Messages

7201

Show"N"Tell ( What you have made with your CNC machine.) / Re: Home-Brew router in process - can't wait to cut!!

« on: August 10, 2008, 10:41:29 PM »

Looking good, but it will even feel better when the first work of art is removed from the machine.
RICH

7202

Show"N"Tell ( What you have made with your CNC machine.) / Re: Afew things I have made

« on: August 10, 2008, 10:31:29 PM »

Nice work and you certainly have my blessing on posting anything related to firearms. Being an avid shooter at one time I appreaciate custom craftmanship and it's quite evident from your postings. Your post brought back some fond memories of a few trips to Remington Arms when they were trying to automate engraving on shotguns. I would guess that a brick of 22's don't last to long with the machine gun but then all the beer bottles are gone and it's time to go anyway.
By all means post some more.
RICH

7203

General Mach Discussion / Re: More TURN Threading Questions

« on: August 10, 2008, 12:48:25 AM »

Hood,
The picture was a tough one to take and the lighting was crucial as reflections disfigure the thread form.
I was curious as to how the actual cutting would turn out since I never did any flank cutting. The cutting tool was just a
sharp 60 deg. Don't have any of those fancy forming full or partial ones.
From top to bottom with comments:
45 deg flank cut - the flank side is smooth and at 30 deg and you can see the 45 deg ragged cut done on the back side
                         of the thread. But it did do a "avg" 45 deg and you can see the steps. So as expected no nut will go on
                         to that thread.
                         I think this one will really show just how well a lathe will work. Should backlash, timing, etc. be sligtly
                         off it will show up on the back side. A .001 step looks like a mountains ridge when magnified.
0 deg radial cut - the nut fit just fine. 1000 grit paper was used to clean the top edge burrs. It's probably the cleanest cut
                        thread of them all.
29.5 deg flank cut - The nut fit rather snugly. I didn't clean it up any and there was a little bit of belly on the flank side.
15 deg flank cut- The nut didn't fit on this one and you can see the difference in the thead form ( 45 deg total instead of
                         60 deg ).
I made the test nut by drilling and tapping a piece of oct shaped rod and checked it with go / no thread gage.
Hate to make generailized statements, but would quess that if a your lathe can't provide a good radialy cut thread then
you may never get a good flank cut one.
Next test should be interesting to see what happens when the spindle slows down some 25 to 50%.
One thing thats nice with CNC is that I can also duplicate a grappy thread!
RICH
 

             

7204

General Mach Discussion / Re: More TURN Threading Questions

« on: August 09, 2008, 12:39:23 PM »

Hi All,
The attached shows a comparison of some thread cutting tests. One is a radial cut and three a flank cut. All were cut using G76 with I=0, 45, 15, 29.5. So a few questions.........
1.Can you name the I used from top to bottom?
2.Which did the test nut fit on?

Here's a hint, all cut using the same tool and settings.
 :)RICH

7205

General Mach Discussion / Re: Motors are jerky and whine a lot...

« on: August 09, 2008, 07:45:50 AM »

I hope the computer is not a dell latitude or some other one with onboard graphics. Did you try your laptop with the battery removed? Just for kicks do the driver test with it in and out as it does make a difference.
RICH

7206

General Mach Discussion / Re: Overheating motors

« on: August 09, 2008, 07:20:41 AM »

Ernie,
Suggest you get in touch with Geco, try to talk to Mariss , and ask him how to test the drives. You just take a few
Ohm measurements and you will know if you blew your drives. I don't remember the sequence anymore. Steppers have an insulation rating ?? 90 C ?? and if you exceed it then they may be shorted. You can test the steppers by measuring winding resistance of the phases. ( of course with power off! ) I would be leary of re-using a "smoked" motor!
Geco may allow you a one time replacement of a single drive " tell them your willing to make a true confession-thats where
you inform them how you blew the drive in writing", hey, a few moments on a note pad may get you one drive at no cost.
May I suggest you review your power supply ie; that each drive is fused and additionaly that you have that cap on the drives and the resistor values are correct per Geco instructions.
Sad for your losses but lets not duplicate again.

RICH

7207

General Mach Discussion / Re: More TURN Threading Questions

« on: August 08, 2008, 10:57:54 AM »

Hood,
0 for radial cutting so will start with 29.5 for flank cutting.
BTW, not trying to be a purist on the measurements, info given is a whole lot better than the nut is loose or tight and for most folks they coudn't even measure the angle of the cut accurately. So I'm happy what is being cut. Will try 15, 30, 45 ( just for kicks ) on flank cutting to see how  the threads look for comparison. Will a write up on threading ( good grief don't want to do treatise on it) but thoughts are for the
newbie.
RICH

 

7208

General Mach Discussion / Re: More TURN Threading Questions

« on: August 08, 2008, 07:33:29 AM »

Using the G76. Art was kind enough to send me a Mach test file which he recently did. I assume the next release of Mach will include the fixes. When monitoring in diag screen, the threading box should turn green and STAY ON for every thread cycle. Mine was not doing that as shown by the test. So the comments I made are actualy incorrect and that's the reason the post was modified adding a clarification.
I needed to confirm that my lathe backlash setting was correct, etc, as it dosn't take much for a thread to get screwed up. With the machine mechanics confirmed, a working program, and the knowledge that threads can made to tolerance
on my punny lathe, I can now play and see effects of the program.
Will deliberately do things like heavy cuts, radial & flanked cutting, testing the limits of a small machine. The electronic 
gearing will allow for around a  50% rpm reduction from started rpm. Dry running showed it's working but don't know
the quality the threading that will be produced. This may sound like a waste of time to some but it's darn good practical
experience on my part using a CNC punny lathe. 
RICH

7209

General Mach Discussion / Re: More TURN Threading Questions

« on: August 07, 2008, 11:41:46 PM »

Hi All,
Still fooling around cutting threads. Dimensional results are good; Pitch diameters are .001 to .003 over the length of the
thread, the pitch cut for all practical purposes is right on ( hard to measure at the bottom of the v but stays witin .001),
using a sharp 60 deg tool and the v as cut is about 62 deg when done radialy. Will try flank cutting some and see how things turn out. Will be interesting to see how the electronic gearing compensates when the spindle speed really drops.
So far with minor drops, a few rpm, things seem good at the practical level.
Now if the fix comes out along with the SS also providing threading and backlash compensation life will be really good.
RICH

7210

General Mach Discussion / Re: Very basic question about tool diameter compensation

« on: August 07, 2008, 10:55:24 PM »

RChadwick,
1mm is a small endmill and it won't take much to snap it off when plunging or cutting. I use 1/32" (.031 dia and even 1/64") in my engraving machine and as you know they are not cheap. Keep depth cuts approx equal to 1/2 the diameter or less keeping chips out of the cutter path, better yet, experiment with an 1/8 end mill to gain some experience on the plexiglass ( goes for some of the other plastics also). Plexiglass is a pain to cut, it will wrap around that little bit and break it in a heartbeat. Need to keep the cutting cool using water, cold air gun, cutting fluid, to name a few.
 
When in doubt on how things will cut you can always dry run a program with a tooth pick in the chuck. They are cheap!
Have made a spring loaded tracer which uses ball point refills for checking out a pattern on paper.

Just a few things to think about.
RICH