Injection Moulding Check-ring Mixers

Maddock and pin mixing elements can be used, but the more efficient interacting pegs or cavities cannot be used in the same manner as for extrusion described in Chapter 9. The rotor and stator would move completely out of register as the screw reciprocates. Although techniques have been devised, they required greater space than is normally available [1, 2]. 

---

The disadvantage is that there will be less screw available for melting/pumping, and the length of the mixer is restricted. Although initial costs will be lower than for addon mixers, the need for occasional replacement of worn injection moulding check rings may also apply to extruders. 

Figure 10.5 View inside injection moulded caps with back lighting, (a) Without check ring mixer, (b) With check ring mixer.

By transferring the check ring mixer concept to extrusion, the mixer can be accommodated within the barrel as part of the screw. Being without the non-return valve function required for injection moulding it can be described as a floating... 

Figure 10.4 18 mm Injection moulding (TMR type) check ring cavity mixer, (a) Components, (b) Assembled. 

---