250 μL nominal capacity
Compare stored volume with nominal volume per step. Test the 100 and 500 μL alternatives using the same target dose, fluid and back pressure, and include refill time.
250 μL Miniature Piston Pump with POM and Other Custom Pump Head Options
SM-250-PEEK is a 250 μL miniature piston pump for reagent dispensing, reaction-liquid addition and metered dosing in compact instruments. The configuration shown uses a PEEK pump head; custom heads in POM and other materials are available to meet project requirements. A stepper motor drives the reciprocating piston for programmed aspiration and dispensing.
Fluid ports are available in 1/4-28 UNF or M6, with 2000 steps per full stroke. Full-stroke repeatability is specified at ≤0.5%, with an expected service life of 5 million cycles; the accuracy specification is confirmed for the selected configuration. Valve assemblies, optical sensor feedback and a controller are available as options for metered dosing and fluid-path switching.
OEM customization includes PEEK, PMMA, PSU or POM pump heads and ceramic, stainless steel or PEEK pistons, with seals selected for reagent chemistry. Tubing, dispensing probes and mounting arrangements can be configured to suit the instrument envelope and liquid-handling sequence.
Application Areas:
SM piston pump configurations
Select capacity, pump head material and accessories, then save different configurations for your inquiry.
| Nominal capacity | 250 μL |
|---|---|
| Pump head material | PEEK (polyetheretherketone); Opaque |
| Piston / seal | Ceramic / UHMWPE (ultra-high-molecular-weight polyethylene) |
| Fluid port | 2 × 1/4-28 UNF flat-bottom ports; M6 optional |
| Basic motor configuration | 1.8°; 2000 steps per full stroke |
| Nominal resolution | 0.125 μL/step (250 μL ÷ 2000 steps) |
| Other stroke configurations | 2400-step configuration; 2400 steps per full stroke; 0.104167 μL/step / 4000-step configuration; 4000 steps per full stroke; 0.0625 μL/step |
| Working stroke | 12.7 mm |
| Mounting | 4 × M3; spacing 15 × 35 mm |
| Accuracy / repeatability at 100% stroke | 0.5% / 0.5% |
| Repeatability at 2% stroke | 1.5% (with backlash compensation) |
| Backlash | <1.0%; validate compensation for precise dosing |
| Fluid pressure | <0.30 MPa |
| Expected service life | 5 million cycles (pure water, room temperature, 50 kPa back pressure) |
| Fluid / ambient operating temperature | 15–40 ℃ / 10–40 ℃ |
| Operating humidity | 30%–85% RH, non-condensing |
Nominal resolution is capacity divided by full-stroke steps, not the minimum reliable dose. 2% of 250 μL is 5 μL. Validate actual reagent results at this dose with the selected valves, tubing, back pressure and drive settings.
Low-range repeatability assumes backlash compensation. Match wiring, ports and mounting holes to the supplied version; do not transfer them between series.
Features and selection criteria
SM-250-PEEK is designed for aspiration and metered dispensing inside instruments. The miniature design uses a 28-size stepper motor. Check capacity, working stroke, four-hole mounting and drive configuration together.
Opaque head
For opaque heads, confirm air removal through tubing, discharge and operation. Check PEEK (polyether ether ketone) compatibility for fluid composition, concentration and temperature, including the piston, seals and valves. Head material alone does not establish corrosion resistance of the whole fluid path.
Compact mounting
4 × M3; spacing 15 × 35 mm. Check working stroke and mounting dimensions separately. Leave room for fittings, wiring and moving parts.
Calculate for the selected stroke
2000, 2400 and 4000 steps represent different full-stroke configurations. Step angle alone does not identify the stroke; calculate volume per step for the selected version.
Pump and control integration
The SM bare pump requires a stepper driver. For an integrated valve and communication control, check SMVD. RS-232, RS-485 and CAN belong to the corresponding driver configuration and cannot connect directly to bare motor leads.
Operating conditions and maintenance
Fluid temperature 15–40 ℃, Fluid pressure <0.30 MPa. Expected service life 5 million cycles (pure water, room temperature, 50 kPa back pressure); validate with the actual fluid, drive and maintenance conditions.
Capacity, stroke and dosing steps
Compare stored volume with nominal volume per step. Test the 100 and 500 μL alternatives using the same target dose, fluid and back pressure, and include refill time.
250 μL configuration comparison
| Stroke configuration | Full steps per stroke | Nominal volume per step |
|---|---|---|
| 2000 steps | 0.125 μL/step | |
| 2400 steps | 0.104167 μL/step | |
| 4000 steps | 0.0625 μL/step |
Nominal step calculator
Nominal steps
200steps
25 μL ÷ 250 μL × 2000 steps = 200 steps
Nominal steps are for command conversion, not the minimum reliable dose or measured accuracy.Calculated from capacity and full-stroke steps; volume per step is rounded for display. Validate microstepping, backlash, bubbles, valves and tubing at the target volume.
Confirm full stroke and microstepping separately.
Backlash compensation methodThe 2000/2400/4000-step entries are series options; switching the table does not change the supplied unit. Convert full steps to commands for the chosen microstep mode.
Head, piston and wetted materials
This model has a PEEK (polyetheretherketone) head and ceramic piston. For opaque heads, confirm air removal through tubing, discharge and operation. Check PEEK (polyether ether ketone) compatibility for fluid composition, concentration and temperature, including the piston, seals and valves. Head material alone does not establish corrosion resistance of the whole fluid path.
| Head material | Selection considerations | Compatibility checks |
|---|---|---|
| PMMA (polymethyl methacrylate)Transparent | Consider when priming and bubbles must be visible. | Not resistant to alcohol or strong acids, including during cleaning. |
| PSU (polysulfone)Transparent options | Another candidate when transparency is required. | Confirm resin grade, fluid and seal combination. Material name does not change the pump temperature limits. |
| PEEK (polyetheretherketone)Opaque · Current head | Consider for opacity or further chemical compatibility assessment. | Check formulation, concentration and temperature; not resistant to every acid, alkali or solvent. |
| POM (polyoxymethylene)Opaque options | Compare against head geometry and fluid requirements. | Confirm acids, oxidizing cleaners and prolonged immersion separately. |
These are SM material comparisons; confirm head, port and seal as a set. Zirconia ceramic, SUS316L or PEEK pistons may be assessed per project; this ceramic configuration does not cover other pistons. Include UHMWPE seals in compatibility checks.
View material compatibility referencesMotor, driver and winding connections
SM motor versions have different current, resistance and wire colours. Check the motor label and matching drawing before driver setup; the 28-size housing is insufficient identification.
Configuration 1 · 0.67 A/phase
| Drive voltage | 24 V DC |
|---|---|
| Rated phase current | 0.67 A/phase |
| Winding resistance | 7.2 Ω ±10% |
| Winding inductance | 5.1 mH |
| Terminal / wire colour | Winding |
|---|---|
| 6 · Blue | Winding terminal A |
| 4 · Red | Winding terminal C, paired with A |
| 3 · Green | Winding terminal B |
| 1 · Black | Winding terminal D, paired with B |
Positions 2 and 5 of the six-position connector are unused. Verify pins 1, 3, 4 and 6 from the specified viewing direction; EA motor phase numbering cannot be reused.
Wiring diagram
Rated phase current is a winding parameter, not power-supply input current. Check peak/RMS definitions. After setting microstepping and ramps, recheck motion, temperature rise and dispensing.
Match the control sequence separately for integrated SMVD.
Stepper motor acceleration and decelerationUse the integrated drive’s specified supply, address and protocol. Initialize and home before motion commands; check busy and error responses. Convert protocol position units using stroke and microstepping; they are not μL.
Optical-sensor wiring and homing
Three-, four- and five-wire sensors have different supply and output definitions. Match the supplied version. Homing detection does not provide closed-loop feedback throughout motion.
4-wire optical home sensor
| Terminal / wire | Connection and function |
|---|---|
| Red | LED anode; connect a series current-limiting resistor before power-up |
| Black | LED cathode |
| White | Signal output; use a matching pull-up resistor |
| Green | Output logic supply return |
For a red-wire supply of 5 V, 12 V or 24 V, reference series resistors are about 200 Ω, 470 Ω or 1 kΩ respectively. Check board input levels and the white output pull-up. Measure blocked and unblocked states before setting the homing level.
Wiring diagram
Validate post-trigger stopping clearance for the mechanism, speed and stopping method. Recheck home position and usable stroke after motor, sensor or drive changes.
Port matching and first-use procedure
Flat-bottom ports and seals
2 × 1/4-28 UNF flat-bottom ports; M6 optional. Match fittings, seals and tube OD as a set; even identical threads require checking port depth and sealing face.
Small doses and tubing rigidity
For doses up to 20 μL, rigid tubing after the shut-off valve is recommended. Diameter, length, valve location and connections all affect delivery.
Check fluid and ambient conditions
Fluid 15–40 ℃, ambient 10–40 ℃, humidity 30%–85% RH, non-condensing.Keep cleaning and extended operation within these limits too.
Check model and conditions; install with power off
Confirm SM-250-PEEK capacity, head, harness and ports. Fluid temperature: 15–40 ℃; ambient: 10–40 ℃. Stop the instrument and disconnect power before changing wiring or fluid connections.
Secure using the four-hole mounting face
4 × M3; spacing 15 × 35 mm. Position the bracket using the mounting drawing, preferably with the outlet upward for air removal. Leave slack in tubing and wiring to avoid pulling on the head.
Match ports and seals
2 × 1/4-28 UNF flat-bottom ports; M6 optional. Check hole depth, tube outside diameter and seals together. Recommended torque for the corresponding plastic fittings is 0.25–0.30 N·m. Do not substitute PTFE tape or thread sealant for a flat-bottom seal.
Connect motor and optical sensor
Identify both windings for the selected motor, then check sensor wire colors, supply, current limiting and pull-up circuits. Verify 50 μL winding resistance separately from other SM versions.
Verify direction, stroke and homing
Basic full stroke is 2000 steps. Check direction and sensor state at a controlled speed, then verify stopping clearance after triggering. Recheck command units when changing microstepping; do not use the mechanical limit as the operating endpoint.
Prime, remove air and verify delivered volume
With an opaque head, check air removal through tubing and discharged fluid. Coordinate aspiration, valve switching and dispensing. Collect repeated target doses and verify backlash compensation. For dosing up to 20 μL, rigid tubing downstream of the shut-off valve is recommended. Avoid prolonged dry running.
Acceptance at the target operating point
Record fluid, temperature, backpressure, target and individual collected volumes, tubing, valve timing, drive and compensation settings. Compare mean error and repeatability; retest with the same method after any change.
Maintenance and troubleshooting
- Fluid change and cleaning
- For opaque heads, confirm air removal through tubing, discharge and operation. Check PEEK (polyether ether ketone) compatibility for fluid composition, concentration and temperature, including the piston, seals and valves. Head material alone does not establish corrosion resistance of the whole fluid path. Record cleaning concentration, contact time and temperature. After changing fluid, recheck leakage and delivered volume.
- Saline or crystallizing fluids
- Before shutdown, clean using a validated procedure to prevent residual fluid from drying and crystallizing on the piston and seals. The rinse must be compatible with the entire wetted path.
- Small-dose variation
- First rule out bubbles, valve timing and tubing elasticity, then check reversal compensation. This series has a backlash specification of <1.0%; do not apply that percentage directly as a fixed compensation.
- Motor vibration or missed position
- Check winding connections, phase current, microstepping and acceleration/deceleration, then mechanical and fluid resistance. Stop the drive if it jams; do not repeatedly force it against the end of stroke.
- Leakage or cracked pump head
- Stop use and check fluid compatibility, fitting seals and assembly loads. Retain the product label, photos and operating records, and contact service.
After maintenance, recheck home position, priming and target volume. Contact technical support for disassembly or jamming.
Frequently Asked Questions
Nominal capacity is 250 μL with 2000 basic full-stroke steps, or 0.125 μL/step. This ratio converts motion commands. Validate the minimum reliable dose at the target volume, accounting for bubbles, backlash, valve operation and tubing elasticity.
Piston Pump Configured for Your Instrument
Share the target volume, fluid compatibility, port type, control method, installation space, and service-life requirements. The Foreach engineering team can help confirm the pump configuration and wetted materials.