JMC Closed-Loop Stepper Motors (iHSS / iHSSC)
The iHSS series combines a stepper motor, optical encoder and power stage in a compact unit. A position deviation is corrected immediately by the electronics – no step losses occur. This makes the motors as precise as a servo at low speeds, yet smoother-running and considerably cheaper. Available from 0.48 Nm (NEMA17) to 12.2 Nm (NEMA34), optionally with integrated holding brake. Models with the suffix “C” (iHSSC) have additional reverse-polarity protection; if the model name ends in “-SC”, a holding brake is integrated.
Why Closed-Loop Instead of a Classic Stepper Motor?
A normal stepper motor runs “blind” – if it is overloaded it loses steps, and the machine loses its position without noticing. The closed-loop stepper motor monitors its position via an encoder and corrects immediately. The result: no lost steps, less heat, smoother running and better torque utilisation. For most CNC routers it is the ideal balance of precision, smoothness and price.
Comparison Table: all JMC Closed-Loop Stepper Motors
Filter by frame size or brake. On a smartphone the table can be scrolled horizontally to see all columns. A click on “Buy” takes you straight to the article in the shop.
| Model | Type | Buy | Size | Flange | Holdingtorque | Shaft Ø | Shaft len. | Pilot | Hole pitch | Length excl. shaft | Inputvoltage | Rec. | Max. current | Controlsignal | Reverseprotect. | Brake |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| iHSS42-24-05 | iHSS | Buy | NEMA17 | 42×42 mm | 0.48 Nm | 5 mm | 24 mm | 22 mm | 31 mm | approx. 76 mm | 24–50 VDC | 24 V | 4.5 A | 5–24 V | – | – |
| iHSS42-24-07 | iHSS | Buy | NEMA17 | 42×42 mm | 0.70 Nm | 5 mm | 24 mm | 22 mm | 31 mm | approx. 89 mm | 24–50 VDC | 24 V | 4.5 A | 5–24 V | – | – |
| iHSS57-36-10-21-38 | iHSS | Buy | NEMA23 | 57×57 mm | 1.0 Nm | 8 mm | 21 mm | 38 mm | 47.14 mm | approx. 87.5 mm | 20–50 VDC | 36 V | 4.5 A | 3.3–24 V | – | – |
| iHSSC57-36-20-21-38 | iHSSC | Buy | NEMA23 | 57×57 mm | 2.0 Nm | 8 mm | 21 mm | 38 mm | 47.14 mm | approx. 113 mm | 20–50 VDC | 36 V | 4.5 A | 3.3–24 V | Yes | – |
| iHSSC60-36-30-21-38 | iHSSC | Buy | NEMA24 | 60×60 mm | 3.0 Nm | 8 mm | 21 mm | 38 mm | 47.14 mm | approx. 117 mm | 20–50 VDC | 36 V | 5.0 A | 3.3–24 V | Yes | – |
| iHSSC60-36-35-21-38 | iHSSC | Buy | NEMA24 | 60×60 mm | 3.5 Nm | 8 mm | 21 mm | 38 mm | 47.14 mm | approx. 132 mm | 20–50 VDC | 36 V | 5.0 A | 3.3–24 V | Yes | – |
| iHSS60-36-30-31 | iHSS | Buy | NEMA24 | 60×60 mm | 3.0 Nm | 8 mm | 31 mm | 36 mm | 50.00 mm | approx. 117 mm | 20–50 VDC | 36 V | 5.0 A | 3.3–24 V | – | – |
| iHSSC60-36-30-21-38-47-SC | iHSSC | Buy | NEMA24 | 60×60 mm | 3.0 Nm | 8 mm | 21 mm | 38 mm | 47.14 mm | approx. 117 mm | 36 V (motor) | 36 V | 5.0 A | 3.3–24 V | Yes | Yes |
| iHSS86-60-45 | iHSS | Buy | NEMA34 | 86×86 mm | 4.5 Nm | 14 mm | 30 mm | 73 mm | 69.58 mm | approx. 120 mm | 24–80 VDC | 60 V | 6.0 A | 3.3–24 V | – | – |
| iHSSC86-60-45-SC | iHSSC | Buy | NEMA34 | 86×86 mm | 4.5 Nm | 14 mm | 30 mm | 73 mm | 69.58 mm | approx. 120 mm | 24–80 VDC | 60 V | 6.0 A | 3.3–24 V | Yes | Yes |
| iHSS86-80-100 | iHSS | Buy | NEMA34 | 86×86 mm | 9.5 Nm | 14 mm | 38 mm | 73 mm | 69.58 mm | approx. 175 mm | 24–100 VDC | 80 V | 6.0 A | 3.3–24 V | – | – |
| iHSSC86-80-100-SC | iHSSC | Buy | NEMA34 | 86×86 mm | 9.5 Nm | 14 mm | 38 mm | 73 mm | 69.58 mm | approx. 175 mm | 24–100 VDC | 80 V | 6.0 A | 3.3–24 V | Yes | Yes |
| iHSS86-80-120 | iHSS | Buy | NEMA34 | 86×86 mm | 12.2 Nm | 14 mm | 38 mm | 73 mm | 69.58 mm | approx. 202 mm | 24–100 VDC | 80 V | 6.0 A | 3.3–24 V | – | – |
| iHSSC86-80-120-SC | iHSSC | Buy | NEMA34 | 86×86 mm | 12.2 Nm | 14 mm | 38 mm | 73 mm | 69.58 mm | approx. 202 mm | 24–100 VDC | 80 V | 6.0 A | 3.3–24 V | Yes | Yes |
All figures according to the manufacturer’s datasheet / product page. Type “iHSSC” (C) = with additional reverse-polarity protection. Suffix “-SC” = with integrated holding brake (24 V DC, approx. 150 mA). Control signal: pulse/direction (PUL/DIR) + enable.
How the Closed-Loop Stepper Motor Works
Inside, a high-pole stepper motor operates alongside an optical encoder. The integrated power stage continuously compares target and actual position. If the shaft deviates – for example due to a load spike during milling – the electronics immediately increase the current and bring the position back. Unlike with an open-loop stepper, the machine cannot “lose steps” unnoticed. At standstill and low speeds the closed-loop stepper motor delivers its full, high holding torque, which makes it particularly suitable for the typical forces on CNC milling axes.
Advantages over the Open-Loop Stepper Motor
Thanks to position feedback, step losses are eliminated entirely, and positioning accuracy is maintained even under load. Because the motor only draws as much current as it currently needs, less waste heat is generated than with a classic stepper motor that is permanently energised at rated current. The uniform running at low speeds avoids resonances. Two status LEDs (green/red) indicate the operating state, and a fault output reports faults back to the controller.
No Tuning Required
Unlike a classic servo system, the closed-loop stepper motor requires no elaborate tuning. It is ready to use out of the box; fine adjustments are possible if needed via DIP switches or software (RS232).
Control & Connection
The motors are controlled via standard pulse/direction signals (PUL/DIR) plus enable – like an ordinary stepper motor driver. The control signal voltage is, depending on the model, 3.3–24 V or 5–24 V, so the motors work with almost any CNC controller, including Estlcam terminal adapters, Eding CNC, CSMIO and Beamicon-based systems.
The input voltage depends on the frame size: NEMA17/23/24 operate at 20–50 VDC (24–36 V recommended), the NEMA34 models at 24–80 or 24–100 VDC (60–80 V recommended). Higher voltage improves torque at higher speeds. The power supply should cover the current demand of the simultaneously accelerating axes with reserve. Notes on sizing can be found under Wiring & Commissioning.
Models with Holding Brake (-SC)
Models with the suffix “-SC” in the name have an integrated holding brake supplied with 24 V DC (approx. 150 mA). It only releases when the 24 V supply is present, no alarm is active and the enable signal is released. On power failure the brake engages automatically and holds the axis – ideal for vertical Z axes so that the assembly does not drop.
Reverse-Polarity Protection on iHSSC Models
The additional “C” in the type designation (iHSSC) marks models with integrated reverse-polarity protection on the supply voltage. If the power supply is accidentally connected with reversed polarity, this circuit protects the electronics from damage – regardless of whether a brake is present.
Typical Applications
CNC Routers of All Sizes
The classic: on the X, Y and Z axes of gantry and table routers, closed-loop stepper motors provide precise, step-loss-free motion at a very good price-performance ratio. Small machines use NEMA17/23 (0.48–2 Nm), medium ones NEMA24 (3–3.5 Nm), large and heavy machines NEMA34 (4.5–12.2 Nm).
Vertical Axes with Brake
For the Z axis or suspended loads, the “-SC” variant with integrated holding brake prevents the axis from dropping on power failure – an important safety and precision feature.
Lathes, Indexing Heads & Special-Purpose Machines
The high holding torque of the large NEMA34 motors (up to 12.2 Nm) suits heavy feed and rotary axes, indexing heads and special-purpose machines where torque and positioning accuracy at moderate speeds matter.
Retrofitting Existing Machines
When converting older machines, the compact units replace entire driver cabinets. Because driver and motor are combined, the wiring effort drops considerably.
More practical examples can be found on the page Application examples.
JMC Closed-Loop Stepper Motors from Stock
All torque classes, with and without brake, plus accessories in the shop.
All closed-loop motors in the shop For comparison: servo motors