[CrazyRonny]

Is there a way I could change the speed of my lathe without having to always change the Belt. Like putting the belt to obtain the max speed and only control the rpm of the motor with an electronic "gizmo".

********This is my lathe**********

Thank's

[pfeist]

Replacing the 1hp AC motor with a 2hp DC motor, DC power supply, speed control and tachometer comes to mind...

But don't ask me how to put all that together :-)
Fortunately, there are lots of folks here that are considerably brighter than I am...

Paul F.

[HuFlungDung]

Ronny,

You could do as Paul F suggested. It is either that, or purchase a 3 phase motor, and a variable frequency AC inverter to supply the power to it. This has been discussed in many places on these forums already. The good news is that doing this will double the value of your machine! The bad news is that it will likely cost you double what you spent already to do this

[Chagrin]

surpluscenter.com sells inexpensive (~$50) motor speed controllers and DC motors that'll go with 'em. After that you'd just need a potentiometer, 3-position switch, and maybe an E-stop button. You should be able to swing this under for under $100.

[CrazyRonny]

It's seem simple to go the DC way but something seem to be wrong, or maybe I don't understand something.... Why manufaturer go the AC way with belt and pulley in the disign of there machine? Why not put a DC motor and speed controller from the start to have easy variable speed?

Ron

[HuFlungDung]

Ron

You will perhaps notice a lack of torque when attempting to run the lathe in the top belt range, but with a low rpm on the motor. A lathe is not like a mill: in a mill, the cutter takes a constant amount of power per chip cut regardless of the rpm (in a given material). In lathe work, the amount of power required to turn at a large diameter is much greater than at a small diameter, given equal depths of cut. So you might find that you will have a certain useful speed range in each belt groove setting, but your motor will not have sufficient power to cut at low motor rpms in high range.

[Kookaburra]

Ronny,

If you go the dc brushed motor way there are also devices around that will allow you to put an encoder on your motor instead of a tachometer. These devices allow you to input a pwm frequency for programmed speed control, or from a pot, as well as a step and direction input. This will allow you to switch between velcity and axis control modes, thus giving you the ability to have a spindle speed controller and the ability to lock the spindle in with the other axes on your lathe and drive it as a rotary device for live tool milling or controlled thread cutting.

[CrazyRonny]

Kookaburra I want to cnc my lathe in a near future, so having the possibility to have a spindle speed controller will be great.
But i'm a little lost on how to do all this.... Where to start and with what material. I read a lot on the forum but there is so many possibility that I get lost... What controller to drive the servo, what size of servo, etc...

Ron

[Al_The_Man]

Ron, There is a couple of ways you can go, as Hu mentioned there is the 3 phase 220v motor with VFD run from 240 single phase in to the VFD, (the VFD converts a Rectified (DC) supply to 3 phase variable freq. out.
The other is look for a large DC motor on ebay, this can be a large servo motor as used on some of the very big lathes, you will not be using it as a servo but they usually have a tach on them, some makes to look for are Gettys, Inland, Kollmorgen Fanuc etc. And look for DC amplifiers 6hp Westamp is one that was plentifull on ebay at one time. The main thing is they have +-10 analogue control.
Be wary about surplus treadmill motors and controllers as some are just a SCR controlled Universal motors (AC/DC).
The other thing you will need is an incremental encoder on the final drive of the spindle (chuck speed), This encoder will synchronize the lathe servo motors for threading etc.
Obviously, if you want to thread and use the constant surface feed cutting method, you will have to look for a control that incorporates this feature.
Some manufacturers have universal controls, i.e. Lathe/mill/plasma etc. others have the unique features built in for the type of machine you are going to retro-fit.
Al

[TyRex]

how do you find the price for that lathe??? I cant see it anywhere

[CrazyRonny]

Originally posted by TyRex
how do you find the price for that lathe??? I cant see it anywhere

I paid $2000/can. for this lathe at my local dealer. You d'ont find price anywhere from the link I submit because it's the company site and they don't sell directly, you have to buy from a resseller.

Ron

[CrazyRonny]

Al_The_Man,

Thank's for the answer... but I still don't know exactly what to buy or to look for to have all the part to complete my cnc project. I will begin to look for the brand of motor you suggest me it's a start.

I think I will start a new post that will ask exactly what cnczone member will put on this lathe to cnc it if they own this lathe. Everything with part# and web link.

Thank's

Ron

[Kookaburra]

Ronny,

As Al said, the +/- 10v feature on a vvvf drive will allow you to control a much larger motor. I guess you need to determine what power you really want. I can point you to a drive that will control a 200V 25amp brushed dc motor or, off the same device, use the +/- 10v control facility to control the vvvf drive using a pmw or step/direction pulse input. These drives will be available on the market in approx. 4 weeks.

[CrazyRonny]

Kookaburra Thank's for your answer. But I think I will need to take some electrical formation because it's look like chinese to me.... vvvf drive??? +/- 10v control facility??? using a pmw??? step/direction pulse input???
I think I have some homework to do before I could go into a project like this. It's look like it's to much thing to learn at the same time, and I don't have lot of time right know to put in this.
I think I will begin with a small cnc 3 axes small router or small mill type project for my first project to begin to learn the basic.

Ron

[RotarySMP]

For most home CNC:
Your controller software takes G-Code and interprets into signals on the parallel port. The most common format is one pin to signal steps, and a second pin to signal change direction. Each axis thus uses two pins. Your stepper or servo drivers takes the motion commands and converts it into motion by controlling the motor phases (steppers) or power to the motors (servos).

For spindle control, most drivers (whether VFD's for three phase AC motors or PWM controllers for DC motors) will need a command signal such as 0V (no RPM) to +10V (full RPM). For a manual machine, this is simple to do, as you just use a variable resister (Pot) to throttle a 12V DC line into the driver.

This is the tricky part for home CNC, as there is no way to directly get a 0-10V signal from the parallel port, so you will need to send a digital signal. Then you will need a widget to convert this signal into 0-10V. There is not even a standard (the equivelent or Step/dir) for this.

The Ugly Solution:
The easy, ugly solution is to set up a little stepper motor and stepper driver. Configure speed as a motion Axis, and use that stepper to drive a Pot. This can be done in TurboCNC.

The elegant solution:
For a lathe (where you have only two axis, and the associated limits, home switches etc) you will probably only be using one parallel port. If you add a secon port, you can define say 8 pins as spindle control pins, and use these 8 bits to provide 256 different levels. You will need to write the code in TurboCNC to do this, but place holders are in the code into. You then need to design an electronic widget to read these pins of the parallel port and convert this into a voltage.

The Practical Solution:
A guy in Oz, Peter Hohman is offering a nice spindle speed controller (Digi-speed) and Jerry and Tony from TurboCNC have written the required code into V4 (in beta testing). The TurboCNC will interpret spindle on off,direction and speed G-codes and send step/dir signals (needing only two LPT pins) to this controller. It converts these signals into 0-10V and cna thus be used to control any motor controller of this configuration (it seem the most common, from Sherline and minimill size up to multiKW three phase VFD's ).

http://www.homanndesigns.com/

[kreutz]

Here are a couple of videos posted by HJoszi a while ago. The spindle motor is a DC servo motor controlled by HP UHU drive with additional regenerative brake circuit.

[ame="http://www.youtube.com/watch?v=eB1AaByTjYc"]YouTube - UHU lathe video[/ame]

Machining titanium...

[ame="http://www.youtube.com/watch?v=q91HbJocS4Q"]YouTube - UHU mini turn[/ame]