On 2/3/2012 3:19 AM, emc-users-requ...@lists.sourceforge.net wrote: > Beware - of these gotcha's > > > > No jog in feedhold! - So don't break an insert or get a swarf ball > > around a tool!!! > > > > Taper thread pitches are measured along the hypotenuse ??? > > ... > > Unfortunately any changes to EMC only happen if you can do it yourself > > even when you can prove it's sensible or Industry standard. Committee > > member ego's seem to overrule standards or common sense. > > > > Explains really why it's still a niche application with so few users... > > Really? I've followed the "no jog in feedhold" many times on this list - I'm still surprised at the discussion that comes up by how it should be "obvious" that when a tool is "broken" that you can just keep on cutting from where it failed. The ones that claim this as a "need" indicate to me that they really haven't been in the situation. My Mazak 410 VMC doesn't have jog in feedhold (brand new in 2008)- does that mean they owe me $100,000 back? Not at all - heck, in many circumstances, I can't even open the door in feedhold - it's a safety thing. The item that keeps escaping me is that one believes they can stop the machine just as the tool breaks in the toolpath (which by definition is physically impossible along a lateral plane), replace it, and pick up from where you "left off". From production to prototyping - it doesn't happen. You either have to back up a few blocks or operations into the program to cut the scallop that the tool left, or scrap the workpiece and start again. Neither requires "jog in feedhold" - it requires stopping the program. And LinuxCNC is quite capable in that department, just like EVERY other control out there. In regards to a "rats nest" - from a turning workpiece to a turning tool - if you're getting a buildup of a continuous spiral from your cut, the cutting conditions are not correct. Aluminum, titanium and many polymers do tend to spiral - it is an indication of incorrect tool application. Feeds, speeds and depth of cut are no longer the realm of a secretive tool maker - they are well published, even equivalents for import/generic HSS tooling. Granted, most mini mill spindles are lacking the speed to run a 1/8" diameter cutter properly - the easy (and appropriate) solution is to program a Z+ raise in between machining operations - just a little higher than the clearance plane is sufficient - where you can then SAFELY hit feedhold and clear the swarf. Also something that traditional feedhold operations are capable of. In regards to the tapered threads - go ahead and look up how that thread is supposed to be cut - and measured - from Machinery's Handbook or an equivalent - Unless you're using a custom gage for checking, you're going to be measuring.....along the hypotenuse! If you need to convert, the math is rather simple. Open a calculator app, or go retro and consult an antique known as a "chart". I'm not responsible for programming or defining either of the above functions in LinuxCNC - I do tend to implement LinuxCNC as my control of choice in a number of installations - many of them hobbyists - that require instruction in the proper use of CNC equipment. (They thought that the 30 second cameo they saw on "American Chopper" showed them all they needed to know.) These things aren't photocopiers - the 100 hours you put into getting a mini mill cutting its first chip should be supplemented with 500 hours of learning proper machining and programming techniques. Even if using a free waterline CAM program is what you want, knowing how to write a couple lines of manual G code really is a requirement. I don't let anyone touch my machines that can't tell me how to use G04 and block delete.
Just some rambling from someone who doesn't blame the control, Ted. ------------------------------------------------------------------------------ Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
