Hi there,
Why do you need 8 kg/min flow? That sounds like an awful lot of flow for a 6 mm nozzle. Even 4 kg/min sounds like a lot.
My guess is that the instability comes from the media 'clumping' as it flows to the nozzle. At too high flow rates you actually get less effective peening because there is not enough air to propel the shot at the needed velocity.
I would settle on a stable flow and then adjust the machine to get the parameters that I need, eg, saturation, coverage, intensity, etc.
Mike W.
