Miniature Inductive Sensor Accurately Detects Position of High-Speed Spindle


High-speed machining centers often feature automatic tool-changers that help maximize productivity. A Swiss drive-motor manufacturer uses sensor technology to detect the position of a machine’s main spindle before initiating the tool-change sequence. Contrinex miniature inductive sensors detect the position of a slotted centering-disc mounted on the motor shaft with exceptional repeatability and positional accuracy better than 0.01 mm.

Customer Values

  • Highly accurate, repeatable sensing performance in demanding conditions
  • Embeddable miniature sensor with minimal effect on machine dynamics
  • Fit-and-forget operation with excellent resistance to shock and vibration
  • Affordable, highly reliable solution

Specific Product Advantages

  • Lightweight, hermetically sealed miniature sensors
  • V2A/AISI 303 stainless-steel construction with vacuum-encapsulated electronics
  • Best-in-class 0.8mm sensing distance

    Customer Application

    Modern machining centers execute multiple metal-cutting operations at a single station, often deploying a separate tool for each operation. Time spent changing tools is non-productive, reducing efficiency and machine utilization. Automating tool-changes keeps lost time to a minimum but requires highly accurate positional measurement of the main spindle to prevent damage occurring.

    After completion of an operation, the main spindle of the machine comes to rest. Only after it reaches the null position – the point at which the tool disengages completely – is the tool-change sequence initiated. Reliable detection of the null position requires exceptional accuracy and repeatability in sensing the position of a shaft previously rotating at up to 14,000 rpm.

    A miniature sensor, capable of withstanding mechanical shock, high levels of vibration and an oily environment, must detect the position of a slotted centering-disc mounted on the drive-motor shaft. The required angular resolution translates to a positional accuracy of better than 0.01mm.

    Customer Solution

    Contrinex inductive sensors are designed for exceptional long-term reliability and repeatability in demanding environments, and lightweight sensors from the Miniature range are ideal for this application. Constructed from V2A/AISI 303 stainless steel with PPE sensing faces and hermetically sealed cable entries, these embeddable M5-diameter sensors take up minimal space.

    The centering disc is mounted in a rotary-encoder housing fitted to the drive-motor shaft. The 25mm-long sensor is embedded directly in the wall of the housing and the sensing distance of 0.8mm eliminates any risk of accidental collision with the disc. The sensors are configured with an industry-standard PNP normally-open interface, connected to the customer’s control system via a flexible, oil-resistant PUR sheathed cable.

    Vacuum-encapsulated electronics ensure excellent resistance to shock and vibration, and no additional electrical or mechanical protection is required. Fit-and-forget operation keeps maintenance requirements to a minimum, overcoming the mechanical fragility of alternative optical-sensing encoder technology.

    The sensor detects the position of the centering disc, reliably and repeatably, with an accuracy better than the required 0.01mm. Contrinex Miniature inductive sensors provide a highly effective and affordable solution.