setting the colour of the shapes you determine which sort of cutting is used.

    Because the machine I have access to is big it can be used to cut quite thick materials (the kids make simple wooden furniture with it). My own use is limited to ply and acrylic up to 5 or 6mm thick.

    It's also quick - took just a couple of minutes to cut out the ply pieces for the box for my KAP TX and not much longer to cut the pieces for my EOS M rig.

    image

    PS I forgot to say - laser cutters won't cut metal of course - you need a plasma cutter or high pressure water cutter for that (the school has a plasma cutter too - but the cuts it makes are much too wide and inaccurate to cut aluminium pieces for rigs or picavets - I know, I tried the latter).

    PPS I also forgot to say that you need a good extraction system - laser cutting produces not just smoke but also noxious fumes. The ply has to be suitable for laser cutting too - needs the 'right sort' of glue.



  • Laser cutting machines users have the software which will convert the drawing in instructions in the machine software language.
    Usually the drawing is issued from specific vectorized softwares and file extension must be compatible. Only the laser cutting machine owner can inform on the needs.

    One feature to know is the thickness limit on aluminum which usually is half of steel.

    Water jet cutting is also possible for outlines but may not be suitable for small diameter holes.
    Usually small pieces need some uncut places to maintain them during cutting. Specialists will provide all necessary information before to start the job.
  • Oops - I should have said the laser cutter I have access to won't cut aluminium. It's clear that there are machines that will - see here for example.
  • Ah, I actually assumed I would not be able to use aluminum with a laser cutter. In my post I meant I would switch from nibbling aluminum to laser cutter something like plywood or plastic. But I'll check on the machine's capabilities at the maker space.

    I may also need to check on equipment at the local schools. :-)
  • In uk schools the equipment is in "design technology" departments. The head of it at my local school decided to set up a FabLab one evening a week - use of the machines (which includes 5 3D printers) is free!
  • Safest thing to do is ask them what materials they can run through their machine and what file formats they'll take. This is one nice difference between the machining industry and the fabrication industry. Machine tools will almost always assume you're feeding them G-code. Fabrication tools (plasma cutters, laser cutters, etc.) will almost always provide you with other options like DXF and WMF.

    If you've got something like Illustrator, my guess is you could do exactly what Dave's doing. If not there are inexpensive and free 2D CAD programs that'll generate a DXF they can use. Again, safest thing to do is ask them what they recommend. Since they're trying to appeal to the maker community and not to industrial customers, chances are they've worked out an inexpensive set of tools and file formats that'll get you going in short order.

    If you do wind up cutting metal, Christian raised a good point: small holes tend to suffer unless you're on a high end machine. Good news is if it can at least make a rough hole in the right place, you can use it to cut pilot holes that you can later go back and re-drill with the correct (larger) drill bit. One of the machinists I used to work with showed me a neat trick: With a CNC mill you have to load every tool you intend to use in a tool holder. He had a part that had almost a dozen different sized holes it needed. Rather than load twelve tool holders he loaded just one with a pilot drill. Once the mill had drilled all the pilot holes he went back later and opened them up using the correct sized drill on a drill press. Same idea, and it works well as long as you can stand 0.005" kind of tolerance on hole centering.

    Dave, that's cool about the school near you! I have access to machine tools, but zero access to 3D printers and laser cutters (our laser cutter broke). That's fantastic that they open it up to the public for free!

    Tom
  • Dang! One other thing I probably should've mentioned: When looking at all this stuff, also run your drawings by a couple of metal suppliers to see what their price would be. A while back I made some fiber spools for work that would've been a pain to make conventionally, so I looked around for waterjet services and found that the same place I'd been buying our metal from also did waterjet cutting. I had the plates made out of 1/8" 6061 aluminum, each being 20" in diameter. If I remember right they wound up being something like $65 apiece. I don't know how they price their work, but my guess is the material cost and cut length for these far exceeds anything a KAP rig would require. I'd hope it would be significantly less.

    Regardless of how you get it done, laser and waterjet cutting of metals leaves a pretty rough edge at the cut. Plan to spend some quality time with some combination of fine files, stones, sandpaper, Scotchbrite, whatever your favorite combination is to make the edges kite line, cable, and user friendly.

    Tom
  • edited March 2016
    I have a Full Spectrum 40 watt laser and like it a lot. Using numerous software programs, simply press print and it sends the design to the laser. Typically I use Corel Draw, but any vector drawing program, such as Inkscape works fine. I have opened decorative font images and clip art in MS Word and laser cut from there.

    Initially my wife was skeptical of of the cost, but together we have made hundreds of items as gifts. Laser cutting designs on wood cutting boards has been extremely popular.

    Some examples. https://www.flickr.com/photos/diederich/albums/72157632241144030


    Dave - contact me directly, and I will be glad to some laser cutting for you at no charge.

  • Wow, thanks for the offer Dave! That gives me some extra motivation to convert ideas into dxf files. If I get far enough with that, I'll contact you to make some sort of arrangement.

    Which reminds me: Cris, you still owe us a thread on your new EOS M3 rig. I have questions. :-)


  • Dave, that thing is kick butt! I love that it interacts just like a printer. MAN that clears away a lot of cobwebs from legacy systems. Trade out whatever I said in my last two posts with, "Follow Dave's link to his stuff, and go to the Full Spectrum web site."

    Tom
  • edited April 2016
    I think an update on my laser cutting adventures is overdue so here's a summary of what I've been up to for the last 6 weeks.

    Nirvana

    With Dave Diederich's offer to do some cutting for me, I figured the next step would be learning the design tools. I quickly settled on OpenSCAD. This seemed like a good fit for my background - describing the geometry of parts and assemblies with a programming language feels pretty natural to this long-time computer programmer. Progress was slow at first but accelerated quickly. Before long I had a set of rail-mounted components for frame corners, axles, gears, brushless DC motor mounts, etc. I also wrote some OpenSCAD modules that create box joints in mating plates.

    Taking Shape

    Then I realized I needed to make some test pieces to calibrate the tight-fitting dimensions. Taking Cris' advice, I designed some test plates with various holes sizes to test the fit of a Skyshark P200 spar in my components. I also made up tests of my box joints and threw in some 48 pitch gears. I sent these design files to Dave and an online service called Ponoko.com. The tests revealed some problems. First, there were scaling issues. I was exporting .SVG files from OpenSCAD for the laser cutting. And different programs use different scaling factors on SVG files. I thought 96 units per inch was a standard but Inkscape (and, specifically, the Ponoko.com inkscape template files) use 90 units per inch. So the first set of parts I got back were sized wrong and I couldn't use the hole size gauge I'd made. Still, I was able to see the box joints worked well. The gears worked but ran a little rough. I hadn't accomodated the kerf of the laser cutting process so the teeth weren't shaped as accurately as one would like.

    So a second round of test pieces seemed in order. I learned how to use the offset function in OpenSCAD to adjust for the kerf on all the pieces. (By comparing the dimensions of the first cut pieces to the design files, I was able to determine the kerf width was 0.2mm.) And I fixed the scaling factor issue. So a second order went out to Ponoko and I got back pieces that were perfectly dimensioned. A test plate that was 2 inches wide measured 2.000 on my calipers. The gears in this batch looked and felt perfect even when run with 48P plastic gears from servo city. And using the hole gauge, I found that 0.292 inches was the proper hole size for a smooth fit on a P200 spar.

    Dimensional Testing

    Hole Test Gauge

    I completed my rig design, then, and sent in an order for the full kit. This time, I ordered the gears to be cut from 0.193 inch Delrin. All the other parts were plywood again. Everything arrived on Friday. The delrin gears were a bit disappointing. It appears the material flowed in the cutting process so the teeth look rough. I'm not sure they are usable.

    Laser Cut Delrin

    And I discovered a couple dimension errors in my design so some of the pieces will have to be re-ordered. The fit of my spars in the holes is much tighter than I wanted. I don't know if this is just variations in the process or due to the fact that I painted everything. The paint may be gumming up the holes just enough. Either way, a little sanding should get things sliding well.

    It seems that painting the wood *before* cutting would be a big advantage. That may drive me to try out a maker space in Silver Spring, MD for my next laser cutting attempt.

    Dave Wheeler
  • An alternative to painting would be tung oil on top of an optional Danish oil stain. I don't think the dimensional change would be as severe and the wood would be protected.

    Tom Gautier
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