On Thursday 03 September 2015 11:24:34 Gene Heskett wrote: > On Thursday 03 September 2015 07:50:59 Peter Blodow wrote: > > Hello Gene, > > I have beeen following your description of what you were doing to > > you machinery for weeks now, but I must confess that I have lost > > track on the way, can't imagine in most cases what you are > > describing. How about mailing a couple of picture of your goodies so > > I can re-read your mails and get an image of your "new" shop > > equipment? > > I'll take my camera out with me today, and post some pix on my web > page in the next day or so. > > I am quite likely guilty of switching the referenced machine in the > word "the" in the middle of a sentence, and I'm sure that can be > confusing. > > In re the lathes control box, has two 2M542 stepper drivers in it, > with a 4" 12 volt computer fan blowing on the heat sinks of each one. > Power supply is a full wave bridge, choke input filter, with about 12k > uf's filter caps. To get operating voltage for the fans, an LM317 was > setup to output about 17 volts, which spins the fans right up. Then > from that 17 volts, a 7805 makes 5 volts for the C1G BoB. Because the > sink tab on an LM317 is also the center, output terminal, and therefor > electrically hot, I had mounted it with an insulator kit using the > thin si rubber insulator. No grease in deferrence to the si rubbers > life expectancy. > > Bolted to half a square foot of 1/4" thick alu plate should have been > enough heat sinking, but apparently was not, particularly when, in the > process of putting a pcb on the outside of the box to carry a 5 pack > of 5 pin, 2.54 spaced plugs so that everything could be unplugged if I > needed to move the lathe out and work on it, but I misswired the plug > for the encoder creating a short on the 5 volt line from the BoB. > Fairly close to instant toast for the LM317. > > But it did work for a couple years until the dummy sitting in this > chair screwed up. > > I thought that LM317 was the last one in local captivity and ordered > some switching buck switchers from China but they are still 10 days > away. So finding a bag of 8 or 9 LM317's will rescue me till they > arrive. Their improved efficiency will reduce the load on the motor > supply transformer and should reduce the overall heat level in that > box by at least 20 watts. But this will do in the meantime. > > In the meantime I used the same pwm driven servo amp that Pico sells > for the spindle motor driver in the new mill, so what I learn about > using a limit3 to reduce the brutality of a motor reversal will get > taken back to the lathe, where I have 50 lines of hal code and about 7 > code modules doing a much gentler reversal that results in several > turns of overshoot from the position specified in the G33.1 command > line. I added some more code to latch the spindles position when the > motion module issued the reversal command, and when it had actually > made a couple degrees of motion in the new direction. With a 20 lb > chuck, and doing a rigid tap at 300 rpms, the overtravel was just > short of 3.5 full turns of the chuck. > > Even with the limit3 to soften the turnaround, the mill can do that > same reversal and get back to full speed in about 1 second, at 2500 > rpms! > > So I am learning that A: Jons servo amp is one tough bit of gear, and > B how to exploit it to do something that on the lathe would only have > succeeded in burning up another of those plastic timing belt sprockets > that I have probably burned up 20 of in the 15 years I had that piece > of junk. But now I have on hand, a new head, with all metal backgears > in it, and a conversion kit to change the chinese belt out for the > much taller cogs XL belt, but it came from fleabay with a very small > tooth count, 10 I think, and bored for the 8mm OEM motor shaft, but I > had made a jackshaft to replace that motor, driven by a 3" polygroove > pulley from the nominally 1" pulley on a treadmill motor. So I bought > some 16 coggers with a 10mm bore to replace the 10 cogger that boring > to 9mm destroyed, so now I need to make a new jackshaft with a 10mm > nose for these sprockets. And I may have to order a longer XL belt if > I can't lift the jackshaft enough to make this one fit. Realisticly, > milling some off the top of the jackshaft frame would be quicker than > obtaining the longer belt. > > On top of all that, the treadmill motor has now developed a rumble > that says the load end bearing on the armature now has square balls in > it. And the flywheel/fan/pulley I will have to remove to gain access > for replacing it, is superglued to the motor shaft as its not a keyed > drive, but screwed to the shaft, self tightening in the treadmill use, > but I'm turning both ways so I glued it on. I hope I can get it hot > enough to make the glue release. I noted yesterday that the fan has > some wobble I had not noticed before, so its possible the shaft itself > is bent, those polygrove belts don't slip when the chuck make a stop > in about 2 degrees of rotation because the toolpost has tipped the > whole carriage into the work, digging a ramp about 100 thou deep as it > tips and stopping it in about 10 degrees of motor shaft rotation from > 4000 rpms. That this rumble started after the last such instance is > clue #2. > > The fix for that is to swap the rubber compound assembly for a 2x2x4 > block of steel, which will allow me to bore the QC holders 10mm > holddown bolthole at the right rear of the block, which in turn will > place the cutting forces on the middle of the carriage as opposed to > hanging off the front, making the right edge of the carriage lift a > thou, tipping the tool into the work to start the the whole show all > over again. > > Or a new lathe big enough to do what I ask this one to do. But the > shops 2 layers of OSB flooring wouldn't handle that weight without > picking it up and pouring a concrete slab under it. > > Now theres a word picture for you. :) > > That has me scanning fleabay for another motor, and becoming resigned > to remaking the mount to the jackshaft. Sigh. > > As Guilda Radner was fond of saying, its always something... > > I'll get some newer pix & post them over the next 2-3 days.
Mid afternoon PS: The LM317T is in and working, but that 1.75x3.5" bit of 1/8" alu for a heat sink is running just under 150F after about 20 minutes running. The draw of a 3rd fan will also make it run even hotter, so there is a point of vanishing returns to such thoughts. I may have to add a 3rd fan, but have no clue what to hang it from. It will no doubt get more air with the lid closed, spillage from the end of the X motor driver. The theory was when I built that box was to have enough air moving inside it to carry the heat to the outside walls for normal radiant cooling. That way, flying swarf stands a very small chance of ever entering the box. Its also sitting on a 5 foot tall wooden chest of drawers I made for a toolbox about 15 years ago, and about 18 inches above the lathes centerline. Swarf gets up there by way of the air hose when I am cleaning up but not otherwise. Its sitting out there smoke testing, but has not been "run the lathe" tested yet. Thats about an hour away. :) Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Monitor Your Dynamic Infrastructure at Any Scale With Datadog! Get real-time metrics from all of your servers, apps and tools in one place. SourceForge users - Click here to start your Free Trial of Datadog now! http://pubads.g.doubleclick.net/gampad/clk?id=241902991&iu=/4140 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
