CNC Router Size March 17, 2013, 12:37:51 PM I am getting ready to purchase a small hobby-level CNC router/mill (I will have both spindle speed ranges). I'm trying to think about what physical sizes of jobs I may wish to use it for. The small CNC machines have working areas of 12x23x4" and 28x28x4".The smaller one is a little more rigid and will work better for PCB work. The larger one would be big enough for just about any home projects it seems, but those rare instances could also be done manually (for example, large speaker boxes with a circle jig). The larger CNC router frame costs over 50% more than the smaller one. Other than price and rigidity, they are otherwise the same in terms of performance - they provide the same fairly small servo motors, but ones that the frame can hold up fine with a sane cutting speed in aluminum with 1/4" end mills.Can you guys provide any valid projects that could make more use out of something larger than 12x23" in a home environment? With the 17" full width of the table, it seems big enough to replace my MDF baffles for my subs in the trunk with 12" subs (11" cutout). I can't think of any other reasons off the top of my head, but I also don't want to regret getting the smaller unit that is easier to store, but provides finer control for electronics work. I'd hope that if I needed more space, I could move up to a much more rigid larger unit when I also have "excess shop floor space" in a future house. Quote Selected
CNC Router Size Reply #1 – March 17, 2013, 03:49:29 PM Honestly, a cnc router is a bit of a pain.I have about 3 cnc home built routers, a laser engraver modified to cut wood, and a reprap, a plastic extruding machine.One router uses a cheap harbore freight router, another uses a large dremel, and the other a small one.The way I feel about it personally, if your building one part, it easier to just do it by hand. If your looking at manufactoring them, then it makes sense. I think it will become more of a toy as time goes on, and will eventually collect dust. Quote Selected
CNC Router Size Reply #2 – March 18, 2013, 12:01:49 AM I can't really build one part as a prototype. An example project (after initial prototyping onto cheaper materials) will be making an aluminum heat spreader/mount for LEDs, which will reflect light through the opening in a HID projector's front optics. You can mockup all you want in CAD, but only CNC will get the angles pretty correct. I can't manually cut a bowl into a chunk of aluminum with precise angles for reflecting the light out through the optics with decent beam control.These machines are a bit of a step up from most home built units made out of MDF (there are certainly some decent ones out there). They have the precision to be able to make me PCBs with fairly small traces. They can also get me the intake plaques that I want with great definition. Why not have intake cover plates with the T-bird logo embossed into the top? The stuff I want to do cannot easily be done by hand. With CNC I can just sit at a computer, design it, then tell the machine to go. Swap out the end mill at least once and get a very nice final product. I will be using a 3000-12k rpm 300W spindle and a 16k-35k 700W spindle with very low runout figures.I'm pretty sure I can get plenty of use out of a CNC mill/router. I just don't know if I will wish that I had the larger machine. Quote Selected
CNC Router Size Reply #3 – March 18, 2013, 03:10:55 AM The reason for having the same sized motors on both the larger and smaller machines is speed. The bigger the motor, the slower it moves. Cutting aluminium means it has to be sturdy. Before linerar bearings were being made, my dad built his using angle iron and about 6 skateboard bearings on each slider. It moved incrediblly well and was percise, but it was so heavy and slow it was almost useless. Things have come a long way since 1995.What really speeds things up is using a belt instead of a direct drive allthread and rail system like many of the commercial machines use. Most home built kits actually use ohc timing belts to get the strenth and accurancy needed.The reason behind the reprap, is it is a rapid prototype machine. You make your prototype part out of plastic, then you modify it for eaxact size and fit, and then you can get a mold done for casting. Machining a solid block of aluminium is by far the best way from an mechanical stand point, but if you could get a rough casting done and then only machine the parts that need to be exact, it will be cheaper and much more efficient in the long run. Just something to consider.If your decent with a cad program, you'll love it t death, and I hope you post the results. Good luck. Quote Selected
CNC Router Size Reply #4 – March 18, 2013, 11:27:01 PM My normal process it to buy the biggest I can afford to keep the future regret at bay. However, I can't think of anything off the top of my head bigger than 12x23. I would like to place an order for those LED projectors! :D Quote Selected
CNC Router Size Reply #5 – October 13, 2013, 11:48:38 PM Finally getting back to this project - I have a living cnc router, and this weekend have started with some simple MDF spacers for some subwoofers. The CNC was missing steps, which has apparently been coming from speedstep on the CPU in the PC causing timing issues. I am stilling getting a couple pauses in a 15 minute time span which need to be worked out, and get some better ways to clamp down the work, but accuracy is really good. I have managed to stop breaking 1/8" endmills. I haven't tested the max speed they can do, but 150 inches per minute worked for a bit before the endmill couldn't take it any longer. Using 20 inches per minute has provided some very smooth, perfect circle cuts. Hoping to get some more complex work designed soon to try out. Other than these small issues that remain to be worked through for improved accuracy, and some resonant harmonics in the frame that could potentially cause an issue on a longer running cut, it's all doing good.Anyone have some recommended design software? Some seem to take way longer than needed to draw up some circles... Quote Selected
CNC Router Size Reply #6 – October 14, 2013, 12:54:41 AM are you using stl files, or what extension does the software require? Quote Selected
CNC Router Size Reply #7 – October 14, 2013, 12:11:35 PM Quote from: Haystack;423355are you using stl files, or what extension does the software require?Exported g-code files using extensions .nc, .ncc, .tap, .txt. I am using Mach3 for the CNC control.There are some things that are acting real dumb, such as return-to-home defaulting to moving the x-y axes first, then the z-axis. There are a lot of little things that I need to work through with Mach3, but it is also the software most used by hobbyists, with plenty of support online.I worked on disabling many services on the PC last night, and trying to further limit CPU states, so I will need to try a few more runs to see how it behaves. Hoping to also get rid of exact stop mode, so it runs continuous between lines of g-code.I'm just happy to see it actually work - there were a lot of little things that needed to be purchased or changed during testing over the months. Waiting for parts to ship made the build process take forever. Quote Selected
CNC Router Size Reply #8 – October 14, 2013, 03:21:59 PM The machine has a working area of just under 24x16x3". I'd play it safe and say 23.5x15.5x2.7" with where I have the limit switches. I also haven't come up with a permanent way to clamp down work, but I have some ideas. Quote Selected
CNC Router Size Reply #9 – October 14, 2013, 04:11:26 PM use big bull dog clamps like they use on large papers instead of staples.using g-code, just about any software should work. Quote Selected
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