Hello Guest it is September 15, 2019, 09:18:10 PM

Author Topic: Problems threading on the lathe  (Read 330052 times)

0 Members and 1 Guest are viewing this topic.

Re: Problems threading on the lathe
« Reply #120 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?

Offline ART

*
  • *
  •  1,698 1,698
  • Tough as soggy paper.
    • View Profile
Re: Problems threading on the lathe
« Reply #121 on: March 03, 2009, 09:14:23 PM »
Hi Trevor:

  Im still checking the code, but Brian is out of town till end of week and I need to discuss some thigns with him to help track it down.
Expect another week ro so till I can answer as to what it may be and perhaps a fix.

Art
Re: Problems threading on the lathe
« Reply #122 on: March 03, 2009, 09:24:38 PM »
Ok Thanks Art, I am glad that you are working on it!

Offline RICH

*
  • *
  •  7,358 7,358
    • View Profile
Re: Problems threading on the lathe
« Reply #123 on: March 14, 2009, 05:57:11 PM »
TrevorH,
You had asked the following question:

"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?"

I looked at it out of curiosity a few different ways.
In one way i looked at the HP to shear the cut and had to make some engineering judgements.
Another way was based on SME research out of a 20 year old book i have. Yet another used more current
testing information. The last way was some computer programs which use info from form SME ( Society of Mechanical Engineers ) which is nothinig more than the material removal rate. I assumed a sharp v cut with 10 passes and a high shear stress value. Four or more ways .......all in the same ballpark.

HP required: 0.1 to 0.14

Now you need to find out your motor characteristics for the 1 hp motor you are using.
 
RICH


Re: Problems threading on the lathe
« Reply #124 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

Offline ART

*
  • *
  •  1,698 1,698
  • Tough as soggy paper.
    • View Profile
Re: Problems threading on the lathe
« Reply #125 on: March 16, 2009, 10:52:20 AM »
Hi Guys:

 Sorry for the delay, we're discussing the trouble and we need to know if CV being off fixes this weirdness.

Thx
Art
Re: Problems threading on the lathe
« Reply #126 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

Offline ART

*
  • *
  •  1,698 1,698
  • Tough as soggy paper.
    • View Profile
Re: Problems threading on the lathe
« Reply #127 on: March 16, 2009, 11:12:41 AM »
Hi Trevor:

  Well, we know that a series of G32's will erronously activate the X and create a taper IF the spindle is slowed down.
I suspect the next move may be CV'ing in somehow. So Id like to know if the G32 series will still screw up if CV is turned off
during the series. Id appreciate it if anyone can tell me if thats so..

Art
Re: Problems threading on the lathe
« Reply #128 on: March 16, 2009, 01:51:30 PM »
Hi Art,
I am at someones house and will try to test later today. Problem still exists if CV is not used.
 But just let me make sure.
RICH
Re: Problems threading on the lathe
« Reply #129 on: March 16, 2009, 06:29:23 PM »
Art, sorry to say all the work I do in the lathe is in Exact Stop mode and I have this problem of a wayward X axis during threading. I've just gone in the workshop and checked again and yep, exact stop.

Attached is my .xml file and one of my G-Code files that I had problems with. I've just run that again and whilst in the (air) cut, slowed the spindle down during the "cut" with the VFD and sped it up again on the way back. And yep, the next cut has X motion. I also noticed, if the spindle is still changing speed at the end of the Z coming back to the start point, the Z axis is then stuck (VERY slow moving) and I have to stop the code - I hadn't noticed that before, but this never happens in real operation.

Hope that helps and I'm very grateful you guys are looking into this.

Woody.