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Why measure oven temperature? Elcometer says it is vital to have accurate measurement in your oven.

To ensure a successful cure of a powder coating for a quality, long-lasting finish, it is critical to accurately measure the temperature/time profile of the cure oven, particularly when loaded with the components to be cured.

Oven temperature/time profile is influenced by the thermal loading of the oven, therefore it is not sufficient to just set the oven zone controllers to an appropriate temperature value and expect the temperature/time requirements to be met.

An unsatisfactory cure results in a significant reduction in the quality of the final coating in terms of gloss, colour and adhesion. Too high a temperature can burn the coating and too low a temperature, or insufficient time at the required temperature, can result in an incomplete cure.

How to accurately measure an oven temperature

An oven data logger makes taking measurements and capturing the information simple, providing valuable data about the entire coating cure process. An oven logger is a measurement logging device with several connections for thermocouples. It is placed in a box which protects it from the high temperatures involved as it passes through the oven with any components, recording the temperature profile through the oven.

Although commonly known as an 'oven logger', it is not the oven temperature that is the critical measurement, but the temperature of the component.

Not all components are alike and there is rarely a uniform density. Therefore, if not adjusted to suit the component being coated, the oven temperature settings may lead to under cure, coating burn, poor adhesion, discolouration, loss of gloss and other visible defects.

By using magnetic or clamp type air and surface temperature probes, temperatures can be monitored both on and around the product and recorded by the data logger, providing valuable information about the time taken to heat the component to the cure temperature and how long this temperature was maintained.

Monitoring and making adjustments to the oven temperature ensures that the product is brought to and held at, the specified temperature to ensure consistent quality of cure and visual properties at all times.

The Elcometer 215 Oven Data Logger

Ideal for testing powder or liquid coatings in batch or conveyor ovens, the Elcometer 215 Oven Data Logger is an easy-to-use, battery powered temperature data recorder that uses up to six K-type thermocouple probes to monitor the cure process. Complete with an efficient thermal barrier kit, the oven data logger is protected from temperatures of up to 250[degrees]C for a period of 100 minutes.

Storing up to 260,000 readings, or eight production runs, the oven data logger allows the user to control the cure process for a wide range of products and applications. The data-logging interval can be set by the user from eight readings per second to one reading per hour. The Elcometer 215 also features a menu driven LCD screen which can display individual channel temperatures.

Six different clamp or magnetic K-type thermocouple probes can be connected to the logger simultaneously for measuring surface or air temperatures, with strong, flexible and easy-to-dean, Teflon coated cables in a variety of lengths. The probes have a continuous maximum operating temperature of 250[degrees]C and their low mass and optimised shape eliminates influence on the temperature of the component.

The Elcometer 215 in action

Manufacturers of architectural aluminium facade products, Multi Fab, has recently purchased the Elcometer 215 to use within their conveyor oven to measure the temperature profile of their powder coated aluminum sheetmetal products for the construction industry. The Suffolk based company, who are part of the EAG (English Architectural Glazing) group, are renowned for working on the M&S building in Westfields, Stratford and the BBC building at the Television Centre in London.

Since purchasing the Elcometer 215 Oven Data Logger, Multi Fab has continuously used the product daily, using all six probe connections; two air probes to test the oven temperature and four surface probes to test the temperature of the component to ensure a consistent quality cure and improved finished product. As part of their quality inspection regime, the powder coaters also use ElcoMaster data management software to manage and assess its oven temperature profile, allowing them to generate professional quality inspection reports in seconds.

It's what you do with your data that counts

ElcoMaster is free, easy-to-use data management software ideal for the management and assessment of temperature profile. ElcoMaster allows the user to create and store unique oven profile setups; name each of the six channels; set sampling rates, number of batch runs and start/stop triggers and transfer them to the oven data logger. When one or more runs have been recorded, the data can be downloaded to ElcoMaster via USB.

Using the industry accepted cure value calculation; ElcoMaster also provides instant pass/fail information by comparing the production run temperature to the coating supplier's cure requirements.

Different powder types can be created and stored in ElcoMaster by simply entering the cure schedule into the software, creating a custom 'paint'. This can be downloaded into the logger, ready for batch logging.

Professional inspection reports in seconds

At the click of a button, ElcoMaster produces fully customisable reports, including the coating type and temperature curve, together with the duration of the drying process at the maximum and minimum cross-linking temperatures. The report will show the probes, the duration of the process and the probe positions. It will also display a simple cure pass/fail calculation from the collected data. The product data sheet, product images and graphics can also be incorporated for a professional, easy-to-read report.

Measuring the quality of the cured coating

The effectiveness of the cure process and the quality of the final coating can be assessed using portable test instruments either directly on the coated component or on a coated test panel that has passed through the oven cure process with the components. The most common parameters to be assessed against the coating specification are coating thickness, gloss and adhesion.

The Elcometer 456 Coating Thickness Gauge provides incredible accuracy on smooth, rough, thin and curved surfaces. Taking up to 140 readings per minute the digital gauge measures dry film thickness on up to 31 mm of coating on ferrous or nonferrous metal substrates and can store up to 150,000 readings in 2,500 batches, ideal for a busy powder coating operation.

Gloss

Gloss assessment of the coating after cure should be carried out to ensure a consistent appearance quality. Using an optical measurement, light is directed on to the surface at a fixed angle and the amount of reflected light is monitored at the same angle.

The Elcometer 480 Glossmeter provides the very latest in gloss measurement technology, providing accurate gloss and haze in a single reading. Available in single (60[degrees]), dual (20/60[degrees]) and triple (20/60/85[degrees]) angle versions for maximum accuracy and resolution in all gloss applications, the Elcometer 480 stores up to 40,000 readings in up to 2,500 batches.

Adhesion

Adhesion for powder coatings is generally assessed using the cross hatch adhesion test as defined in ISO 2409 and ASTM D3359 Method B. Both methods use a matrix of cuts through the coating to the substrate at right angles to define a set of squares. Adhesion is determined by assessing the damage to the coating with zero damage being ISO rating 0 (ASTM rating 5B) and greater than 65% damage being the ISO rating 5 (ASTM rating 0B).

These tests reference the use of adhesive tape to remove the damaged squares from the substrate. The Elcometer 107 Cross Hatch Cutter Kits are available as ISO 2409 or ASTM D3359 versions with the appropriate tape and selection of cutters as defined in the test methods.

For a quantitative, definitive adhesion value, the Elcometer 510 Automatic Pull-Off Adhesion gauge accurately measures the strength of the bond between the coating and the substrate on flat or curved surfaces. Using 10, 14.2, 20 or 50mm reusable dollies, the Elcometer 510 has a measurement range of up to 100MPa, with an accuracy of [+ or -] 1% and stores up to 60,000 readings in up to 2,500 batches.

All your measurement data in one place--in one report

Like the Elcometer 215, the Elcometer 456, Elcometer 480 and the Elcometer 510 are compatible with ElcoMaster, allowing all measurement data to be stored, compared and reviewed in one place and added to one professional inspection report at the click of the button.

To find out more about the Elcometer 215 Oven Data Logger or the full range of Elcometer inspection equipment visit www.elcometer.com.
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Title Annotation:MEASUREMENT
Publication:Finishing
Date:May 1, 2019
Words:1432
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