Diaphragms

Precision-Molded Diaphragms for Fluid Control, Actuation, and Separation

A rubber diaphragm is a flexible molded membrane that deflects under pressure to separate two fluid or gas chambers, transmit force, or actuate a mechanical response. It provides a hermetic boundary between media while converting pressure differential into controlled movement with no sliding seals, no lubrication, and no metal-to-metal contact at the sealing interface.

Moldtech engineers and manufactures custom rubber diaphragms to your exact geometry, compound, and deflection specification. Every part is produced in-house at our 50,000 sq. ft. facility in Lancaster, NY.

How Rubber Diaphragms Work

A diaphragm is clamped at its perimeter and deflects across its active area in response to pressure or mechanical input. The geometry of the diaphragm determines the stroke, pressure response, and force output of the assembly.

Three primary diaphragm types:

Flat diaphragms deflect uniformly across the membrane. They are used in low-stroke, high-cycle applications such as pressure regulators, relief valves, and sensing elements. Stress concentrates at the clamped perimeter during deflection.

Molded profile diaphragms incorporate a pre-formed convolution or dome geometry that distributes flexural stress more evenly across the membrane cross-section. They are used in pump chambers, actuators, and control valves where stroke length and cycle life are primary design requirements. Moldtech’s compression and transfer molding process is well-suited to these geometries.

Rolling diaphragms use a fabric-reinforced elastomer sleeve that rolls along a cylinder bore rather than flexing. They provide long, linear stroke with near-zero lateral force, making them the preferred choice for precision actuators, positioners, and pneumatic cylinders.

Elastomer Materials

Diaphragm compound selection is driven by the media in contact with each face of the membrane, the operating pressure and temperature range, required flex cycle life, and any applicable regulatory standards.

Additional compounds available: Aflas (TFE/P), Hypalon (CSM), Butyl (IIR), SBR.

For medical device and food processing applications, Moldtech produces silicone diaphragms using LSR and HCR silicone molding in cleanroom-controlled environments to meet FDA and USP Class VI requirements.

Fabric Reinforcement

Diaphragms subjected to high pressure differentials, long stroke cycles, or applications requiring dimensional stability under load are manufactured with fabric reinforcement bonded into the elastomer body during molding.

Fabric reinforcement increases burst pressure rating and extends flex cycle life without adding significant stiffness to the active deflection area when properly positioned in the laminate.

Specialty Formulations

Available for applications with specific performance or regulatory requirements:

• Food grade
• FDA-compliant
• Metal detectable
• Flame retardant
• Antistatic / ESD / RFI
• Electrically conductive
• Thermally conductive
• High / ultra strength
• Fabric-reinforced

Design Considerations

Rubber diaphragms can be produced in flat, domed, convoluted, and rolling profiles across a wide range of diameters, thicknesses, and bead or clamping geometries. Design optimization is driven by the following:

1. Operating pressure differential across the diaphragm faces
2. Required stroke and deflection geometry
3. Flex cycle life at operating conditions
4. Chemical compatibility with media on both faces
5. Temperature range in service and during sterilization (for medical and food applications)
6. Regulatory compliance (FDA, NSF, USP Class VI, MIL-spec, automotive)
7. Clamping geometry and bead profile for the mating housing

Wall thickness and durometer are specified together to achieve the required pressure-stroke response without exceeding the elastomer’s flex fatigue limit at the operating cycle count. Fabric reinforcement layer placement is determined by the burst pressure requirement and the location of peak stress during deflection.

Moldtech’s thermoset rubber injection molding process produces diaphragms with tight dimensional tolerances and consistent flash control across high production volumes. For aerospace and military applications requiring AS9100-compliant documentation, Moldtech’s quality system supports full traceability from raw material to finished part.

Sealing and Performance Capabilities

Sealing

• Hermetic separation of fluid and gas chambers with no dynamic sliding contact
• Perimeter bead or flange profile matched to mating clamp geometry
• Compound selected for compatibility with media on each face independently

Pressure and Actuation

• Operating pressure differential range from fractions of an inch of water column up to several hundred psi depending on geometry and reinforcement
• Stroke and force output specified per application
• Rolling diaphragm configurations available for long linear stroke with near-zero side load

Cycle Life

• Flex cycle life specified and validated per application requirement
• Fabric reinforcement available for extended cycle life in high-frequency applications
• Compound and geometry selected together to minimize stress concentration at the clamped perimeter

Applications

Rubber diaphragms are used wherever controlled flexible separation, pressure response, or force transmission is required between two media:

• Pumps: diaphragm pumps, dosing pumps, fuel pumps, bellows pumps
• Valves: pressure regulating valves, relief valves, back-pressure valves, solenoid valve actuators
• Actuators and positioners: pneumatic and hydraulic actuators, valve positioners, control cylinders
• Medical devices: drug delivery systems, fluid management assemblies, ventilators, diagnostic equipment
• Pressure sensing and control: pressure switches, transducers, regulators, vacuum controllers
• Food and beverage processing: FDA-compliant diaphragm valves and pump chambers for sanitary fluid handling
• Aerospace and defense: fuel system regulators, pneumatic actuators, environmental control systems

Get a Quote for Custom Rubber Diaphragms

Rubber diaphragms are engineered to order. Contact Moldtech’s team to define the compound, geometry, reinforcement, stroke requirements, and regulatory standards for your application.