On Thursday 14 May 2009, Gary Fiber wrote: >I just watched a special a few nights ago about the Trieste. In 1961 >I was 9 but seem to remember some newspaper accounts of the dive. >Pretty interesting how we go to great lengths to shield, special >connectors etc and find something simple like automotive wire works >fine for video in some cases. >Most of the pole line I had detectors on had tramp brackets for 30 >KHz as I remember and was old Western Union telegraph open wire lines. >Western Union had abandoned the pole line and the railway, Norfolk >and Western in this case, took them over. I think that pole line was >there a long time before those high tension power lines were overhead >of it. I also worked on grade crossing motion detectors for flashers >and gates when on the railway. > >OK back to CNC.. :) > >What in heavens name are you doing with the Z axis, jacking >houses? ;) That sure is heavy built. Should stand up to lots of use >and abuse too.
The basic design of the micro and mini mills puts the drive screw behind the post, which causes the way too short gib shoes to bind on the post really bad. Long before I put motors on it, I stuck a bath scale under the head and cranked it down. By the time I had 5 pounds showing on the scale, the screw was badly bowed with several hundred pounds of force on it, it was all being stopped by the binding of the head sled on the post. I first replaced the 20 tpi with a 10 and made a new nut assembly but left it behind the post. Same problem, a 425 motor was locked and cogging at about 3 pounds of push. So I turned the head 90 degrees to make room for the screw down the front of the post and planted the screw as far out on the casting as I could get it. The drive is the nuts, trapped between two ball thrust bearings hidden in those alu blocks, being turned by the 425 behind the blocks which drives the screw up and down. It can, with a 17 to 42 geardown in that timing belt, still do nearly 40 ipm up and down if I limit the accel settings so it takes about a second to get to full speed. Something in the 1.25 area seems to work fairly well but the constant swirps of the accel curve are a bit strange to listen to. I can double the accel settings if I cut the rapid in half, so its all a huge trade off. I can set the jog at 1 ipm, drive down on the scales and it stops at about 155 pounds. I can now drill holes in most anything but one of my Avanti table saw blades, I had to EDM those so I could mount it on the rotary and sharpen it. And experiment I need to repeat as I've been saving old blades for a while. >I think some use double sided tape to stick down PC boards. I read on >someone's site he used Scotch 667 double sided tape so I got a roll >and will try it. Others use carpet tape. I may give that a shot. Obviously clean the table off with alky first so the tape will stick. :) >Others use vacuum clamps. Have a look at http://www.drewtronics.net/ Neat, and wonder of wonders, I actually have one of those little pumps! Hummmm... >Andrew has a pretty nifty vacuum clamp pictured on his site. >I have some 1/16 inch thick single sided PC board I got about a >hundred years ago at the Findlay, OH hamfest. When I moved to Seattle >I chopped up with a skill saw to something I could pack. It was a 4' >x 4' sheet. It won't flex much when I attempt to mill it I hope. It will anyway. :( >I bought a cash box, biggest I could find at officemax and built the >cnc control electronics in that. Have a 24 volt, 12 amp switching >supply I got from www.mpja.com powering it inside of the control box. I tried to use switchers early on, but the xylotex, as do most such drives, expect to see a huge capacitor at the output of the supply because they pump current both ways, which can make the switchers output voltage rise a half a volt and it will shut itself off thinking it has an over voltage error. You may be able to stop that with another big capacitor across the supply, but not all switchers will be stable when that is done, and some may see the added cap as a short at startup and do an instant shutdown. I gave up and built an analog supply out of some old TRT-1 parts. It weighs about 35 pounds. The caps are about 75,000 uf. Big cans. The TRT-1 being the original 2" wide quadruplex broadcast video tape recorder. Running the original used about 10 kwh and kept a 1 horse air compressor busy too. For me, probably overkill, but hey, it works & doesn't heat even for lights out stuff :) >I sat here for a couple of days it seems trying to figure out where >to start with the cnc router this is my first cnc. I am mechanical >and electronic inclined but with all the adjustments and settings in >the software it was a bit confusing for sure. And my "mill" is really >small so many of the .ini files the axis travel is too much and >examples to big to see the table move about.. >Home position is near the right front quadrant almost against the >limits of the X -Y axis travel. The home location point is a 1/8 inch >reamed hole that is located opposite corner of the table 5.5 inches >left and 5.5 inches deep from the right front corner when homed. > >I was trying to figure out what to put into the stepper conf table >travel settings as my home position would be with in the available >table travel. I suspect I need to shorten the table travel distance >in the stepper conf. and let the Home position be outside of that >range. I have picked up 3 limit switches an am intending on using >them for home switches. I should install some, but haven't damaged anything without them, yet... >Then trying to figure out which is the X and Y axis. I figured the X >is across the front of the machine and the Y is the axis that travels >to and from the Z axis. Correct. >Did a google search and I find the Axis' referred to as X and Y can >be either direction so many instances of that on the net its gets >confusing. Nothing concrete it seems. >So my machine for now the X axis moves across left to right under the >Z axis bit and the Y moved towards and away from the Z axis bit >Looking through EMC2 manuals, as I have printed most, never seems to >say anything about cnc nomenclature. Which direction the X axis moves >and Which direction the Y axis moves normally. Might be a good >addition sometime. Generally, you want the bit to move on the workpiece in the same direction as the pressed arrow on the keyboard, so the arrow pointing left moves the X table to the right, or the bit to the left. Ditto, the down arrow 'pulls' the bit toward you by moving the Y table to the rear. Page up/Page down are of course the Z motions, down being into the workpiece. The A axis if you have one, is run by the [] keys, with the [ being counter clockwise in my lashup. If it doesn't run the right direction, you can reverse the scale setting for that axis, or if the scale seems to be moving correct in the onscreen display but the motor is running backwards, then reverse one but not both of the motor windings where they are hooked to the drive. Obviously with power off too else you break the mirror and let all the smoke out. Then it doesn't work at all. :( >"You have this new to you cnc machine what >now?"... "Do I need a ruler or let the software do the measuring for >me for initial setup etc". "What about home position where is it or >how do I find it". Might be good for another wiki or maybe its >already there and I don't know where to look. > >So its been a good exercise using the brain and this is the simple >part. Wait until I need to do offsets to make the circuit boards etc. >I have not read the manual yet but figure what I have read on this >list that something that i will need to do. Start at home and have >the axis move an inch and start milling the board. More reading and >printing for sure. > >Anyway the table moves, the Z axis drops down and up, sometimes sits >there and hums though like its stuck but it moved freely by hand. Slow the accel settings down then. > >I have other means of making circuit boards but figured it would be a >hoot to sit there with a soft drink watching a little mill chew its >way through copper making traces and then drilling the through holes >no less. :) Yup, with a VBGrin. >I suspect I have written enough for now. And I'm going to snip the rest. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) God shows his contempt for wealth by the kind of person he selects to receive it. -- Austin O'Malley ------------------------------------------------------------------------------ Crystal Reports - New Free Runtime and 30 Day Trial Check out the new simplified licensing option that enables unlimited royalty-free distribution of the report engine for externally facing server and web deployment. http://p.sf.net/sfu/businessobjects _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
