Converting a Glass Lathe to a CNC Lathe
If you are considering turning your manual glass lathe into a CNC (computed numerically controlled) lathe, the first thing you will need to think about what you will be using it for in order to decide if this will be a beneficial change for you. In general, CNC machines are geared more toward production work while manual machines are the preferred type for artists and craftsmen, since you get a more hands-on feel with a manual device.
CNC machines require some basic knowledge and capability with computers. For instance, you will need to be comfortable with file navigation and using multiple programs to control your lathe. It is recommended that beginners do the programming themselves, in order to get a feel for how it works.
Although they are not necessary for conversion, kits are available from manufacturers which will include some of the basic parts you will need, such as software, drives, and motors.
While you can use the regular acme screws your lathe already comes with for conversion, these cause more backlash and have more friction. A better alternative would be to switch the acme screws with ball screws.
CNC machines use motors instead of hand wheels, so you will need to add a couple of these to your machine. Two common types of lathe motors are servo and stepper motors.
While servo motors are often considered the “best” type for CNC machines, they are more complicated and take the most computing to direct. They are best for high acceleration and variable speed.
Stepper motors are pole motors that turn the shaft by using pulses of current. They are good for precision shaft orientation and high to low-speed torque. These are the recommended motors for beginners, since they are less expensive and easier to control.
A motor can be hooked up with a rigid aluminum coupling by drilling a hole in each end of the motor and in the size shaft. Use setscrews to attach.
You will also need a drive for each motor you attach. What kind of drive depends on the type of motor you use, so make sure to find drives that are compatible with your motors. You will also need a power supply for the drives. A large linear one with a capacitor filter is recommended. Many other types of power supplies will be incompatible.
You will need to hook the drives up to your computer. To do this, simply connect the drives to the parallel port in your breakout board.
Any computer will work, but if you want to use a Mac, make sure you can find software that is compatible. Most CNC software runs on Windows only. CAD/CAM software is the most popular one to use. You will also need a G-code interpreter for programming. This will make things easier, although it is recommended that you write your own programs by hand initially so that you can get a feel for how it works. This will be beneficial later on if you have to correct lines of code by hand.