On Friday, February 03, 2012 10:03:07 PM Ted Hyde did opine: > On 2/3/2012 3:19 AM, [email protected] 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.
I couldn't agree more Ted. G04 Pseconds stops axis motion for seconds. I use it a lot, after getting ready to probe a spot, by sending myself a (msg, hook up the probe dummy!) & waiting long enough in case its not hooked up. As for block delete, never tried it, but I have written some conditional skips using the o<words>. That probably won't qualify me to run your machinery and I don't expect it to. As for knowing all there is to know about linuxcnc, no one of my "maturity" will live long enough to get it all, somewhat because the short term near photographic memory that I had at 50 just isn't there anymore 27 years later. No clue if that may be from sugar damage but I am told it is possibly a contributing factor by the sawbones who try to beat some sense into this old man. The only thing I fuss about linuxcnc doing, because it has done it 5 or 6 times this evening, is that the latest 2.6.0-pre from the master-rt link, has crashed my machine about every third time I quit it while fine tuning my backlash settings this evening. I made the top side of this board tonight, one copy only and the backlash comp being too high jumped right out at me when inspected with a very strong glass, so while I was waiting for Chris to get back to me on another problem that I believe to be a bug but may be my lack of howto knowledge also, I was trying to fine tune the backlash settings in my .ini file. I'm 2 to 3 thou closer to ideal now, so I shouldn't have obvious backlash overshoots when an axis reverses on the next attempt. That I suspect may also help achieve a more uniform trace width, it sure can't hurt. OTOH, if I could have done the bottom too, and starting the top.drill was a show stopper on the 2nd tool goto tool change command, its sitting at an indicated 0.100", am told to goto Z6 so I have room to change the tool, and it refused because that would have been beyond the limits of +-9 inches on the z axis. Huh????? Something internal was rather hosed, but what do I know... Anyway, if I could have also done the bottom, it would be a plumb usable board, so the promise is still the carrot dangling in front of me. That was when I installed the latest build, which is now crashing on quit, 1 out of 3 on average. Yeah, Murphy lives here too.. ;-) Cheers Ted, 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) My web page: <http://coyoteden.dyndns-free.com:85/gene> A man is like a rusty wheel on a rusty cart, He sings his song as he rattles along and then he falls apart. -- Richard Thompson ------------------------------------------------------------------------------ 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
