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I have disassembled my SMD reworking airgun (to determine the cause of a 5-E error) and in aigun I have found a paper-like coating wrapped around the heating element that totally crumbled to dust and little pieces when I touched it. enter image description here

What is the purpose of this coating? Could I use the aigun without it or I will get some problem?

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Mica sheets are used as electrical insulators for heatsinks , heater guns and microwave ovens , maybe (salvage) from old toasters

enter image description here

It prevents the body plastic from melting and is rated by thickness. The heater coil also has high AC voltage on it.

Looks like you cooked it maybe by blocking the intake air or cheap quality inadequate thickness.

Good luck.

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  • \$\begingroup\$ thanks for the answer. BTW the plastic is used just for the handle, the heating element is placed in a steel pipe. \$\endgroup\$
    – AndreaF
    Commented Dec 25, 2019 at 20:29
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    \$\begingroup\$ OK then its for electrical safety \$\endgroup\$
    – Tony Stewart EE75
    Commented Dec 25, 2019 at 20:29
  • \$\begingroup\$ I estimate the wire gets to dim red 1000'C but reduced airflow can raise the temp and make it more red and degrade the mica \$\endgroup\$
    – Tony Stewart EE75
    Commented Dec 25, 2019 at 20:32
  • \$\begingroup\$ I wonder if the gun actually senses voltage induced on the pipe. 5-E error \$\endgroup\$
    – Tony Stewart EE75
    Commented Dec 25, 2019 at 20:34
  • \$\begingroup\$ Interesting question. This error usually is caused by some disconnected cable that prevents the correct temperature control, but I have checked them and seems all well connected and other than cooked coating I don't see anything wrong. (Also I'm wondering if this thing is toxic, since the thin dust is easy to be inadvertently inhaled). \$\endgroup\$
    – AndreaF
    Commented Dec 25, 2019 at 21:20
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That is a heat shield to protect the body from damage.

You need to replace it before using the airgun again.

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