Plastics Technology

NOV 2018

Plastics Technology - Dedicated to improving Plastics Processing.

Issue link:

Contents of this Issue


Page 46 of 67

So, if you're trying to justify spending the money, you might ask questions like these: • Can you v alidate this type of method (especially in a regulated industry)? • Can you prove equivalency to current methods being used? THE EXPERIMENT When we were kicking the tires on the idea of using IR images for process development and troubleshooting, we had to answer the same questions. What we decided to do was put some different methods to the test side by side in our normal clean-room envi- ronment for comparison. We compared a calibrated, two-zone, handheld pyrometer; a calibrated, fast-response immersion probe; a calibrated, standard 0.125-in. diam. immersion probe; and a TIC. Our methodology was as follows: 1. Take multiple purge samples on one machine. 2. Measure some of the samples with the fast-acting immersion probe (most used melt-temperature measurement method at our shop); not pre-heated. 3. Measure some of the samples with the standard 0.125-in. diam. immersion probe (one of the more readily available probes in our shop); not pre-heated. 4. Measure each sample with the IR camera. 5. Measure some samples using all three methods at the exact same time. 6. Measure and document time to equilibration. THE RESULTS We immediately noticed that the temperature from the IR camera was within 2-4° F of the handheld measurements we were col- lecting. Furthermore, we noticed that the IR camera was by far the fastest; the fast-response immersion probe was the second fastest; and the thicker 0.125-in. probe was the slowest. What really got us scratching our heads was the amount of time that it took for all three methods to equilibrate. The more shocking revelation was when we graphed the data for all three measurement methods, which highlighted how the IR camera was producing an accurate "right now" measurement of the melt. The graph revealed that the IR camera generated an instanta- neous measurement of temperature; the fast-responding probe took nearly 30 sec to equilibrate to the IR camera; and the other immersion probe took another 30 sec to equilibrate to the fast- response probe and camera. Using this data, we decided that it was well worth our time and money to purchase a camera to supplement our current methods of melt-temperature measure- ment and machine-performance analysis. We identified several machine problems aside from the experi- ment using the melt probes that normally would go unnoticed. For example, we had a nozzle-body heater that was running too hot, but the machine's controller read that zone as being at the proper tempera- ture because the heater was piggybacked to another zone that was not heating properly and it was compensating for the heat discrepancy. LESSONS LEARNED The camera does a number of tasks for us—from allowing our setup technicians to evaluate water flows, to detecting melt temperatures, to helping our building maintenance crew troubleshoot HVAC problems and diagnose electrical issues. One of the biggest advantages of using an IR camera for process verification and troubleshooting is the non-contact aspect of getting data. Part ejection temperature, mold-water flow, and dryer opera- tion can all be verified while the machine is running parts. Melt Water lines that are not flowing can be identified quickly using thermal infrared cameras. The greenish-looking line is blocked or turned off. Verification of barrel heats can be performed easily and quickly with TICs. This thermal image shows a failing nozzle-body heater. @plastechmag 45 Plastics Technology T H E R M A L I M A G I N G

Articles in this issue

Archives of this issue

view archives of Plastics Technology - NOV 2018