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Messages - TrevorH

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1
General Mach Discussion / Re: Problems threading on the lathe
« on: March 27, 2009, 06:04:04 PM »
Success,          I had a chance to try out the new version today, and although I only had time to cut two threads they both came out great.  I am using the P. Port, and I am not sure if anyone else had had success using the PP, but it worked great for me.  I cut a 1/2-13 in delrin, and a 1/4-20 in cheap alum, and both are beautifull.  Thanks to Art, Brian, and everyone else who had a part in finding, and fixing the problem.  If nothing else it will  make us all appreciate threading a little more than we would have otherwise.  I know I just stood in amazement watching while a thread was cut in a dozen passes just as I had hoped, and with no extra funny moves in between!  Thanks!!!

2
General Mach Discussion / Re: Problems threading on the lathe
« on: March 17, 2009, 11:22:56 AM »
Sure, I will wait for the fix from art, this is all for fun for me anyway, I did just have a thought though, Art, would a reduction of 50 rpm do it?  I am still curious about the box under turning Diag showing a percentage label on it.  As I have said before if I have a reduction of 20 RPM it says 20% on the box.  Is this just a label that the program doesn't even care about, or is it actually seeing it a a 20% reduction, if so I could see a 50rpm loss being seen as a 50% loss.  I am probably grasping at straws, but I just don't think that all of us could be experiencing an "actual" real world loss of 50% of our set RPM.  One of us would have noticed that by now as there is a big diffirence between 200 and 400 rpm even with a puny lathe like some of us have.  I am excited though as I bet that you are close to a solution!!

3
General Mach Discussion / Re: Problems threading on the lathe
« on: March 17, 2009, 11:01:57 AM »
Art, I am being pretty bold in kinda disagreeing with you since you are now doubt "the man", and I mean no offence, so let me appologize in advance, but there is absolutely no way that I am loosing 50% of my rpm.   The problem occurs for me with a much smaller loss of rpm as I have said before.  I feel very confident about this, but i will try to see if I can get time later today to test it one last time to make myself feel better about my standpoint.  If I am wrong I will be more than willing to admit it, but I am sure that I am not going from 400rpm down to 200 rpm while threading..........

Trevor

4
General Mach Discussion / Re: Problems threading on the lathe
« on: March 16, 2009, 09:21:05 PM »
Art, Yes that is exactly what I believe several of us are describing, I can say that for me the variation in spindle speed has to be over 10rpm.  The lathe diag screen says variation percentage, but I think that it is showing a variation in rpm, not a percentage, for example 400 rpm set point dipping to 380 rpm shows a 20% spindle speed error which is actually more like 5% I think.  Thanks

Trevor

5
General Mach Discussion / Re: Problems threading on the lathe
« on: March 16, 2009, 11:00:15 AM »
Art, are you doing some testing, or would you like one of us to do some testing for  you?  Is constant V something that I can switch off during threading, as I do recall I do have my config set to constant v, not exact stop, am I thinking of the same thing, or way off.  If you would like something tried out let us know and I am sure that one of us can do it within less than a day, and I am sure willing to try whatever you might suggest.  Thanks

Trevor

6
General Mach Discussion / Re: Problems threading on the lathe
« on: March 15, 2009, 03:23:56 PM »
Rich, Thanks for the research.  It is interesting just how little HP may be required to cut threads.  I guess that leads me to believe that what in fact may be more important is the torque required to deliver the mentioned HP at a relatively low, and very steady RPM.  My motor is rated at 1hp, but at 2500 RPM,much higher than the 5-600  that it is turning when threading.  Thanks again for the input

7
General Mach Discussion / Re: Problems threading on the lathe
« on: March 03, 2009, 09:24:38 PM »
Ok Thanks Art, I am glad that you are working on it!

8
General Mach Discussion / Re: Problems threading on the lathe
« on: March 03, 2009, 08:24:09 PM »
It has been a couple of days, is everyone out of Ideas, or just busy with life outside of CNC?

9
General Mach Discussion / Re: Problems threading on the lathe
« on: March 01, 2009, 07:53:30 PM »
Here is another related, but dangerously general question.  Just how much hp do I need to cut a 1/2-13 thread in 6061 at 400 rpm in lets say 20 passes or less.  Assuming that everthing else such as tool geometry/ rigidy and such are assumed to be ideal?  I am considering the purchase of a VFD and motor, so I would like some opinions.  Do I need 1hp, 2hp, 3-5hp?  Let me know as if I am going to buy one I would only like to do it once.  I realize that I have asked a question whose answer could be dependent on alot of variables, but some educated guesses, or better yet pieces of practical experience would make my descision easier.  Thanks.

10
General Mach Discussion / Re: Problems threading on the lathe
« on: March 01, 2009, 07:27:44 PM »
 Art, can the problem be seen while running the code one line at a time, The simple answer is yes, but only if you do it just right.  I tried to run the exact same g32 routine that I have been working wit one Line at a time, and at first I thought the problem was not present.  I could it the single button, then the cycle start button over and over watching one move at a time.  I would manually change the spindle speed during the cutting pass, and at first I would wait a couple of seconds in between moves, and the problem did not appear.  Then I tried again this time clicking the mouse button over and over as quickly as I could again while varying the spindle speed, and to my suprise the problem appeared again.  I did this a few times since I found it quite interesting.  All of this was done while just cutting air, maybee I should try it while actually cutting?  Let us know if you want some other specific tests done, and I am sure that one of us can do it for you.  Thanks for the help.


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