Recently Conducted Uniformity Test Confirms that Despatch Oven Exceeds Critical Uniformity Requirement for Contact Lens Curing

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A contact lens manufacturer received confirmation that the Despatch LNB Oven exceeds the stringent +/- 3.0°C uniformity requirement for curing contact lenses.

To manufacture contact lenses, a monomer resin called “hydrogel” is injected into molds and heat-cured in an oven. The process polymerizes the hydrogel to produce hard, slightly flexible lenses. The lenses are then removed from the mold and transferred to a downstream hydration process.

These hydrogel thermal curing cycles can be relatively long—up to 34 hours—and require a reliable oven with uniform internal temperatures, an inert nitrogen atmosphere, and accurate ramp and soak time and temperature controls.

A contact lens manufacturer wanted to verify that the large chamber (48x50x38in) Despatch LNB oven they were using would meet the stringent +/- 3.0°C uniformity requirement for their process. The chamber was loaded with their product and a nine point temperature uniformity test was performed by a Despatch process engineer. A temperature uniformity of +/- 0.8°C was achieved which greatly surpassed the customer’s expectations.

The Despatch LNB is a custom-designed oven built for process repeatability and reliability. The LNB’s operating range is from 60°C to 150°C (140°F to 302°F), with horizontal airflow producing precise temperature uniformity. An internal nitrogen atmosphere system is standard and will reduce oxygen concentrations to as low as 1000 ppm as required to prevent distorted or discolored lenses.

About Despatch: Despatch Industries has specialized in thermal processing for over 100 years. Despatch industrial ovens and other thermal products are used for a host of critical applications, focusing on the electronics, healthcare, materials, transportation, and industrial markets.

Headquartered in Minneapolis, Minnesota, Despatch Industries has regional offices located throughout the world, allowing its staff and sales representatives to build strong relationships with global customers and to provide engineering, design and technical solutions and quality customer service support. A global sales and service network allows the company to provide local sales and product support to customers worldwide. For more information, visit http://www.despatch.com.

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Roger Dullinger
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