OEM Factory Direct CMK2 Series Medium Bore Pneumatic Cylinder Manufacturer Double-Acting Round Body Air Cylinder Compatible With CKD

Product Detailed Description：

The CMK2 Series is CKD's benchmark medium bore cylinder, engineered for general-purpose industrial automation where reliability and corrosion resistance are non-negotiable. Bore sizes from 20 mm to 40 mm cover the most common light-to-medium force requirements, with standard strokes from 5 mm to 750 mm.

The defining characteristic of the CMK2 is its all-weather construction: the piston rod, rod-end nut, tie rods, tie-rod nuts, and cushion valve bodies are all fabricated from stainless steel as standard. Combined with the hard-anodized aluminum tube and zinc-plated steel end covers, this provides corrosion resistance far exceeding typical general-purpose cylinders in its class — making the CMK2 suitable for outdoor installations, washdown areas, and humid factory environments where lesser cylinders would rust within months.

The series offers exceptional variant coverage. The standard CMK2 is double-acting with single rod. CMK2-S provides single-acting spring return for fail-safe applications. CMK2-P and CMK2-R add stroke adjustment capability — extend-side and retract-side respectively — for precision hard-stop positioning without external stoppers. CMK2-M incorporates an internal non-rotating guide mechanism, preventing piston rod rotation within the standard body envelope. A wide range of self-clinching (caulked) variants allows the cylinder to be permanently assembled into OEM equipment as a non-serviceable, lifetime component.

The square rod cover enables direct mounting without brackets — bolt the cylinder directly to the machine frame for the lowest possible profile. Alternatively, a comprehensive accessory range (foot, flange, trunnion, clevis) covers every installation scenario.

Application Industries:

General Automation & Assembly,Packaging Machinery,Food & Beverage Processing,Textile & Apparel,Electronics Assembly,Medical Device Manufacturing,Printing & Converting,Outdoor & Humid Environments,Machine Tool Auxiliary

Product Feature:

• Square Tube Body — 4-Sided Switch Mounting The square aluminum extrusion provides flat, parallel mounting surfaces on all four sides. Auto switches and magnetic sensors can be mounted on any face without brackets or clamps. This design flexibility simplifies machine layout and enables easy field retrofits. Compatible with all standard reed switches (D-M9B, D-A93, D-A54) and solid-state magnetic sensors (CS1-G, D-M9N).

• Adjustable Air Cushion at Both Ends Each end cap features an adjustable cushion screw. Fine-tune deceleration for your specific load and speed using only a flathead screwdriver. The pneumatic cushion absorbs kinetic energy at end-of-stroke, eliminating metal-to-metal impact, reducing operating noise, and extending seal service life. For initial setup, fully open both screws, then tighten gradually until the piston decelerates smoothly without bounce.

• Hard Anodized Aluminum Body — Lightweight and Durable The square aluminum tube undergoes hard anodizing for superior surface hardness, wear resistance, and corrosion protection. The internal bore is precision-honed to a smooth finish for low friction and extended seal life. At approximately 30% lighter than equivalent steel-bodied cylinders, MB1 reduces moving mass in dynamic and high-cycle applications.

• Pre-Lubricated — Maintenance-Free Operation Each cylinder is factory lubricated with high-performance lithium-based grease. Designed for oil-free (non-lube) operation throughout its entire service life. No daily oiling, no weekly inspection, no scheduled re-lubrication. If your compressed air system already uses an oil-mist lubricator, the cylinder remains fully compatible — do not add oil to a system that was previously non-lube.

• Chrome Plated Piston Rod — Smooth and Long-Lasting The piston rod is induction hardened and hard chrome plated to a minimum thickness of 20μm. Surface roughness Ra < 0.4μm ensures smooth operation with minimal seal friction. Excellent wear and corrosion resistance under normal industrial conditions. For washdown, food-grade, or highly corrosive environments, a stainless steel (SS304 or SS316) piston rod is available as an option.

• Wear-Resistant Piston Seal The piston employs a double Y-shape lip seal design with automatic wear compensation. As the seal lip gradually wears over millions of cycles, internal pressure forces the lips outward, maintaining consistent sealing performance. This design extends seal life by approximately 50% compared to conventional O-ring piston seals.

Specification：

Customization Options

Product Advantages

• Full stainless steel external components — standard, not optional. The piston rod, rod-end nut, four tie rods, tie-rod nuts, and cushion needle valves are all stainless steel as the default specification. Most competing cylinders in this bore class use zinc-plated carbon steel tie rods and nuts that begin rusting within months in humid environments. The CMK2's stainless hardware provides lifetime corrosion resistance at no extra cost.

• Square rod cover — direct mounting without brackets. The front rod cover is machined square with through-holes, allowing the cylinder to be bolted directly to a flat mounting surface. This eliminates the cost, height, and alignment complexity of foot brackets — the cylinder sits flush against the machine frame for the lowest possible installed profile.

• Self-clinching (caulked) variant for OEM integration. For high-volume OEM applications where the cylinder is a permanent, non-serviceable component of the machine, the CMK2 self-clinching variant uses a rolled-joint assembly instead of threaded tie-rod nuts. This reduces part count, eliminates the risk of tie-rod loosening from vibration, and delivers a tamper-proof, lifetime-sealed cylinder at a lower cost than the serviceable tie-rod version.

• Stroke adjustable variants — built-in precision stops. CMK2-P (extend adjustable) and CMK2-R (retract adjustable) incorporate a threaded stroke adjustment mechanism directly into the cylinder. Turn the adjustment screw to set a precise mechanical stop position — no external hard stops, no separate stopper cylinders, no custom fixture machining. Ideal for applications where the stroke end position needs fine-tuning during machine setup or changes between product runs.

• Non-rotating variant — compact anti-rotation. The CMK2-M uses an internal guide mechanism to prevent piston rod rotation without adding width, height, or external guide rails. For applications requiring fixed angular tooling orientation, this provides the functionality of a guided cylinder within the footprint of a standard round-body cylinder.

• Hard-anodized aluminum tube — bore protection. The cylinder tube is hard-anodized internally, creating a wear-resistant, corrosion-resistant surface that protects the bore from scoring and pitting. Combined with the stainless external components, this delivers a cylinder that withstands both internal wear and external environmental attack.

• CKD CMK2 1:1 dimensional replacement. All mounting dimensions, tie-rod spacing, port locations, rod-end threads, and accessory interfaces are manufactured to CKD CMK2 specifications. Drop-in replacement: no adapter plates, no re-drilling, no plumbing changes.

Application:

• Pick-and-place & assembly — compact body fits tight fixtures, light weight enables fast cycles on robots
• Clamping & fixturing — CNC, welding, and test fixtures where the cylinder must stay within the tool envelope
• Packaging & conveying — stoppers, diverters, and dense multi-cylinder mounting on packaging lines
• Food & beverage — non-copper material variants compatible with washdown environments
• Medical & laboratory — clean, compact design for diagnostic and lab automation equipment
• Cleanroom & semiconductor — low particle generation, non-outgassing materials
• Low-speed precision — micro-velocity variant down to 1 mm/s for gluing, dispensing, and optical alignment
• High-temperature — heat-resistant variant up to 150°C for ovens, molding, and engine test stands
• Printing & textile — roller engagement, tension control, and high-cycle cutting mechanisms

Installation and Usage：

• Mounting: Square rod cover allows direct bolting to a flat surface without brackets — the lowest-profile method. Alternatively, use LB foot bracket, FA/FB flange, CR trunnion, or CA/CB clevis. Loosely tighten bolts, cycle full stroke 2–3 times to self-align, then torque to specification.

• Piping: Connect compressed air tubing to both ports. Port threads are Rc (PT) as standard — use compatible fittings with thread sealant. For speed control, install one-way flow control valves with meter-out control.

• Air supply: Use compressed air filtered to 40 μm or finer. Lubricated or non-lubricated operation acceptable. Maximum working pressure: 1.0 MPa (10 bar).

• Cushioning (air cushion type): Start with cushion needle valves fully closed. Cycle the cylinder and gradually open each valve until the load decelerates smoothly without hard bottoming.

• Stroke adjustment (CMK2-P/CMK2-R types): Loosen the lock nut on the stroke adjuster screw. Turn the screw to set the desired stop position. Re-tighten the lock nut before operation. Verify the adjusted stroke with a dry cycle before loading.

• Side load prevention: Ensure the load is aligned axially with the piston rod. Round-body cylinders are not rated for lateral loads — use a non-rotating variant (CMK2-M) or external guide if side forces are unavoidable.

• Corrosion protection: The stainless steel rod, tie rods, and nuts provide built-in corrosion resistance. In outdoor or washdown environments, also protect the port fittings and tubing from direct water spray.

• Long-term storage: Retract the piston rod fully, apply anti-rust oil to exposed surfaces, and install dust caps on air ports. Store in a dry environment.

FAQ

Q1.CMK2 vs. 24N2A — how to choose?

A1.CMK2: round-body tie-rod, bore 20–40 mm, stainless hardware standard, CKD standard. 24N2A: ISO 6432 round-body, bore 16–25 mm, stainless steel barrel, Camozzi/Festo/SMC standard. Choose CMK2 for CKD compatibility and stainless tie-rods. Choose 24N2A for ISO 6432 multi-brand interchangeability.

Q2. CMK2 standard vs. self-clinching type — which one?

A2. Standard (tie-rod): serviceable — seals can be replaced. Best for end-users and maintainable equipment. Self-clinching (caulked): permanent rolled assembly, non-serviceable, lower cost. Best for high-volume OEM integration where the cylinder is a lifetime component.

Q3. What mounting options are available?

A3. Direct mount (square rod cover — lowest profile, no bracket needed), foot bracket (LB), front/rear flange (FA/FB), center trunnion (CR), clevis (CA/CB). All brackets are bolt-on CKD-compatible accessories.

Q4. What port thread type does CMK2 use?

A4. Rc (PT) tapered thread as standard. Use PT-compatible fittings with thread sealant. G (BSPP) and NPT options available as customization.

Q5. What routine maintenance?

A5.Wipe exposed rod weekly. Check for air leaks monthly. Verify stroke time and cushioning quarterly. Replace seals annually if exceeding 2 million cycles. Tie-rod construction allows seal replacement without demounting the cylinder body.

Q6. Where is the air leak coming from?

A6. Port fitting (re-seal), rod seal (replace if hissing), or tie-rod cover O-ring (remove cover, replace O-ring). Stainless tie-rods do not rust — leaks from tie-rod areas are O-ring failures, not corrosion.

Q7. Direct replacement for CKD CMK2?

A7.Yes — 1:1 dimensional match. Same mounting dimensions, tie-rod spacing, ports, rod threads, and accessory interfaces. Drop in, bolt down, reconnect.

Q8. What warranty?

A8. 12–18 months against manufacturing defects. Free replacement for valid claims. Seal kits and repair videos provided. Samples ship within 3 working days.

Factory Advantages and Certifications

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