In order to increase the density of the filler in the heating rod and increase the thermal conductivity of the filler without reducing the insulation resistance, the tube diameter must be compressed after the powder is filled, which is called "shrink tube"
The Purpose of Shrinking:
The purpose of shrinking the tube is to reduce the diameter of the tube, so that the density of the filling material in the heating tube can 3.5g/cm3. Then it can meet the technical requirements for using the electric heating tube.
Commonly Used Shrinking Methods:
1. Use a drawbench;
2. Compress with rotary forging hammer machine;
3. Reduce diameter with tie roller.
No matter which method is used, the parameters will change during the tube diameter compression process, that is, as the tube diameter decreases, the tube length will extend, and the resistance value of the spiral wire in the electric heating tube will also change.