On Tuesday 07 July 2015 01:12:30 Cecil Thomas wrote: > Gene, > This probably doesn't apply to your situation but when I made the > encoder wheel for my jet 9x20 lathe (the disc was made from one of > those non-functional plastic discs they include in a spindle of dvds > or cds fortunately this one was black)I did the following:
I have never bought a spindle of cd/dvd that included such a disk. I have tried to cut a regular one, but the coating doesn't cut clean, ripping off additional, like old paint, chips, making it clear in the wrong places. I tried spraying a black enamel on some lexan about 50 thou thick, but found it was far harder on mills than brass or alu. When the mill is a .0312" (1/32") breakage was rampant at any feed rate. This brass sheet is rigid enough to make a good disk, and I have also made good disks out of the painted alu sheets, about 15 thou thick, salvaged from a failed dishwashers door, one of those with a different color of paint on each side of two such sheets, so if you didn't like the kitchen color scheme, changing it was a simple as removing the retainer strips & putting a different color for its front face. But its both hard on mills because it is alu, dulling them rapidly from its alox coat under the paint, so I prefer to use the brass kickplate. > Mount all the interrupters on a piece of pc board which is superglued > to a little bracket made of aluminum flashing bent till the > interrupter is straddling the disc and the bracket has a 90 degree > "foot" which would sit nicely on the cast iron frame of the spindle > housing if there was some way to attach it. I have then on a board, but have not made any "feet" yet. This is a good idea for the test setup and rigging it out of 1/16" thick, 3/8" alu angle was on my mind. But this is good too, and I have a whole box of those magnets. But the motor mount plate looks quite a bit like a cad plated alu die casting. I did pick up a small metric tap & die kit which includes 3mm, and those I have. 6-32 is relatively huge so I'll probably use the 3mm's, but will mill an adjustment slot in the foot. > Take a 3/8 diameter super magnet and put it on the foot. It will > hold the aluminum bracket nicely in place for tweeking. > > You can now move the spindle and watch the interrupters on the scope > or with the halscope and tweek them till the duty cycle and > quadrature is good enough and the index is happpening only once per > cycle. Exactly. > When you are happy apply a drop of super glue between the foot and > the frame and wait till it sets up. > > When it is set then drill and tap the foot for a 6-32 screw and snug > it up. > > Believe it or not it takes about the same amount of time to do it as > it takes to describe it. No math needed. Just put 'em where they > need to be and nail 'em down. That I think is assuming each is on its own pcb? I have these lined up on some of that copper ring per hole style breadboard pcb from the shack, so they are spaced on 100 mil centers with a blank unused hole between the 3 of them, eg fixed spacing so I have to adjust the cycle count, and slot widths in the disk to get the proper quadrature. One of the things that makes it difficult is that because I have never been able to make cool radii compensation work so that the backplot shows a line where the actual cutting edge of the tool travels, I have been forced to make my code do its own compensation. This works, but the backplot is wrong, showing a very skinny slot because it traces the center of the tool and not the cutting edges path. Any time I have tried to do the cutter comp stuff, I get a message that there is not enough room between the moves to do it, even if the tool is a .0312" dia tool, and the entry move in air is better than a damned inch! If someone can explain to me how to make that cutter comp work, so the backplot would show the line _AT_ the cutting edge of the tool, I could come a lot closer to seeing the result in the backplot (I think). As is, I am adjusting such things as the width of the slot in the gcode, and making the first scratches on the disk before I can see what I've got. Ideally for me, the backplot, which shows the tool diameter, should paint the whole tool, not some one pixel line at the center of the tool. Having the toolpath if its a cylindrical tool, paint the whole tool would be extremely helpfull. As is = Frustrating. Is there such a "switch" in the backplot code that would "make it so"? Maybe I should try to translate my presently fixed angle offsets for each side of the slot, into a percentage of the step angle? It seems like I ought to be able to make that automatic as I vary the encoder disks cycle count. Anyway, I think at a cycle count of 66, I have about the right spacing to make a decent quadrature output, but is the slot width correct to get a 50% duty cycle? DamnedIfIKnow. Make it and try it doesn't seem to be the best way to run this train. Thanks for the magnet hints Cecil, I'll see if there is a ferrous surface to use. > Cecil > > > ---------------------------------------------------------------------- >-------- Don't Limit Your Business. Reach for the Cloud. > GigeNET's Cloud Solutions provide you with the tools and support that > you need to offload your IT needs and focus on growing your business. > Configured For All Businesses. Start Your Cloud Today. > https://www.gigenetcloud.com/ > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users 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> ------------------------------------------------------------------------------ Don't Limit Your Business. Reach for the Cloud. GigeNET's Cloud Solutions provide you with the tools and support that you need to offload your IT needs and focus on growing your business. Configured For All Businesses. Start Your Cloud Today. https://www.gigenetcloud.com/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
