UV transparent object detection sensors revolutionise transparent plastic detection

For manufacturers operating high-speed thermoforming lines, the reliable detection of transparent plastic sheet has long been a critical yet challenging task. Ensuring consistent material tension during the unwinding process is paramount for efficient production of blister-trays, and conventional visible-light sensors often fall short, leading to frustrating false detections and costly downtime.

Thermoforming equipment is a workhorse in plastic packaging, particularly for the continuous production of blister-packs. The process involves in-line vacuum-forming of clear thermoplastic material into semi-rigid trays, which are then filled and sealed. Maintaining the correct tension of the continuous reel-stock material as it feeds into the loading station is crucial for consistent product quality and line efficiency.

Traditional photoelectric sensors using visible light struggle with the inherent transparency of the material. They often cannot reliably differentiate between "material present" and "material not present", especially with varying thicknesses, shapes, or speeds of the plastic sheet. This can lead to erratic feeding, material wastage, and frequent interruptions to production.

UV technology: seeing what others can't

The breakthrough lies in the use of polarised ultraviolet (UV) light at a specific wavelength (275 nm). At this wavelength, commonly used transparent plastics exhibit significantly higher absorption of UV light compared to visible light. This fundamental difference is what allows the new sensors to detect even the thinnest transparent materials with exceptional accuracy.

Contrinex C23 transparent-object reflex sensors, for example, utilise this patented UV technology. These miniature cubic devices, strategically mounted between the reel feeder and the loading station, constantly monitor the presence of the transparent material loop.

There are a number of reasons why this UV approach is so effective:

High Absorption Factor: The strong absorption of UV light by transparent plastics creates a clear and distinct signal, ensuring a high operating reserve even with very thin films.

Insensitive to Light Distortion: Unlike visible light, UV light at this wavelength is largely unaffected by the transparency, thickness, shape, or speed of the target, eliminating multiple switching on a single target.

Elimination of Blind Zones: Autocollimated optics ensure there are no blind zones, allowing for reliable detection close to the sensor or through small notches in the material.

Contamination Tolerant: These sensors boast very low sensitivity to dust, liquid droplets, and splashes - common challenges in factory environments - further enhancing their reliability.

Boosting efficiency and reducing downtime

For UK manufacturers, the benefits of adopting these UV transparent-object sensors are clear:

Reliable Detection: Consistent and accurate detection of transparent plastic targets, even the thinnest materials, minimises false detections.

Reduced Manual Intervention: Reliable operation means less need for operators to constantly monitor and adjust the line, freeing up valuable personnel.

Maximised Uptime: By avoiding false detections and unplanned stoppages, production throughput is maintained at optimal levels, leading to significant cost savings.

Simplified Setup and Maintenance: Simple one or two-step teach procedures optimise initial sensor set-up, and remote sensitivity retrieval or updates via IO-Link minimise the need for manual adjustments.

Proactive Maintenance: A stability alarm highlights reduced sensitivity, flagging the need for preventative maintenance before any performance degradation occurs, preventing costly breakdowns.

Advanced features for modern factories

Beyond the core UV technology, these sensors offer additional features that make them ideal for modern factory automation:

IO-Link Integration: PNP versions come with IO-Link serial connection protocol enabled at no additional cost. This allows for remote sensitivity parameter retrieval and updates, simplifying machine integration and maintenance.

Robust Construction: Ecolab-certified plastic housings with an IP67 rating ensure durability and suitability for stringent environments, including those involved in packaging medical products.

Wide Operating Range: A sensing range up to 1200mm, adjustable via a teach button or IO-Link, accommodates a full range of machine geometries.

A clear vision for the future

For packaging operations using transparent packaging, the adoption of UV transparent-object sensors represents a significant leap forward in reliability and efficiency. By seeing what was once unseen, these innovative devices are helping manufacturers maintain high-speed production, minimise downtime, and ultimately, deliver high-quality packaged goods to the market.

This technology provides a robust and cost-effective solution, ensuring that factories remain at the forefront of automated packaging innovation.