Yuqori haroratli muhandislik plastmassalarini -qayta ishlaydigan issiq yuguruvchi tizimlar uchun termojuftlarni qanday tanlash mumkin?

High-temperature engineering plastics such as PEEK, PPS, LCP, and PEI present extreme demands on hot runner thermocouples due to their elevated processing temperatures, typically ranging from 350°C to 420°C. The first selection criterion is the thermocouple type. For sustained operation above 350°C, Type K thermocouples are commonly used, but they experience accelerated oxidation at these temperatures, leading to drift. Type N thermocouples (Nicrosil-Nisil) offer superior oxidation resistance and stability at high temperatures, making them the preferred choice for high-temperature applications. They have a lower drift rate-typically 0.5°C per 1000 hours at 400°C, compared to 1.5°C for Type K. The second criterion is the sheath material. Standard stainless steel 304 will oxidize and scale at 400°C, reducing its mechanical integrity and potentially contaminating the resin. Inconel 600 or 625, with their high nickel-chromium content, form a protective oxide layer that resists scaling and maintains strength. For ultra-high temperatures above 400°C, consider superalloys like Haynes 214 or alloy 59. The third criterion is the probe diameter. Thinner probes (0.5-1.0 mm) offer faster response, which is essential for high-temperature plastics that degrade quickly if overheated. However, thinner probes are more susceptible to oxidation-a trade-off that must be balanced. A 1.0 mm Inconel probe is a good compromise. The fourth criterion is the insulation material. High-purity, densely packed magnesium oxide (MgO) is standard, but for temperatures above 400°C, ensure the MgO is specially processed to remove moisture and to have a high density (>95% nazariy zichlik) elektr qochqinning oldini olish uchun. Beshinchi mezon - sovuq uchi muhrlanishi. Yuqori haroratlarda sovuq uchi yuqori haroratli epoksi yoki ulagich sohasida 250 gradusgacha bardosh beradigan-metall plomba bilan yopilishi kerak. Oltinchi mezon - kompensatsiya kabeli. Kabel izolatsiyasi qolipdagi atrof-muhit harorati uchun baholanishi kerak. Silikon izolyatsiyasi 300 darajadan oshib ketishi mumkinligi sababli, shisha tolali{10}}zanglamaydigan po'latdan o'ralgan izolyatsiyalangan kabellar tavsiya etiladi. Ettinchi mezon - kalibrlash. Yuqori{14}}haroratli termojuftlar faqat quyi nuqtalarda emas, balki haqiqiy ishlov berish haroratida sozlanishi kerak. 350 daraja va 400 daraja ball bilan kalibrlash sertifikatini talab qiling. Sakkizinchi mezon - almashtirish oralig'i. Tezlashtirilgan driftni hisobga olgan holda, yuqori{20}}haroratli termojuftlarni tez-tez-odatda har 3000-5000 ish soatida yoki yiliga almashtiring. Ushbu mezonlarga asoslanib termojuftlarni sinchkovlik bilan tanlab, yuqori haroratli muhandislik plastmassalarining protsessorlari barqaror haroratni nazorat qilish, degradatsiyani minimallashtirish va sensorning ishlash muddatini uzaytirish, barqaror sifatga ega yuqori unumdor qismlarni ishlab chiqarishni ta'minlashi mumkin.