Temperature Measurement

Profiling in paint cure ovens

April 2020 Temperature Measurement

Although oven profiling has been used for many years in the automotive coatings industry, it has come a long way from its humble beginnings. Updated technologies now provide a range of benefits that allow the paint shop or production manager to understand, control and optimise oven cure processes with ever more accuracy and efficiency. The paint shop manager is now able to maximise the coating quality of finished products, ensuring customer satisfaction and the efficiency and productivity of the complete paint finishing operation.

Automotive paint cure application challenges are overcome by the Oven Tracker XL2 system, developed specifically for the automotive paint industry to improve paint quality, line productivity and process efficiency. For successful paint cure, irrespective of the paint chemistry being used, there is a critical need to be able to measure and control the temperature of the car body as it travels through the oven. Today paint ovens are controlled in a sophisticated fashion with static thermocouples located in each zone to give constant feedback on the ambient temperature of the oven. Although this data is helpful, it does not give the full picture.

Oven temperature profiling

To cure the paint to specification (cure schedule), the critical information required is the peak metal temperature and the time that peak metal temperature is maintained. The control thermocouples in the oven cannot provide this data. Oven temperature profiling is the only truly accurate method by which the oven paint cure process can be monitored to determine that the paint cure schedule has been correctly achieved. The oven profiling system is designed in such a way that it is able to travel with the car body through the cure oven, measuring continuously the product temperature at selected locations on the car body. At the end of the process, the collected temperature creates a thermal profile of the product from which the cure schedule can be measured and validated.

One of the biggest challenges of oven profiling in an automotive paint shop is the sheer scale of the operation. The Oven Tracker XL2 has been developed with key features that allow sequential testing of multiple ovens without the need to download profile data between runs. The XL2 logger can be programmed to perform multiple runs (up to 10), so that each oven can be tested and its data stored separately in memory. Complementing the multiple run operation, the user can employ a unique feature called SmartPaq. Prior to the run, the user can program the logger with critical target performance criteria. The data collected is then analysed against these criteria at the end of the run and the logger displays whether the criteria have been achieved or not. This makes profile qualification as easy as checking for a Green Pass LED and then moving on to the next oven with confidence and without any need to download data. If the LED is red, it is immediately known that there has been a process problem.

Another innovation by Datapaq, is the MicroMag thermocouple. This encapsulated magnet design allows reliable direct use during production and also use on a test car during profiling. The miniature surface and air thermocouple can be placed into the tightest of recesses, ideal for car body shell areas that are difficult to access. Due to its low thermal mass, the MicroMag provides response characteristics that challenge those of exposed junction thermocouples, while it has the additional advantage of quick and easy attachment to ferrous substrates.

Datapaq has worked with key automotive manufacturers to develop a barrier technology that allows not just one or two ovens to be tested sequentially, but the complete paint operation from start to finish in one single run. The ‘single pass’ method is used with a test car, allowing the system to be installed off line. The test car is then installed onto the paint line after the e-coat dip tank and allowed to run through the entire paint line, as if a production car. Completing the run in one operation removes labour (about 60% cost saving) as the system does not need to be installed and removed for each oven. The thermal barrier is designed to protect the system during the process (including delays) without any risk of the data logger overheating. The single pass barrier is completely silicone free, as are all standard Datapaq barriers used in automotive paint operations and gives protection at 150°C for 13 hours.

Consistency of cure

A challenge of any automotive paint operation is getting consistency of cure on all areas of the car. In many plants, engineers are working to very tight operating variables. To help with these important criteria, the Datapaq Insight software can perform an automatic temperature difference analysis to highlight problem areas within the process. The Insight system has been developed to allow customisation of the full report generated to include the specific data and information required. If necessary the archived data can be used to generate SPC charts to show how key parameters are changing within time. Within the Insight software, the SPC program automatically produces SPC charts without any need for data export or use of the SW packages.

As a leading manufacturer and service provider for temperature profiling systems, Datapaq provides a complete offering for monitoring, logging and profiling of temperatures in applications involving furnaces, ovens or dryers.


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