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Thread: CNC plans - DIY kit? Thoughts?

  1. #11

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    Quote Originally Posted by mmarien View Post
    I did the majority of my project with CNC. I bought a 6040 CNC router when I started the ribs. I had a local place CNC cut a plexiglass jig as my router wasn't big enough. The local place was happy to do the plexiglass jig. I know another place that will CNC laser cut 4x12 sheets of aluminum no problem. I'm not sure why the holes need to be punched.

    I did all the small plexiglass parts and all the wood rib parts. For sure my ribs were accurate because of the CNC. Putting the rib jig together was just a matter of assembling the parts in the pre drilled holes.

    Attachment 8980

    Attachment 8981

    I also had all the metal parts CNC laser cut locally. My CNC router can't cut 4130 steel. All of the stuff I outsourced was from the DXF files I supplied. They did the conversion to gcode and optimized the parts on the material I supplied. The cost was a few $ per part. Money well spent.

    Attachment 8982

    I recently learned how to cut Aluminum with my CNC router.

    Attachment 8984

    Attachment 8983

    The parts I did myself were converted to from dxf to gcode with some software I purchased (~$150). For sure adding a CNC router to your inventory of tools adds another level of skills needed to complete a project whether it's DIY or outsourced. For me, the $2G I spent on the CNC router and learning to use it was time and money well spent.

    As mentioned most of the kits are already done with CNC. I think it's a good idea to start sharing CNC code for plans built projects. Sky's the limit when you put your mind to it.

    Attachment 8985
    Those images look really nice. How easy is it to run your files on a machine made by a different company? Now that you have your parts optimized, I'd think you could give or sell those files to someone building the same model of plane, so long as they also bought plans from whoever is authorized to sell them (avoids copyright problems). Thanks for sharing your experience!

  2. #12

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    I'm not an expert when it comes to CNC machines but gcode is universal to CNC machines as far as I know. The program I use doesn't produce any machine specific code. Here is an example:

    ( Made using CamBam - http://www.cambam.co.uk )
    ( Rib Nose 9/22/2016 6:18:08 PM )
    ( T3 : 0.125 )
    G20 G90 G91.1 G64 G40
    G0 Z0.125
    ( T3 : 0.125 )
    T3 M6
    ( Profile1 )
    G17
    M3 S1000
    G0 X-0.0613 Y6.363
    G0 Z0.1
    G1 F10.0 Z-0.05
    G3 F30.0 X-0.0274 Y6.1925 I26.433 J5.1783
    This is the start of the gcode for the rib nose pieces seen in the pictures I posted above. To cut out one rib nose piece from 1/4" plywood, I move the router bit to a place on the wood piece and zero the router. When I run the code it cuts out one nose piece. I move the router and zero it again for the next piece. I believe I could use the same gcode on any CNC machine and it will cut out a same nose piece as my CNC router.

    However, the gcode is based on a specific size router bit. Put in the different size router bit (or laser cut the part) with the same gcode and your part will be a different size. I've made that mistake a few times.

    For sure when I outsourced the cutting, they had a program that read my drawing files and optimized the layout on my material in a few seconds. There was no extra charge for that. However, all the work was in preparing the drawing files in a format they could read. It wasn't gcode. It was AutoCAD DXF format which is a standard drawing format that plenty of programs can read. With that in mind, the DXF files are probably more useful than the gcode files.

    There is no doubt that my CNC router is my favorite tool. It makes very accurate and precise parts over and over again. Would the drawing files or gcode be worthwhile to the next builder? Probably depending on how they used them. Would kit suppliers be willing to supply digital drawings or gcode? Probably not for free. Unless you have your own CNC equipment it's probably less expensive to have the kit supplier supply the parts rather than the gcode. If it's a plans built and you are sharing gcode on a user forum, that is a different story.

    I don't believe there are any copyright issues. All the work I did to create the gcode is my original work.

  3. #13
    DaleB's Avatar
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    I don't think you'll find a kit manufacturer eager to share CAD files to let other people mass produce the parts they're trying to sell. It's got to be a tough enough road as it is trying to sell kits.

    In my case, I toyed with the idea of making drawings and generating gcode to cut out some parts for my project. I decided that I could probably do it twice or three times (or 10) in the time it would take me to do that work. None of it would interest the rest of the tiny handful of people building the same airplane I am, I'm afraid. If the design used more CNC-friendly parts than it does, it might be a different story.

    But to answer the question about running Gcode on different machines... Gcode is a standard language, more or less, but portability would be about nil. Every machine is different in how it can handle "feeds & speeds", and even the controllers are different in how they handle some commands. The code CamBam produced that worked on mmarien's machine would probably not work so well on my much different machine driven by LinuxCNC and using a very different spindle motor, etc. There are also differences in how zeroing the tool is handled, etc.

    It's the same with 3D printing. If you look at 3D printer objects (like on Thingiverse), they're not distributed as gcode because every printer is different. My I3 Mega requires different settings, speeds, temperatures, etc. than my brother-in-law's delta-style printer, even though they both are driven by gcode.
    Measure twice, cut once...
    scratch head, shrug, shim to fit.

    Flying an RV-12. Building a Fisher Celebrity.

  4. #14

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    Quote Originally Posted by mmarien View Post
    I'm not an expert when it comes to CNC machines but gcode is universal to CNC machines as far as I know. The program I use doesn't produce any machine specific code. Here is an example:



    This is the start of the gcode for the rib nose pieces seen in the pictures I posted above. To cut out one rib nose piece from 1/4" plywood, I move the router bit to a place on the wood piece and zero the router. When I run the code it cuts out one nose piece. I move the router and zero it again for the next piece. I believe I could use the same gcode on any CNC machine and it will cut out a same nose piece as my CNC router.

    However, the gcode is based on a specific size router bit. Put in the different size router bit (or laser cut the part) with the same gcode and your part will be a different size. I've made that mistake a few times.

    For sure when I outsourced the cutting, they had a program that read my drawing files and optimized the layout on my material in a few seconds. There was no extra charge for that. However, all the work was in preparing the drawing files in a format they could read. It wasn't gcode. It was AutoCAD DXF format which is a standard drawing format that plenty of programs can read. With that in mind, the DXF files are probably more useful than the gcode files.

    There is no doubt that my CNC router is my favorite tool. It makes very accurate and precise parts over and over again. Would the drawing files or gcode be worthwhile to the next builder? Probably depending on how they used them. Would kit suppliers be willing to supply digital drawings or gcode? Probably not for free. Unless you have your own CNC equipment it's probably less expensive to have the kit supplier supply the parts rather than the gcode. If it's a plans built and you are sharing gcode on a user forum, that is a different story.

    I don't believe there are any copyright issues. All the work I did to create the gcode is my original work.
    Thanks much for your answers. My only concern with copyright is that it is possible to make parts without the original plans. I certainly wouldn't expect the code for free from the vendor, either the plans owner or someone else. I see a lot of value in giving someone a pile of metal and a USB drive and getting a kit plane back. I also see there is a bit of effort making code that can be easily and quickly used, and that effort is worth some money.

  5. #15

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    Quote Originally Posted by DaleB View Post
    I don't think you'll find a kit manufacturer eager to share CAD files to let other people mass produce the parts they're trying to sell. It's got to be a tough enough road as it is trying to sell kits.

    In my case, I toyed with the idea of making drawings and generating gcode to cut out some parts for my project. I decided that I could probably do it twice or three times (or 10) in the time it would take me to do that work. None of it would interest the rest of the tiny handful of people building the same airplane I am, I'm afraid. If the design used more CNC-friendly parts than it does, it might be a different story.

    But to answer the question about running Gcode on different machines... Gcode is a standard language, more or less, but portability would be about nil. Every machine is different in how it can handle "feeds & speeds", and even the controllers are different in how they handle some commands. The code CamBam produced that worked on mmarien's machine would probably not work so well on my much different machine driven by LinuxCNC and using a very different spindle motor, etc. There are also differences in how zeroing the tool is handled, etc.

    It's the same with 3D printing. If you look at 3D printer objects (like on Thingiverse), they're not distributed as gcode because every printer is different. My I3 Mega requires different settings, speeds, temperatures, etc. than my brother-in-law's delta-style printer, even though they both are driven by gcode.
    I disagree about someone mass-producing parts. When I buy plans, I'm buying a license to use the plans to build one airplane. If I want to build another plane of the same type for a family member, the plans I've seen indicate I'm supposed to buy another set of plans and they will have a different serial number than the first set. Buying the CAD files would fall under the same license agreement- I can use that code for a single plane. Beyond that, I could see such code as an up sale. Vans, Sonex, and others sell plans, kits, and quick-build kits. Each step up is a higher cost to the builder. I see this as being between plans and a kit, and priced accordingly. Someone who only sells plans, Hummelbird(?), might see increased sales if parts could be made more easily.

    Having said that, I'm reading from mmarien's real-life experience that there isn't much savings in money over a kit that exists.

  6. #16

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    Okay... I have some experience doing this. I've bought plans for a CH-640. I'm going to CNC most of the parts out, predrilled, using solidworks. What little I've done matches the OP's expectations. I've cut out part of my rudder using some test aluminum, and it came out beautifully, matched holes and everything. I'm now waiting for more aluminum to show up before continuing it.

    Some makerspaces have a 4x8 router. While not optimal, the one I'm using does aluminum decently even though it's designed for wood. I've got to make fast cuts with shallow DOCs. I've found drilling works better then milling when possible, and I'm piloting most holes with a drill when I can. For example, I'm drill out to 5/32, then milling it to #12. I've already used it to mill 3/8" 6061-T6 with mild success (and it's some of my first attempts!), but I've got usable parts. With some careful gcode, I can do 12' parts as well, just requiring adjustments between cuts. I'm hitting my required tolerances.

    G-code isn't universal... it's not quite a standard, more like an idea. There's not an official standard for it that everyone follows. In solidworks you select a post-processor and that'll generate the gcode for your machine. Any GCode is highly tailored to your machine. Some of it is based on the hardware you machine has. I'm using one that has a 18k rpm router motor with no coolant, so I need to use tiny 1/8" single flute (aka o-flute) endmills, at a really shallow DOC. The cnc paths will be totally different from a machine that's designed for cutting aluminum... which will use 1/4" 4 flute endmills cutting through 1/8" Al in a single cut, with a super rigid structure.

    Best bet would be handing out solidworks files organized into sheets, and letting the cutter worry about generating the gcode itself.

  7. #17

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    Quote Originally Posted by kunnis View Post
    G-code isn't universal... it's not quite a standard, more like an idea. There's not an official standard for it that everyone follows. In solidworks you select a post-processor and that'll generate the gcode for your machine. Any GCode is highly tailored to your machine. Some of it is based on the hardware you machine has. I'm using one that has a 18k rpm router motor with no coolant, so I need to use tiny 1/8" single flute (aka o-flute) endmills, at a really shallow DOC. The cnc paths will be totally different from a machine that's designed for cutting aluminum... which will use 1/4" 4 flute endmills cutting through 1/8" Al in a single cut, with a super rigid structure.
    I don't agree with your statement that gcode is not quite a standard. I do agree that the gcode is tailored to the machine you are using. What is standard about gcode is that I can create gcode for any CNC machine with the my software. The gcode you create with your software will be slightly different than the gcode I create with my software but the part will be the same if we run them both on the same CNC machine.

    My inexpensive CNC router is also made for wood or plastic and not water cooled but I also figured out how to cut aluminum. Maybe not as quickly as you did but I eventually figured it out. See my thoughts on cutting aluminum here:

    http://myhatz.blogspot.com/2020/11/2...-aluminum.html

  8. #18

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    I've seen that post. That's one of several that got me seriously looking at trying to cnc route parts!

    Also look into drilling. It's got a great material removal rate.

    Re: "I can create gcode for any CNC machine" That's where it starts getting a bit sticky. You need to have the right postprocessor for your machine. But you wondering about the drawing files being useful to the next guy... I'd love to have a set of drawing files for the ch-640, that'd make my build so much easier.

    For cutting thin sheet metal, read about superglue fixturing. Put a piece of blue tape down on your bed, blue tape on your part, and glue the two together. You get a decently solid bond, but you can peel the blue tape off when the cut is done.

    You can also learn about setting avoids and origins, and cut out a part in multiple steps. You can cut any length you want, as long as it fits within the width if your machine. That's how I'm cutting 12' parts out on a 4'x8' bed. I set the last 6 feet as an avoid area, cut the first 6 feet. Then setup another CNC job, where I avoid the first 6 feet, and have the origin set to one of the holes that was cut in the first pass so I can get proper lineup.

  9. #19

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    Happy to hear that my blog helped you get started in CNC. I envy your 4'x8' bed.

    Thanks for the tips. I seen a youtube video about gluing the tape together trick but haven't tried it. I've been having relatively good luck with carpet tape. I'll maybe have another look at gluing the tape together.

    I figured out the trick of moving large pieces over the router bed using and index hole. I'm limited to 21"x15" but cut my turtle deck floor and my floor boards. The floor boards or 72" so I cut them in 4 separate cuts by moving them in the router. I haven't cut the final version, just prototypes from press board. My blog on the turtle deck is here:

    http://myhatz.blogspot.com/2020/06/2020-june-turtle-deck.html

    I also used the match hole cutting to make my seat frames.

    http://myhatz.blogspot.com/2021/05/2021-may-seat-mounts.html

    A side effect of drafting all the parts for CNC is that I formalized the drawings and have a nearly complete set of As-Build drawings for my project. Useful as I deviated from the original plans in a lot of places. Nothing structural, just cosmetic.

    Good luck on your build. I'm pretty sure you'll find more uses for CNC on your project than you could imagine when you started.

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