Stepper Motors and Micro-Stepping

Syringe pumps are widely used in microfluidic applications because of the high accuracy and pulseless flow that can be achieved; those characteristics are reached thanks to micro stepper motors.

What is a stepper motor?

Micro stepper motor is a brushless DC motor that moves in little steps to complete a full rotation, therefore unlike regular motors are capable of offering precise angular movements and hold the torque.

How do stepper motors work?

There are different constructions and modes to drive a micro stepper motor. Hybrid Synchronous Stepper Motor is the most commonly used, which combines the permanent magnet and variable reluctance construction allowing maximum power in a small size. In stepper motors, the rotor and the stator have divisions similar to the teeth in a gear wheel, the alignment of those teeth is the way to control how the rotor moves. The most straightforward driving mode is the full step, however, in this mode the vibration and the noise between steps is evident.

How the stepper motors control accuracy?

Typically, angular accuracy in micro stepper motors is around ±1.8° or 200 steps per revolution, however, when higher resolution is necessary micro-stepping arise as an excellent solution. Micro-stepping is a way of controlling the current to the stepper motor windings (or stator) through pulse-width modulated voltage, which means that the current flowing to the windings have a sin waveform. This control method allows dividing every 1.8 degrees step up to 64 times, generating 0.028° angle step or 12,800 micro-steps per revolution, which provides smoother and precise operation.

How the stepper motors control resolution?

Although micro-stepping enhances torque production, low-speed motion and resonance, some torque ripple, vibration, and noise remain since real drives cannot reach ideal micro-stepping. Therefore, it is essential to avoid the called “empty resolution” where the division of the steps is higher than practical for the motor constraints. The empty resolution means that the torque produced by the step is insufficient to overcome the friction of the component being driving, generating a jerky movement.

Stepper motor applications

The main advantages of micro stepper motors are precisely repeatable steps, the precise increment in movements and higher torque at low speed. However, some drawbacks to these motors are low efficiency, limited torque at high speeds and no feedback. The attributes of stepper motors make them ideal for precision applications like medical scanners, 3D printers, CNC, camera platforms, plotters, robotics, and automation process. In syringe pumps the stepper motor is crucial to confer stability and reliability, avoiding pulse flow and variation in the flow rate.

Chemyx syringe pumps.

Chemyx syringe pumps use a micro-stepping motor which provides higher accuracy and precision, The Fusion 100, Fusion 4000 and NanoJet Stereotaxic Syringe Pump have a 0.9 ° stepper motors with micro-steeping, for Fusion 4000 the step motors provides 0.0939 um per step, this excellent tune motion allows the flow rate of 0.0001 uL/min. In these way, Chemyx syringe pump systems offer high quality and performance than do-it-yourself devices. The quality of the Chemyx step motors allows smooth flow for biotechnological, chemical, biochemical and material applications.

Summarizing

Typically, angular accuracy in stepper motors is around ±1.8°, Chemyx provides 0.9 ° stepper motors which is better than conventional models.

Concluding remark

So far we address the functioning of step motors and its role in Chemyx syringe pumps, micro-stepping is a straightforward integrated technology included in a Chemyx syringe pump, it allows an excellent tune motion with high precision and accuracy. If you want to know more about the Chemyx syringe pumps and the possible applications for your field of knowledge, please visit Chemyx website.

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