On 05/20/2014 08:39 PM, Gene Heskett wrote: > Greetings docs maintainers; > > I found this after noon that there is a large interaction between the > driveline value, and the J and K values.
My understanding from studying the G76 source is that the J value is intended to be depth of cut for the first pass. But the first pass is based on I, and I is based on the drive line location, which is based on the initial tool location just before G76 is invoked. I is intended to be the tool clearance, or space between the initial tool position and the surface of the workpiece. This assumes that the workpiece has already been turned down to the thread's major diameter in the case of an external thread. The position the tool is in is sort of a data input defining one end of the drive line and therefore the thread diameters and thread length. So if you find the major diameter of the thread in question and add I, that will be the X value the tool needs to be in before starting G76. Also note that I, J and K follow the setting of the G7 diameter or G8 radius mode. Figure out the distance you want for the tool clearance, for G7 enter it for I, for G8 double it and enter for I. The same goes for J and K, even though none of theses values correspond to any real diameters. If you happen to set J equal to K, G76 should take one cut with a depth of cut equal to J, except I believe setting J equal to K will throw an error so make K just a tiny bit bigger. After G76 cuts J, the next depth of cut is J multiplied with a degression factor which makes the depth of cut smaller for each pass. Passes are run until just before reaching K. At this point K is used for the final pass and any spring passes. So the last pass ends up at the initial tool position, plus I and K. R sets the behavior of the degression factor, with 2 giving the chip produced on each pass the same cross sectional area, or close to the same chip load. Which is not the same as equal depth of cut in this case. The number of passes needed will depend on J, and the rate of degression (R) on J. The source code looks like this: depth = full_dia_depth + cut_increment * pow(++pass, 1.0/degression); Making J as large as you can really reduces the number of passes. Changing the value of I should not have any affect on the number of passes. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/ ------------------------------------------------------------------------------ "Accelerate Dev Cycles with Automated Cross-Browser Testing - For FREE Instantly run your Selenium tests across 300+ browser/OS combos. Get unparalleled scalability from the best Selenium testing platform available Simple to use. Nothing to install. Get started now for free." http://p.sf.net/sfu/SauceLabs _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
