Published June 7, 2026
If you own a CNC router, mill, or engraver running open-loop stepper drivers, you have probably experienced the frustration of a ruined part caused by lost steps. Converting to closed-loop stepper control is the most effective upgrade you can make. This guide walks you through the entire conversion process using uStepper closed-loop stepper motor controllers.
CNC machining involves cutting forces that vary unpredictably with material density, tool sharpness, depth of cut, and feed rate. When the cutting load exceeds the motor's available torque, the rotor stalls while the controller keeps sending pulses. The result is a lost step, which shifts the coordinate system. The next cut happens in the wrong place, and the workpiece is ruined.
With closed-loop stepper control, the uStepper controller detects the stall within milliseconds and applies corrective torque. The motor never loses position, even under sudden load spikes. For anyone machining expensive materials like aluminium or hardwood, this is a game changer.
Disconnect power and remove the existing open-loop driver boards from your CNC controller. If they are socketed (like on a RAMPS board), carefully pull them out. Note the wiring of the motor coils so you can reconnect them correctly.
Clean the rear shaft of each stepper motor with isopropyl alcohol. Peel the encoder magnet from its backing and press it firmly onto the centre of the rear shaft. The magnet is self-centring and requires no adhesive.
Align the uStepper controller's PCB over the rear of the motor so the hall-effect sensor sits directly above the encoder magnet. Use the supplied M3 screws to fasten the controller to the motor's rear face. Both NEMA 17 and NEMA 23 mounting patterns are supported.
The uStepper controller has screw terminals for motor windings and power, and a ribbon cable header for step/direction signals.
Each uStepper controller has a small trimpot to set the motor current. Turn it to match your motor's rated phase current. The microstepping resolution is set via DIP switches on the PCB. For most CNC work, 1/32 microstepping provides a good balance of resolution and smoothness.
The uStepper comes with pre-tuned PID values that work well for most setups. If you need to optimise further, you can adjust the PID gains via the UART interface. Increase the proportional (P) gain for stiffer response, and adjust the integral (I) gain to eliminate steady-state error. The derivative (D) gain dampens overshoot. Start with the default values and make small adjustments.
Run a simple test program that moves each axis back and forth over a known distance. Measure the actual position with a dial indicator or digital calliper. Repeat the same move ten times — closed-loop control should return to within a few microns of the same position every time.
Then perform a real cutting test. Cut a rectangle and measure its dimensions. With closed-loop stepper control, the dimensions should match the CAD model exactly, with no layer shifts or missed steps.
Users who convert their CNC machines to closed-loop stepper control with uStepper typically report:
Converting your CNC machine to closed-loop control is one of the best investments you can make in your workshop. Learn how to get started with uStepper or browse our product sheets to find the right controller for your machine.
Browse our product sheets to find the right uStepper for your project, or visit the shop to order.