What Size Steppers for Mini Lathe?

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SteveHGraham
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Re: What Size Steppers for Mini Lathe?

Post by SteveHGraham » Mon Jun 02, 2014 10:23 am

Thanks for the Gecko link, Oldvan. That makes picking motors a lot easier.

I still don't know what I'm doing, but I notice that people on CNC forums with bigger lathes debate whether they should go to NEMA 34, and the conversion outfits go with NEMA 23, so I think 23 will be fine.

If this works out I really want to build a wood router. Manual routing is one of the most annoying, dangerous, easy-to-ruin processes there is. If you don't do it every week, you have to relearn the finer points every time you do it, and usually, something will get marked up in the process.
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hammermill
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Re: What Size Steppers for Mini Lathe?

Post by hammermill » Mon Jun 02, 2014 10:38 am

well as you learn and grow you will never have enough motors for cnc projects. when you build you mounting plates drilling them out for the differient size bolt patterns would make changing easy latter on.

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Re: What Size Steppers for Mini Lathe?

Post by SteveHGraham » Mon Jun 02, 2014 11:30 am

Studying is making this worse and not better!

I don't even know the basic components I need. I know I have to have two motors, and motors need controllers. I just found out you have to have a separate controller for each motor. And the whole mess needs a power supply of its own. It looks like this junk runs between $125-$300, depending on where you get it and what you get.

I assumed this whole mess would run off my garage PC, but I am becoming confused about that. I don't know where the controllers go. Do they go in the PC, or do I need a cabinet?

I have an old PC that runs XP, and I never use it. I can put it out here if I I can't use my existing garage PC.

Is there some place where I can get a primer on this stuff? I signed up over at CNC Zone, but that place is too nerded up. They don't answer questions.
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hammermill
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Re: What Size Steppers for Mini Lathe?

Post by hammermill » Mon Jun 02, 2014 11:48 am

lets treat this a valuable pig and eat him in small bites.

http://www.cnccookbook.com/CCLatheCNCHome.htm

this seems to be a good start for getting familiar with parts. and learning what the words mean and how they relate. I thought you had bought a kit already. but lets start with the basics

motor
drivers for motors
controller to direct drivers
motor power supplys

safety and control limits and e stop, indicator lights

computer type

here is a overview

http://probotix.com/diagrams/3-axis_Sid ... dia.v2.jpg

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SteveHGraham
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Re: What Size Steppers for Mini Lathe?

Post by SteveHGraham » Mon Jun 02, 2014 12:07 pm

I am rooting through that. Thanks again.

It brings me real joy to see that half of the steppers out there are rated in Nm and the others in oz-in. Apparently I want at least 2.1 Nm.

Do you have any idea whether I'll be able to run this crap out of my garage PC, or should I use a dedicated box?

That drawing you linked to suggests that I need a separate cabinet for the controllers and breakout board.
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hammermill
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Re: What Size Steppers for Mini Lathe?

Post by hammermill » Mon Jun 02, 2014 12:16 pm

controller,breakout board excetra call all be mounted in a cabinet. together. wether your computer will work depends on a few variables such as do you need a controller because of software that has a parallel port or can it function via usb????

lots of questions for each step a large flow chart may help you get it under control.


if you get motors and a driver you can play with it and build understanding of each process.

again eating the valuable pig one bite at a time. :)

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Re: What Size Steppers for Mini Lathe?

Post by SteveHGraham » Mon Jun 02, 2014 1:06 pm

Won't I need a hardware controller for each motor? Surely I can't run them straight out of my PC's motherboard ports.
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Re: What Size Steppers for Mini Lathe?

Post by ctwo » Mon Jun 02, 2014 1:29 pm

Windows XP will run Mach3 just fine. I assume you are going to run an open loop system, so you should not need need a very fast PC, but you will need parallel support for most controllers, so make sure you can get the motherboard drivers.

Open loop means your PC sends pulses to the motors, but never checks if the motors actually moved to where they were told. Closed loop means there is a sensor on the motor that reads the motor's actual position, and the PC keeps sending pulses until the motor gets to where it's supposed to be.

If I were building this, I would buy a package since this is how I got my rotary table into motion.

Here is a 3-axis kit for $250, inlcudes motors, drivers, power supply, and BoB. These are the same drivers and similar motors that I got going in Mach3. It was easy...

http://www.ebay.com/itm/SALE-2-Axis-Nem ... 1e79c258e3


Or you could get better components from Gecko or look at Keling... Keling has a driver that you plug right into the wall, but they cost over $150 ea. Nice drivers though...
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Re: What Size Steppers for Mini Lathe?

Post by hanermo » Wed Jun 04, 2014 7:38 am

Those 542 drivers are really good.
Hiss much less than geckos, due to newer circuitry.

I am sure the wantai motors are fine, as well.
(never used them).

I highly, very very highly, recommend driving geared up, 1:2-1:3, with proper timing belts.
A lathe can really use the resolution.

HTD belts are cheap and good, ime, GT and T5 is "maybe better" but more expensive.
Cheap couplers are not too good, imo.

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Re: What Size Steppers for Mini Lathe?

Post by daGrouch » Mon Jun 30, 2014 11:45 am

I did about the same thing and started with eBay 460 oz 23's. A year later I bought a 1000 oz NEMA 34 kit. The 34's run at 60 volts and the 23's at 36 volts. While messing around I hooked the 23's to the bigger 34 drivers / power supplies and they ran much better. the 34's are still in the box. That was an expensive lesson. I also burned out 2 of the motor drivers since I left the handles on the machine and use it manually. Manually turning a stepper back feeds electricity into the drivers and I went a bit fast. Fortunately they are pretty easy and cheep to repair.

I feel that Longs and Wantai kits are under-driven. Also, take the ratio advice to heart. They have more torque at low speed.

Use a dedicated computer for Mach3. Windows doesn't multi-task that well at the driver level Mach uses. I put all the power supplies, drivers, and break-out boards into an old mid tower computer case.

Holler if you need more detail.
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Re: What Size Steppers for Mini Lathe?

Post by SteveHGraham » Mon Jun 30, 2014 11:52 am

hanermo wrote:I highly, very very highly, recommend driving geared up, 1:2-1:3, with proper timing belts.
A lathe can really use the resolution.

HTD belts are cheap and good, ime, GT and T5 is "maybe better" but more expensive.
Cheap couplers are not too good, imo.
I take this recommendation seriously, but right now, I just want to get this thing running. Once I succeed at that, I can try to improve it.

Thanks for the motor info, Dagrouch. I plan to go with the smaller motors. I haven't picked a package yet. I think I'll have the lathe prepared mechanically by the end of this week.
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hanermo
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Re: What Size Steppers for Mini Lathe?

Post by hanermo » Thu Feb 12, 2015 6:34 am

Oldvan .. you misread what I wrote.

You need to have about 10x more steps than you hope to achieve in the real world.
About 10x with steppers, and 5x more with servos.

So, to get 1 micron physical, actual, real resolution, I need to have about 0.2 microns (0.1 microns with steppers) as my step size.
1 micron is what I need, and am working towards 0.5 microns.
This will be done with my new, scratch built lathe.

Everything has slop (looseness), bends (has compliance), and inaccuracies.
The only question is how much.

Everything bends .. e.g. screws are inherently springy.
Thus a rigid scew is better, and thats why a bigger screw, which is more rigid, is better.
It will have less compliance, and will more accurately position and repeat to where it needs to be.

The previous post & recommendation is a distillation of how things are.

Below something about me ... and what I do.


I build this stuff for a living, and my lathe has about 8000€ invested in cnc upgrades.
(2 lathes, 5 versions).
I have about 20.000 hours of cnc experience, full time since 2003.
I scratch built a portal cnc mill in steel, 2000 kg, 1600x500 mm table in steel. This took a total of 13.000 hours, full time.
Its now undergoing an upgrade to bigger screws (40 mm diameter) and ac servos.
Controller is a Pokeys, with 8 axis upgrade (4 axis / 125 kHz under mach3).
Works extremely well for a simple mill.
http://www.poscope.com/PoKeys57E

I also have lots of factory training, building cnc machines.
I was the manager for sales for the worlds largest cnc builder, for Spain, and increased sales 11-fold.
We had over 65 engineers on our staff.
This will not be the case for most other people.

My lathe is meant to make perfect screws .. to less than 1 micron nominal error throughout.
This is specialist stuff, for things like labs, optronics, high precision leadscrews, measurement systems etc.

My lathe is a test bed .. and I got it to have physical, actual, real, 1 micron resolution in about 2006.
Using servos with 10.000 count encoders (us digital e6) to dc motors I built (gecko 320 servos driving modified treadmill motors at 68V DC).
This is old stuff, not at all good from my current p.o.v., just good for testing and learning.

My CNC lathe (current).
The X axis is a ballscrew kit I made.
Double-tensioned (=overconstrained). This means half the free length ie 8 times more stiff.
0.750 diameter vs 15 mm original.Doubles stiffness. Total 16 x stiffness of original x axis.

My stuff is better compared to industrial VMCs and turning centers, and I myself use these types of components.
I also import and sell these components.

The Z axis is now a 32 mm ground class 1 ballscrew.
Brushless servos for x,z, and c = the spindle.
Spindle is a 2.5 kW AC brushless servo.
Now building mounts for it.

Controller is CSMIO,IPS, with ENC encoder threading, at 4 Mhz.
ww.cslabs.eu
Controller costs about 1500€ in various bits and pieces, + about 500€ in din rail stuff (100 packs of connectors, bus bars, ferrules, crimping kits, color coded wires, etc etc etc), extra 24V power supplies (isolated IO from servo drives), differential 24V IO and differential servo drives etc.

Money is not an issue - only bang / buck.

When the lathes current upgrade cycle is done, soon, it will have
x: 400W servo, 4000 counts, 1:3,
z: 750 W AC brushless servo, 10.000 counts, 1:3
c (spindle): 2.5 kW servo, 10.000 counts, 1:3 to 1:1 to 1:6 (indexing). High stiffness belts (probably HTD 8 mm, 50 mm wide).
b: (tailstock) 400W servo
y: 400 W servo
Live tools: 750 servo
Subspindle: 750 servo

I have 13 servos and 10 steppers new in boxes, just doing mounts for them.

Pics when the upgrades are done.
I cannot show the stuff as-is, only after its cleaned up.
Sorry - but I need to live of this stuff.

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