Hi all; Looking at how to write the code progression to carve this vise screw, I get the impression that for best circular accuracy, I should cut a 90 degree arc at a time. But OTOH, the circularity is done with the harmonic drive, supposedly advancing y at its current z depth, 8mm per turn of the B axis. So an 18" screw means a Y motion of 457.2mm from where ever it starts, and a pitch of 8mm because its a 2 start, is 57.15 turns of the B axis.
That's 20574 degrees. So, can I start at y=0 b=0 and run to y=457.2 b=20574 in one gcode move? I intend to try something like that, pull z up 10mm at the end. drive b another 180 degrees then put z back at this runs depth, and come back to Y=0 b=180. thereby cutting the 2nd start on the back-trace. Then leave z alone but advance b, y by a couple thou, run to the far end on the 2nd start, take z up, take out the 180 offset from b, put z back down, and come back on the 1st start path, thereby cutting both paths in both directions. So the math at the starting end of the run will involve the addition of 3 vars for b, b advancing for 1 turn total, the total turns in degrees, and the 180 in and out, and 2 for Y, 1 for the total distance, and the starting offset calculated from B's offset, while the loop is controlled by the incremental advance of Z until the depth of cut has been reached. b,y,z will only trace the tooth shape once. But the rotary will catch hell. Does this make sense? This will not be a quick job as the speed will be b limited to about 4 rpm by the 50/1 ratio of the b drive, plus a 53 tooth on the drive output and a 60 tooth on the b axle. The yz will be the shape of the simple buttress with a zero degree load face, tracing a 30 degree back-face. I might have to run y a few thou at a fixed z to get the flats described is the simple buttress in the left view of the Wikipedia page on buttress threads, although the size of the cutter and shape of it, a ball nose 1/16" with a .25" LOC means there might be a higher wear point. But its a vise screw that should wear in quickly. Painted with hot carnaba wax for a lifetime lube. I used a ball nose to do the backside 30 degree angle smoother. I have code to calibrate the BSCALE in the .ini file to several decimal points, based on running it 103 turns ack the home switch, recording the steps at the 3rd turn and the 103rd turn, subtract the start count from the finsh count and /100, probably more accurate than the printed drive is. The whole design philosophy is its a $10 drive, break it, wear it out, print another for $9 worth of PETG and a bucks worth of crosman bb's for bearing balls. Comments? Thanks all. 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, 1940) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
