Messages

5591

General Mach Discussion / Re: Problems threading on the lathe

« on: October 14, 2009, 08:49:43 PM »

ART,
Yes.
All the code  is generated by the threading wizard and the m1076.m1s is set to true. You get two G0 moves prior to start of the thread. Before Cycle Start is clicked to begin the threading, i always waite some time, not moving the mouse etc. and don't do anything during the threading. Once i opened the threading diagnostics window after a thread pass and it caused a major lead error in the next pass. So i don't even touch the mouse etc during the threading post Cycle Start.

BTW, we checked the spindle rpm out today. The home built counter can read to 1us and is better than digital storage scopes as the sampling rate,  and other stuff can be changed. The index pulse was used for input. Basicaly the instrument does what your advanced diagnostics provides minus the graphing.  Anybody using a mechanical rpm reader or tach, well I will say, the diagnostics in Mach lathe is better!

RICH

5592

General Mach Discussion / Re: Problems threading on the lathe

« on: October 14, 2009, 11:05:15 AM »

ART,
Post when you want to try something.
Appreciate the effort your putting into the threading.
RICH

5593

General Mach Discussion / Re: Dell PC any good ?

« on: October 13, 2009, 10:15:03 PM »

Jeff,
I think i tried everything know to man! The signal out of the port has ringing on the signal that you actualy get multiple pulses to the drives. The steppers have the sound of someone tapping them with a mallet and axis speed is limited to about 5-7 ipm. New pc  120ipm, no problem. BTW, with SS that pc is fine,but, the SS dosen't have
----------- remember my promise! 
RICH

5594

General Mach Discussion / Re: Problems threading on the lathe

« on: October 13, 2009, 10:05:02 PM »

ART,
Tests for posted version in reply #532.

TEST#1 - 115RPM / .1P / SCRIBBING TEST STOPPED
I stopped the scibbing test at pass # 11 because on the third pass timing went bad.
The first three passes had a .009" / inch Decrease.
The following 8 passes had a .003 / inch Increase.
Both were single line scribes.

TEST#2 - 115RPM / .1P / 40 passes  ( retest to see if test #1 would repeat )
I left the spindle run for a few minutes.
Single scirbe at .003" Increase in lead.

Picture #1 shows test #1 &2

TEST#3 - 402 RPM / .1P / 40 passes  ( to test scaling due to rpm change )
The first 10 passes were  visualy consistent and a .002" / inch Increase.
Then a slight change at pass # 11 and consistent passes until 21.
Pass 21 changed the lead and was consistent to #39 and there was a .0055" / inch Increase.
Pass 39 changed the lead to a Increase of .008" / inch Increase
SO three passes, and at some time interval ( pass 11, 21, 39 ) you got an increase of lead.
Picture #2 shows the three intervals.

SO this is a mixed bag, but, the change in lead over a some time period reminds me of what I and
others have experienced with the current threading, that sometime during the complete threading cycle,
one or two passes are cutting deeper.( I don't think that is really what happens, i think it's a change in lead
as you can't see / measure it when actual full cut threads are being done. )

I should have left test #1 go on to see what would have happened.

I am going to go back to the version that gave a .002" / inch lead error and expand that testing some.
See if it behaves stable. Can i repeat the one test done?, will there be any pass changes?, scaling at rpm?

Any comments?

RICH

5595

General Mach Discussion / Re: Dell PC any good ?

« on: October 13, 2009, 06:19:28 PM »

What DEll model? ON board graphics?
I have a Optiplex GX520 which requires using a SmoothStepper to run my machines.
RICH 

5596

General Mach Discussion / Re: Problems threading on the lathe

« on: October 12, 2009, 01:04:19 PM »

Hood,
Didn't take it that way my friend.
These tests are being done with the new computer and converted lathe. There is no comparison, so to spead of, to the Sherline lathe relative to repeatabilty and accuracy. I think the same about the computers. In fact, i am right with you in thinking. Current testing would be one system taken to some level and used as a basis to compare other combinations. I can then mix and match computers, lathes,SS and see what happens.

It could be that what is good for one system is bad for another. If another person starts testing and gets different results, should be able to relate or question more intelligently.

 I am still a little concerned about the motor i am using as to rpm and Wednesday a friend will be coming over and we will test and see what we get. You can't use some of the rpm tach's since they read to .05% +- 1 rpm and that isn't good enough. We may not be able to do any better. Gets back to component verses the lathe system as a whole.

I certainly don't want to waste Art's time. Hopefully he's getting a lot of comparative info for his use.
Darn if i am not learning a lot.

Just some thought's,
RICH

5597

General Mach Discussion / Re: Problems threading on the lathe

« on: October 12, 2009, 12:22:16 PM »

ART,
TEST:  REPLY #526 / SPINDLE SPEED AVERAGING / NO ADVANCED THREADING / VER.028
115rpm / 40 passes/.1P

Not zero but close. The threading was done to a 2" length.
The lead increase is .002" per inch. I measured along the length in 4 quadrants of the
piece. Lead as follows:
.5"  - .001"
1.0" - .002"
1.5" - .003
2.0" - .004'

Single scribed line. I wanted to make sure, so see attached pic taken at 100X magnification.
The first scribed line looked just as good as the last one along the length." like that.
Just a sharp V and no sloping towards the root.

I can't test anymore until I get back on Tuesday.

How about another tweak if you think worthwhile? If the additional testing with finer picthes goes sour for some reason then i can pull back to this one for comparison when finer pitch's or increased speeds are tested.

HMM......like my music prof used to say......
"Perfection is allways sought after, never achieved, but much is to be gained in the pursuit of it."  

RICH

5598

General Mach Discussion / Re: Problems threading on the lathe

« on: October 12, 2009, 10:31:22 AM »

Art,
 Enjoy the feast. Will do a quick test and post. If it's good, then will do more tests when I get back.
RICH

5599

General Mach Discussion / Re: Problems threading on the lathe

« on: October 12, 2009, 10:15:04 AM »

Hood,
SS is still in the old pc and I'll get around to installing it in the new one. I am also curiuos.
Just been focused on trying to improve threading when using the PP with a single pointed tool. Comparitively, using the SS would be an apple and not an orange.The file I recently posted about lead error says it all.  I am also curiuos, if as shown by changing the feedrate, if it will hold true for long threading. That was like zero for a 2" length, which implies, 4"  of threading should work fine. The long thread would magnify any lead error.

On the practical side of things, in all these years , i have only needed to do very accurate threading to 6" or so and that was for replacing a screw and nut in crossslides. The screw was matched to the nut and was done with a manual lathe. I am hoping that we can refine PP threading to equal a manual lathe. For threading it would be per the
file i posted.

BTW, this testing is not about "Rich's" threading. It's in light of the typical hobbiest that will use Mach threading with
a low end CNC system ( if that is a way of saying it ). It will be nice to be say to a user, with confidence, that his problem is the lathe system.

Any suggestions appreciated, as more viewpoints are a lot better than one,
RICH

5600

General Mach Discussion / Re: Problems threading on the lathe

« on: October 11, 2009, 10:47:11 PM »

ART,
With averaging on  got a single line scribe and the increase in lead was 0.0033" / inch.
Made a big difference.
RICH

MODIFIED: All the other tests were done with averaging on.
                I will be out and about, returning on Tuesday. I may have some time early tomorrow to do some testing.
                Experiment as you wish. I am looking to the day when that lead goes to 0.000" / inch or exceeds my equipment.
                Then will try longer cuts, heck, still got 20 feet of copper tubing to play with!
BTW: For excitement all you have to do is forget to do a reset back to G94 after threading, dam a trueing cut
 can realy move fast.