A pneumatic cylinder is the common linear reciprocating actuator on automated production lines: it is powered by compressed air and converts air pressure into straight-line mechanical motion. Its strengths are “fast motion, low cost, usable in cleanrooms and explosion-proof environments”, making it a basic component on SMT, EMS, semiconductor, packaging and food lines. Common bores are 6–100 mm, strokes 5–1000 mm and operating pressure 0.1–0.7 MPa, in double-acting or single-acting versions, with optional reed switches and built-in air cushioning. Typical uses: SMT fixture clamping, robot pick-and-place, tray lifts, gate opening/closing and press pushing.
This series covers general industrial cylinders (standard double-acting, single-acting, miniature, thin, compact and more).
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Specifications (typical range)
| Item | Range |
|---|---|
| Action | Double acting (common) / single acting (push or pull spring return) |
| Bore | 6, 10, 12, 16, 20, 25, 32, 40, 50, 63, 80, 100 mm (miniature 4–6 mm; large 125–200 mm custom) |
| Stroke | 5, 10, 15, 20, 25, 30, 40, 50, 75, 100, 125, 150, 200, 250, 300, 500, 1000 mm (standard) |
| Operating pressure | 0.1–0.7 MPa (standard), 0.05–1.0 MPa (special) |
| Medium | Dry, clean compressed air (5 μm filter + lubricator recommended; some lube-free types) |
| Operating temperature | −5 °C to +60 °C (standard); high-temperature −10 °C to +80 °C; low-temperature custom |
| Port thread | M3 / M5 / Rc1/8 / Rc1/4 / Rc3/8 / Rc1/2 (depends on bore) |
| Standards | ISO 6432 (miniature) / ISO 15552 / ISO 21287 (thin) / JIS B8354 / maker’s own specifications |
| Sensing | Reed switch / magnetic switch (NO/NC, NPN/PNP, powered/non-powered) |
| Cushioning | None / rubber bumper / air cushion (adjustable) / external shock absorber (sold separately) |
| Mounting | Foot, flange, trunnion, clevis, flange plate, custom fixture |
Note: these are typical ranges; actual bore, stroke and sensing depend on machine design, load, cycle frequency, space and the brand catalog. Model on this page: SMC CQ2B40-25DMZ (bore 40 mm, stroke 25 mm); other bores, strokes and types available on request.
Applications
Cylinders are basic components of SMT, EMS and semiconductor machines and packaging lines, used from fixture clamping to robot joints. Four typical applications in electronics manufacturing MRO purchasing:
- SMT fixture clamping and pressing: SMT placement fixtures, IC programming fixtures and test socket pressing mechanisms. Short-stroke, small-bore cylinders (bore 16–25 mm, stroke 10–30 mm) with reed switches to confirm clamping. Mostly double acting; high cycle rates make cylinder life important.
- Robot pick-and-place: tray loading/unloading, PCB transfer and IC flipping mechanisms. Medium stroke, medium bore. Multi-axis combinations (X+Y+Z), each axis with reed switches + speed controllers.
- Tray lifts / pushers / gates: magazine lifts, conveyor diverter gates and barcode-scanning station pushers. Long stroke, large bore. Watch for piston rod bending; for long strokes choose guided models.
- Semiconductor / cleanroom cylinders: wafer transfer, cleanroom automatic doors and anti-static valves. These need low-particle (no dust emission) and anti-static specifications; some applications specify stainless steel bodies. An optional exhaust collection fitting can route exhaust out of the clean area.
Selection guide
| Application | Bore | Stroke | Action | Accessories |
|---|---|---|---|---|
| SMT fixture clamp | 16–25 mm | 10–30 mm | Double acting | 2× reed switches + speed controller |
| Robot pick-and-place | 25–40 mm | 50–150 mm | Double acting | 2× reed switches + built-in cushion |
| Tray lift | 40–63 mm | 100–300 mm | Double acting, guided | 2× reed switches + shock absorber |
| Conveyor gate | 32–50 mm | 50–100 mm | Double or single acting | 2× reed switches |
| Cleanroom | By load | As required | Double acting, low-particle | Stainless steel body + exhaust collection |
Note: this table is a general reference; force (bore), stroke, cushioning and sensor positions depend on machine design, load, cycle time and space.
Pneumatic vs hydraulic vs electric cylinders: why automation lines use pneumatics
| Drive | Force | Speed | Positioning accuracy | Environment limits | Relative cost |
|---|---|---|---|---|---|
| Pneumatic cylinder | Medium (50 mm bore ≈ 1000 N @ 0.5 MPa) | Fast (0.5–1 m/s) | Low (end positions ± 0.5 mm) | None (cleanroom and explosion-proof possible) | Low |
| Hydraulic cylinder | Very high (same bore × 30–50) | Medium | Medium | Oil leak risk, not for clean environments | High |
| Electric cylinder | Medium | Slow–medium | High (μm level) | None | Very high |
Rule of thumb: “light-load, fast motion” on SMT, semiconductor, packaging and food lines almost always uses pneumatic cylinders; heavy pressing, mold opening/closing and hydraulic fixtures use hydraulics; high-precision assembly, multi-point positioning and programmable thrust use electric cylinders. One SMT line may use a large number of cylinders, and the larger the quantity, the more the low cost of pneumatics shows.
Double acting vs single acting: how to choose
| Type | Construction | Force direction | Air consumption | Use |
|---|---|---|---|---|
| Double acting | Ports at both ends | Force in both directions | Higher (air used on every extend and retract) | Clamping, pushing, pick-and-place, speed control |
| Single acting, push type | One port, built-in spring | Air extends, spring returns | Lower (air only to extend) | One-way force, must return when air is lost |
| Single acting, pull type | One port, built-in spring | Air retracts, spring extends | Lower | Must move to a safe extended position when air is lost |
In practice, most SMT and semiconductor machines use double-acting cylinders. Single-acting cylinders are mainly used in safety mechanisms that must return to a safe position automatically when air is lost (such as gates that close automatically or grippers that release to avoid pinching), or where air consumption matters when holding a state for long periods.
Bore and force: how to calculate and choose
Bore determines force. Theoretical force = bore cross-sectional area × operating pressure. At 0.5 MPa:
| Bore (mm) | Area (mm²) | Theoretical force @ 0.5 MPa | Actual force (80%) | Typical use |
|---|---|---|---|---|
| 16 | 201 | ≈ 100 N | ≈ 80 N | SMT fixture clamp (small) |
| 25 | 491 | ≈ 245 N | ≈ 200 N | SMT fixture clamp (medium) |
| 32 | 804 | ≈ 400 N | ≈ 320 N | Robot gripper |
| 40 | 1257 | ≈ 630 N | ≈ 500 N | Robot Z axis |
| 50 | 1963 | ≈ 1000 N | ≈ 800 N | Tray lift |
| 63 | 3117 | ≈ 1560 N | ≈ 1250 N | Pushing |
How to select: calculate the required thrust (load × safety factor 1.5–2.0) → find the bore in the table above → when in doubt, go larger. If the bore is too small for the load, the cylinder will “move slowly, fail to push, or stall midway” — an SMT fixture clamp that does not reach position is a common fault. For long strokes, watch for piston rod bending — when the stroke exceeds 10 times the bore, add external guide rods or choose a guided cylinder.
Selection steps, cushioning and reed switch tips
Selection steps: load (N or kg) → direction of motion (horizontal / vertical / pushing) → bore (force × safety factor 1.5–2) → stroke + guide (required stroke; long strokes need guides) → cushioning + sensing (built-in / external, reed switch positions).
Fit 2 reed switches (double acting): double-acting cylinders usually have 2 reed switches (extended end + retracted end) so the PLC confirms each motion is complete before the next step. The “send the command and wait a fixed time” approach without reed switches misjudges jams and low air pressure. A 3rd switch can be added for a mid-position.
Three levels of cushioning (typical): external speed controller (common, low cost) → built-in air cushion (on most standard cylinders) → external shock absorber (heavy load / high speed). SMT pick-and-place usually needs only the first two; where robots face high impact risk, add a shock absorber to absorb most of the impact energy.
Air quality determines cylinder life: supply air must pass a filter (5 μm) to remove water and dust; most standard cylinders need a lubricator (lubricated type); lube-free cylinders do not need a lubricator because they are pre-greased internally — do not add a lubricator later (the oil washes out the pre-applied grease). Water and dust are the main causes of seal failure.
Troubleshooting: common cylinder faults: (1) air leaks (aged seals), (2) slow motion (insufficient air supply or speed controller too tight), (3) juddering (load beyond design), (4) reed switch not switching (shifted position or burnt out). Set up a maintenance schedule and check seals regularly.
Trademarks: SMC and the model names on this page are trademarks or model names of their owners, used here only to identify the products. JIAHON is not the authorized distributor of this brand in Taiwan.
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