Messages

141

Show"N"Tell ( Your Machines) / Re: VDF/Padovani Rescue

« on: March 19, 2015, 01:46:42 PM »

SWEET!  That's quite a machine; thanks for sharing.  Don't those huge machines require giant electrons?

When you get it working well, please post some videos of that big fellow peeling off some manly sized swarf!

142

General Mach Discussion / Re: AC dimmer via Mach3

« on: March 10, 2015, 02:57:11 PM »

Hook a SMALL stepper to a stock dimmer switch. Use an axis to control.

Now THAT'S my kind of thinking right there, I luv it!

143

General Mach Discussion / Re: Threading on lathe issues

« on: March 08, 2015, 12:12:10 PM »

Spindle speed averaging is the average of the upper and lower timing ( if i recall...) so helps but is not a cure all for a varing or way off
pc kernal / pulse frequency, spindle speed variation, etc. Not sure, but, the rpm used in the cycle is to 4 decimal places ( there were at least 20 different versions
of thread testing routines and just don't recall specifics.)

Ahh, OK, thanks!

144

General Mach Discussion / Re: Threading on lathe issues

« on: March 08, 2015, 10:02:58 AM »

Thanks Rich.

Hey Raul did you make any progress?  Coincidentally I had a little threading job to do in aluminum yesterday that came out great.  Even at 300 rpm in direct drive (too lazy to switch to 4:1 belt reduction) everything stayed in sync.

Couple things I changed, dunno if it was part of my problem.  I checked "Spindle speed averaging" in the spindle tab and set my debounce to 2.  The rpm DRO was WAY more stable after that.  I ran the thread several times with good results.

I don't know if the spindle rpm is read by Mach (when threading) via the rpm DRO or directly off the index pulse input but my setup appears to work better now.  May have been the alignment of the stars & planets...or maybe the tinfoil hat I wore yesterday.

Oh almost forgot, I generated the code in Dolphin which shouldn't have made any difference but was easier (for me) than the Simple Threading Wizard.  I also chose 14 roughing and 4 finish passes.  In retrospect I should have doubled the roughing passes to reduce the load a bit as the last few roughing cuts were peeling off a healthy sized chip (for my little lathe.)  It all came out OK so I'm a happy camper today.  We'll see how things go down the road when I have to do "real" threads in steel.

145

General Mach Discussion / Re: Threading on lathe issues

« on: March 07, 2015, 08:15:30 AM »

Hey Rich, are you using the PP or an external motion controller?

146

General Mach Discussion / Re: Threading on lathe issues

« on: March 04, 2015, 09:33:51 AM »

There really should not be a problem picking up a thread if it has not been removed from the chuck unless you have E-Stopped and the axes is slightly out of position. Having accurate homing would cure that.

That's really encouraging.  The ORAC had accurate homing on the X-axis then and now has it on the Z so it should be able to recover from a faux pas.  That's assuming I learn to use run from here properly.

Also, does Dolphin generate good threading code for Mach?

147

General Mach Discussion / Re: Threading on lathe issues

« on: March 03, 2015, 10:29:23 AM »

Ok was just curious when you mentioned having issues with 16mm dia and threading and 4:1 reduction. I would have thought there would have been plenty torque for even the standard 2mm pitch on the 16mm dia.

Sorry, I better set the record straight in case someone reads this thread down the road and gets the wrong impression about Mach’s ability to thread based on my feeble attempts.

My memory is apparently knackered because I found out last night that I was wrong when I said I was having trouble with ¾ hp @ 4:1 reduction doing 16mm threads.  I dredged up an old post and found my problem was with 22mm x 1.5 (ER16 size - I guess that’s where the 16 came from) and that problem actually occurred before I had built the belt reducer.

After getting the belt reducer working, I later failed at cutting 50mm x 1.5 (ER40) threads in steel…a totally different ball game!  Even then I don’t think it was so much a lack of torque issue but more to do with my errors and lack of knowledge.  The completed thread wasn’t too bad looking but was oversized.  When I tried to go back & “run from here” with a deeper cut, something went horribly wrong and I had to e-stop.  It was all over then as I never could pick the thread back up and had to finish the part on the manual lathe.

I need to gather up some scrap stock (along with my courage) and spend a day or 2 cutting practice threads until it either works consistently for me or I can clearly determine that my machine will not thread properly until further hardware improvements are made.

Until then, I'll keep me big mouth shut about threading.

148

General Mach Discussion / Re: Threading on lathe issues

« on: March 02, 2015, 09:04:17 AM »

Milton what is your max rpm?

1600 in direct drive, 400 in belt-reduction mode.

149

General Mach Discussion / Re: Threading on lathe issues

« on: March 01, 2015, 05:23:20 PM »

I think it's not so much a lack of torque slowdown under load but more of a variation around the set speed which shows up in the Mach spindle speed DRO as a small but constant up & down reading at all loads.  (No I don't have "Closed loop spindle control" checked.)  I also have a fairly slow Z-axis motor/drive.

 I think it's the KB DC speed control that causes it or my indexing disc slot width.  My disc/slot is very close to the OP's and is supposed to be OK.  I was going to try a wider slot or putz around with the KB but stopped trying to iron out the problem when the time spent/finished part ratio got too high to continue.

When things calm down a little around here I'm going to give it another shot or maybe just thread aluminum or acetal.

150

General Mach Discussion / Re: Threading on lathe issues

« on: March 01, 2015, 03:55:27 PM »

I use .057 and have threaded successfully on easy stuff.  I think Mach is OK but my machine lacks the spindle power & stability needed for doing steel over 16mm dia.  I'd kill for 1 - 2 rpm variation under load.  I have a 3/4 hp Baldor DC motor that's belt reduced about 4:1 and it's still too puny.  Maybe one of these days I'll stumble across a 1.5kw servo drive real cheap.  That'd fix it.

Fortunately I don't really HAVE to do CNC threading much since I have another lathe that'll do the jobs I HAVE to do.