Having consistent and accurate oven temperatures is very important when powder coating. Knowing what temperature your part is at when it is in the oven is essential. I will be talking about how to do this using an infrared thermometer.
An infrared thermometer, also called IR thermometer, also called IR Temp Gun can measure the temperature of an object without actually touching it. They display the temperature on an lcd screen. They also usually have a laser pointer to help you accurately read temperatures. I'm sure you can see how a tool like this would be helpful when powder coating. In case you don't see the importance, take a look at this scenario to see how great these tools can be: You just finished spraying your powder on your part, and you stick it in the oven. Lets use an example cure schedule of 400 degrees F for 10 minutes(your powder will specify your cure schedule). So you have the part in the oven, you shut the door and you set the temperature for 400 degrees. You DO NOT start the 10 minute timer when you shut the oven door. The 10 minute timer starts when the entire part itself has reached 400 degrees. The easiest way to tell when your part has hit 400 degrees is with an infrared thermometer.
How to read the Temperature of a Part in the Oven:
Lets learn how to use this tool. The simplest way is to simply set the temp on your oven, and when you see that your oven is up to temp, that is when you can start checking with the IR thermometer. I simply open the door every couple minutes to take the temp, and adjust the oven temperature accordingly. When the part is at my desired temperature, that is when I start the timer. I check the temp about 4 times in a 10 minute long cure. However, opening the oven door does allow some heat to escape from your oven, which changes the readings that you just took. This is why its important to not leave the oven door open for a minute, just open the door quickly, get your IR thermometer in there, check the temperature, and shut the door. Just make sure not to burn yourself, it is a hot oven after all. Also make sure not to accidentally hit the part with the IR thermometer.
When you first start using the IR thermometer, you will probably be checking the temperature every 30 seconds, don't worry, that is normal. You will learn as you go along how the temperature behaves when dealing with different sizes and different types of metal. The bigger the part, the longer it will take to get up to temp. Iron and steel will take longer to heat up than aluminum. A small part such as a bolt can be up to temp in 30 seconds, a larger part like a wheel can take 30 minutes to get up to the 400 degree temperature. Your ovens efficiency will also have an effect on this, so if you ever change ovens, be sure to check the temperature more often until you learn your new oven.
Sometimes larger parts will heat up inconsistently, you will want to take your temp in a couple different spots to make sure the entire part is up to temp. It is not uncommon to have one side of a part 50 degrees off from the other side of the part. A convection oven helps reduce this affect a lot. If the side of your part closest to the heating element is getting up to temp way faster than the rest, you can put a metal shield over your heating element which will help your oven heat more evenly. If your heating element is on the bottom of your oven like mine, you can just sit a cookie sheet on an oven rack at the lowest position.
Reflections can confuse an Infrared Thermometer
While these IR Temp Guns are very convenient for powder coating, they do have one setback. When you using a highly reflective color like chrome or even a full gloss color, it can skew your readings. The best method to overcome this is to try to find an object with about the same mass and same material as the object you are coating and stick it in the oven with it. The object should be non-reflective, say flat black. Now you can take the temperature of the similar object and use that to estimate when you start your timer. This can be impossible sometimes depending on the size of your oven. For example, you wouldn't be able to fit another wheel sized object in the oven with a wheel in a household oven. What I would do in this case is a test run. Before I spray any powder on the wheel at all, I will put it through an oven cycle. I media blast all my parts before powder coating. The blasted surface has a flat, non-reflective surface, perfect for accurate temperature readings. I simply place the blasted wheel in the oven, set the temperature like I was curing it, and time how long it takes the wheel to reach the desired temperature. Now that I know how long it takes, I just start the oven up and add that time to the cure time, plus a couple minutes for good measure.
Not all IR Thermometers are built the same. The further away you get from the part, the less accurate they will be. This is called the "Distance-to-Spot ratio" or "Optical Resolution". The further away your ir thermometer is reading, the larger the area it is reading. If are trying to take the temperature of a small bolt in an oven 10 feet away, even though your laser is pointed right at the bolt, you are actually taking the temperature of the entire interior of your oven. When you are shopping for an IR Thermometer, you will see it say something like "Optical Resolution - 12:1. What this means is that at a 12" distance, your ir thermoter is reading a spot that is 1" in diameter. Every 12" further you get away from your part, the size of the reading increases by 1". At 48", your reading is 4" in diameter. Think of the ir thermoter giving off a cone shaped beam that spreads out the further away it gets. This will help you accurately use it. This picture probably explains it better than I can:
|This shows the optical resolution of an Infrared Thermometer.|
Now that you know how important these tools are for powder coating. One thing about these Infared Thermometers, is they are considerably cheaper online. There a few big box stores that do carry them, but there is a huge price mark-up on them. You can pay $80 for a no-name brand one at Home Depot, or you can go online and pay the same for the a Fluke mentioned right below here.
If you want an extremely high quality infrared thermometer, Fluke is a very trusted name. I would recommend the Fluke 62 Max+. It has a 12:1 Distance-to-Spot Ratio and it has dual lasers so you know exactly what area you are reading.
If you are on a budget, here is an infrared thermometer that still has great reviews, but won't break the bank and still reads at 12:1: Nubee Infrared Thermomter
On top of being very useful for powder coating, these IR temp guns are useful in the kitchen, around the house, and working on a car. If you have never used one before, you will find yourself pointing it at everything. They are the type of tool that once you have it, you will never want to be without one.
Another essential tool to curing your parts in the oven is very simple: a Timer. It doesn't have to be anything fancy, just as long as it actually works. I personally use an app on my phone.