Impingement mixing, the cleaning piston and recirculation: the working principle of a high-pressure polyurethane mixing head, step by step.
A high-pressure mixing head is the machine part that mixes polyol and isocyanate by impinging them at high speed through opposed injectors in a small mixing chamber, then delivers the mix into the mould. There is no mechanical stirrer; the mixing energy comes from the speed of the fluids.
Working steps
- Recirculation (standby): When no shot is being poured, both components flow through the head back to the tanks, keeping temperature and pressure constant.
- Opening: On the pour command the hydraulic piston retracts and the injector channels open into the mixing chamber.
- Impingement: The components leave the injectors at high pressure, collide in the chamber and mix homogeneously.
- Pouring: The mix flows from the head outlet into the mould; the duration is set by the shot weight in the recipe.
- Closing and cleaning: The piston moves forward and scrapes the chamber mechanically; the head cleans itself without solvent and returns to recirculation.
What determines head life
- Keeping the tolerance between piston and body
- Correct injector setting and injector wear
- Sufficient hydraulic pressure
- Keeping the filters clean
The advantage of a locally made head
MTS Otomasyon designs its own mixing heads and makes them in its machining facility. Parts such as pistons, bodies, injectors and seals are therefore supplied from stock or made at short notice, and the head is tested before it is returned after an overhaul.
Frequently asked questions
Why isn’t the mixing head flushed with solvent? In a high-pressure head the cleaning piston scrapes the mixing chamber mechanically after every shot, so no flushing is needed.
Can an MTS mixing head be fitted to another brand of machine? It can be adapted after checking connection and capacity compatibility; just share your machine details.
