Stuff You'll Need
The Clough42 Electronic Leadscrew is designed to be a maker-friendly DIY project. To assemble it, you will need a few standard components (microcontroller, interface board, display board, and 5V power supply). You will also need a few components selected specifically for your particular lathe and installation (encoder, servo or stepper, driver and power supply).
Every installation uses these same parts, regardless of the lathe size, make and model.
| Part | Image | Notes | Sources |
|---|---|---|---|
| TI LaunchXL-F280049C |  |
Microcontroller that runs the firmware |
Digi-Key Mouser |
| ELS Boost Interface Board |  |
Interface board for connecting everything | eBay* |
| ELS Control Panel Kit |  |
Silkscreened control panel kit with 3D-printed buttons and assembly hardware. | eBay* |
| LED&KEY PC Board |  |
Display and control panel (Not needed if you purchased the above control panel kit.) |
eBay* |
| 5VDC Power Supply |  |
5VDC >1A power supply for controller 5.5mm/2.1mm barrel connector center positive |
eBay* |
*These are affiliate links. When you click one of these links and make a purchase, it helps to support projects like this one.
These parts need to be chosen based on the lathe being converted. The parts listed here are the ones I chose for my Grizzly G0602 benchtop 10x22" lathe. You may need different components to provide the torque required for your lathe.
| Part | Image | Notes | Sources |
|---|---|---|---|
| 5V Quadrature Encoder |  |
Encoder to read the position of the spindle. I used a 1024-pules (4096 count) encoder (Omron E6B2-CWZ6C). Choose an encoder that runs on 5VDC with open-collector outputs. |
eBay* |
| Servo/Stepper Motor |  |
Servo/Stepper motor to drive the leadscrew. I chose a NEMA23 Hybrid Servo Choose a stepper or servo motor with enough torque and speed capability for your lathe. Steppers run open-loop and cannot detect lost steps. Servos typically have higher speed capability. |
eBay* |
| Servo/Stepper Driver |  |
Driver for your stepper or servo motor. I chose a 3-phase hybrid servo driver that matches my servo. If you use a stepper motor, consider a DSP-based digital driver. |
eBay* |
| Servo/Stepper Power Supply |  |
Power supply for your stepper/servo motor. Choose a supply that provides the voltage and current needed for your motor/driver combo. I used a 48VDC supply for my servo. |
*These are affiliate links. When you click one of these links and make a purchase, it helps to support projects like this one.
You will need to determine what size and type of motor you need for your lathe. This will be based on the size of lathe, the torque required to turn the leadscrew, and the maximum speed you will need to turn the leadscrew.
You can use a stepper motor or a servo motor to turn the leadscrew, as long as the driver has opto-isolated step/direction inputs. Most do.
Steppers are usually less expensive than servos, so they can be an attractive option. They have two limitations. First, they are open-loop devices, meaning the driver does not know if the motor has missed steps due to hitting its speed or torque limits, mechanical binding, etc. The controller will continue commanding steps, and it will have no idea that the lathe is in the wrong position. Because of this limitation, it is common to choose a motor and driver that can provide much more power than required, to reduce the chance of missing steps. Open-loop steppers are commonly used in 3D printers and CNC mill conversions. They work fine, as long as you don't lose steps. If you lose steps while threading, you will ruin the workpiece and might break a tool.
Steppers also lose torque as they turn faster, due to the inductance of the coils. At some speed, the torque output of the motor will drop below the torque required to turn the load, and the stepper will miss steps. This limits how fast you can feed your carriage. For a given thread or feed, this limits the top spindle speed you can support. Choosing a higher operating voltage helps to compensate for this effect. If you can use a 36V, 48V, or even 72V stepper and driver, you'll have less trouble than you will with the same motor running on 24V. Just make sure your motor and driver can handle the voltage, plus a safety margin.
Servos are more expensive, but since they have a feedback mechanism (an encoder) the driver can detect and compensate for lost steps. If they are ultimately overpowered and cannot compensate, they can provide an alarm signal back to the controller to let it know it has lost synchronization. Servos usually also have a much higher maximum speed and can maintain torque at high speed. Because of this, you can usually add mechanical reduction to the drive to get more torque. If you use a 3:1 timing belt reduction between the servo motor and the leadscrew, this will triple the torque output, but require the motor to turn three times faster. A servo can probably do this, while a stepper probably can't.
Hybrid servos are a middle ground. They typically consist of a stepper motor with an encoder so a special driver can detect and compensate for lost steps. They are much less expensive than true DC or AC servos, but have some of the limitations of steppers. They can detect lost steps, but they typically still lose torque at higher speeds. In addition to bipolar (four-wire) stepper-based hybrid servos, there are also three-phase hybrid servos. These typically handle higher speeds better than bipolar motors, but not as well as true AC or DC servos.
Inexpensive stepper drivers are typically referred to as "analog" drivers. This is a misnomer, since they are digital devices, but the point is that they don't have microprocessors or DSPs that analyze the motor's performance and compensate for its characteristics and limitations. Stepper motors suffer from a phenomenon called "midband resonance". Under certain conditions (certain step rate and load conditions) vibration builds up in the system until all of the motor torque is consumed overcoming these forces, and the motor misses steps. "Digital" or "DSP" drivers have microprocessors and electronics that can monitor and damp these resonances. These drivers are more expensive, but using one will make your system more resistant to lost steps. The motor also typically runs quieter with a digital driver than with an analog one.
Choose a power supply that provides the voltage and current required for your stepper or servo and driver combination. When buying a power supply, you can choose a switching supply or a linear supply. A linear power supply has a large transformer and filter capacitors and often little else. The voltage isn't regulated, but it's also not sensitive to current spikes. A momentary current demand spike from the motor will usually not cause any issues. A switching power supply has a much smaller transformer and capacitors and uses feedback to control the output voltage and current in real-time. Under some conditions, a current spike can cause it to shut down momentarily, leading to lost steps. If you choose a switching supply, make sure you choose one that can supply more current than you need.