March 21, 2014 at 4:04 am #1436
This is something I have mostly completed before my recent move to WA, minus final guarding, coolant system and some other important finishing touches.
There is a reasonably complete thread covering the conversion here :
A summary of the architecture and major parts used :
Z AXIS : 750W AC SERVO (DELTA) with a hybrid screw (not lead or ballscrew) and timing belt drive
X axis : 400W AC servo (Delta) with 12mm dia ball screw
Spindle : 4kW, 50Nm Servo (Kollmorgen) with timing belt drive, capable of spindle and indexer operation
Carriage and other new components manufactured from 16 & 20mm steel plate weldments with machining done on my Deckel mill
Control system : MACH3 running on a dual core Atom PICO ATX computer running Windows Embedded. Interface to servos and remainder of machine is thru and Ethernet Smooth stepper.
I have had it running and making parts although I fear that I may have bent the very end of the spindle during some part of the whole build process, which is giving a lot of grief at particular spindle speeds, primarily because the large (and heavy) timing pulley for the spindle is mounted (clamped) on at this point 🙁
Other than guarding , coolant system and some other similar issues, I plan to mount a toolpost spindle at some point to allow for some operations relating to my other hobby of rocketry eg radial milling/drilling and similar operations whilst using the spindle in indexing mode.
CSMarch 22, 2014 at 1:02 pm #1437
That was a very interesting read, with a few familiar characters as well i see (@[USER=25]Paul Kelly[/USER] )
We have an older lathe that would certainly benefit from a CNC refit. However for any kind of batch work a tool changer and stock feeder would be essential for efficiency. Has this ever been done? Is it still cost effective vs a second hand native CNC?March 22, 2014 at 10:17 pm #1440
I have a partially completed lathe tool changer that you are welcome to.
PKMarch 23, 2014 at 2:10 am #1442
I’m surprised that you get away with a single indexing pulse for thread cutting, I guess you’ve got a lot of rotating mass keeping the spindle speed fairly consistent?March 23, 2014 at 2:21 am #1443
Yeah, no-one believes the single pulse per rev theory at first.
Take a look at a single point threading tool. There’s no way you are going to load up that tip with a heavy cut….
Here’s a flick of mine turning a 1/8 BSPT thread
PKMarch 23, 2014 at 3:26 am #1448
Paul Kelly, post: 1368, member: 25 wrote: I have a partially completed lathe tool changer that you are welcome to.
Thanks for that Paul I may take you up on that if/when we start to look at doing a conversion. We may even have a gander at yours at some point if you dont mind.March 23, 2014 at 3:59 am #1449
The spindle speed is rock solid independent of load on my setup since the 50Nm servo is running in step and direction mode and closes velocity loop internally.
Another nice aspect of running in this mode is if a stupid deep cut or a crash occurs between tool and job, the servo spindle ramps down on fatal following error saving everything from a catastrophic misery. I’ve seen this in action on this lathe and was very happy it worked so well.
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