Festo FK-M4 Self-Aligning Rod Coupler

Technical Overview

The Festo FK-M4 (Part Number: 6528) is an industrial-grade self-aligning rod coupler designed to attach to the piston rod of compact pneumatic cylinders, such as ISO 6432 cylinders. It effectively compensates for both angular and radial misalignments, ensuring a stable connection to moving components and preventing binding or excessive wear on cylinder seals. Constructed with a galvanized steel housing and case-hardened steel ball pin, it is rated for moderate corrosion stress (CRC 2) and withstands a wide ambient temperature range from -40 °C to 150 °C. The unit features an M4 thread and is entirely free of copper and PTFE, rendering it highly suitable for strict manufacturing environments like lithium-ion battery production.

Key Features

Compensates for both radial and angular deviations in pneumatic cylinder connections.
Constructed with a robust galvanized steel housing and a case-hardened steel ball pin.
Broad operational temperature range spanning from -40 °C to 150 °C.
Free of copper and PTFE, ensuring safe use in Li-ion battery manufacturing environments.
Moderate corrosion stress resistance (Corrosion Resistance Class CRC 2).
RoHS and LABS (PWIS) compliant under VDMA24364-B2-L.

Technical Specification Matrix

Parameter	Value
Size / Thread	M4
Corrosion Resistance Class (CRC)	2 - Moderate corrosion stress
LABS (PWIS) Conformity	VDMA24364-B2-L
Ambient Temperature Range	-40 °C to 150 °C
Housing / Bushing Material	Galvanized Steel
Ball Pin / Washer Material	Case-hardened Steel
Product Weight	15 g

Industrial Applications

1. Li-ion Battery Cell Assembly Automation

Used to connect compact M4 pneumatic cylinders in battery handling stations. Because the coupler is copper- and PTFE-free, it prevents metallic contamination that could cause battery short-circuits. The coupler absorbs angular offsets caused by slight structural shifts, protecting delicate battery fixtures.

Problem Solved

Prevents cylinder rod binding during pick-and-place indexing while maintaining strict compliance with copper-free environment regulations for battery production.

Copper-freePTFE-freeRadial compensationPneumatic cylinder attachment

2. High-Temperature Curing Oven Actuation

Integrated into door mechanisms or part ejectors in thermal processing ovens. The coupler connects the cylinder rod to heavy oven flaps, easily accommodating wide temperature fluctuations up to 150 °C without losing structural integrity or jamming.

Problem Solved

Standard elastomers and plastics fail or bind at high temperatures; the all-steel, high-temperature rated design ensures continuous smooth operation.

150 °C ambient temperatureGalvanized steelThermal expansion compensation

3. Automated Quality Inspection Probing

Deployed on precision pneumatic probing arrays where an ISO 6432 cylinder advances a measurement gauge against machined components. The self-aligning nature of the coupler prevents off-axis loads from degrading the cylinder's internal seals during repetitive, fast-paced probing.

Problem Solved

Eliminates premature cylinder seal failure and erratic friction caused by micro-misalignments between the cylinder stroke axis and the target component.

Angular deviationM4 thread connectionLow friction rod attachment