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Messages - Curtis_F

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1
Thank you for all the replies!

Sounds like an AC Servo is the way to go.

There is some posistional data loss when using anything but a direct drive coupling system, but if Mach 3 will work with a Servo that'll be more than close enough for my work.

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Curtis,
Curious, what are you turning at 30,000 RPM??
Rich,

I, and a bunch of my friends, do model building that often requires very small pins and screws.  Here's what I posed on the CNCZone.com forums when asked this same question:
Quote
The Machinery's Handbook 26th edition says; when cutting Brass with a Carbide cutter the optimal Surface speed is in the 440 to 1170 Feet Per Minute range.

The major diameter of a #0 thread is: .060"
The major diameter of a #2 thread is: .086"
The major diameter of a 1/2" thread is: .500"

Therefore:
Optimal RPM for turning the major diameter of a #0 screw is: 28,000 to 75,000 RPM
Optimal RPM for turning the major diameter of a #2 screw is: 20,000 to 52,000 RPM
Just for comparison;
Optimal RPM for turning the major diameter of a 1/2" screw is: 3,400 to 9,000 RPM

After researching bearings a little I found that the off-the-shelf ones of the size needed to fit around a 5C collet spindle (45mm I.D.) topped out at a little over 30,000 RPM if oil lubrication is used.

Here's a link to the thread at the CNCZone if you're really bored. :-)  http://www.cnczone.com/forums/showthread.php?t=84133

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You should check out the thread "Success, mini machining center . . . " in this forum. I just finished building what amounts to a lathe head using a 5C spindle and it is servo driven. You might get some ideas there.
I'm going to read that right now!


Thank you again,

Curtis F.


2
Aaaaaaaaaand I forgot to mention that I'm looking for an encoder "kit" that'll fit on a 50mm OD shaft.  :-[

I'm desiging the spindle around the C5 collet standards and will be pushing a max operating RPM of about 15k (wanted 30k, but scaled back the design due to bearing costs), which immediately kills most encoders with integreal bearings, thus the "kit" option.

Though I'm still interrested in any recomendations as there's a Mill project after the Lathe and it'll need encoders as well.


Thank you for your time again,

Curtis F.

3
Greetings all,

I'm new to the hobby-cnc world, and am reading everything I can get my hands on to try and get up-to-speed, or atleast not appear ignorant.   ;D  One thing I have decided on is to use Mach 3 as I've read hundreds of good reviews from people who have home-built and/or retro fitted CNC machines.

My current/first project is the design and construction of a CNC mini lathe (4" x 12") and I'm hoping for some reccomendations on Spindle Encoders that are known to be 100% compatible with Mach 3.

I've been looking through the archives here and found posts of people asking for help with some encoders, but I didn't see many posts that talked about encoders working on the first go.

One thing I did learn in reading all the posts is that I really need to have a USB (Smooth Stepper) interface to handle higher RPMs.


And while I'm at it I'm going throw out a really ignorant question:  :-[  For a lathe where I'm going to be doing single point threading is a VFD or a Servo better for the spindle motor?


Thanks for reading, and any enlightenment will be greatly appreciated,

Curtis F.

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