On 3/23/17 10:01 AM, andy pugh wrote: > On 23 March 2017 at 01:23, hubert <h...@hbahr.org> wrote: >> How are you approaching this project? I am assuming that you >> are starting with a plate that will be attached to the 4th axis and >> machining that plate to accept the cam lock studs and cam locks. In my >> case I can get a complete set(6 ea) of locks from my Lathe source for US >> $36. Are there any precautions that I should watch for when I attempt >> this project? > The basis of the project is a harmonic drive with integral motor and > through-shaft. > I have an FHA-25 size, but FHA-32 might be better. > > The current model drives (FHA-25C) seem to have a serially interfaced > encoder, which looks complicated. > The FHA-25B is a model that HD have no data on, but I found a document from > ESO > http://www.ls.eso.org/lasilla/support/electronics/Documentation/PDF/3P6-DSD-ESO-60400-0001.pdf > Which gives the pinout and wire colours (if you look carefully) and > that is a simple quadrature encoder + hall sensor setup and so rather > easier to drive. > > eBay has a few of these drives, at widely differing prices, some with > the dedicated servo amp. > http://www.ebay.co.uk/sch/i.html?_from=R40&_sacat=0&_nkw=FHA-25B&LH_PrefLoc=2&_sop=15 > > Mine is a FHA-25B-3015-E150C-SP > > I am making a pattern to make a cast-iron housing for bolting to my > mill table, designed around a max swing of 250mm. Making extra > castings is trivial at that point. > > The output face of the drive has a circle of 8 x M6 holes on a 74mm > PCD. This is actually slightly awkward for a D1-4 spindle nose, which > has 3 pins and tangential retainers. I could only get 3 bolts in if I > kept the standard tangential retainers, so I am using axial retainers. > D1-5 already has axial retainers, but also has 6 studs. > > I have modelled the D1-5 nose and attempted to fit the 74mm PCD holes > in. It's not pretty. two of the holes are impossible, I think, and the > others need to be counterbored so deep that the heads are lower than > the D1 cams (or they have to go through them). And they eat into the > retaining taper. > http://a360.co/2nMOEnm should let you view the 3D-model of the D1-4. That looks like a D1-5 to me. As my starting point I have a 10" Rotary table that I have fitted with small stepper. I will use it to do form and fit experiments. I am contemplating either purchase of building a Harmonic drive system. SkyFire the builder of my mill offers a complete ready to hook to my Mesa 7I86 8" Harmonic Drive for about $2000. It isn't my dream solution, but doesn't break my bank either. I still need to do more research into Harmonic Drives to determine what is feasible. > > I think that the answer would be to make the dummy-spindle-nose in two > parts, one that bolts to the harmonic drive, and then a second section > that bolts to that which has the taper. > (then in-situ grind the locating taper, ideally).
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