Discuss the various aspects of heat press technology. Transfer paper, inks, plastisol transfers, vinyl cutters, printers, commercial usage, durability, suppliers, etc.
Ok gang, how many have checked their heat press with an infared gun
to see if platen is evenly heated ? Probably not many, but I was suprised to find my new Mighty Press has so much difference between various places on the platen.
Each spot was tested 3 times and the numbers were averaged.
For those that might know, is this acceptable ?
Good to know. I thought my press (Mighty Press)had spots that may be hotter in some areas. Now I know. Thanks. I made a print out.
__________________ There is a center to everything.. I found mine at.. www.heatpressessentials.com Tools to get the job done! www.tbiz101.com (New)Heat Transfer Education
Ok gang, how many have checked their heat press with an infared gun
to see if platen is evenly heated ? Probably not many, but I was suprised to find my new Mighty Press has so much difference between various places on the platen.
Each spot was tested 3 times and the numbers were averaged.
For those that might know, is this acceptable ?
Thanks,
Don
That's pretty close to what I have with my phoenix. I have a cold spot in the middle. The edges are about 7 degrees hotter and overall it's 5-10 degrees above the display temp.
I'll do some measurements tonight and put up some numbers.
I just got a second IR thermometer today. I had to send the first defective one back. While it was still working (I think) I did notice some variation on my phoenix 16 x 20.
I have been told by several people that you can't use an IR gun to test the heating element on a heat press. The reason is that the IR gun will reflect off the heating element and not give you an accurate reading. I believe that Josh at Imprintables might have some type of strip that you can use to test your press. The IR guns work good for screen printing since you are testing the temperature of the ink as it is coming out of the dryer. The ink will not reflect the IR gun. I will try to remember what these strips are called and find a link if possible.
The only thing that is shot out of the gun is the laser beam to show you where it's receiving infrared energy from. RECEIVING is the operative keyword here. In order for a gun to work correctly you have to aim it directly at the source of radiation. If it's off angle, you won't get an accurate reading. In the case of a press, 90 degrees to the surface. It is true that metals may reflect heat (and thus may be appearing to be hotter than they really are to these devices). However, your press is actually hot. It's the source!
I really wish people who keep saying that these things don't work would provide some data to back their claims up. They work very well and are extremely accurate. Now, I'll give you that the cheap Chinese made ones might have a high defect rate but that's a whole 'nother topic.
Some light reading for ya. The pdf goes into the technical details on where they don't work well.
The IR guns work good for screen printing since you are testing the temperature of the ink as it is coming out of the dryer. The ink will not reflect the IR gun. I will try to remember what these strips are called and find a link if possible.
You're actually measuring the temperature of the shirt. The ink has nothing to do with it. You can reasonably assume that if the entire shirt reached the curing temp, the ink did as well.
I am not trying to get into an argument. There are many types of IR guns and some work better than others. You are correct that you have to receive the information to the gun to measure correctly. This means that you have to put the gun at a 90 degree angle from the platten. Much easier to do on a clamshell than a swing away.
Below is one of the posts that I referred to. In this case, Insta (manufacturer of heat presses) and Stitch City were the ones stating this. According to the post, if you want an accurate measuring device - you should use a "pyrometer." No clue what this is. Entire post can be found here (but you will need to scroll down to find the specific message) - Screenprinting and Digital Garment Printing University
Below is another post that talks specifically about one of the companies you mentioned. Again, stating that this is what others have said. Although I have great respect for Brian Walker (been in the industry for almost 20 years and has done just about every type of garment decorating out there). I will see if we can do some tests at the Orlando Show. Mark from Vastex has an IR gun that he uses to test his tunnel dryers and I will see if I can use it to test some of the heat presses at the show. But I don't have any on-contact measuring devices, so not show how effective the test will be.
Sorry if I came off as argumentative. I get frustrated hearing 'facts' that I can't corroborate. Thank you for posting the links. Unfortunately, it doesn't shed any light on as to why there was a discrepancy between the pyrometer and the non contact thermometer.
Why did the pyrometer exactly match the display? I suspect is has to do with with the type of pyrometer used. If it's a thermocouple like the one used by the press itself, I would expect it to provide very similar results. Thermocouples measure temperature differences, not absolute temperatures. Notice that in that thread they didn't mention anything about measuring the temp spread across the platen.
I have measured a 10 degree variation on my press. Take those 10 degrees and add a few more for a possible discrepancy between the press temp and the actual temp and I could see where a 20 degree variance could be observed. My gun is a cheapie from Harbor Freight ant it's always within 5-6 degrees (depending on where you aim it on the platen) of the display.
Brian's statement about reflection makes no sense to me. Again, what exactly is being reflected?
Ok, I think I figured it out... It's not reflection that's the issue, it's emissivity. Turns out that different materials/finishes radiate heat differently. From this article I found:
The emissivity of the object that you’re taking a reading of can also affect the accuracy of the MiniTemp MT4. Simply stated, emissivity is the ability of a material to radiate heat. Dark, non-reflective materials have a higher emissivity rating than lighter, reflective materials. According to the user guide Raytek includes with the MT4, most organic materials and painted or oxidized surfaces have an emissivity of 0.95—which is pre-set in the MiniTemp MT4. As a result, the MT4 will return inaccurate temperature readings of polished or shiny metal surfaces—which was confirmed by the erratic readings I got trying to measure the polished surface of a heat sink in a recently constructed test rig. Raytek recommends painting the object with flat black paint or covering the surface to be measured with masking tape—the latter obviously being the more viable option for most of us. With a small strip of flat black electrical tape in place, the MT4 returned a steady 38°C from the heat sink.
It never occured to me that other presses may have a different finish on the platen. Mine is matte black/graphite colored so it probably works ok on it.
Some IR thermometer have adjustable emmisivity ranges. Mine sure doesn't.
It never occured to me that other presses may have a different finish on the platen. Mine is matte black/graphite colored so it probably works ok on it.
Some IR thermometer have adjustable emmisivity ranges. Mine sure doesn't.
So in layman's terms, it emissivity similar to reflection?
Does that mean that the IR thermometers won't read correctly (or be as accurate as a pyrometer)? I got confused by all the technical stuff.
So in layman's terms, it emissivity similar to reflection?
Does that mean that the IR thermometers won't read correctly (or be as accurate as a pyrometer)? I got confused by all the technical stuff.
Ok, I never thought I'd have to dig up Planck's Law while on the t-shirt quest. This stuff is supposed to be easy guys!
To answer your questions:
1. Yeah. They are inversely proportional.
2. Yes, a spectral pyrometer will be more accurate than a non-calibrated/incorrectly set IR gun.
Happy?
This has been a fascinating little research trip (for me anyway). Getting an accurate temperature reading is a lot more complicated than I initially thought!
It turns out that the toy IR thermometers (sub $100) work just fine. They're just not ideally suited for all applications. Basically it boils down to how closely your material matches the settings that were programmed into your unit. Since these are mass produced items, they're going to have some generic setting.
The spectral emmisivity is the key thing to look out for. Temperature measurement is a BIG deal in steel manufacturing and most high-temp industries. There are a LOT of papers out there dealing with the subject matter.
To make matters worse, I found this article that says:
Flat plates are the least desirable from a emissivity consideration, but are generally the only practical solution when large, uniform areas are required. Surface emissivity becomes the dominate factor when a flat plate design is used.
So what does this mean in practice? The naysayers are right on this one. IR non concacts probably aren't the best tool.
However... I think the shortcomings can be corrected by making the surface we're measuring approximate the material that the things were initially calibrated for. A piece of tape or shirt material might be enough!
Anyway, back to the original topic. Unevenness in surface temperature... The IR Gun is a valid tool to measure relative temp differences. I have verified it by sublimating images on the cold vs hot spots on the same material and comparing them visually. The image quality mirrored the ir temp readings. The cold areas did not sublimate as well as the hotter ones.
I haven't sublimated any large images yet. My test was a few medium sized ones at a very short press time (10s or so). Everything's fine when I press for the full 40-50 seconds.
Mighty Press hot / cool spots diagram 
