FESTO Part No.11121 Standard Cylinder

Modello：11121, Designazione: DSNU-20-25-P-A Standard Round Cylinder

Specifiche di base

Model Code Explanation DSNU-20-25-P-A

DSNU：Round cylinder complying with ISO6432

20：Bore size 20 mm

25：Stroke length 25 mm

P：Elastic end-cap rubber cushioning

UN：Wear-resistant piston sealing ring

Applicazioni tipiche

Automated assembly, sistemi di trasporto, small-size tooling fixtures, macchine per l'imballaggio. One of Festa’s most widely-used miniature round cylinders.

Selezione alternativa

1. Original Festo：DSNU-20-25-P-A Part-No.11121
2. Domestic compatible replacement：SC20-25、MI20-25（ISO6432 standard, fully interchangeable mounting dimensions）

Nota: Confirm cushioning type-P (elastic rubber cushion). Do NOT select variants with pneumatic adjustable cushioning.

Inspection Checklist for Used / Surplus Units

1. Apply compressed air; no internal/external air leakage; piston-rod surface free of pull-through scratches
2. Piston-rod straight, no bending; full-stroke movement smooth without jitter or sticking
3. Both-end rubber cushion pads intact, no hardening or cracking
4. Port threads undamaged, no thread stripping

FESTA 11121 DSNU-20-25-P-A

ISO6432 Key Mounting Dimensions (Bore 20 mm, Stroke 25 mm)

L2: Retracted overall length; Fully extended length = L2 + Colpo(25 mm)

Retracted total length：85 mm

Fully-extended total length：85+25 = 110 mm

Theoretical force @6 bar: Extension force 189 N, Retraction force 158 N

Massimo. permissible impact energy: 0.20 J (-P elastic rubber cushion)

Standard Mounting Accessories

Domestic replacement note: MI20-25 (ISO6432 fully interchangeable dimension). Must select -P elastic rubber cushion version, avoid PPV pneumatic adjustable cushion type.

Customs HS-Code Information

HS-Code：8412310090 Other linear-action pneumatic power actuators (pneumatic cylinders)

VAT rate:13%; MFN import tariff:14%; Export tax rebate:13%

Declaration elements: Principio di funzionamento(pneumatic linear reciprocating drive); Applicazione(automation tooling); Marca:FESTA; Modello:11121 / DSNU-20-25-P-A; Unità: pezzo / kilogram

Full-Version Maintenance & Second-hand Inspection Procedure

1. Pneumatic performance test: Supply air at 0.5-0.6 MPa. Full-stroke movement without sticking; no air bubbles / leakage at end-caps and piston-rod gland.
2. Piston-rod visual check: Surface free of rust and axial scoring; no radial bending; M8 thread without chipping or stripping.
3. Cushion inspection: End-cap rubber cushion pads free of hardening, fragmentation or spalling. -P denotes non-adjustable pure rubber cushion.
4. Barrel inspection: Stainless-steel barrel outer surface without dent or impact damage; G1/8 port threads intact.
5. Lateral load warning: DSNU-20 is NOT designed for heavy radial side-loads. Fit SK-M8 floating joint to prevent premature seal wear.

Ordering Reminders

Part-No.11121 = DSNU-20-25-P-A; Suffix-A stands for wear-resistant piston seal. Do NOT confuse with DSNU-20-25-PPV-A (pneumatic adjustable cushion variant, different part-number, not directly interchangeable).

Working Principle of FESTO 11121（DSNU-20-25-P-A）

This unit is a double-acting ISO6432 miniature round pneumatic cylinder. It converts compressed-air pressure energy into linear reciprocating mechanical motion. Both extension and retraction strokes are powered by compressed air; no internal return spring fitted.

Main Internal Components

Stainless-steel barrel, piston assembly (-A wear-resistant piston seal), piston-rod, anteriore & rear end-caps, P-type elastic rubber cushion rings, bearing guide bushing, two G1/8 pneumatic ports (cap-end chamber and rod-end chamber).

The piston divides inner barrel volume into two hermetic chambers:

1. Cap-end chamber: Rear port side, piston back-face; no piston-rod inside this chamber.
2. Rod-end chamber: Front port side; piston-rod passes through this chamber outward.

Complete Operating Cycle

1、Piston-rod Extension (Push Stroke)

Solenoid valve shifts air path. Compressed-air flows into rear cap-end chamber, while front rod-end chamber exhausts to atmosphere.

Pressure differential acts across piston surfaces, driving piston forward. Piston-rod extends full rated stroke of 25 mm and outputs push force (189 N theoretical @6 bar).

At end-of-stroke, piston strikes front-cap built-in P elastic rubber cushion. Rubber material deforms to absorb kinetic energy and reduce impact noise. P-cushion is purely mechanical rubber type, no adjusting screw, non regolabile. Max allowable impact energy limited to 0.2 J.

2、Piston-rod Retraction (Pull Stroke)

Solenoid valve switches air circuit. Compressed-air is supplied to front rod-end chamber, rear cap-end chamber exhausts.

Air-pressure pushes piston backward, piston-rod retracts into barrel and generates pull force (158 N theoretical @6 bar).

Upon retraction end-stop, piston compresses rear-cap rubber cushion ring to achieve mechanical deceleration.

Principle Details Related to Model Suffixes

1. -P：Dual-end elastic rubber cushioning

Kinetic-energy absorption via compressive deformation of high-molecular rubber rings. Suited for low-speed and low-mass loads. Compared to PPV (adjustable pneumatic cushion): -P cushion has no throttling adjustment. Load and operating speed must remain within limits; overload will fracture rubber cushions.

2. -UN：Wear-resistant piston seal

Modified low-friction piston sealing compound permits long-term operation with oil-free dry compressed air; continuous oil-mist lubrication is not mandatory. It also works reliably with lubricated compressed-air supply.

Electrical Position-Sensing Principle

Magnetic proximity switches can be clipped onto barrel outer groove. The piston incorporates an embedded permanent magnet. As piston travels, magnet triggers external reed / hall-effect proximity switch, sending end-position feedback signals to PLC for extended / retracted status monitoring.

The cylinder cannot stop at intermediate positions; positioning is only available at the two mechanical end stops.

Fenomeni di guasto & Root-Cause Principles

1. Piston-rod creeping / stick-slip: Degraded lubrication, condensed water in air supply, worn sealing elements.
2. Excessive end-stop impact noise: Moving load energy exceeds 0.2 J cushion capacity; rubber cushion is fully bottomed-out.
3. Interno / external air leakage: Degraded piston seals, wiper-seal on piston-rod, or end-cap gasket failure.
4. Only extend or only retract movement: Malfunction of directional solenoid valve; one chamber fails to charge / exhaust air.

Critical Application Note

-P elastic rubber cushioning NOT suitable for high-speed high-inertia loads. If moving mass is substantial, select PPV adjustable pneumatic-cushion variant, otherwise rubber cushions will suffer rapid failure.

All Mounting Methods for FESTO 11121（DSNU-20-25-P-A）

Mounting orientation arbitrary (orizzontale, verticale, inclined installation are all permitted). This ISO6432 miniature round cylinder must be secured by dedicated mounting accessories. Six mainstream mounting configurations available.

1、Barrel Clamping Nut Mounting (Più comune)

Accessorio: M20×1.5 lock hex-nuts (included with cylinder delivery)

Installazione: Pass stainless-steel barrel through machined panel bore; tighten M20×1.5 nuts on both sides to clamp barrel firmly onto mounting plate.

Caratteristiche: Compact layout, minimal space occupation; medium rigidity. Widely-used for tooling fixtures and confined-space installations.

Attenzione: Avoid over-torque which will deform barrel surface. Lateral side-loads are easily imposed onto piston-rod; SK-M8 floating joint is strongly recommended.

2、Foot-Bracket Mounting SNCL-20

Festo Part-No: SNCL-20 (original foot-mount bracket)

Installazione: Fasten foot-bracket onto base plate; rest cylinder barrel inside bracket semicircular saddle; tighten clamping screws to lock barrel. Montaggio orizzontale.

Caratteristiche: High overturning-moment resistance, good mechanical rigidity. Ideal for horizontally-oriented push-load applications such as conveyor tooling.

Limitazione: Localizing on barrel outer circular surface; not recommended for high-cycle high-speed reciprocation.

3、Front-Flange Mounting FNC-20

Festo Part-No: FNC-20 front flange plate

Installazione: Flange plate sits flush against cylinder front-end cap. Fasten flange onto machine frame with cap-screws; piston-rod passes centrally through flange aperture.

Caratteristiche: Highest rigidity, excellent thrust-load capability. Well-suited for short-stroke pressing / stamping applications (perfect match for this cylinder’s 25 mm stroke).

Standard DSNU-20 does NOT support rear-flange mounting; no direct rear-face flange fixation possible.

4、Piston-rod End Clevis / Joint Connection (Load-side Articulation)

This is load coupling, NOT cylinder-body fixation. Connect to piston-rod M8 male thread:

1. Spherical clevis joint SGS-M8: Rod-end spherical plain bearing, permits small angular deflection and mitigates side-load effects.
2. Double-fork clevis SG-M8.
3. Floating joint FK-M8 (Highly recommended): Compensate misalignment and eliminate radial side-loads, prolong seal service life.

5、Rear-End Clevis Trunnion Mounting (Pivoting Cylinder Body)

Accessorio: WBN-20 rear clevis bracket

Installazione: Cylinder rear-end cap is pinned to clevis support. Whole cylinder assembly can swing through limited angular range.

Scenario applicativo: Rocker-arm linkage mechanisms. Cylinder body oscillates during operation; not for rigid pure linear thrust tasks.

Keep swing angle moderate to avoid inducing excessive piston-rod radial load.

6、Intermediate Trunnion Mounting (Centre Pivot)

Accessorio: TC-20 centre trunnion bracket

Installazione: Bracket clamps onto middle section of barrel. Pivot pin allows cylinder rotating around barrel central axis.

Caratteristiche: Cylinder can swing about central pivot point; mostly used in linkage mechanisms.

This cylinder stroke is merely 25 mm; intermediate trunnion configuration is rarely selected; it is more common on long-stroke cylinders.

📋 Mounting Accessories Summary Table (Bore 20 mm)

⚠️ Important Installation Notes

1. This cylinder is equipped with -P rubber elastic cushion; max permissible impact energy 0.2 J. Overload impact will shatter rubber cushion pads.
2. Radial lateral loads on piston-rod are strictly prohibited. Whenever perfect coaxial alignment with load cannot be guaranteed, FK-M8 floating joint must be fitted. Otherwise piston-rod and guide bushing will wear rapidly leading to air leakage.
3. Never strike cylinder barrel with hammer. Apply correct torque to clamping nuts; excessive torque causes barrel distortion and piston sticking.
4. Magnetic proximity switches: Snap-fit into barrel outer circumferential groove for stroke-end signal feedback.