Hi Peter, A previously asked question is very important: how many axes? 3 X, Y, Z? 4 X, Y, Z, A? If the A axis is the rotation of the part along the X axis that would actually be reasonably doable because the A movement could be the rotation of the table supporting the part. More than 4 axes gets complicated to engineer, expensive to build and challenging to program.
A gantry design (spindle moves, table is stationary) would seem to be the logical choice for this project. It is quite possible that this machine could be built so that it can be disassembled. The locations where the machine is supported would need to be very rigid so that when the machine was assembled it could be anchored to these points and the anchoring would provide stability to the frame. Proper anchoring and triangles, triangles, triangles in the design will provide a structure that will make it possible to achieve the + / - 1 mm and probably better (depending on how fast the cutting process occurs). Is there a budget in mind for this project? I wish you success, Jim Fleig ----- Original Message ----- From: "Peter Braroe" <[email protected]> To: <[email protected]> Sent: Tuesday, March 17, 2009 7:13 AM Subject: [Emc-users] BIG CNC machine for making small airplane? > Hello all! > > > > Here are some thoughts: > > > > Precision > > Actually airplanes are a big like boats, not very precise. Consider a > bunch > of aluminum panels put together by hand with rivets, or wood spars with > cloth covering. I fly two different Cessna 172s and they are supposed to > be > identical but have very different feel to them. I think +/-1 mm or worse > would be fine. Probably 1 mm per meter of range would be OK too, > especially > if any error is symmetrical. Look at a 10 meter long wooden airplane from > the 1930s - they fly fine - and I would be very surprised if they had > millimeter precision! > > > > Dimensions > > The wing isn't very thick - perhaps only 4 inches or so. A bit more if it > is > to be done in one block with the "dihedral" i.e. the vee-in-the-middle. > The > fuselage would be no more than 1,5-2 meters from the lowest point to > highest. Less if the "empennage" (i.e. tail feathers) would be made > separately. If one wing where to be made at the time they would be 5,5 > meters each, and the fuselage would be maybe 8 meters - less since the > engine cowling would be made separate. > > > > Assembly from smaller parts > > This is of course an option - but wouldn't it be nice to just put a big > block up and have "instant airplane"! Just add the skin. but I agree that > it's probably wiser to calm down a little and limit the size to say 6 x > 1,6 > x 1,6 meters or so. Even that is of course massive! Then one could do one > wing at the time and then the fuselage. > > > > I am thinking perhaps assembling a frame from scaffolding tubing - then it > can be disassembled too! > > > > The main thing I am thinking about is how to make something work over such > a > long distance as 6 meters. Perhaps a linear motor and a bicycle chain(s) > with a tensioner could be used for the long axis? Those parts are > plentiful! > How to make an accurate sensor is then the question. Although if a beefy > stepper operates the chain cog and an initial calibration is performed > then > perhaps that is good enough. > > > > Has anyone attempted something like this before? Ideas? > > > > Perhaps I will try to build something smaller first and experiment! > > > > Best regards, everyone! > > > > /Peter > > > > > > ------------------------------------------------------------------------------ > Apps built with the Adobe(R) Flex(R) framework and Flex Builder(TM) are > powering Web 2.0 with engaging, cross-platform capabilities. Quickly and > easily build your RIAs with Flex Builder, the Eclipse(TM)based development > software that enables intelligent coding and step-through debugging. > Download the free 60 day trial. http://p.sf.net/sfu/www-adobe-com > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Apps built with the Adobe(R) Flex(R) framework and Flex Builder(TM) are powering Web 2.0 with engaging, cross-platform capabilities. Quickly and easily build your RIAs with Flex Builder, the Eclipse(TM)based development software that enables intelligent coding and step-through debugging. Download the free 60 day trial. http://p.sf.net/sfu/www-adobe-com _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
