"We have several concerns that we would like to collaborate with according to your experience.
I.-What is the best method to measure the curing temperature in the parts in the infrared furnace?
- By direct contact in the parts, Datapaq system?
- By infrared, thermal cameras?
- Adhesive tapes affected by temperature?
II.-What are the curing windows for paintings that pass through the Infrared oven?, is it the same as for a conventional system to say that they cure at 190-200°C 10-11 minutes? or 2-3 min depending on what?
III.-According to the following description of our process, what do you think is the best method to know curing temperatures?
First part: Infrared oven with a length of 5.25 m, temperatures are programmed from 370°C-415°C (shown on the display), the heating is by catalytic radiation system.
Second part: Conventional gas oven, with a length of 8.33 m, temperatures are programmed from 160°C-240°C(shown on the display).
It is a continuous system, (conveyor) at a speed of 1.5 m / min, it is an oven for parts painted in powder paint, (motorcycle parts: chassis, handlebars, legs, etc.)".
We consulted the opinion of Gregorio Garza ([email protected]) of the company Thierica and this was his response.
Regarding the question of what is the best method of measuring the curing temperature in the parts inside an infrared furnace, any of the methods you mention are functional. Really, the best method is the one that best meets and fits your needs and budget.
It should be noted that temperature measurement inside an infrared furnace is very different from the way it is measured in a conventional furnace and that many people get confused when reading the temperature of an infrared furnace since many infrared furnaces measure the temperature of the radiant element not the temperature of the part and this is in order to control the amount of energy that it emits and the vast majority of people think that this is the temperature reached by the pieces inside the oven and it is not so. This temperature only controls the temperature at which the radiant element arrives since the hotter it is, the more Infrared (IR) rays it will emit, and the more IR rays, the more energy the piece absorbs, thus increasing its temperature.
It may be that the radiant element is at 400 C and that the piece only reaches 160 C and this does not mean that the furnace does not work well but that it is necessary that the radiant element is at 400C so that it can emit such an amount of energy in such a way that the part reaches 160C.
Definitely, when working with an IR oven it is important to check with the manufacturer the operation of the oven, be sure of what is the temperature that is being read and if you do not have any system to measure the temperature of the piece directly as IR sensors or another, you will have to create a correlation table, that is, a table that gives you the ratio Radiant Element Temperature VS Part Temperature. Here is the importance of the methods of measuring the actual temperature of the parts.
Returning to the question of which measurement method is the best, any of the methods you mention: thermography (datapaq or direct contact), IR sensors, thermal camera or adhesive tape is fully functional, as I said before, the best is the one that best suits your needs and budget. Below I describe some of the advantages and disadvantages of each method:
I.- Thermography (Direct contact or Datapaq)
This is the most complete way to read the temperature at which the pieces arrive, since it not only reads the temperature but also gives you a graph where it describes the behavior of the temperature of the piece through the oven. This is very useful because this graph shows, the time it took the piece to reach the desired temperature, the time it lasted at this temperature and if that were not enough, it can be configured to read different points in one piece.
Some of its disadvantages is that it has a cost of US $ 5,000 to US $ 12,000 and sometimes it is difficult to justify such an expense.
II.- By infrared sensors:
This is another good method to measure the temperature of the parts, the biggest advantage is that they can be used online, that is, to review 100% of the production, they can be configured to carry out a large number of tasks, such as stopping production if a part does not reach the desired temperature, stop the line if the desired temperature is exceeded, create reports and graphs of the temperature of the parts, etc. Its cost is very varied since it depends on the level of integration that is required. The main disadvantage is that it only tells you the temperature at one point and not its behavior through the oven as in the case of a direct contact thermography. Another of its disadvantages is that it only tells you the global temperature of the object and not of a certain part of the piece.
III.-By thermal camera
It is one of the most advanced technologies. It is a very complete method because it tells you the temperature in three dimensions of the piece. It is mainly used for processes where very delicate parts are painted as parts for security systems, aeronautical parts, etc. It can be used online (check 100% of production) and like infrared sensors can be configured to carry out a wide range of tasks such as stopping production if something does not meet specifications.
The main disadvantage is that they are very expensive and complex systems and even though it is a very advanced technology it does not tell you the temperature behavior of the piece through the furnace.
IV.-Thermotakes
It is the simplest and most economical option but this does not stop being functional. It meets the objective of knowing at what temperature the piece arrives. Definitely, if you do not have a budget for any of the above options this is the option to consider, it is of great help since it is a very simple and reliable method
The second question of what is the window of a piece that passes through an infrared furnace, is usually much smaller than that of a conventional oven. That is, if in a conventional oven you have a window of 20 to 25 min., most likely the same piece with the same paint would only take 12 or 13 minutes, this depends a lot on the composition of the paint and some other factors such as color, the shape of the piece, the wavelength of infrared rays, among others.
It is advisable to analyze the data sheet of the painting, usually there it is described. Otherwise, you should discuss with the paint manufacturer and get some document that supports the process. I have heard of many cases where they have had field problems that the paint falls and in the end the problem was only that they never realized at what temperature and how long the pieces had to be baked.
Having a document, process sheet or some other document that supports each of your processes is very important because in case you have a problem in the field, this document is a guarantee that your work was done according to the manufacturer's specifications.
Regarding the third question, according to the process you describe, I recommend that if you have the budget to buy a Datapaq or TempGard you acquire it and that you make at least one thermography of each of the products they paint, where you monitor the critical points (which are most exposed to abrasion, action, chemistry etc.).
Of each of your pieces, analyze each thermography and make the necessary adjustments to comply with what your technical sheet or process sheet asks of you. Once the thermography is correct you need to archive them as this serves as a backup for any problem in the field that may exist. In case you do not have a budget you can buy an infrared gun (digital infrared thermometer) cost between US $ 100 and US $ 300 with this you can check the temperature of the pieces when leaving the oven. The thermal camera I do not recommend for its cost and infrared sensors are not a good option due to the diversity of products you handle.
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