Stepper drivers come in two different forms: integrated and removeable. Integrated means they are part of the board and are not installed separately; when you buy a mini Rambo, the A4892 chips are soldered directly to the board; on a classic RAMPS, the stepper driver plug into specific ports on the board. If you have separate drivers, that does mean you’ll have to source those as well as the control board if you’re building a 3D printer, however if they ever fail, you only need to replace that single driver (which is usually below $15 each) rather than desoldering a bad driver or getting an entirely new control board if you blow a driver on an integrated board (which could be $150 mistake). With removeable boards, there’s the Pololu footprint and Bigfoot footprint; Pololu is a standardized footprint, whereas Bigfoot is specifically made for Panucatt boards and to allow for more current and larger chips.

Keeping the Drivers Cool
While the stepper drivers are smart enough to shut down if they start overheating, that does mean you’re going to be skipping steps in your print. Some drivers just need a heatsink attached to the chip and call it a day, while others may need that and a fan blowing cool air onto the board.

Stealthchop and Spreadcycle
A staple of Trinamic drivers is StealthChop and Spreadcycle. Stealthchop is for quiet, low-current performance, which means your printer may be completely silent, save for the bearings rolling across the smooth rods, but it also means move too quickly, too abruptly, or snag on some tipped over supports and your 3D printer may skip steps. Spreadcycle is basically the “normal” mode and will power through and perform as you would expect. They’ve also come out with Stealthchop2 which is even better than before, so where before it may skip a step, now it can counter it with no problem at all.

On a base level, that about covers what analog stepper drivers are, how they work, and should hopefully give you an idea of what you might want in a 3D printer. If you’ve gone ahead and swapped out the stepper drivers in your 3D printer, I’d love to hear what you’ve upgraded to.

A few years back, I became interested in attempting to propel a wheeled robot using stepper motors. This is not the usual method for propelling a robot. A more typical approach is to use two traditional DC motors. Individual differences in the two DC motors are then accommodated by optical feedback that provides data which can be used to match the speed of the two motors.

The characteristics of stepper motors that appealed to me were their ability to precisely turn a wheel at a calculated distance and their ability to brake. Stepper motors are not a panacea for robot propulsion. They are heavier, use more power, and have far less torque than traditional DC motors. In addition, they cannot be operated at great rotational speeds and the faster they run, the less torque they have. One needs to be careful in selecting a stepping motor. It has to have enough holding torque for robot propulsion. In general, you will find the weight and size of a stepper motor needed to drive a given size robot larger than traditional DC motors.

Stepper motors come in two basic types: bipolar and unipolar. Bipolar stepper motors need drivers that can alternately supply current in both directions through the motor’s coils, while unipolar stepper motors always run the current in one direction through the coils — which also means a simpler driver circuit. We will only be discussing unipolar stepper motors in this article.

In addition to axial construction, pancake stepper motors have two other unique features: an ironless core and lack of a commutator. These construction principles give pancake motors several performance advantages over conventional cylindrical motors. First, because the armature contains no iron, there is no cogging effect, which is traditionally caused by the magnets in the stator attempting to align themselves with the iron in the rotor. Cogging makes it nearly impossible for conventional motors to achieve smooth motion, and pancake motors are the only motor type with no cogging or torque ripple.

Also, no iron means minimal inductance and no stored energy to be dissipated during commutation, so there’s no arcing of the brushes. Brush wear is a significant drawback to traditional brushed motors, but with no arcing, brush wear is greatly reduced and brush life is improved in pancake motors.

The low inductance of pancake designs also means that they have low electrical time constants, allowing current to flow very quickly into the armature for virtually instant torque production. Peak torque production is also higher in pancake motors due to their lack of iron. In conventional iron core motors, the magnetic field of the armature can demagnetize the permanent magnets, so peak current (and, therefore, peak torque) is limited to just 2 to 3 times the continuous rating. Pancake motors, without iron in the armature and with an axial magnetic field, can withstand peak current up to 10 times the continuous rating, for higher peak torque.

The second unique feature of pancake motors is that in addition to the copper conductors, the commutator is also printed on the armature. This design allows the brushes to run directly on the armature surface. The lack of a separate commutator ring, in conjunction with the flat overall design, make pancake motors very compact, especially when compared to conventional cylindrical motors. Their thin design, along with a low inertia (due to the absence of iron) allows pancake motors to achieve extremely fast acceleration and deceleration.

Pancake motors such as (nema 6 motor or nema 8)were originally designed to drive the capstans on tape machines, where a very compact footprint was required, along with the ability to start and stop rapidly. Their uses have expanded, but pancake motors are still found primarily in applications that require a slim profile, smooth motion with no torque ripple, extremely fast acceleration and deceleration, or high peak torque.

Nema23 vs Nema17 Stepper Motor for the engineering challenged

“Linear Stepper Motor” is an induction machine, its operating principle is the use of an electronic circuit, it will become time-DC power supply, multi-phase timing control current, this current of stepping motor power, the stepper motor to normal operation drive stepper motor that is powered sharing, multi-phase timing controller.

Although the “Linear Stepper Motor” has been widely used, but not as a general stepper motor DC motor, AC motor use in practice. It must only constitute a control system using the dual-ring pulse signal, power driver circuit. Thus stepping motor with good but not easy, it involves a lot of expertise in mechanical, electrical, electronic and computer. Stepper motor as the performance element, it is one of the key commodity mechatronics, widely used in a variety of automated control systems. Conduct follow microelectronics and computer technology, the demand for stepper motor over time, has used in various fields of national economy. Stepper motor control can only be operated by a digital signal, pulses stepper drives, in a short time, the control system announced a few too many pulses, that is, the pulse frequency is too high, will cause the stepper motor stall. To resolve this question, it is necessary to choose the acceleration and deceleration of the way. In other words, in the stepping motor at the start, gradually rising to give the pulse frequency, pulse frequency demand deceleration gradually reduced. That is, we often say that the “deceleration” approach.

“Linear Stepper Motor” transfer rate, is based on changing the input pulse signal to the changes. Theoretically, to drive a pulse, the stepper motor is rotated by one step angle (broken when a subdivision step angle). In fact, if the pulse signal changes too fast, because the damping effect of the stepping motor inside the counter electromotive force, the magnetic reaction between the rotor and the stator will not follow the change in the electrical signal, will cause stall and lose steps.

Stepper motors are known for their accurate positioning capabilities and high torque delivery at low speeds, but they require careful sizing to ensure the motor matches the load and application parameters, to minimize the possibility of lost steps or motor stalling. Adding a gearbox to a stepper motor system can improve the motor’s performance by decreasing the load-to-motor inertia ratio, increasing torque to the load, and reducing motor oscillations.

Decrease load-to-motor inertia ratio
One cause of missed steps in stepper motor applications is inertia. The ratio of the load inertia to the motor inertia determines how well the motor can drive, or control, the load — especially during acceleration and deceleration portions of the move profile. If the load inertia is significantly higher than the motor inertia, the motor will have a difficult time controlling the load, and overshoot (advancing more steps than commanded) or undershoot (missing steps) can occur. A very high load-to-motor inertia ratio can also cause the motor to draw excessive current and stall.

Motor Inertia Ratio

JL = inertia of load

JM = inertia of motor

One way to reduce the inertia ratio is to use a larger motor with higher inertia. But that means higher cost, more weight, and trickle-down effects on other parts of the system such as couplings, cables, and drive components. Instead, adding a gearbox to the system reduces the load-to-motor inertia ratio by the square of the gear ratio.

i = gear reduction

Increase torque to the load
Another reason to use a gearbox with a stepper motor is to increase the torque available to drive the load. When the load is driven by a motor-gearbox combination, the gearbox multiplies the torque from the motor by an amount proportional to the gear ratio and the efficiency of the gearbox.

To = torque output at gearbox shaft

Tm = torque output at motor shaft

η = gearbox efficiency

But while gearboxes multiply torque, they reduce speed. (This is why they’re sometimes referred to as “gear reducers” or “speed reducers.”) In other words, when a gearbox is attached to a motor, the motor must turn faster — by a factor equal to the gear ratio — to deliver the target speed to the load.

No = speed output at gearbox shaft

Nm = speed output at motor shaft

And stepper motor torque generally decreases rapidly as speed increases, due to detent torque and other losses. This inverse relationship between speed and torque means it’s only practical to increase speed by a certain amount before the motor is unable to deliver the required torque (even when multiplied by the gear ratio).

Reduce resonance and vibration
But speeding up the motor does have a benefit. The additional speed required by the motor when a gearbox is installed means the motor operates outside its resonant frequency range, where oscillations and vibrations can cause the motor to lose steps or even stall.

In addition to ensuring the gearbox has the correct torque, speed, and inertia values, it’s important to choose a high-precision, low-backlash gearbox — especially when connecting the gearbox to a stepper motor.

Recall that stepper motors with gearbox operate in an open-loop system, and backlash in the gearbox degrades the system’s positioning accuracy, with no feedback to monitor or correct for positioning errors. This is why stepper applications often use high-precision planetary gearboxes, with backlash as low as 2 to 3 arcminutes. And some manufacturers offer stepper motors with harmonic gears that can exhibit zero backlash under most application conditions.