Thread: GH1440 Lathe Bed Conversion
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24-02-2017 #1
I am perhaps the only one with experience, who has done this, so...
At this time, after 3-4 trials, I have a 2.5 kW AC brushless servo as the spindle drive, at 1:3 belt drive, via HTD 8-30 belts, on a very strong, sturdy, rigid frame of approx 60 kg mass.
So I get 0-1000 rpm, with a C axis or "live cnc spindle".
Servo is 10.000 counts at 1:3 belt drive for 1:30.000 counts at spindle.
This is not rigid enough for milling.
And my 600€ belt drive 30 mm wide, 8 mm profile, taperlock pulleys, 24:72 teeth at spindle, setup is very, very industrial, so...
The setup is excellent for turning and lathe use.
I get 90 Nm at spindle.
Spindle motor is 10 Nm cont, 30 Nm peak (3 secs) x 1:3 = 90 Nm at all rpm.
I will use it as-is, until I switch to a secondary, likely a (double) worm drive or planetary at 1:10, at some point.
My experiences, working at this for 10+ years.
Steppers are no-where near accurate enough.
Even the best belt drives are not accurate enough.
HAAS uses a gear on the spindle, for C axis use.
But they use a class 9 ultra-precision gear for the C axis, only, switch it in-out, and the gear grinder cost 9M$, I have met the guy who sold it.
So my system is better/similar to simpson of cubestudio, and not good enough in rigidity for C axis.
I use a bigger/more accurate servo, and similar/bigger belts (his are also HTD-8, I think mine were wider).
And my lathe is a 12x, fwiw..
Hth.
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24-02-2017 #2
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24-02-2017 #3
Last edited by hanermo2; 25-02-2017 at 10:26 AM.
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25-02-2017 #4
But I thought you had built this as a personal machine?
At least that's what you seem to claim until anybody asks you for prove.
And just so you know Valfar, Hanu has posted about this mythical machine for many years on various forums/email lists, and although his theory is reasonable, nobody has ever seen any kind of prove that such a machine actually exists. Whenever pushed for evidence, the excuses I've seen are he has no camera, he can't because of confidentiality, or the toys simply get launched out the pram, so make up your own mind.Avoiding the rubbish customer service from AluminiumWarehouse since July '13.
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24-02-2017 #5
Thank you Hanermo2 for the valued information.
I read your concentrated post at least 10x times to understand what's in there, but I think I got there in the end.
I understand steppers driven by belts are not accurate enough, and steppers driven by gears are rigid, suitable for the application, but the problem with these is the backlash. Is that correct? It does make sense, as the belt at the end of the day is made out of flexible material, unlike gears which are made out of steel.
When you say you'll be switching to secondary, do you mean you'll add another servo stepper for the C axis, but driven by a worm gear or a gearbox?
In my headstock I still got there a secondary spindle with spur gears all over it. There's also a clutch mechanism on the front panel which can engage the secondary spindle with the main spindle. So I might be able to direct connect a servo stepper for the C axis to that secondary spindle. But the trouble would be the backlash between the spur gears, and probably less accurate than a belt drive.
Today I grabbed a 2.2kW motor (that was quick!), but don't know many details about it yet. It was free of charge and it's blue :) . Next I'll need to invest in some VFD and play with it to understand the process.
I'll keep reading here in there.
Cheers!
LE Have found this 'CNC Lathe Spindle Encoder' design http://ve7it.cowlug.org/spindle-encoder.htmlLast edited by Valfar; 24-02-2017 at 10:05 PM.
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